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PCS Unit 2 - Distribution, Defence and Repair > Week 5 - DNA Replication, Transcription and Translation > Flashcards

Week 5 - DNA Replication, Transcription and Translation Flashcards

1
Q

What are the subunits of DNA and RNA?

A

nucleotides

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2
Q

What does each nucleotide contain?

A

a five carbon sugar, a nitrogenous, base, a phophate group

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3
Q

What is five carbon sugar in DNA?

A

deoxyribose

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4
Q

What is a nucleoside?

A

base + sugar (no phosphate group)

eg adenosine, guanosine

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5
Q

How are sugars in nucleic acids linked to one another?

A

by phosphodiester bridges

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6
Q

What is a nucleosome?

A

a particle made of histone proteins with approximately two turns of DNA wrapped around them

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7
Q

How many hydorgen bonds hold together G and C?

A

3, A and T linked by 2

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8
Q

What is needed for DNA replication?

A

single stranded template

DNA polymerase enzyme

deoxynucleoside triphosphates (dATP, dCTP ect)

a primer

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9
Q

What is a primer?

A

a short piece of nucleic acid base-paired to the template, acts as a start point, a 3’ -OH group

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10
Q

What enzyme catalyses the formation of the primer?

A

primase - an RNA polymerase that synthesises a short stretch of RNA complementary to the DNA strand

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11
Q

What enzyme partially unwinds the DNA replication fork?

A

DNA helicase

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12
Q

In what direction does DNA synthesis occur?

A

5’ to 3’

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13
Q

Which strand is synthesised continously?

A

the leading strand

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14
Q

How is the lagging strand synthesised?

A

as short fragments called Okazaki fragments

RNA primer is degraded ands replaced with upstream Okazaki fragment acting as primer

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15
Q

What enzyme extends the ends of chromosones?

In what cells does this occur?

A

telomerase

germ-line cells and to a lesser degree stem cells

telomerase is also found in cancer cells

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16
Q

What is the end replication problem?

A

On the lagging strand there is an incomplete 5’ end after removal of the RNA primer which cannot be filled because there is no upstream Okazaki fragment

chromosones shorten each time they replicate

17
Q

What is an intron?

A

a non-coding portion of DNA

DNA sequences that are present in the gene but not in the corresponding RNA

18
Q

What is an exon?

A

a coding portion of DNA

19
Q

What is a promotor?

A

a DNA sequence that signals the start of a gene

a binding site for RNA polymerase

20
Q

What is a codon?

A

a triplet of nucleotides representing an amino acid

eg UUU - Phe, AGU - Ser

21
Q

What does the term degenerate mean in reference to the genetic code?

A

same amino acid may be represented by more than one codon

eg Asn - AAU and AAC

22
Q

What is the initiation codon?

A

AUG

23
Q

What are the three termination codons?

A

UGA, UAG, UAA

24
Q

What is translation?

A

synthesis of a protein from mRNA

second step in gene expression

25
Q

To what part of the tRNA molecule does mRNA bind?

A

the anticodon

26
Q

What is an aminoacyl tRNA?

A

a tRNA attached to their amino acid

an amino acid is ‘activated’ by attaching to tRNA

27
Q

How many different types of aminoacyl-tRNA synthetases are there?

A

20

they are the enymes that link tRNAs to their aminoacids and there most be 20 different types for each type of amino acid

ATP is required for the reaction

28
Q

What is the overall size of the human ribosome?

A

80S

large subunit - 60S

small subunit 40S

DO NOT add them together to make 100

29
Q

What size are mitochondrial ribosomes?

A

55S

30
Q

What are the three tRNA binding sites on the ribosome?

A

P (peptidyl) site, the A (aminoacyl) site and the E (exit site)

31
Q

What does the translation cycle involve?

A

binding of aminoacyl-tRNA (requires GTP)

the peptidyl transferase reaction (peptide bond synthesis)

translocation (movement of the ribosome one codon along the mRNA - needs GTP)

32
Q

What site does the first aminoacyl-tRNA (Met) bind to on the ribosome?

A

P site

33
Q

What is the mechanism of action of the antibiotics ethryomycin and clarithromycin?

A

inhibits bacterial protein synthesis by inhibiting the peptidyl transferase reaction and translocation

34
Q

What is purpose of the peptidyl-transferase reaction?

A

to form peptide bonds between adjacent amino acids during translocation

35
Q

What enzyme carries out transcription?

A

RNA polymerase

36
Q

What is the process of removing introns called?

A

splicing

37
Q

What DNA bases are purines?

A

adenine and guanine

2 ring structure

PCS Unit 2 - Distribution, Defence and Repair (12 decks)

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