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enzyme makes telomere of lagging strand usingand internal RNA template (not the DNA itself). Is developmentally regulated.Phosphodiester linkage
Erwin Chargaff determined that
- Amountof adenine = amount of thymine
- Amountof cytosine = amount of guanineAlways an equal proportion of purines (A and G)and pyrimidines (C and T)
- information– it must contain the information necessary to make an entire organism
- transmission– it must be passed from parent to offspring
- replication– it must be copied in order to be passed from parent to offspring
- variation– it must be capable of changes to account for the unknown phenotypic variationin each species
studied Streptococcuspneumoniae, a pathogenic bacterium causing pneumonia. Discovered 2 strains ofstreptococcus – S strain is virulent, R strain is nonvirulent. He infected micewith the strains to understand the difference. Discovered transformation.Modern interpretation is that genetic material was actually transferred betweenthe cells.
Discuss the findings and thesignificance of experiments by Alfred Hershey and Martha Chase who used labeledT2 bacteriophage.
– performed X-raydiffraction studies to identify the 3D structure. Discovered that DNA washelical. Using Maurice Wilkin’s DNA fibers, found that molecule has adiameter of 2 nm and makes a complete turn of helix every 3.4 nm.
- discovered informationconcerning the molecular structure of nucleic acids and its significance forinformation transfer in living material.
RNA Nucleotide –
§ Sugar - is ribose.
§ Monomers- ribonucleotides
§ Bases - purines – adenine and guanine (A&G) and pyrimidinescytosine and uracil, (C&U) instead of thymine.
§ Phosphate groups – ATP, GTP, CTP, UTP
DNA Nucleotide –
§ Sugar - is deoxyribose.
§ Monomers- deoxyribonucleoties
§ Bases – purines – adenine and guanine (A&G) pyrimidines –thymine and cytosine (T&C)
§ Phosphate groups – dATP, dGTP, dCTP, dTTP.
mRNA – a type of RNA that carries the code for aspecific protein. In the early stages of protein synthesis, the mRNA issynthesized from a DNA template during transcription.
the fact that in most cases in the genetic code,used by all life on earth, there is one particular amino acid that is specifiedby more than one three base combination of the four nitrogenous bases – calleda codon
a set of three adjacent nucleotides, also calleda triplet, in mRNA that base pair with the corresponding anticodon of the tRNAmolecule that carries a particular amino acid, hence specifying the type andsequence of amino acids for protein synthesis.
an enzyme that catalyzes the esterification of aspecific amino acid or its precursor to one of all its compatible cognate tRNAsto form an aminoacyl-tRNA. It attaches to the accurate amino acid onto thecorresponding tRNA.
N-terminusor amino terminus of a polypeptide
C-terminusor carboxyl terminus of a polypeptide
the RNA splicing variation mechanism in which the exon of the primary gene transcript, the pre-mRNA, are separated and reconnected so as to produce alternative ribonucleotide rearrangements.
· Describe and discuss the components ofthe central dogma
o Information only flows from DNA -> RNA -> PROTEIN. In transcription, DNA -> RNA. In translation, RNA -> PROTEIN. Retroviruses can violate this order using reverse transcriptase to convert their RNA genome into DNA.
o Transcription – DNA directed synthesis of RNA, only template strand of DNA is used, U is replaced by T in RNA, and mRNA directs synthesis of polypeptides.
o Translation – synthesis of polypeptides, takes place at ribosome, requires several kinds of RNA.
