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Genetics > DNA Structure & Replication > Flashcards

DNA Structure & Replication Flashcards

1
Q

what is a nucleotide monomer made of?

A

a phosphate group, ribose, nitrogenous base

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2
Q

which nucleotides are purines?

A

adenosine & guanosine

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3
Q

which nucleotides are pyrimidines?

A

thymidine & cytidine

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4
Q

how are single strands of DNA formed?

A

connecting nucleotides via covalent bonds from the phosphate groups to the deoxyribose sugars

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5
Q

within our body, when is DNA single stranded and not double stranded?

A

during replication

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6
Q

what does it mean for DNA to be “anti-parallel”

A

single strands are upside down compared to eachother, 5’ and 3’ ends are opposite from one another

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7
Q

how are single strands bound in double-stranded DNA?

A

by many weak hydrogen bonds between nitrogenous bases

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8
Q

what is “base-pairing”

A

binding between specific nucleotides

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9
Q

which base-pair is easier to break? G-C or A-T?

A

A-T (2 hydrogen bonds) whereas G-C has 3

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10
Q

describe the Watson and Crick “semi-conservative model” for DNa replication

A

double stranded DNA parent strand is separated into two single strands, each of which is used as a template to synthesize another strand of DNA, the resulting daughter DNA molecules consist of one parent strand and one newly synthesized strand

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11
Q

Double stranded DNA molecules are wrapped up with proteins inside the cell in order to form what structures?

A

chromosomes

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12
Q

What phase does DNA replication occur during?

A

interphase

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13
Q

What structures does DNA replication result in?

A

two sister chromatids

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14
Q

Where does DNA replication start? What does this create?

A

at multiple origins of replication, creating replication bubbles

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15
Q

What is the purpose of having multiple origins of replication?

A

makes replication go significantly faster, it is more efficient

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16
Q

purpose of helicase

A

separates dsDNA into single strands at the origin of replication

17
Q

purpose of single strand binding protein

A

keeps strands apart and prevent rewinding of the double helix

18
Q

purpose of topoisomerase

A

releases mechanical stress in front of helicase

19
Q

purpose of primase

A

makes the RNA primer (small section of dsDNA) that allows the DNA polymerase to start synthesizing

20
Q

how is the RNA primer removed

A

via a nuclease

21
Q

How does DNA polymerase add nucleotides?

A

creates a new covalent bond between the last deoxyribose sugar group and the phosphate group of a free floating nucleotide monomer

22
Q

How is the leading strand synthesized?

A

continuously in the 5’ to 3’ direction

23
Q

How is the lagging strand synthesized?

A

in Okazaki fragments because DNA polymerase can only synthesize in the 5’ to 3’ direction, uses multiple RNA primers that the DNA polymerase jumps to

24
Q

How many base pairs in the human genome?

A

3.1 billion

25
Q

What is a byte? What is a bit?

A

byte = 8 bits
bit = one digital piece of info (0 or 1)

26
Q

How many bits are needed to encode (A, T, C, G)?

A

Two: A(0,0) T(0,1) C(1,0) G(1,1)

27
Q

How many GB in the human genome?

A

0.775 GB (7 powerpoints)

28
Q

How does DNA polymerase detect errors?

A

mismatch is sensed as a bulge, DNA polymerase backs up and breaks the covalent bond cutting out incorrect nucleotide, then DNA polymerase resynthesizes correct nucleotide

29
Q

If DNA polymerase doesn’t catch the errors, what enzyme does?

A

nucleases cut out incorrect nucleotides and DNA polymerase resynthesizes

30
Q

structure of dsDNA of prokaryotes

A

circular

31
Q

structure of dsDNA in eukaryotes

A

linear

32
Q

How do eukaryotes solve the issue of a 3’ overhang after a round of replication?

A

telomerase uses its own RNA template to extend the 3’ end and then DNA polymerase can make a new Okazaki fragment

33
Q

What happens to telomere length as humans age?

A

telomere length declines due to decreased telomerase activity, which increases mortality

34
Q

What problem does having short telomeres present?

A

ends of telomeres can’t form protective T loop, the cell detects the free end as a dsDNA break and so it puts a stop to cell division and the cell gets old

35
Q

Which strand poses the 3’ overhang issue?

A

lagging strand

36
Q

which enzyme connects the Okazaki fragments of the lagging strand?

A

ligase

Genetics (9 decks)

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