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Which of the following are covalent bonds?
A. peptide bonds
B. carbon-carbon double bonds C. phosphodiester bonds
What are covalent bonds?
atoms share elections
What are hydrogen bonds?
an interaction of a H atom and an electronegative atom
What are ionic bonds?
one ion accepts e-, other ion loses e-
know the Central Dogma of Biology.
-DNA sequence encodes info
-DNA transcribed into RNA (transcription)
- Synthesis of proteins according to code in RNA transcript (translation)
chloroplasts- light > sugar for plants
made of RNA and proteins, fn: RNA synthesis
golgi apparatus- modify protein and lipids, sort proteins/ lipids, synthesize cells carbs
lysosome- break down and recycle materials
mitochondria- power house ATP synthesis
List the biological functions of carbohydrates.
when phospholipids get thrown into water, they lineup spontaneously to form a bilayer,with negatively charged polar head groups pointed outward toward water and thehydrophobic tails pointed inward, toward each other and away from water
What are the functions of biological membranes?
composition of a phospholipid
membranes are lipid bilayers with floating proteins
has polar hydrophilic head
has long non polar hydrophobic tail
deltaG = deltaH - T deltaS
Total energy= energy available + energy lost to entropy
deltaG = change in free energy
deltaH = enthalpy or heat energy change
deltaS = change in entropy
used to slow down or stop a chemical reaction. bind to either active site or elsewhere but hinder enzymes ability to accelerate conversion of reactants to products.
Which of the following types of inhibitors bind to the active site of an enzyme? A. an irreversible inhibitor
B. a competitive inhibitor
C. a non-competitive inhibitor D. an allosteric inhibitor
What is the function of cholesterol in animal membranes?
Breakdown of carbohydrates to release energy
Glucose is the most common carb used by cells
What are the products of meiosis?
4 daughter cells that contain half the number of chromosomes as the parent, each genetically unique
What are the features of the replication fork?
How does DNA polymerase replicate DNA?
incoming nucleotides are accepted if they are correctly base pair with the template, the 3’ OH of the growing strand attacks the high- energy phosphate bond of the incoming nucleotide, proving energy to drive the reaction
- Individuals inherit two copies of each gene, one from the mother and one from the father
- When individuals form reproductive cells, the two copies separate equally in the eggs and sperm
The two copies of each gene segregate into gametes independently of the two copies of another gene
Individuals with a genotype corresponding to a trait do not actually show the phenotype either because of environmental effects or because of interactions with other genes
Phenotype is expressed but with a different degree of severity in different individuals
State the first and second laws of thermodynamics.
two molecules with identical molecular formulas but that have different structures are called:
proximity with each other due to:
Sodium has 11 electrons arranged in three energy levels. The outer level has only one electron. In order to become stable, the atom loses an electron thus exposing the previous level with 8 electrons and subsequently becomes an ion with:
What type of bonding is likely to occur between two strands of DNA?
The primary chemical bond found in most large organic molecules is the ___________bond.
When we see COOH written as part of a chemical formula we recognize this as_____
When a solute diffuses in a solvent it’s entropy ____
A __________ chemical bond is most likely to create a molecule that has an electrical charge.
Some diseases, such as Tay-Sachs, are caused by the defective breakdown of cellular components. Which of the following organelles is defective?
Some patients with defective mitochondria in their muscles are extremely limited in their ability to exercise. Muscle biopsy followed by microscopic examination of the mitochondria, reveal that they are of normal size, but their inner membranes are not as convoluted as normal mitochondria. How can this mitochondrial defect cause the described symptoms in the patients?
Hydrogen bonds between peptide backbone components form a distinct helical structure.
“Hydrogen bonds between peptide “backbone” components on one polypeptide and R-groups on another polypeptide contribute to the overall function
Disulfide bonds formed between cysteines stabilize the overall structure of this protein isolated from the bacterium.”
There are extensive ionic interactions between positively charged R-groups and negatively charged R-groups on the polypeptide
There are hydrogen bonds between peptide backbone components that form neither an α-helix nor a β-pleated sheet.
