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Principles: Biochemistry > Biochemistry of Nucleic Acid > Flashcards

Biochemistry of Nucleic Acid Flashcards

1
Q

What is the genome

A

total DNA in each cell
carries genetic information which is stored in the nucleotide sequence
the sequence determines the amino acid sequence of polypeptide chain

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2
Q

What is DNA

A

polymer

2 complimentary antiparallel helices that contain a sugar phosphate backbone on outside and bases on inside

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3
Q

what elements is DNA composed of

A

C, H, N, O, P

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4
Q

2 types of nucleotide shape

A

purines and pyrimidines - join together by hydrogen bonds

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5
Q

where does transcription take place

A

nucleotide to nucleotide in nucleus formation of RNA from DNA
pre-mRNA formed then undergoes splicing to form RNA

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6
Q

where does translation occur

A

nucleotide to amino acid
RNA to polypeptide chain
occurs in cytoplasm

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7
Q

difference between DNA and RNA

A

RNA has a hydroxyl group on second carbon whereas DNA only has a hydrogen atom

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8
Q

what is a nucleoside

A

base and sugar

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9
Q

what is a nucleotide

A

nucleoside + phosphate group

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10
Q

what bases occur in DNA

A

adenosine
cytosine
guanine
thymine

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11
Q

what bases are pyrimidines

A

uracil
thymine
cytosine

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12
Q

what bases occur in RNA

A

adenosine
cytosine
guanine
uracil

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13
Q

what bases are purines

A

adenosine

guanine

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14
Q

during polymerisation off DNA/RNA what is a phosphodiester bond formed between

A

a free 3’ OH group and 5’ triphosphate

consumes 2 high energy bonds

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15
Q

what does each gene produce

A

number of different proteins

only small number of genes are expressed

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16
Q

what does carbon 1 have attached

A

a base

17
Q

what does carbon 5 have attached

A

a phosphate

18
Q

where can new nucleotides only be added to

A

free 3’ OH group forming phosphodiester bond

19
Q

how do nucleotide analogies work as drugs

A

ZDV and AZT = retrovir
analogue of thymidine
incorporated into growing viral of DNA
Lachs 3’ OH group therefore chain elongation is terminated, prevents transcription

20
Q

How does ZDV work as a drug

A

reverse transcriptase has a higher affinity for ZDV than human DNA polymerase so turn RNA into DNA infecting host cell and uses DNA to make products which makes new viral cell

21
Q

why is DNA antiparallel

A

one 5’ to 3’

one 3’ to 5’

22
Q

what must take place before cell division/mitosis

A

DNA must replicate so daughter cells have complete compliment of genome
replication is semi-conservative

23
Q

what is DNA replication catalysed by

A

DNA polymerase

24
Q

what is the role of DNA polymerase

A

adds nucleotides to growing DNA strand
cannot start DNA synthesis on its own
requires an RNA primer to start replication

25
Q

why do eukaryotic genomes have many origins of replication

A

replication starts simultaneously at several points in genome
bidirectional
ensures replication can be finished in reasonable time

26
Q

why is DNA replication discontinuous

A

nucleotides can only be adde to the free 3’ end therefore synthesising in a 5’ to 3’ direction

27
Q

what is the leading strand

A

always has a free 3’ end

28
Q

what is the lagging strand

A

as DNA can only be added to 3’ end the 5’end being replicated must be replicated in short segments called Okazaki fragments
primer binds as DNA unwinds then nucleotides added
as more template unwinds more primers bind and catch up with itself

29
Q

what is the role of helicase

A

unwinds DNA, stops It rewinding

30
Q

what is the role of DNA ligase

A

primers distend, then DNA ligase joins nucleotides by forming phosphodiester bonds between them in the lagging strand

31
Q

what is RNA primer synthesised by

A

primase

32
Q

what is the replication fork

A

unwound DNA
leading template strand (3’ to 5’)
lagging template strand (5’ to 3’)

33
Q

what are the building blocks for DNA replication

A

dATP, dTTP, dCTP, dGTP

34
Q

what do they 3 phosphates do

A

one phosphate group forms phosphdiester bond

leaves two phosphates as pyrophosphate - energy supply

35
Q

what can incorporation of the wrong nucleotide result in

A

can create mutations
can be deleterious
errors occur once every 10000-100000 base pairs

36
Q

what activity does DNA polymerase have

A

3’ -> 5’ exonuclease activity
removes incorrect nucleotide
improves error rate
proofreads and repairs

Principles: Biochemistry (6 decks)

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