Describe the structure and function of transfer RNA.
o Structure – Clover shaped, single stranded molecule. It has loops formed by the base pairing of complementary bases. At the top is an anti-codon and at the bottom is an amino acid.
o Function – tRNA molecules carry amino acids to the ribosome for incorporation into a polypeptide
Describe the structure of ribosomes.
o Has multiple tRNAbinding sites:
- P site – binds the tRNAattached to the growing peptide chain
- A site – binds the tRNAcarrying the next amino acid
- E site – binds the tRNAthat carried the last amino acid
o 1 – Activation – 5’ Nterminus amino acid is joined by its carboxyl group to the 3’ OH of the tRNA byan ester bond.
o 2 – Initiation –Ribosome binds to the 5’ end of mRNA with the help of initiation factors.
o 3 – Elongation –additional amino acids are added to the polypeptide
o 4 – Termination – the Asite of the ribosome faces a stop codon (UAA, UAG, or UGA)
o Initiation – Ribosomebinds to the 5’ end of mRNA with the help of initiation factors.
§ Aminoacyl tRNA synthetase(an enzyme) catalyzes the bonding between the specific tRNAs and the aminoacids that their anticodon sequences call for. The product of this is anaminoacyl-tRNA molecule.
§ This aminoacyl-tRNAtravels inside the ribosome, where mRNA codons are matched throughcomplementary base pairing to specific tRNA anticodons.
§ The amino acids that thetRNAs carry are then used to assemble the protein.
o In termsof structure, RNA and DNA are similar. They consist of 5 carbon sugarsconnected via phosphate groups with a nitrogenous base attached. The differenceis that RNA has ribose as a sugar and DNA has deoxyribose, DNA does not havethe 2' hydroxyl group that RNA does (hence the name, it is missingone oxygen.) This actually makes DNA more stable than RNA though. The otherdifference is in the bases. DNA has adenine, cytosine, guanine and thymine. RNAhas the same except that it uses uracil in place of thymine.
- DNA is the centralgenetic material of life. It is basically blue prints to your existence. To bereally basic, its essential function is to store information.
- RNA does a lot of thework. RNA is transcribed from a DNA template, which is then used by ribosomesto create proteins, the real workhorse of life. These types of RNA are calledmRNA (messenger RNA), tRNA (transfer RNA, carries amino acids to growingpolypeptide chains/ribosomes) and rRNA (ribosomal RNA, a part of ribosomes.)
o Introns are non-codingsequences and exons are sequences that will be translated.
o template strand is thesequence of DNA that is copied during the synthesis of mRNA. The coding strandis the opposite strand, which is the strand with a base sequence directlycorresponding to the mRNA sequence. It corresponds to the codons that aretranslated into protein.
o Transcription is thesynthesis of RNA from a DNA template. The structure of DNA is not changed inthe process.
- Location – prokaryotes–cytoplasm/ eukaryotes – nucleus
- Required - RNApolymerase and transcription factors
- Produces - mRNA, tRNA, rRNA, and non coding RNA
o Translation is thesynthesis of a protein from an mRNA template.
- Location – prokaryotes –cytoplasm/ eukaryotes – ribosomes on ER
- Required - ribosomes
- Produces – Proteins
- mRNA – contains codonsto be used for translation into protein - brings message from DNA. Codes for proteins.
- tRNA – carries the aminoacid and brings it to the site of protein synthesis based on the matching ofthe anticodon that it has and the codon of the messenger. Is smaller and hasclover-leaf structure. Used to transport amino acids to the ribosomes.
o Codon is a tripletsequence in the mRNA transcript which specifies a corresponding amino acid – ora start or stop command. Found on mRNA. Written in the 5’->3’ direction.
o Anticodon – thecorresponding triplet sequence on the tRNA which brings in the specific aminoacid to the ribosome in translation. It is complementary to the codon. Ex: ifcodon is AUU, the anticodon is UAA. There is no T in mRNA because it isreplaced with U. Found on tRNA. Written in 3’->5’ direction.
o Activated amino acid –product formed by the condensation of the acyl radical of an amino acid andadenosine 5’-monophosphate. Formed in the first step of protein biosynthesis.
o Charged tRNA – producedin two steps – amino acid activation and transfer.
an enzyme that is responsible for making RNAfrom a DNA template. In all cells RNA polymerase is needed for construction RNAchains from a DNA template, a process known as transcription.
a group of genes or a segment of DNA thatfunctions as a single transcription unit. It is comprised of an operator, apromoter and one or more structural genes that are transcribed into onepolycistronic mRNA.