Peptide bonds form between the monomers.
Which one of the following would be found in the cells of a blade of grass but not in the cells of an insect feeding on that grass?
Which one of the following cellular compartments does not have a double membrane structure separating it from the rest of the cell?
non-virulent bacteria can be prevented from being transformed into virulent bacteria if the debris from heat-killed virulent bacteria is first treated with:
Using Chargaff’s rules, you can determine that the DNA of an organism that contains 30% adenine would contain guanine.
Which of the following correctly indicates the complementary base pairing of adenine in DNA and adenine in RNA?
Which of the components of an amino acid differs from one amino acid to another?
the pH of a solution is 6.6. What is the concentration of protons [H+]?
The hydroxyl concentration [OH-] of a solution is 8.2 x 10-9 M. What is the pH?
The proton concentration of a solution is 3.9 x 10-4. What is the pH?
List the biological functions of nucleic acids
genetic info, energy exchange, metabolic regulation, catalytic
List the biological functions of proteins.
workhouses of cell: structure movement, catalyst, antibodies
List the biological functions of lipids.
structure, energy storage
What polar covalent bonds and nonpolar bonds? Use electronegativity in your definition.
polar- unequal sharing of electrons, EN is different on ends of molecule
non-polar- equal sharing of electrons, EN is the same on opposite ends of molecule
Define hydrophobic, hydrophilic and amphipathic (use polar /non-polar in your definitions).
hydrophobic- likes water, polar
hydrophilic- hates water, non polar
amphipathic- has both hydrophobic and hydrophilic properties
Understand the hydrophobic effect.
when the hydrophobic molecules tend to go to the inside of the structure while the hydrophilic molecules stay on the outside of the structure
What are the four major elements found in biological molecules?
Which bases are purines? Which are pyrimidines?
purines: A, Gpyrimidines: T, C
Understand the chemical linkage between nucleic acids (the phosphodiester bond).
linkage between 2 nucleotides= C-O-P-O-C
C= carbon sugar
What is the chemical sense of a nucleic acid?
Describe the major features of the DNA double helix.
Other than hydrogen bonds, what force holds together the double helix?
What are the differences between DNA and RNA?
DNA- deoxyribose, A/T, more stable, double stranded, double helix
RNA- ribose, A/U, single stranded
Know the differences between RNA and DNA
DNA uses deoxyribose, RNA ribose
DNA uses T, RNA uses U
DNA 5’ end is Monophosphate, RNA Triphosphate
DNA size very large, RNA is smaller
DNA double stranded, DNA single stranded
What are the two major categories of proteins and how do they differ?
fibrous and globular
Know the general structure of an amino acid: what are the four groups bonded to the α-carbon?*
amino group, carboxyl group, hydrogen, side chain or R group
What does hydrophilic mean in terms of amino acid side groups?
What does hydrophobic mean in terms of amino acid side groups?
What does acidic mean in terms of amino acid side groups?
What does basic mean in terms of amino acid side groups?
What is the sense (chemical direction) of a protein?
Distinguish the levels of structural hierarchy in proteins (1°, 2°, 3°, 4°)
1. The primary structure is the sequence of amino acids
2. The secondary structure results from interactions between stretches of nearby amino acids
3. The tertiary structure is the 3D shape of a protein
4. The quaternary structure is the result of protein subunits interacting with one another
What are the two common types of secondary structure in proteins?
What are the structural differences between prokaryotic and eukaryotic cells?
prok: no nucleus, no organelles
euk: nucleus, organelles
What are the main features of the typical prokaryotic cell?
nucleoid, small, high surface area to volume ratio, no organelles, transcription takes place in the cytoplasm, cell wall
List three cellular features of plant cells that are not found in animal cells.
cell wall, chloroplasts, no vacuoles, no lysosomes
endoplasmic reticulum: rough and smooth
endoplasmic reticulum: rough and smooth
Rough: site of protein synthesis
Smooth: site of fatty acid/ phospholipids synthesis
cytoskeleton: what are the three types?
