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Biology, 7th Edition (Book & CD-ROM)
Defects in DNA that change gene function
Mutations can be from three different things: ***
1. change in template for rRNA or tRNA
2. change in coding region for protein
3. change in recognition sites for protein binding
ancestral gene. Humans and other animals have genes that evolved from this ancestral gene.
Frameshift mutation ***
loss or gains of anything other than 3
Frameshift causes... ***
extensive missense. It shifts the reading frame.
How does change in recognition sites for protein binding cause mutation?
DNA change in operator might block binding of repressor protein. It screws up the expression of the genes, not only the coating.
Mutations can change the...
promoter, regions that bind transcription factors. Ex: splicesome binding
Big mutations rearrange chromosomes: 1)
Can recombine coding regions of different genes-exon "shuffling" to make new gene
DNA rearrangements can give genes new transcription patterns
Function is not always changed by coating region, but mostly by
Marty Chalfie, Roger Tsien, Osamu Shimomura
Fuse enhancer promoter DNA to coding regions of Green Flourescent Protein (GFP) from jellyfish. Get regional expression of GFP.
similarity by descent from common ancestor
Important field, computer predictions of the sequence of DNA
How do cells generate variation in heredity needed for variation of evolution?
Mutations and individuals can swap DNA
How can individuals swap DNA?
Eukaryotes-mostly via sex
Prokaryotes-not real sex, but can exchange parts of DNA
Why swap DNA?
b/c of environment: selection pressure, need variation, swapping DNA gives an advantage
Prokaryotic cell division
fission into 2 daughter cells. replicate circular chromosome DNA. Only differences are from mutations or errors.
Bacteria exchange parts of DNA 3 different ways:
transformation, conjugation, or transduction
Take up DNA from outside and incorporate into chromosome
What is an example of transformation?
Griffith's experiments with Smooth and rough pneumonia bacteria
What do you need for transformation?
Cell surface proteins and transport proteins for uptake of DNA (DNA is polar and won't go through lipid bilayer by itself).
Direct transfer of DNA from another bacterium
How is DNA passed in conjugation?
long extensions of membrane called pili. This makes a bridge.
Conjugation can pass plasmids:
small circular DNA, not part of the chromosome
Other kinds of conjugations can pass part of...
chromosome. Can recombine DNA between plasmids and chromosomes
Plasmids passed during conjugation can carry...
valuable info. Ex. R plasmids carry mutant genes that make bacteria resistant to antibiotic drugs. Huge medical problem.
transfer DNA via a bacterial virus (bacteriophage or phage)
infectious agent smaller than bacterium. reproduce in host. contain mostly protein and nucleic acids.
protein that wraps up a viruses nucleic acid, sometimes with membrane lipid envelope
Uses host cell to make more virus in the...
perform enzyme-like catalytic functions
: What does Viral DNA do?
takes over DNA replication and make viral mRNA. Protein and virus assemble together to make macromolecular complex
alternative lysogenic life cycle ***
virus DNA recombines into and out of host chromosome. Like a storage stage for the virus; not making more virus.
(accidental) Virus takes fragment of bacterial DNA from old host, incorporates it into chromosome of new host.
group of physically similar organisms that can interbreed in nature
Are there seperate species in bacteria?
Yes and sometimes. It''s possible to make single stranded DNA or double stranded DNA.
Bacterial genomes are...
Viruses for Eukaryotic hosts
Can be RNA or DNA, double stranded or single.
Retrovirus RNA is converted to DNA by...
Reverse transcriptase. ex: HIV virus, causes AIDS
can take over and disrupt tissues by producing more virus. can import and abnormally express genes from humans and others.
Occasional viruses pick up...
Difficulties with primordial soup
synthesis problems, clutter and diffusion problems, chirality (most sugars are right handed, most AA are left handed)
mirror images. cannot be superimposed
Miller's Freeze experiment ***
can create organic molecules. they can convert molecules to one chiral form.
What could you get self-replicating polymers with?
RNA can be... ***
an enzyme and a template.