· Describe the major components of the lac operon
o Five Components:
- Promoter – a specificsegment of DNA to which RNA polymerase attaches to begin transcription of mRNAfrom an operon
- Operator – sequence ofnucleotides located between the promoter and structural genes
- Repressor – proteinwhich can bind to the operator, thus inhibiting the promoter from binding whichin turn leads to NO transcription because RNA Polymerase was not able to bindor move along the DNA.
- Inducer – substancewhich can activate or inactivate a repressor
The lac operon isnegatively regulated by a repressor protein. The lac repressor binds to theoperon to block transcription. In the presence of lactose, an inducer molecule(allolactose) binds to the repressor protein. The repressor can no longer bindto operator and transcription proceeds. Even in the absence of lactose, the lacoperon is expressed at a very low level.
A small infectious agent that can replicate onlyinside the living cells of an organism. Can infect all types of organisms.
Humanimmunodeficiency virus (HIV)
Acquiredimmune deficiency syndrome (AIDS)
Describe the rationale for, or mode ofaction of, some of the drugs used in the fight against HIV
o They reversetranscriptase inhibitors – AZT is the 1st drug licensed for clinicaluse and is selective for HIV.
o Also target a proteasethat cleaves polyprotein for viral replication and assembly.
o Block viral entry –fusion inhibitor blocks fusion of viral envelope with plasma membrane of targetcell
o Integrase inhibitors –one drug targets viral integrase protein
o Combination therapy –use a combo of drugs. It has entirely eliminated the HIV virus from manypatient’s bloodstreams. Highly active antiretroviral therapy (HAART) has cutthe U.S. Aids death rate by 3/4ths since mid 1990s.
o Prions – proteinaceusinfectious particles that cause transmissible spongiform encephalopathies(TSEs) such as Mad cow disease, Scrapie in sheep and the Creutzfeldt-Jacobdisease in humans.
o Viroids – tiny nakedmolecules of circular RNA that cause disease in plants.
o Angiosperms undergodouble fertilization. In fertilization, one sperm fertilizes the egg forming azygote, while the other sperm attaches to the two polar nuclei for the triploidendosperm (3N)
o Stamen – male reproductive organ that produces pollen. Consistsof:
- Anther – where pollen is
- Filament – talk thatanther is attached to
o Carpel – female reproductive organ that produces fruit and iscomprised of:
- Ovary – where fruit isformed
- Stigma – top wherepollen is gathered
- Style – how pollentravels to ovaries
o petals – brightly colored t attract insects, or small (ornon-existent) in wind pollinated plants
o sepals – protected the flower when it was in bud form
- estrogenstimulates the anterior pituitary to secrete LH about midcycle
- LHsurge causes the Graafian follicle to burst, releasing its secondary oocyteinto the Fallopian tube
- Ifoocyte is not fertilized, it disintegrates
- Ifit is fertilized, it completes meiosis II, forming a mature ovum and secondpolar body
- Fusionof the nuclei from the ovum and the sperm produce a diploid zygote
- Canbe prevented with birth control of prevention of embryo implantation “plan b”
- HypothalamicGnRH stimulates anterior pituitary to secrete FSH and LH
- FSHstimulates the Sertoli cells to facilitate sperm development
- LHstimulates the Leydig cells to secrete testosterone
- Controlledby negative feedback
- fish– fertilization is external in bony fish and internal (cartilage fish)
- amphibians– external and most develop in water
- reptiles– amniotic egg (exytaembryonic membranes-adaptive for land)
-most are oviparous
- birds– amniotic egg
- internal fertilization
- endotherms – mostincubate eggs to keep warm
o Asexual –
- Advantages – no need tofind a mate, faster than sexual reproduction, and offspring will be identicalto parent and more able to adapt to environment
- Disadvantages – nogenetic variability
o Sexual –
- Advantage – increasedvariability which allows more diverse gene pools, less chance of passing genedisorders
- Disadvantages – onlyhave the population is able to reproduce, you have to find a mate, and noguarantee fertilization will take place
- Advantages – produce alarge number of offspring as compared to internal fertilization, quicker andincreases chance of mother survival, parents do not have to take time inraising kids
- Disadvantages – has tooccur in aquatic environment, which limits distribution of animals, alsoexcessive sperm and eggs are wasted
- Advantages – affords thespecies a better chance of reproductive success by protecting the sperm and eggfrom external predation, cuts down on excessive sperm and egg amounts beingused to ensure that there are an adequate number of survivors, can occuranywhere
- Disadvantages – numberof offspring are limited. If the species is under stress, it may not work totheir advantage.