a. microtubules: intracellular movement
b. actin filaments: muscle contraction, movement of cells
c. intermediate filaments: structural role
cytoplasm/cytosol- cell contents (cytosol everything except organelles)
What does amphipathic mean with respect to lipids?
has both polar and non polar ends, helpful in Na/K pump
What are the characteristics and functions of:
a. fatty acids
a. fatty acids- long CH chain with carboxyl (double bonded O and OH attached to a C), amphipathic (polar head, non polar tail), used in cell membrane
b. triacylglycerols- used for energy storage,all are hydrophobic and form oil droplets inside the cell, large number can be packed into a small volume (efficient energy storage), has doubled bonded O
d. phospholipids- major lipid found in the cell membrane, hydrophilic head (glycerol/ phosphate group), hydrophobic tail (fatty acid)
How does saturation of a fatty acid affect its melting point?
Which vitamins are lipid-soluble? What are their functions?
structure of the phospholipid bilayer (which part is hydrophilic/hydrophobic).
What is the difference between simple diffusion and facilitated diffusion?
What is the difference between primary and secondary active transport?
sequence of events of the sodium-potassium pump.
Define phototroph and chemotroph; define autotroph and heterotroph.
Define metabolism; catabolism and anabolism (use ATP in your definitions).
Know the structural components of ATP, ADP and AMP.
Define endergonic and exergonic (use ∆G, spontaneous/nonspontaneous in your definition).
anabolism and catabolism, but in terms of Gibbs free energy, enthalpy and entropy.
anabolism- products have more chemical energy then the reactants (negative enthalpy) and are less disordered (positive entropy), yielding a positive △G
catabolism- products have less chemical energy than the reactants (positive enthalpy) and are more disordered (negative entropy) yielding a negative △G
What are the general steps of an enzymatically catalyzed reaction?
Understand the activation energy profile for an enzymatic reaction.
activation energy= energy required to start rxn
when activation energy is low, rxn is faster
enzymes reduce a.e. by stabilizing the transition state
rate of a.e. increases b/c a.e. is reduced
What are inhibitors? What are the two general types?
Describe the two kinds of reversible inhibition.
define carbohydrate, and differentiate between aldose and ketose sugars.
monosaccharide, disaccharide, polysaccharide and complex carbohydrates.
What kind of bond links carbohydrates together?
Know the four stages of cellular respiration and their cellular locations, starting and ending materials.
Define oxidation and reduction.
What is the role of NAD and FAD in cellular respiration?
What are the two ways in which ATP is produced in cellular respiration?
Where does the energy needed to create ATP come from in cellular respiration?
What happens to pyruvate in the absence of oxygen?
What is the overall reaction of photosynthesis? How does it compare to cellular respiration?
What is the input for The Calvin Cycle? The output?
Where does the ATP and NADPH that is needed in the Calvin Cycle come from?
In the light reactions, which photosystem splits water? Where does the needed energy come from?
Where does ATP synthase in chloroplasts get energy to phosphorylate ADP?
What happens when rubisco uses O2 instead of CO2? (What is the output of photorespiration?)
Which of the following statements is true?
A. All triacylglycerols and all phosphoacylglycerols have the same fatty acids in them
B. All triacylglycerols have the same fatty acids, but the fatty acids in phosphoacylglycerols vary C. The fatty acids in triacylglycerols vary, but all phosphoacylglycerols have the same fatty acids in them
D. The fatty acids in both triacylglycerols and in phosphoacylglycerols vary
triacylglycerols and in phosphoacylglycerols vary
4. Some diseases can result from defective transport across the membrane. For example, cystic fibrosis results from a chloride ion transporter that does not function. Which of the following would be affected when this transporter does not function?
A. the chloride concentration gradient B. the electrical gradient of the cell C. Both A and B
D. Neither A nor B
Long, saturated fatty acid tails ____ lipid mobility and ____ membrane mobility
Which of the following is not a typical component of an animal cell’s plasma membrane? A. protein
C. nucleic acid
Passive transport of a molecule across a lipid bilayer only occurs against a concentration gradient.
Phospholipids will gather together and form membranes only if the appropriate enzyme is present.