"RNA World" hypothesis
RNA is the only thing that does this. Acts like ribozymes
Two step self-replication
one acts like template for complimentary strand. The complimentary strand makes original enzymes that make the process more efficient.
Chemical natural selection
ribozyme replication not accurate. Select for ribozyme variants that are better at linking nucleotides.
This is better with RNA because
RNA is better at linking phosphate backbone. Made efficient by picking enzymes that make more of themselves.
Have short polypeptide-can bind to selective DNA or RNA sequence. RNA acted as a template for forming proteins and the protein then aided in replication of RNA
RNA does not self replicate. DNA does. DNA is much more stable then RNA, better storage of nucleotides
fatty acid membranes, instead of phospholipid membranes. Much more permeable. No active transport of diffusion.
Order of process ***
DNA to RNA to protein
have membrane bound organelles including nucleus containing the DNA
Eukaryotes made metabolic processes to be...
more efficient. Greater complexity=specialized. Allows cells to get bigger.
Semi autonomous organelles
act like small organisms. capable of replicating and dividing. can move. remnants of bacteria
DNA to RNA to proteins: Pro vs. Eu
Pro is all together
Eu is all in different parts
strands of chromosomes
site of rRNA synthesis from chromosomes, assembly of large and small ribosomal subunits. Assemble rRNA and proteins
two lipid bilayers. (2 membranes for each lipid bilayer)
Can mRNA pass through a lipid bilayer?
Can proteins pass through a lipid bilayer?
It depends of kind of protein. Ones that have hydrophilic and hydrophobic parts are hard to get completely through
complex of proteins, filter. active transport pore. in inner and outer nuclear envelopes
active transport complex of about 30 kinds of proteins. selectively recognizes proteins through lock and key
mRNA sorting ***
binds adaptor and export proteins that interact with pores. Machine recognizes specific proteins
What do you need to recognize adaptors?
5' cap, poly A tail and splicing
protein sorting by signal sequence
AA sequence that allows binding to nuclear import protein by lock and key
: Endoplasmic Reticulum
Network of membrane enclosed tubes, discs
rough er vs. smooth er
rough has ribosomes(translates proteins) and smooth does not
ER membrane is continuous with
the outer nuclear envelope
Smooth ER ***
no protein synthesis. Site of phospholipid and steroid (cholesterol) synthesis. Also a process storage (of Ca
) and others.
The endomembrane system traffics...
transmembrane proteins that are exported, or secreted, from the cell
What do the proteins do that were made by rough ER?
Either make transmembrane proteins or get proteins out of the cell by exocytosis
"Pulse-Chase" experiment with radioactive amino acid
Use cell that secretes lots of protein
add radioactive AA to tag something for a short period of time
Add lots of non-radioactive AA
What did this verify? ***
movement of radioactive proteins from the rough ER to the Golgi and eventually outside of the cell
ER signal sequence
allows insertion through ER membrane.ribosomes are slightly attached to the membrane and allow protein to float around inside of ER
Secreted proteins move from ER to...
stack of flattened membrane bound discs. There are diff enzymes in diff stacks for processing proteins
Processing of proteins
some cleaved to make smaller polypeptides, some linked to other proteins, and some linked to other molecules, like carbohydrates
when proteins covalentely link to carbohydrates
in plant and fungal cells for digestion, processing and storage. membrane wrapped
Vesicle formation and trafficking
can fuse with or pinch off from cell membrane or intracellular membranes. endo, pinch and bring in. exo, fuse and bring out
How are proteins secreted?
via transport vesicles in the ER and secretory vesicles in the golgi
Trafficking of vesicles
end in "somes." endosomes, exosomes, etc
contain digestive enzymes and reduce AA
What is the correct order for protein secretion? ***
ER, transport vesicle, Golgi, secretory vesicle
What happens to the lipids in a secretory vesicle?
They wind up in the cell membrane
intracellular rods and fibers that support the cell
Movement of vesicles
Attach to cytoskeleton and move with motor proteins. (change shape, grab vesicle and walk along the cytoskeleton)
Prokaryotes vs. eu.