o Clitoris and penis
o Labia majora and scrotum
o viviparity – young develop within mother and nourishment from blood
o oviparity – fertilized eggs are deposited outside mothers body to complete development
o semen – total mixture of male reproductive fluid
o sperm – located in semen, male gamete or reproductive cell
o urethra female – used for urine
o urethra male – urine and semen
– rapid division of thezygote into a larger and larger number of smaller and smaller cells (blastomeres)– varies on amount of yolk
acrosomal reaction - reaction that takes place in acrosome of the sperm whichthe membrane around it fuses with the plasma membrane of the oocyte exposingthe contents of the acrosome so that it can go bond and allow fertilizationtake place
– leads to amodification of the zona pellucida that blocks polyspermy; enzymes released bycortical granules digest sperm receptor proteins ZP2 and ZP3 so that they canno longer bind to spermatozoon
- leadsto blocking polyspermy
- enzymesreleased by cortical granules digest sperm receptor
- ectoderm– exterior. Epidermis of skin, nervous system, sense organs
- mesoderm– middle. Skeleton, muscles, blood vessels, heart, blood, gonads, kidney,dermis of skin
- endoderm– inner. Lining the digestive and respiratory tracts, liver, pancreas, thymus,thyroid
– composed of
- trophoblast – outer layers of cells, contributes to placenta
- blastocoel – central fluid-filled cavity
- inner cell mass – located at one pole. Forms developing embryo
fastblock to polyspermy
–Ca++ from intacellular stores in the egg endoplasmic reticulum. Ca++ is firstreleased at the site of sperm entry, and during the next minute, a wave of freeCa++ passes through the egg. This Ca++ reults in the fusion of corticalvesicles with the egg plasma membrane, releasing their contents into the spacesurrounding the egg, called the perivitelline space. This raises the vitellinemembrane, and inactivated binding receptors on the vitelline membrane. Thus,any additional sperm are released from the vitelline membrane and no more bind.
- amnion – encloses amniotic fluid
- chorion– located near eggshell in birds. Contributes to placenta in mammals.
- Yolksac – food source in bird embryos. Found in mammals but not nutritive.
- Allantois– unites with chorion in birds, forming a structure for gas exchange. Inmammals, contributes blood vessels to the developing umbilical cord.
o ectoderm- most exterior layer ex. Skin
o mesoderm- middle layerex.skeleton and muscles
o mesoderm- middle layer ex. Skeleton and muscles
o endoderm- inner mostlayer ex. Line digestive tract
o acrosomal- reaction that takes place in acrosome of thesperm which the membrane around it fuses with the plasma membrane of the oocyteexposing the contents of the acromsome so that it can go bond and allowfertilization to take place
o cortical- leads to a modification of the zonapellucida that blocks polyspermy; enzymes released by cortical granulesdigest sperm receptor proteins ZP2 and ZP3 so that they can no longer bindspermatozoon
Describe thecomposition/structure of the placenta, including information on the fetalcomponent and the maternal component.
o Placenta is comprised ofthe chorionic frondosum (fetal component)
o Decidua basalis (mother component)
- Decidua basalis isformed under the influence of progesterone and highly-characteristic cells
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