The diffusion of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration is referred to as __________.
The sodium/potassium pump is an example of:
Which of the following is not a function or characteristic of membrane proteins?
B. catalytic activity
C. blood clotting
D. receptor sites
In the operation of the sodium-potassium pump:
phosphorylated with ATP as the source of the phosphate
Which of the following describes ATP hydrolysis?
C. often coupled to a reaction that has a positive ΔG D. A, B and C are true
E. Only A and B are true
D. A, B and C are true
Autotrophs typically obtain their carbon from:
The potential energy in a molecule of ATP is held in the:
B. repulsion of the phosphate groups from each other
18. Anabolic pathways of metabolism are pathways that _____________.
build complex molecules from simple ones
Which of the following reactions is most likely to be exergonic?
A. the synthesis of a phospholipid from glycerol and fatty acids B. the replication of DNA from free nucleotides
C. the formation of cellulose from individual glucose molecules D. the digestion of protein from food into amino acids
D. the digestion of protein from food into amino acids
It is often stated that the phosphate bonds in ATP are “high energy,” but in fact, they are not notably high in energy. Rather, they are easy to break, and the ΔG of hydrolysis is a “useful” quantity of energy. What makes the phosphate bonds easy to break?
C. The negative charges on the phosphate groups repel each other.
Which of the following reactions would you predict could be coupled to ATP hydrolysis to ADP + Pi to make it energetically favorable (spontaneous)?
A. phosphoenolpyruvate + H2O Æ pyruvate + Pi, ΔG –14.8 kcal/mol
B. glucose 6-phosphate + H2O Æ glucose + Pi, ΔG –3.3 kcal/mol
C. glucose 1-phosphate + H2O Æ glucose + Pi, ΔG –5.0 kcal/mol
D. glutamic acid + NH3 Æ glutamine, ΔG +3.4 kcal/mol
D. glutamic acid + NH3 Æ glutamine, ΔG +3.4 kcal/mol
Animals such as humans are classified as:
Which one of the following would most likely be a product of a catabolic reaction? A. a complex carbohydrate like cellulose
B. a nucleic acid like RNA
C. a motor protein like myosin
D. a lipid like cholesterol
E. an amino acid like tryptophan
E. an amino acid like tryptophan
An uncatalyzed reaction has a higher ΔG than the same reaction when catalyzed by an enzyme.
An uncatalyzed reaction has a higher activation energy than the same reaction when catalyzed by an enzyme.
Activators and inhibitors that bind to enzymes at positions other than the active site of the enzyme bind to a(n) site on the enzyme.
The reactions in the pathways of glycolysis and the citric acid cycle harvest the high-energy electrons stored in glucose. Therefore, these pathways _______________ .
A. are catabolic pathways
In most living cells, which one of the following is not a product of cellular respiration? A. carbon dioxide
E. All of these choices are products of cellular respiration in most living cells
The gain of electrons is referred to as:
Which one of the following represents the reduced forms of the two major biological cofactors?
A. NAD+ and FAD
B. NAD+ and FADH2
C. NADH and FAD
D. NADH and FADH
Which of the following is a net product of glycolysis?
A. 2 acetyl-CoA
B. 2 pyruvate
C. 1 ATP
the most oxidized form of carbon is:
Which of the following is a net product of the citric acid cycle for each molecule of pyruvate generated in glycolysis?
A. 3 ATP
B. 3 NADH
C. 3 FADH2
the energy from the movement of electrons through the electron- transport chain is directly used to
In human cells such as muscle tissue, the product of anaerobic respiration is:
The approximate yield of ATP from the full oxidation of a molecule of glucose is:
The pH in the stroma of the chloroplast should be ________ compared to the thylakoids due to the _______ concentration of hydrogen ions in the thylakoid lumen.
During photosynthesis, ____ is reduced to _______
A. water; carbon dioxide
B. carbon dioxide; glucose
C. oxygen; water
D. glucose; oxygen
E. carbon dioxide; oxygen
is reduced to .