Pro-diffusion would work
Eu-diffusion won't work because they're bigger
intermediate. stable "girders."
What is the major role of these?
to move things inside and move proteins around in the cell
More on microtubules ***
helical polymer made of individual dimers of alpha and beta tubulin proteins. (polymer made of proteins). Dimer is a polymer of 2. Can be stable "girders" but can also move things
More about intermediate filaments
mostly stuctural meshwork under membranes. many diff types. Same family as nuclear laminin (thick cloth). gives shape
Microtubules can move things three different ways: ***
1)push or pull things by rapid lengthening or shortening
2)using attached motor proteins
3) slide past each other via motor proteins
In animal cells, microtubules often emerge from
centriole in the centrosome-made in microtubules, made of 2 centrioles.
microtubule organizing center. two cylinders, each with a ring of 9 microtubule "triplets". 1 centrosome in animal cells
Movement by motor proteins: kinesin
"walks" vesicles along microtubule. Require E. E stored in phosphate bonds in ATP
Sliding microtubules move
cilia-short and many- and flagella-long and few. Fine bendable projections from cell, enclosed by cell membrane.
How do the cilia and flagella work?
they can either move by pushing water or stay still in membrane and create a flow for other things to move
contain mictotubules organized into ring- 9 pairs in ring plus 2 central("9+2") Pairs connected by dynein=motor protein
More about microfilaments
narrow, double helix made of actin proteins
How do microfilaments move? ***
1) shortened or lengthened by removal or addition of actin
2) slid pass each other with motor proteins=myosins
Both drive actively changing extensions of cell membrane
end with "podia" blobby=pseudopodia. fine=filopodia.
What does the movement of microfilaments do? ***
shortens muscles, other changes in cell shape and cytoplasmic "streaming" in plants (circulate cytoplasm)
Does endocytosis require energy?
Yes. any shape change needs E.
Does waving cilia require E?
mitochondria and chloroplasts. where most of the ATP comes from in eukaryotic cells
produce chemical E from sugars and other compounds. machine for making ATP. lots in cytoplasm. has 2 membranes, inner and outer
in plants and some protists. site for photosynthesis=site for production of E from sunlight. also has 2 membranes
mito and chloro contain some of their own DNA, mRNA and ribosomes. They reproduce in cells by fission. Resemble free-living bacteria. have transcription and translation
organisms living together in direct and intimate contact. endosymbiont theory
Win win situation
endosymbionts get nutrients from the host cell. mitochondria, like endosymbionts, make ATP for host cell.
Bacteria has diff kinds of metabolism
pro has more than eu but eu is good at specialization
Mitrochondria produce ATP in the
2nd and 3rd steps of respiration
(glucose) + 6O
+ 6H2O + ATP (energy)
spontaneous, but you'd have to wait a long long time
Respiration of the monosaccharide glucose via
a series of enzyme-catalyzed reactions. this lowers the Ea for the reaction to make it go
in cytoplasm(not in mitochondria). 6 carbon glucose lysed into 2 3-carbon pyruvates, get ATPs and electrons
Pyruvate then enters the...
Kreb (Citric Acid) cycle in mitochondrial matrix
Broken into CO2's, get ATPs and electrons
in mitochondrial matrix, electrons + O2 ---> ATP
atom that gains electrons (reduces charge)
atom that loses electrons (gains charge)
Reduction-Oxidation (REDOX) reaction
when one is reduced and one is oxidized. A + B ----> A- + B+. Product has more electrons than what it started with
Electron carriers are reduced by
high energy electrons
NAD+ + 2e- + H+ ----> NADH
FAD + 2H+ + 2e- ---->FADH2
NADP+ + H+ + 2e- ----> NADPH
What does this do?
Grabs electrons and stores in high energy state or builds intermediates
Every step in glycolysis and Kreb cycle is..
catalyzed by a seperate protein enzyme
More about glycolysis
1) initial steps require phosphate from ATP
2) More ATP is produced than initially used
3) electrons are captured in NADH
Yields: 2ATP + 2NADH
Could glycolysis occur if there was no ATP?
organic, polar, needs transportation protein
After Pyruvate enters the mitochondrion matrix...
