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IB Biology HL > Replication, Transcription, and Translation > Flashcards

Replication, Transcription, and Translation Flashcards

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1
Q

what classifies the replication of DNA?

A

it’s semi-conservative and depends on complementary bases

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2
Q

describe the steps of DNA replication?

A
  • helicase unwinds the double helix and separates the two stands by breaking hydrogen bonds
  • DNA polymerase links nucleotides together to form new strand using pre-existing one as template
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3
Q

what is transcription of DNA?

A

synthesis of mRNA copied from the DNA base sequences by RNA polymerase

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4
Q

what is translation of DNA?

A

synthesis of polypeptides on ribosomes

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5
Q

how is the amino acid sequence determined?

A

by mRNA according to genetic code

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6
Q

how do codons correspond to amino acids (ratio)

A

codons of three bases on mRNA correspond to one amino acid in a polypeptide

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7
Q

what is translation dependent on?

A

complementary bases pairing between codons on mRNA and anticodons on tRNA

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8
Q

how do you determine codon correspondence to amino acid using genetic code?

A
  • codons are made up of 3 nucleotides of RNA that code for an amino acid
  • 1st letter on left, 2nd on top, 3rd on right
  • AUG is a start codon, also codes for Met (Methionine)
    –> all polypeptides start with Met
  • 3 stop codons
  • for example UCG codes for Ser
  • anticodon is complementary codon, U + A are complementary, C + G are complementary
  • for example, anticodon of UAG is AUC
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9
Q

what does DNA structure suggest?

A

a mechanism for DNA replication

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10
Q

What do nucleosomes do structurally?

A

help supercoil the DNA

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11
Q

how does replication differ on leading and lagging strands?

A

continuous on leading and discontinuous on lagging

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12
Q

what 6 enzymes carry out DNA replication?

A

Polymerase I, polymerase III, DNA ligase, DNA primase, DNA helicase, topoisomerase

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13
Q

does all DNA code for proteins?

A

No, some regions of DNA have other important functions

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14
Q

what did the results of the Hershey and Chase experiment explain? and describe the experiment

A
  • it was known proteins had only sulfur and DNA had only phosphorus
  • they injected the cell with virus with radioactive sulfur and virus with radioactive phosphorus
  • blender and centrifuge used to separate genetic material into pellet and non-genetic into leftover liquid
  • majority radioactive phosphate in pellet and radioactive sulfur in liquid, confirming protein was NOT genetic material
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15
Q

how is gene expression regulated?

A

by proteins (methyl groupd) that bind to specific base sequences in DNA

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16
Q

what impacts gene expression externally?

A

environment of a cell and organims

17
Q

what do nucleosomes do in mRNA?

A

regulate transcription in eukaryotes

18
Q

which way does transcription occur?

A

5’ to 3’ direction by RNA polymerase (which is the only enzyme in transcription)

19
Q

what are the sense and antisense strands of DNA?

A
  • antisense is template strand of DNA during transcription
  • sense is the other strand of DNA
20
Q

what does splicing of mRNA do?

A
  • increases the number of different protein an organism can produce
21
Q

what does initiation involve in translation?

A
  • small ribosomal subunit binds to tRNA carrying methionine and mRNA (binds to 5’ cap end of mRNA in eukaryotes)
  • large ribosomal subunit attaches: completing translation initiation complex
  • initiation factor proteins bring components together with GTP
22
Q

what does the synthesis of a polypeptide involve? (elongation)

A
  • elongation factors add amino acids one at a time
  • 1 GTP hydrolyzed for each codon read
  • goes 5’ to 3’ end of mRNA
  • polypeptide bond form between amino acids
  • 3 sites: E (exit), P (peptide), and A (amino acid)
  • ribosomes translocates tRNA in A site to P site
  • tRNA in P site to E site for release (GTP used)
23
Q

what does termination involve? (in translation)

A
  • elongation continues until stop signal on mRNA reached
  • release factor adds water molecule to chain of amino acids
  • connection of tRNA at P-site is broken off
  • everything detaches: tRNAs, large and small ribosomal subunits etc
24
Q

difference between free and bound ribosomes?

A
  • free ribosomes synthesize proteins for use within cell
  • bound ribosomes synthesize proteins for secretion (outside of cell) or use in lysosomes
25
Q

when does translation occur in prokaryotes?

A

translation can occur immediately after transcription in prokaryotes (not in eukaryotes) due to abcense of nuclear membrane

26
Q

Outline the 6 steps of DNA replication

A
  1. topoisomerase relieves strain, helicase unzips DNA separating 2 strands
  2. SS binding proteins prevent reconnection
  3. RNA primase synthesizes small chain of RNA primer at begin sit (replication occurs in 5’ to 3’ direction, follows the 3’ to 5’ template)
  4. DNA polymerase III adds matching nucleotides one at a time to 3’ end of strand (leading is continuous, lagging is discontinuous making Okazaki fragments.
27
Q

describe the structure of nucleosomes and their role in control of gene expression + transcription

A
  • nucleosomes consist of central core of 8 histone proteins and DNA coiled around proteins
  • nucleosomes supercoil to allow tight packing of DNA
  • histone proteins can be chemically altered and affect whether or not gene is expressed (aka epigentics)
  • these markers can result from the environment and pass through generations (for example identical twins)
28
Q

describe methylation and acetylation in terms of gene expression + transcription

A
  • acetyl or methyl groups can be added or removed from histones
  • acetylation can neutralize positive charge, loosen nucleosomes, and increase chances of transcription (active)
  • methylation can be added, tighten up packing, decrease chance of transcription
  • transcription (DNA to RNA with RNA polymerase) can happen easier when histones are loosen and genes are expressed.

IB Biology HL (13 decks)

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