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Genetics > DNA > Flashcards

DNA Flashcards

1
Q

what did scientists initially believe was the molecule of inheritance?

A

proteins

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2
Q

who was Frederick Griffith

A
  • experimented with smooth and rough forms of Streptococcus pneumoniae (causes meningitis in children)
  • discovered that when rough forms of the bacteria was mixed with heat-killed smooth bacteria, living smooth form was recovered
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3
Q

define transformation

A

the ability of a substance (DNA) to change the genetic characteristics of an organism

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4
Q

what did Avery, Macleod and McCarthy do?

A

did experiments to find the “transforming principle” (the molecule of inheritance)

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5
Q

what did Chase and Hershey do?

A

experiments with bacteriophages

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6
Q

what are bacteriophages made of?

A

about equal parts protein and DNA

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7
Q

what is DNA made of?

A

phosphate group, deoxyribose sugar, nitrogenous base

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8
Q

define purines and pyrimidines

A

purines have a two ring structure - adenine and guanine
pyrimidines have a one ring structure - thymine and cytosine

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9
Q

how are nucleotides linked?

A

by phosphodiester bonds

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10
Q

what was Rosalind Franklin responsible for?

A

x-ray diffraction data

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11
Q

what did Watson and Crick discover about nitrogenous bases?

A

the ratio of both A:T and G:C is 1:1

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12
Q

how many H-bonds are there between the bases?

A

3 H-bonds between guanine and cytosine
2 H-bonds between adenine and thymine

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13
Q

define anti-parallel

A

one DNA strand is running in the 5’ to 3’ direction and the other one is running in the opposite direction

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14
Q

our DNA runs in a ________-_________ helix

A

right-handed (meaning it moves UP to the right)

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15
Q

what is the semi-conservative model of DNA replication

A

one strand from the parent is conserved in the daughter DNA helix

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16
Q

what did Meselson and Stahl do?

A

prove that DNA replication is semi-conservative

17
Q

what are the phases of DNA replication

A

initiation and elongation

18
Q

why is the origin of replication __ __ rich?

A

AT, because AT has two H-bonds so it’s easier to pull the strands apart as opposed to GC which have 3 H-bonds

19
Q

how does DNA replication initiate?

A

the initiator protein recognized a specific sequence in the origin of replication and binds to it, pulling the strands apart for DNA helicase to come in and unwind enough DNA to create the replication bubble

20
Q

what does DNA polymerase need to lay down a new strand of DNA?

A

free 3’ OH (RNA primer)
DNA polymerase can only add nucleotides to the 3’ OH

21
Q

what does DNA pol III do?

A

extends DNA using RNA primers and
proofreads (exonuclease activity)

22
Q

lagging strands are called

A

Okazaki fragments

23
Q

what does DNA pol I do?

A

removes RNA primers and fills in the gap from the 3’ end, proofreads, and fills the gaps

24
Q

what does DNA ligase do?

A

seals the nicks between the 3’ OH and 5’ PO4 by making phosphodiester bonds

25
Q

what are topoisomerases?

A

enzyme that makes nicks in circular chromosomes to relieve torsion and prevent supercoiling

26
Q

how are large chromosomes replicated?

A

many replication bubbles are made at once

27
Q

what sequence is repeated hundreds or thousands of times in the telomeres?

A

TTAGGG

28
Q

what is telomerase

A

enzyme that restores the telomeres in juvenile chromosomes. adult somatic cells don’t express telomerase and chromosomes get a little shorter each time

29
Q

what are the stop codons?

A

UAG, UAA, UGA

30
Q

what is the start codon

A

AUG (met) - proteins always with AUG

31
Q

define intragenic expression

A

restoration of gene function by one mutation cancelling the other in the same gene

32
Q

what is a degenerate code?

A

multiple codons code for the same amino acid

33
Q

where does protein synthesis take place?

A

cytoplasm

34
Q

what are nonsense codons?

A

UAA, UAG, and UGA (stop codons) that don’t correspond to any amino acids

Genetics (9 decks)

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