3 carbon pyruvate loses 1 carbon as CO2 as it binds to Coenzyme A to make Acetyl-coA.
Acetyl CoA adds its...
2 carbons to a 4 carbon oxaloacetate, making a 6 carbon citric acid (citrate)
The cycle then takes the 6 carbon and
produces the 4 carbon again. Two carbons are lost as CO2 (needs to run twice for one glucose)
Yield of Kreb cycle: ***
1 ATP, 3 NADH, 1 FADH2
Glycolysis: glucose (6C) --->
2 pyruvates (3Cx2), yields 2ATP, 2NADH
Binding Coenzyme A (x2): 2 pyruvates--->
2 acetyl coa's (2C) + 2CO2, yields 2NADH
Kreb cycle (x2): 2 acetyl coA's----->
4CO2, yields 2 ATP, 6 NADH, 2 FADH2.
Per glucose, glycolysis and Kreb cycle give...
2 ATP Each, 4 total (pathetic)
But, convert electrons to energy via
substrate level phosphorylation
glycolysis and kreb cycle make ATP by taking phosphate from high energy subtrate molecule and binding ATP.
2 parts of oxidative phosphorylation ***
electron transport chain and ATP synthase
Electron transport chain
uses electrons to pump H+ into space between mitochondrial membranes (H+ needs to be pumped because it's too polar to diffuse)
Where are the pumps?
in the inner membrane. uses energy from electrons. Three different pumps in a row. Each grab electrons in diff. E states. O2 grabs electrons at the end to make H2O.
Electrons in the chain are often carried by ***
metal atoms, iron or copper, surrounded by protein
iron-containing ring. similar to heme that carries O2 in blood. stores E. imbedded in transport proteins.
Second step is ATP synthase
uses diffusion of H+ back across membrane to make ATP. uses a turbine (backwards pump). goes from high concentration of H+ to low concentration
Inner and outer membrane
acidic environment because of H+
Total per glucose is about 32-38 ATP. 40% efficient. rest of E is lost as heat.
Evolution? Some prokaryotes have electron transport chains. Why?
Reduces acidity of the cytoplasm and drives co-transport (get H+ concentration high on outside to drive other molecules in)
What if there is no oxygen? ***
The electron transport chain will quickly stop pumping H+ ions and the cell will start to run out of NAD+.
What will happen to glycolysis and Kreb cycle if there is no oxygen?
they will quickly shut down
If there is no NAD+,
no glycolysis or Kreb cycle. (There is a limited pool of NAD+)
What is the solution?
Add steps to regain NAD+ from NADH by fermentation
to get NAD+ back if there in no O2.
What are the two types of fermentation? ***
Lactic acid, used by us. pyruvate---> lactate. Needs 2NADH and get 2 NAD+.
Ethanol fermentation, used by yeast. Pyruvate---> take C off to get CO2.
Can the products of fermentation enter the Kreb cycle?
No. No NADH for oxidative phosphorylation. You do get 2 ATP per glucose with Fermentation
Respiration can use _____ feedback... ***
negative, for allosteric control of enzyme activity. EX: ATP or citric acid inhibit glycolysis. keep cell at homeostasis. Too much ATP slows it down
Where do animals and fungi get E?
From many organic molecules, not just glucose. From eating other animals and fungi and photosynthesis in plants
A tree gets most of its non-water mass from
surrounded by 2 membranes
space inside inner membrane
membrane-bound discs in stroma. They are stacked into grana
Light reactions ***
Use light energy to make ATP, electrons in NADPH and O2. happens in the thylakoid membranes.
Dark reactions ***
use ATP, electrons in NADPH and CO2 to make sugar. happens in the stroma
Dark reactions. Carbon fixation, reduction, and regeneration.
Carbon fixation ***
3 ribulose biphophate (RuBP) + 3 CO2 ---> 6 3 carbon chains (short-lived), using Rubisco enzyme
produces 6 G3P's, 1 of which is removed from the cycle and is used to make sugars.
