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BIOC192 2024 > Lecture 16 - Genetic changes and protein function > Flashcards

Lecture 16 - Genetic changes and protein function Flashcards

1
Q

What carries out translation?

A

RIbosomes

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2
Q

Where does translation occur?

A

the cytoplasm

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3
Q

What is the purpose of translation?

A

Making a polypeptide chain using the message encoded by mRNA

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4
Q

What does mRNA do?

A

Tells amino acids the correct order to join together in

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5
Q

What are ribosomes?

A

complex structures made of protein and rRNA

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6
Q

How do ribosomes work?

A

They work like enzymes to catalyse protein synthesis (peptide bond reaction)

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7
Q

What are the four unique bases in DNA?

A

Adenine, Cytosine, Guanine, Thymine

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8
Q

What are the four unique bases in RNA?

A

Adenine, Cytosine, Guanine, Uracil

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9
Q

How is the four-base code of DNA translated to the 20 different amino acids?

A

The DNA/RNA is read in sets of three called codons

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10
Q

What is the codon system known as?

A

Since it is common across all life it is known as the universal genetic code

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11
Q

What reads the codons in mRNA?

A

tRNA

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12
Q

What is the complementary sequence to the mRNA codon called in tRNA?

A

anti-codon

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13
Q

What does cytosine pair with?

A

Guanine

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14
Q

What does adenine pair with?

A

Thymine (in DNA) or Uracil (in RNA)

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15
Q

What are the key features of tRNA?

A
  • Anticodon
  • Amino acid attached
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16
Q

How does tRNA create a peptide chain in the correct order?

A

Every codon/anti-codon sequence has a particular amino acid that it pairs with. The tRNA attaches to the amino acid and only the amino acid that matches that tRNA molecules anti-codon will be able to attach

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17
Q

What happens during translational initiation?

A

The ribosome, mRNA, and first tRNA come together to form the translational initiation complex. The first tRNA always codes for Methionine

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18
Q

What happens during translational elongation?

A

The ribosome moves along the mRNA, adding amino acids to the growing peptide chain

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19
Q

What happens during translational termination?

A

A stop codon indicates the peptide chain has all the necessary amino acids and causes the translational complex to break apart. The newly formed peptide chain releases

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20
Q

How many possible codons are there?

A

64

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21
Q

How many amino acids are there?

A

20

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22
Q

How many codons code for ‘stop’?

A

3

23
Q

Which amino acids have only one codon that codes for them?

A

Methionine, Tryptophan

24
Q

What does codon redundancy do?

A

As most amino acids have multiple codons that code for them, this allows for some flexibility in gene sequence without changing the protein

25
Q

What does genetic variation mean?

A

differences between the DNA sequences of members of the same species

26
Q

How much does the genome vary between humans?

A

0.1%

27
Q

What does genetic variation help with?

A
  • determine who is who
  • helps species survive
  • helps organisms adapt to their environment and any changes that occur
28
Q

What are different forms of a variant called?

A

alleles

29
Q

What are genetic variants classified by?

A
  • Number of DNA bases involved
  • Style of DNA sequence involved
  • Location of the change
30
Q

What is a SNP?

A

single nucleotide polymorphism, a single base change in the DNA sequence

31
Q

What is an INDEL?

A

insertion-deletion, the addition or removal of one or more bases

32
Q

Where do regulatory variants occur?

A

In transcription factor binding sites in the promoter

33
Q

Do genetic variants always have effects?

A

No depends on where it is in the genome and the type of variant

34
Q

Do variants in the regulatory region change expression of a gene?

A

Sometimes as they may change the amount of protein that is produced

35
Q

What type of variation may change the amino acid sequence?

A

Variants within the exon of a gene

36
Q

What do the majority of gene variants do?

A

Neutral - no effect

37
Q

What different things can SNPs that change a codon do?

A
  • Code for the same amino acid
  • Code for a different amino acid
  • Code for a stop, causing a truncated protein
38
Q

What may InDels that are not a multiple of 3 base pairs cause?

A

A frame shift, usually resulting in serious consequences for the protein

39
Q

What do the consequences of a missense genetic variant depend on?

A
  • Where in the protein the amino acid change occurs
  • how chemically similar/different the two amino acids are
  • Whether the amino acid breaks an essential structure
  • The original function of the protein
40
Q

Can every type of protein be affected by a genetic variant?

A

Yes

41
Q

When will a variant be lethal?

A

When a variant causes complete loss of function to a protein essential for life

42
Q

What contributes to the wide variety of differences between organisms?

A

The fact that every type of protein can have any type of genetic variant

43
Q

What is the gene name for the two alpha-haemoglobin chains?

A

HBA1

44
Q

How many coding variants are there for the HBA1 gene?

A

> 500

45
Q

What is the gene name for the two beta-haemoglobin chains?

A

HBB

46
Q

How many coding variants are there for the HBB gene?

A

> 1400

47
Q

What is a coding variant?

A

Any variant found in the exons of a gene

48
Q

What causes sickle cell anaemia?

A

Mutation in HBB E6V gene - 6th amino acid in beta-haemoglobin changed from glutamic acid to valine. Causing Hb protein to clog blood vessels

49
Q

What causes Methaemoglobinaemia?

A

Mutation in HBB H64Y - 64th amino acid in beta-haemoglobin changed from histidine to tyrosine. Fe3+ haem unable to bind oxygen

50
Q

What are the majority of recorded variants in Haemoglobin?

A

synonymous or benign missense changes

51
Q

What examples of pathogenic missense variants of haemoglobin?

A

Sickle cell anaemia, Methaemoglobinaemia

52
Q

What do consequences of missense genetic variants to an organism depend on?

A
  • How important the proteins job is
  • Whether another protein can compensate for the changed proteins function
  • The inheritance pattern of the protein
53
Q

How do tabby and solid cats vary?

A
  • ASIP in cats creates tabby stripes
  • Due to genetic variant : 2-bp deletion in exon 2 of ASIP (c.123delCA), known as the “non-agouti allele” solid cats have a non functioning ASIP
  • Causes a frameshift which disrupts the proteins function

BIOC192 2024 (25 decks)

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