43. Photosynthesis is the pathway used to synthesize carbohydrates from:
The fluid-filled interior compartment of the thylakoid network is referred to as the:
The most abundant protein on Earth is:
46. The reducing agent during the Calvin cycle is:
Leaves absorb the least amount of light in the ___ range of the visible spectrum
Chloroplast ATP synthases are powered by the flow of protons from the:
thylakoid lumen to the stroma
Photorespiration results in:
D. the consumption of ATP and the loss of CO2
Reactive oxygen species are detoxified by a category of molecules referred to as:
List the four essential elements of cell communication
a. signaling cell
b. signaling molecule
c. receptor molecule
d. receptor cell
Describe the four steps involved in cell signaling.
Define each of the four types of signaling
Define ligand and ligand-binding site. What happens to the receptor when the ligand binds?
List the three types of cell surface receptors.
Define kinase and phosphatase.
kinase- enzyme that adds a phosphate group to another molecule (phosphorylation)
phosphatase- enzyme that removes phosphate group (de-phosphorylation)
List the three types of cytoskeleton. Which type has the largest diameter? The smallest diameter?
Microtubules: what is the composition? The functions? What is the centrosome?
composition- two tubulin proteins (alpha and beta), combine to form tubulin dimer
function- maintain shape of cell, provide tracks for transport of material from one end to another
centrosome-in animal cells, the “main” microtubule, others radiate outward of the centrosome
Microfilaments: what is the composition? The functions?
composition- polymers of actin monomers, arranged into a helix
function- reinforce the plasma membrane and organize the proteins associated with it
Intermediate filaments: what is the composition? The function?
composition-polymers of intermediate filament proteins, these proteins differ from one cell type to the other
function- combine to form strong, cable like structures in the cells (mechanical strength)
List the three types of cellular movement.
1. cell movement itself
2. change in cell shape
3. movement of molecules/ organelles within
Define extracellular matrix, cell-adhesion molecules, and cellular junctions.
extracellular matrix- proteins and polysaccharides connected to tissues and organs
cell adhesion molecules- cell surface proteins that attach cells to each other and to the extracellular matrix
cellular junctions- the regions where cells adhere to other cells or the extracellular matrix
belt-like junctional complex of cadherins that goes around the circumference of the cell
hold the plasma membrane of adjacent cells together, use cadherins
prevent passage of materials in between cells:
formed when a set of integral membrane proteins arranged in a ring connects to a similar ring of proteins in the membrane of another cell
of plant cells are connections between the plasma membranes of adjacent cells that permit materials to pass directly from the cytoplasm of one cell to the cytoplasm of another (desmosomes of plants)
Integrins are the prominent cell adhesion molecules extracellular domains bind to the extracellular matrix proteins in the basal lamina and their cytoplasmic domains are linked to intermediate filaments of the cytoskeleton
What are interphase and M phase of the eukaryotic cell cycle?
M phase: the time during which the parent cell divides into two daughter cells
interphase: time between 2 successive M phase
What are G1, S, G2, and G0 phases of the eukaryotic cell cycle?
How is DNA organized in eukaryotic cells? Use histones, chromatin, chromosomes and karyotype
DNA is organized with histones and other proteins into chromatin, which can be looped and packages into chromosomes. The portrait formed by the number and shapes of chromosomes representative of a species is called its karyotype.
Define haploid, diploid, sister chromatids, centromere, and kinetochore.
haploid:a cell with 1 complete set of chromosomes
diploid: a cell with 2 complete sets of chromosomes
sister chromatid- 2 homologous chromosomes (identical copies)
centromere- what holds together the 2 sister chromatids
kinetochore- forms the site of attachment for a single microtubule, associated with the centromere (each on one side)
What happens in prophase I of meiosis? Use synapsis, bivalent, and chiasmata in your answer.
-each replicated chromosome condenses into 2 sister chromatids held together at the centromere
-synapsis: the homologous chromosome pair with each other side by side
crossovers –connections that form from breakage and rejoining between sister chromatids
- a 4 stranded structures called a bivalent forms
-w/in the bivalents are cross like structures called chiasmata, which are visible crossovers between non-sister chromatids
How is cytokinesis different in male sex cells versus female sex cells?
female: cytoplasm divided unequally in both meiotic divisions
-most cytoplasm in one cell called oocyte, which will develop into a functional cell
male: cytoplasm divided equally
Describe synthesis on the leading strand and the lagging strand.
