Unit 3 Flashcards by Tyanna Lansiquot

What did Frederick Griffith discover in 1928?

Demonstration of bacterial transformation.

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What bacteria did Frederick use and what were the describe the strains of this bacteria?

Streptococcus pneumoniae
Smooth- lethal bc of pathogenic peptidoglycan
Rough- NonLethal

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What did Frederick add to the rough form of Strep that caused it to become lethal? (R—>S)

Heat

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The phenomenon of bacteria changing from the R strain to S strain is called _____?

Tranformation

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The material response for transformation is the ____?

Transformation factor

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What did Avery, McCarthy, and McLeod discover in 1944?

That the transforming factor was acidic extract from the nucleus (DNA) by using reductionist biology.

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How did Avery, McCarthy, and McLeod discover that DNA was the transforming factor?

By using a T2 phage labeled w/ 35S (radioactive proteins) or 32P(radioactive DNA) to see which would enter when the page was infected.

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What did Chargaff discover in 1950?

That DNA composition varies between species and that in any species the complimentary bases are equal.

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What is Chargaff’s Rule?

A% = T% , C%= G%, (A%+T%) + (C%+G%) = 100%

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What did Rosalind Franklin produce from using x-ray crystallography to study acidic fraction of calf thymus nuclear material along w/ Maurice Wilkins?

X-ray Diffraction (images of DNA)

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Using the images of DNA Franklin was able to produce what were Watson and Crick able to do?

Crick was able to deduce the width of the helix and the spacing of the nitrogenous bases.

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What does Watson and Crick’s semi-conservative model tell about DNA replication?

Replication predicts that when a double helix replicates, each daughter molecule will have one old strand (derived or “conserved” from the parent molecule) and one newly made strand.

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What does the enzyme helicase do in DNA replication?

unwinds the double helix

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What does the enzyme topoisomerase do in DNA replication?

relieves the strain of twisting caused by unwinding of double helix, breaks, swivels, and rejoins bonds

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What does the enzyme primase do in DNA replication?

Makes a primer (starting point) for synthesis of a new DNA strand

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What does the enzyme poylmerae do in DNA replication?

Polymerizes a new strand of DNA by adding nucleotides

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What does the enzyme ligase do in DNA replication?

ligates or joins together nucleic acids

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What are the three stages of DNA replication?

initiation, elongation, proof-reading and repair

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Where does replication of DNA begin?

At sites called origins, where the two DNA strands are separated, opening up a replication “bubble”

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Each nucleotide that is added to a growing DNA strand is called _____?

a nucleoside triphosphate

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An enzyme called _______ catalyzes the lengthening of telomeres in germ cells

Telomerase

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What is the function of telomeres?

The seals that eukaryotic chromosomal DNA molecules have at their ends nucleotide sequences. They also postpone the erosion of genes near the ends of DNA molecules

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_____ are the link between genotype & phenotype .

Proteins

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What are the two stages of gene expression?

Transcription and translation

What did Archibald Garrod suggest in 1909?

That genotype dictate phenotypes through enzymes that catalyze reactions, and thought that the rare inheritable disease Alkapeonuria reflected the inability to synthesize a certain enzyme

What did Beadle and Tatum come up with?

The One Gene Hypothesis by exposing bred mold to x-rays which caused mutations

What is the One Gene Hypothesis?

States that each gene dictates production of a specific enzyme

What is the One Gene Hypothesis called and why?

One Gene–One Polypeptide Hypothesis, because not all proteins are enzymes and many proteins are composed of several polypeptides, each of which has its own gene

RNA is the intermediate between ____ and ___ they code for.

DNA genes, proteins

RNA polymerase catalyzes the action of new codons in what direction?

5' to 3'

Define transcription.

Synthesis of RNA under the direction of DNA

Define translation.

Synthesis of polymerase under the direction of RNA

_____ are the site of translation.

Ribosomes

Define codons.

triplets of bases, the smallest units of uniformed length that can code for all 20 amino acids

What did Walther Flemming discover in 1882?

lampbrush chromosomes

What direction are codons read by the translation machinery?

5' to 3'

What are the three stop signals?

UAG, UAA, UGA

All polypeptides start with what codon?

Methyanine, AUG

RNA synthesis is catalyzed by ____ which unwinds the DNA strand and hooks together RNA nucleotides.

RNA polymerase

What is the base pairing rule for RNA and DNA synthesis?

Antiparallel

Where does transcription start in bacteria?

The promoter

Where is transcription signaled to stop in bacteria?

By the terminator

What is the stretch of DNA transcribed?

Transcription unit

What are the stages of Transcription and Translation?

1. initiation 2. elongation 3. termination

In the initiation of transcription, what are the function of promoters?

They are the regions of DNA that signal the initiation of RNA synthesis

What is the function of transcription factors?

To mediate the binding of RNA polymerase and the initiation of transcription

A promoter sequence called ____ is crucial in forming the initiation complex in eukaryotes.

TATA Box

A gene can transcribed simultaneously by several ____

RNA polymerases

Describe termination in prokaryotes.

The polymerase stops transcribing at DNA sequence called TERMINATOR

Describe termination in eukaryotes.

The Pre-mRNA gets cleaved from the growing chain, the polymerase continues on then falls off

How do eukaryotes modify mRNA after transcription?

By modifying it at the start 5' with a modified G(guanine) cap or at the end 3' with an A(Adenine) tail

What are some of the functions of the mRNA modifications?

facilitate export of mRNA to cytoplasm, protect the RNA from hydrolytic enzymes, an help ribosomes attach at 5' end for translation

What are non-coding protein stretches or intervening sequences?

Introns

What are expressed sequences ?

Exons

The splicing of loops of introns is done by? And what do they consist of?

Splicesome, protein and small RNAs that recognize splice sites

What are three properties of RNA that enable it to function as an enzyme?

1. it can form 3D structures 2. it contains functional groups 3. it can complementarily bond w/ other nucleic acids

What two steps are required for translation to occur?

1. correct match of tRNA and an among acid | 2. correct match of tRNA anticodon and mRNA codon

What are the sites on the large subunit ribosome and their functions?

A- hold tRNA that carries the next amino aid P- holds the growing polypeptide E- the exit site