Regeneration of RuBP ***
Remaining 5 G3Ps + ATP regenerate 3 5-carbon RuBP's (starting Material)
How many times do you need to run? ***
Three times to harvest an organic molecule. Use 9 ATP's, and 6 NADPH's. get 3 CO2's
light energy. Chlorophyll a and b. Magnesium containing ring. Light excited electrons in ring to higher, unstable energy.
accessory pigments. Absorb diff. wavelengths of light, protect chlorophylls from bleaching. This is the color you can see in leaves because the chloroplasts are dying
Pigments in photosystems
use light to excite and donate electrons to electron acceptor. Water is the electron donor.
Photosystem II is first
gives high energy electrons to H+ pumping electron transport chain.
What does Photosystem II do? ***
Pumps H+ into the thylakoid and uses the H+ gradient to drive ATP synthase. Again, uses electrons from H2O.
Then Photosystem I
get and excites electrons from H+ pumping electron transport chain.
The excited electrons can go one of two directions: ***
1) donated to NADP+ to make NADPH
2) Go back to H+ pumping electron transport chain to make ATP
Choice after photosystem I creates two different schemes. 1) Non cyclic (the Z scheme)
makes both ATP via H+ pumps and NADH after PSI. Creates NADPH
2) Cyclic ***
Makes ATP via H+ pumps, but no NADPH
Why would you chose to do the cyclic scheme instead of the non-cyclic? ***
The non-cyclic scheme makes about equal amounts of NADPH and ATP. The calvin cycle needs 9 ATPs and 6 NADPH. Use the calvin cycle to make more ATP
Plants get almost all their energy from
plants get almost all their carbon from
Differences in: carbon source-
Organic(heterotroph) or inorganic(autotroph)
Differences in: energy source
molecules(chemotroph) or sunlight(phototroph)
Plants get almost all their electrons from
Electron donors and acceptors: Plants- ***
H2O is donor and oxygen is acceptor
In animals and fungi ***
Reduced organic molecules is the donor and oxygen is the acceptor
Electron donors and acceptors in bacteria... ***
have lots of possiblities, eu. are limited. this is why pro. can live in diff. environments
single celled eu. first eu. to evolve
collection of individuals. some protists and pros. form colonies
"true" mulitcellular life
fungi, plants and animals
Plants and fungi have
cell walls outside cell membrane. allows cells to stick together. There are breaks in the cell walls that allow for direct contact between cells
Cell wall is made of
polysaccharides and proteins
single celled or multicellular. Cell wall is made of chitin polysaccharide.
"cells" in long tubes
cells often seperated by wall and membrane by these
Pores in walls
connects membranes, big enough for nuclei, organelles and metabolites to pass through
cell walls mostly made of cellulose polysaccharide.
pores in cell walls that connect cell membranes. Can pass RNA, proteins, nucleic acids and small organic molecules, but too small for nuclei and organelles
What does plasmodesmata connect? ***
The smooth ER of two cells
no cell was, but jelly-like extracellular matrix. mixture of proteins and polysaccarides. flexible
long protein fibers, connective tissure
large polysaccharide. make jelly coat
what happens when you age?
extracellular matrix begins to break down
Most animal cells are not_____, but can be connected by ***
syncytial, gap junctions: small pores between some(not all) animal cells. Ex: sponges, muscles.
What can pass though gap junctions? ***
Monomer, ions, small monosaccharides, not macromolecules
Animal cells also adhere using
Cell Adhesion Molecules (CAMs) in membranes. Protein with carbohydrate in membrane. Use lock and key binding to protein on adjacent cell
bind cell adhesion molecule to identical molecule on other cell
bind to different molecule
binding also by...
indirect binding by linker molecule
Animal cells can be arranged in many different ways. Connective tissue:
cells relatively loose
Tightly attached cells organized into flat sheet. ex: organs and skin
polarized. Two sides: apical and basal
extracellular matrix that underlies the basal side (collagen)
Junctions between epithelial cells
specialized CAMs (homophilic adhesion molecules) at each. ex: Cadherin. Little room for diffusion, seals it up
Junctions from epithelial cells to extracellular matrix
EX. connection to basal lamina uses integrin: binds to cytoskeleton and collagen
How do cells signal?
