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Medical Cell Biology and Genetics > Topic 13: Gene Expression > Flashcards

Topic 13: Gene Expression Flashcards

1
Q

What is a gene?

A

Sequence of amino acids in a polypeptide or a sequence of nucleotides in an untranslated RNA

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2
Q

What does ‘the code carries the function’ mean?

A

DNA code needs to be copied into an RNA molecule and then transformed into something functional

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3
Q

What are the 3 main differences between DNA and RNA?

A
  1. RNA has a C2 hydroxyl (oxyribose sugar) while DNA has a C2 (deoxyribose sugar) hydrogen
  2. RNA contains U while DNA contains T
  3. RNA is single stranded while DNA is double stranded
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4
Q

What are the three main types of RNA?

A

Ribosomal RNA
transfer RNA
messenger RNA

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5
Q

What is ribosomal RNA?

A

Associates with proteins to form ribosomes

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6
Q

What is transfer RNA?

A

Match an mRNA codon with amino acid it codes for

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7
Q

What is mRNA?

A

Carry coding sequences for protein synthesis

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8
Q

What are the 3 things needed for transcription?

A

DNA, RNA polymerase, NTPs

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9
Q

In which direction is transcription?

A

Synthesis from 5’ to 3’

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10
Q

What are the 6 steps of transcription initiation?

A

Transcription factor binds to TATA box
more transcription factors bind to upstream sequences
RNA polymerase recruited
DNA helix unwinds
formation of ‘transcription bubble’ (17bp)
transcription initiates directionally 5’ to 3’

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11
Q

What are the 5 steps of transcription elongation?

A 
Template strand read 3’ to 5’ 
RNA synthesis from 5’ to 3’ complementary to template strand 
Single-stranded RNA molecule is made 
Transcription bubble advances
DNA helix re-winds behind it
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12
Q

What are the 2 steps of transcription termination?

A

Primary RNA molecule produced

RNA processing to produce mature RNA

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13
Q

What is RNA processing?

A

Post-transcriptional modifications

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14
Q

What are the 3 RNA processing modifications for rRNA and tRNA?

A

Chemical modifications and cleavage and folding

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15
Q

What are the 3 post-transcriptional modifications for mRNA?

A

5’ Capping
Splicing
3’ Tailing

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16
Q

What is the purpose of capping?

A

Adding a methylated-G on 5’ end of mRNA to provide protection

17
Q

What are the 2 reasons for tailing?

A

Adding 3’ polyA tail by polyA polymerase for protection and regulation

18
Q

What is splicing?

A

Highly accurate removal of introns from primary transcript to produce mature mRNA out of leftover exons

Done by spliceosomes

19
Q

What is the definition of coding strand?

A

Non-transcribed DNA strand

Bc it’s exactly the same as the RNA strand produced

20
Q

What is the definition of template strand?

A

Transcribed DNA strand

21
Q

What are the 2 components and its quantity in prokaryote ribosomes?

A

3 rRNAs

70S ribosome

22
Q

What are the 2 components and its quantity in eukaryote ribosomes?

A

4rRNAs

80S ribosome

23
Q

What is the structure of a tRNA molecule?

A

3 hairpin loops that form a 3-leafed clover, one of which that contains a anticodon which can recognize and decode a mRNA codon

Also contains a amino acid attached to its end

24
Q

How does tRNA function as the genetic adaptor?

A

Translates the 3 nucleotide codon sequence in mRNA into its suitable amino acid

25
Q

What are the 3 main things we need for translation?

A
  1. Mature mRNA
  2. Ribosomes
  3. tRNAs charged with activated amino acids
26
Q

What are the 5 steps of initiation of translation?

A

Recognition of cap by tRNA*-Met
Recognition of AUG by anticodon of initiation complex
Initiation factors involved
Recruitment of large 60S ribosomal subunit
Assembly of functional ribosome

27
Q

What are the 2 products of initiation of translation?

A

80S initiation complex with tRNA*-Met in P site on AUG on mRNA and empty A are

EPA site from 5’ to 3’

28
Q

What are the 6 steps of elongation?

A

Binding of amino acyl-tRNA on A site
Peptide bond formation catalyze by peptidyltransferase
Translocation - ribosome moves one codon from 5’ to 3’
Uncharged tRNA in E-site
Growing polypeptide pushed into exit tunnel
Elongation factors involved

29
Q

What is the product of translation elongation?

A

Peptidyl-tRNA in P site and empty A site, ready for next elongation cycle

30
Q

What are the steps in translation termination?

A

Peptidyl-tRNA in P site and empty A site with stop codon
Binding of release factor
Release factor recognizes stop codon
Hydrolysis releasing free peptide and uncharged tRNA from P site
Dissociation of ribosome into subunits

Medical Cell Biology and Genetics (14 decks)

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