What is the purpose of RNA primase? DNA ligase?
What are the functions of helicase, single-stranded binding proteins, and topoisomerases?
helicase- unwinds the parental double helix at the replication fork
single-stranded binding proteins-bind to the single-stranded regions of the parental strands; protect them from degradation and prevent them from coming back together
topoisomerases- work upstream of the replication fork to relieve the stress caused by unwinding the double helix at the replication fork
What were the results from a true breeding yellow seed plant with a true breeding green seed plant?
all offspring had yellow seeds
What are the results from self-fertilization of the F1 plants (from above)?
Define allele, genotype and phenotype.
genotype- internal expression of genes
phenotype- external expression of genes
Explain Mendel’s Principle of Segregation.
Individuals inherit two copies of each gene, one from the mother and one from the father, and when individuals form reproductive cells, the two copies separate equally in the eggs and sperm
Explain Mendel’s Principle of Independent Assortment.
The two copies of each gene segregate into gametes independently of the two copies of another gene
3. Why has thymine replaced uracil in DNA?
Thymine helps to guarantee fidelity in replication
5. Where does transcription take place in prokaryotes? Eukaryotes?
Prokaryotes: both in cytoplasm
Eukaryotes: transcription in the nucleus, translation in cytoplasm
6. Define template and nontemplate strand.
template strand- is the original stand of DNA, the strand that is read
non-template strand- same sequence as RNA transcript, but U is replaced with T
7. What is the function of the bacterial sigma factor?
to initiate transcription
8. Describe the transcription bubble.
14 bp in length, strands are separated, growing RNA transcript is paired with template, bubble is 8 bp in length
What is the enzyme responsible for RNA synthesis (transcription)?
How does RNA polymerase add nucleotides on to the growing chain (5’ or 3’ end)?
Where does the energy come from to synthesize RNA?
3’ -OH of the growing strand attacks the high energy phosphate of the incoming ribonuecotide
the RNA transcript that comes off the template
How does the primary transcript differ in eukaryotes and prokaryotes?
Eukaryotes: barrier between transcription and translation (nuclear membrane), undergoes a complex process of chemical modifications (RNA processing), 3 kinds of chemical modifications occur before the mRNA is translated by the ribosome
Prokaryotes: both processes occur in the cytoplasm, there is no nuclear envelope to specially separate transcription from translation, takes place in the mRNA, contains the info for more than one gene
List the three major modifications to eukaryotic primary transcripts.
What is the protective function of the 5’ and 3’ modifications?
help stabilize the RNA transcript since the single-stranded nucleic acids can be unstable and susceptible to breakdown by enzymes
What is the advantage to alternative splicing?
gene expression regulated, tissue specific
Amioccyl tRNA synthesis
initiation factors (IFs)
Elongation factors (EFs)
Release factors (RFs)
Where does ricin come from? How is it toxic?
ound in castor beans, common weed in dry climates
inhibits protein synthesis:
- removes single adenine base
- ribosome can no loger function
-protein synthesis stops
-cell death occurs
-repeated over and over
What is the function of tRNA? How does its secondary and tertiary structure differ?
function: carries out translation
tRNA= transfer RNA
secondary structure- cloverleaf structure
tertiary structure- L shaped 3D structure
What is the function of aminoacyl tRNA synthetase enzyme family?
connect specific amino acids to specific tRNA molecules
Describe the codon (mRNA) – anticodon (tRNA) interaction in translation.
codon (mRNA) first base pairs with the last base in the anticodon (tRNA) because they must be antiparallel, most codons specify an amino acid according to genetic code
nderstand this description: the genetic code is triplet, degenerate, and continuous.
triplet: ribosome moves over mRNA 3 bases at a time
degenerate: more than one triplet can code for the same amino acid
How did Khorana’s experiments identify the amino acids encoded in UUU, AAA, CCC and GGG?
synthesized an mRNA consisting of all U ribonucelotides
10. What are the three stages of translation? What components are needed in each step?
distinguish monocistronic mRNA and polycistronic mRNA
monocistronic mRNA= eukaryotic mRNA, initiation complex forms at the 5’ cap and scans along the mRNA until the first AUG is encountered
polycistronic mRNA= prokaryotic mRNA mRNA mol have no 5’ cap, initiation complex is formed at one or internal sequences present in the mRNA (shine-dalgarno sequence)
What is the start codon? What amino acid does this code for?