1) cytoplasmic connections
2) without cytoplasmic connections
Via cytoplasmic connections
syncytieal cells can pass everything. Plants use plasmodesmata and animals use gap junctions (Take a long time to signal)
Signals without cytoplasmic connections: Signaling molecule= ***
ligand. Either membrane bound (short range) or secreted (short or long range).
Signal binds and activates specific
receptor by changing it's shape
What is a diffusible signal that can go through membranes? ***
Steroids. Hydrophilic and hydrophobic parts. lipids, testosterone, and estogen, etc. All molecules can signal
steroid binds receptor protein in cytoplasm and nucleus.
Receptor-steroid complex is a ***
transcription factor that binds to DNA. It turns on transcription of genes with matching enhancer DNA
Other than lipids and gasses,
most signal cannot diffuse through lipid bilayer. ex. proteing and AA. Receptor is usually transmembrane protein.
Range within cell: whole cell example:
signals that turn on (or turn off) transcription
Range within cell: local:
Signal affects part of cell near receptor. EX. Signal changes assembly of nearby microfilaments or response to food.
No amplification if... ***
activated molecule only activated one target molecule (protein-protein binding)
Amplification if... ***
activated moleucule is an enzyme
Example of no amplification
Activated G protein binds and activates single target protein
Activated enzymes amplify signal
protein kinases: enzymes that add phosphates to specific proteins, activating or inactivating them.
Cascades of kinases can... ***
amplify weak signals
Positive feedback ***
can amplify or lengthen time of signal (Goes back to receptor and makes more)
Negative feedback ***
can decrease or shorten time of signal (Doesn't make more receptor). Nervous system and light sensors
go through membranes, activates cytoplasmic receptor that becomes a transcription factor
Some signal transduction pathways use...
small, non protein messengers=second messengers. inside the cell.
big examples of second messengers ***
lipids from membrane lipids, cyclic AMP (cAMP) from ATP, and CA2+ from outside cell or storage in ER
major component of transduction pathways. ATP---> cAMP + 2P. cAMP stimulates protein kinase.
can a second messenger also be a signal between cells? ***
Second messengers through gap junctions?
Yes. Ca2+ wave via gap junctions and positive feedback.
Do all multicellular eukaryotes have sexual reproduction?
From single parent. in pro. or multicellular eu.
From two different parents, eggs and sperm of germ line
immobile and usually larger. Most contain yolk that serve as nutrients (we don't have yolk because of placenta)
mobile and usually smaller. swims by flagellum. DNA in nucleus. Big mitochondria
combining genetic info. sperm membrane fuses with egg membrane. sperm has enzymes that digest extracellular matrix of egg.
First steps, fertilized egg... ***
divides to form embryo
first divisions. can occur without growth, forms blastula
many cells indistinguished from one another.
Cells mover to make germ layers in
gastrulation in the gastrula
outermost, makes skin, nervous system
middle, makes muscles and internal organs
innermost, makes digestive system (stomach, esophagus, etc.)
Each germ layer subdivides into specific organs (skin brain heart, liver, muscles, intestines, etc)
Organogenesis: neurulation: ***
formation of central nervous system in vertebrates.
in neurulation, the ectoderm ***
pinches off a long tube=neural tube. the neural tube forms brain and spinal cord.
Do differentiated cells have different DNA? ***
No, mostly have the same DNA
Differentiated cells all contain the same ***
making an embryo that contains the DNA from a differentiated adult cell
If cell is limited,
If cell allows for making of all cell types,
DNA is lost,
DNA is not lost
Process of cloning
take differentiaeted cell and take out nucleus, take unfertilized egg and take nucleus out. Sub nucleus into egg.
what makes differentiated cell diff? ***
Same DNA, but diff. gene expression (mRNA and protein).
Why are they diff?
Diff signals from diff parts of embryo or diff. determinants inherited during cell division
Signals form one set of cells can change differentiation of adjacent cells example
Dorsal mesoderm from amphibians signals to dorsal ectoderm to make neural tube. cells incorporated into host by induction
molecule inherited from one parent cell by only one daughter cell, makes that cell diff.
Example of cytoplasmic determinant ***
gray crescent in frog embryo. if daughter cell inherits gray crescent, they are normal. if they do not, they only develop belly tissue.
What is a cytoplasmic determinant? ***
Not known yet. Proteins or mRNA
Cytoplasmic determinants vs. cell-cell signaling
most embryos use both
can make more than one cell type
Early in development, most cells are.. ***
pluripotent-can make several cell types. ex. stem cells
Later in development,
most cells lose potency, and become determined as a specific cell type
But we retain some stem cells
undetermined cells capable of forming a wide range of tissues in response to signaling
change in cell size
increase in cell number
Synthesis or S phase
Mitotic or M phase
Gap 1 (G1)
period between M and S phases
Gap 2 (G2)
period between S and M phases
Cell cycle checkpoints
control proliferation. 3 big checkpoints
G1 checkpoint ***
cell large enough, nutrients, signals? If it fails, it goes to G0.
G2 checkpoint ***
Happy, DNA duplicated
chromosomes attached to cytoskeleton for movement, in anaphase
Example of checkpoint: MPF
complex of two proteins, drives cell through gap checkpoint. spikes at mitosis
The cyclin concentration
Increases as the cell matures
Binds and activates... ***
cyclin dependent kinase (CDK) to create active MPF. allowed to move on to G1
Failure in CDK
can cause cancer. Rb protein normally stops cell cycle at G1
What happens with CDK?
normally inhibits Rb protein. Rb mutation are common. lose inhibitor of checkpoint.
Pro. cell division
circular chromosome. Make a copy of chromosome, divide cell by fission into two daughter cells
linear DNA in a complex of proteins. Different chromosomes contain genes.
What is the order for a cell based on pluri and totipotent? ***
stem to pluripotent to determined
Every cell is totipotent untill... ***
it gets signals from other cells
In gastrulation, cells are
In organogenesis, cells are
T/F. The egg differentiates into 3 germ layers
False, the blastula does
The protein kinase or phosphorylation cascade don't show amp.
The mesoderm forms muscles and internal organs
The cells that got the grey crescent formed dorsal mesoderm
The egg contains yolk and is mobile
F, sperm is mobile
Can Ca2+ diffuse through the membrane>
No, but can be transported
Daughter cells have same DNA as parent
Daughter cells have half the DNA of the parent before fertilization
DNA is not joined, proteins are joined. Joined at the centromere=center of the chromosome
Seperate sister chromatids to make seperate chrmomosomes
The center of a chromosome is a ***
A chromatid has ***
one double helix
A chromosome has ***
it depends. 1 helix before replication and 2 helixes after.
double stranded. attache into single chromosome at centromeres, ends are telomeres
Microtubules are organized by ***
centrosome with two centrioles
2 sister chromatids together = ***
arranges and moves chromosomes. Some attach to centromeres others attach to nothing
How does the mitotic spindle work?
proteins surrounding centromere, control movement by shortening and sliding using motor proteins
What about the nuclear envelope?
Remains in a few protist and yeast, in most eu. it is lost during mitosis and remade after seperation
What happens in G2?
the centrioles are duplicated
chromosomes condense, spindle forms, nuclear envelope breaks down
Chromosomes line up along metaphase plate
chromatids seperate, move to poles
The cell cycle
Interphase (G1, S, G2) 90%
Mitotic phase 10%
subdivision of the cytoplasm into two cells
Animal cells form...