Which component of the ribosome catalyzes peptide bond formation?
RNA in the large subunit
Where does the required energy for the formation of peptide bonds come from?
by the breaking down of high energy bonds of GTP with elongation factors
What terminates translation?
stop codon (UAA, UAG, UGA)
How does methylation of cytosine change gene expression?
adds methyl group to the base cytosine, make CpG islands which can change over time in response to the environment (providing a new way to turn genes on and off) can cause cancer
How does chromatin remodeling change gene expression, in general?
the nucleosomes are repositioned to expose different stretches of DNA
Specifically, what changes allow for chromatin remodeling (think
addition/removal of different chemical groups
define “epigenetic effects” of eukaryotic gene regulation.
regulation of gene expression caused by mechanisms other than changes in the DNA sequence, aka manner which the DNA is packaged, causing changes in gene expression, can be inherited but are often reversible and responsive to changes in the environment
How is the second copy of the X chromosome inactivated in XX individuals?
after a fertilized egg with 2 X chromosomes implants in the mother’s uterine wall, one X chromosome is selected AT RANDOM and inactivated, as cell division continues inactivation persists in each cell lineage the same X that was originally inactive remains inactive
How do enhancer and promoter sequences regulate transcription?
Alternative mRNA splicing: know the insulin receptor example given in lecture.
alternative mRNA splicing- DNA sequence is cut in different ways to yield different proteins
in liver cells:
-exon 11 is included in the mRNA
-the insulin receptor produced from this mRNA has low affinity for insulin
RNA-editing: how is RNA changed and what are the results of this change?
RNA transcripts become substrates for enzymes that chemically modify bases in the RNA resulting in:
- a change to the nucleotide or amino acid sequence
The result is that transcripts from the gene can produce multiple types of proteins even in a single cell
In general, how do small regulatory RNAs regulate gene expression?
by binding to transcripts and blocking translation or causing degradation
Specifically, how do miRNAs regulate gene expression? siRNAs?
miRNAs- inhibits translation by causing mismatches in base pairs of mRNA
siRNAs- causes degradation of the RNA transcript, no mismatches of mRNA
Why is gene regulation simpler in prokaryotes than eukaryotes?
-DNA is not packaged into chromosomes
-no nuclear membrane separating the process of transcription and translation
-mRNA is not processed
-transcription regulation can be positive or negative
Define positive and negative reulation. Use activator protein and repressor protein in your answer.
positive regulation: a regulatory molecule (activator protein) binds DNA in order for transcription to take place
negative regulation: regulatory molecule (receptor protein) binds DNA in order for transcription to be prevented
What is an operon?
region of DNA that includes the coding sequence for multiple genes that get transcribed together into a single mol of mRNA
What important elements does the Lac operon contain?
gene coding sequences (lacZ/ lac Y region)
regulatory sequences (promoter, operator, CRP-cAMP binding site)
What happens to gene expression of the Lac operon in the presence of glucose?
cAMP levels are low, cAMP-CRP complex doesn’t form, CRP doesn’t bind the lactose operon
transcription doesn't occur
What happens to gene expression of the Lac operon in the presence of lactose, and no glucose?
cAMP levels are high, cAMP binds to CRP causing shape change of CRP, CRP binds DNA and activates transcription, the repressor can’t bind, lactose operon induced
lactose converted to allolactose binds to the repressor and prevents it from binding to the operator, RNA polymerase is recruited and transcription occurs, lactose acts an inducer b/c it prevents the binding of the repressor protein and allows transcription