cleavage furrow. Requires microfilaments and myosin
Cytokinesis is diff if there is a cell wall
Plants form a new membrane from vesicles fusing in the middle of the cell=cell plate
In meiosis, daughter cells have
half the number of chromosomes (and half as much DNA) as the parent
number of types of chromosomes
haploid gametes to make diploid zygote. Meioses converts diploid cells back to haploid gamete
mitosis is only in diploid cells
in other organisms,
haploid cells can undergo mitosis to produce more haploi cells, multicellular haploid stages in life cycle
Diploid cells have pairs of
homologous chromosomes (with exception of sex chromosomes). Homologues contain same genes and transcriptions units
Homologues are not ***
copies. Each is inherited by a diff. parent
The women have a total of 46 chromosomes. How many homologue pairs do they have? ***
The men have 46 chromosomes. How many homologue pairs do the sperm have? ***
0. They are haploid
How many chromosomes do the sperm have? ***
one of each homologue
two of each homologue, one from sperm and one from egg
Homologues have... ***
same genes, but can have different versions (alleles)
Different alleles of gene have diff...
coding or regulatory DNA. diff. functions.
Seperate sister chromatids (copies) for all chromosomes. You seperate homologous chromosomes
Four haploid cells from one diploid cell via two rounds of cell division
Meiosis I ***
Homologous chromosomes seperate, sister chromatids stay together. Replicated into tetrad
Meiosis II ***
Second division to halve the amount of DNA, no DNA replication, sister chromatids are separate
gametes only get one of two possible alleles
Mendel crossed pea plants because
he could control which ones mated with which. used self pollination. and pea plants had heritable differences
the physical traits the individual has
what genetic info the individual can pass on. Can't see.
both alleles of a gene are identical (AA, aa)
One of the two alleles of that gene is diff (Aa)
control the phenotype even if only one homologue has that allele
Control phenotype only if both homologues have that allele
Mendels law of segregation ***
The two alleles in the parent segregate from each other during formation of gametes
Segregation of alleles during meisosis
homologues go to different cells. They get different versions of the gene.
assume that the two genes are on different (non-homologous) chromosomes.
Independent assortment ***
of non homologous chromosomes. have four different combinations in gametes
How many probabilities are there for one type of chromosome?
2 x 2=4
2 x 2 x 2= 8
number of homologue pairs being considered
round and yellow are dominant
How do you determine which trait is dominant?
Heterozygotic (RrYy) genes on non homologous chromosomes: After replication, metaphase Meiosis I:
These are sister chromatids and need to have the same version of the allele
For punnet squares
put all four combos on top and sides. they need to be on seperate chromosomes
one complication with mendelian inheritance
what if a gene is on a sex chromosome (sex linked)
not sex chromosomes
sex chromosomes ***
not paired, non homologous. In human, the X is larger and the Y is smaller. XX female, XY male
genes on sex chromosomes. no versions of x linked gene on y chromosome, vice versa
This is why
males are more likely to get a disease that is carried on the x chromosome because they don't have another x chromosome (like females) to help it out.
X linked diseases in humans ***
320. hemophilia, color and night blindness, muscular dystrophy, high blood pressure
not sex linked, but sex influenced
Barr bodies ***
inactive/condensed X chromosomes. become inactive at blastula stage. Random X chromosome inactivation blocks transcription and creates genetic mosaic.
Heterozygote has phenotype that is intermediate between that of homozygotes. neither are dominant. Ex: pink flowers
different alleles give different dominant traits. Get both traits. EX: blood groups-diff carbs on blood cells
A can't get B or AB, but can get O
Things can get complicated when...
different genes control the same phenotype. EX: mouse coat color is controlled by B and C, c wins over b
What is two genes are on the same chromosome?
lots of genes on chromosomes, physically linked to each other. Thomas Hunt Morgan
b+ is normal, wild type dominant
b is recessive mutant
If genes are on the same chromosome..
recombines parts of homologous chromosomes. Meiosis I=tetrad from prophase and metaphase
different arms can recombine here. adds more variability to offspring
can't do crossing over
Frequency of crossing over is determined by...
distance between genes
Between adjacent genes,
crossing over rarely occurs
Between distant genes,
crossing commonly occurs
Distance in centimorgans
% of offspring with non parental genotype
errors in chromosome assortment during meiosis
Genes in mitochondria and chloroplasts
sperm do not donate organelles, so purely inherited maternally
reversible change in gene expression (transcription) passed on to offspring
self replicating protein shape. Some shapes cause disease, others don't
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