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bioc192 > Lecture 17: HOW DO GENETIC DIFFERENCES LEAD TO DISEASE? > Flashcards

Lecture 17: HOW DO GENETIC DIFFERENCES LEAD TO DISEASE? Flashcards

1
Q

What do the codons within the coding region of the mRNA do?

A

Specify the amino acid sequence of the polypeptide chain

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2
Q

What does each tRNA have?

A

A different base sequence but about the same overall shape

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3
Q

What does each tRNA carry?

A

An amino acid to be added to the polypeptide chain

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4
Q

What is the first step of initiation?

A

Small ribosomal subunit binds to mRNA

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5
Q

What happens after the small ribosomal subunit binds to mRNA?

A

Large ribosomal subunit completes the initiation complex

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6
Q

What is the first step of elongation?

A

Codon recognition

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7
Q

What happens after codon recognition?

A

Peptide bond formation

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8
Q

What happens after peptide bond formation?

A

Translocation

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9
Q

What is the first step of termination?

A

Ribosome reaches a stop codon on mRNA

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10
Q

What are the stop codons?

A

UAG, UAA and UGA

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11
Q

What happens after the ribosome reaches a stop codon on mRNA?

A

Release factor promotes hydrolysis and release of the polypeptide

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12
Q

What happens after the release factor promotes hydrolysis and release of the polypeptide?

A

Ribosomal subunits and the components dissociate

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13
Q

What is the mutated enzyme which causes PKU?

A

Phenylalanine Hydroxylase

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14
Q

What is the mutation causing PKU?

A

In the coding strand, an A changes to a T meaning an A changes to a U in the mRNA and amino acids change from arginine to tryptophan

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15
Q

What is the PKU mutation (short form)?

A

R408W mutation in PAH gene

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16
Q

What does R408W mean?

A

Codon 408 for arginine (R) is mutated into a codon for tryptophan (W)

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17
Q

What does the R408W mutation in PAH protein result in?

A

Incorrect folding

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18
Q

What does the incorrectly folded PAH protein do?

A

Forms an aggregate that enzymes in the cell degrade

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19
Q

What does normal PAH do?

A

Folds correctly and functions to break down phenylalanine

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20
Q

Why will some mutations have no effect?

A

Because some base changes will result in the same amino acid being produced

21
Q

What is a substitution mutation?

A

A point mutation where there is a change in one letter

22
Q

What will a substitution mutation do?

A

May affect the protein slightly if the substitution results in a change of the amino acid

23
Q

What is a deletion mutation?

A

Frameshift mutation where there is a loss of one letter

24
Q

What will a deletion mutation do?

A

The amino acids following the deletion will be different and so will be consequences

25
Q

What is an insertion mutation?

A

Frameshift mutation where there is gain of one letter

26
Q

What will an insertion mutation do?

A

The amino acids following the insertion will be different and so will be consequences

27
Q

What codon being introduced will have a large effect?

A

Stop codon

28
Q

What do pancreatic beta cells do?

A

Sense how much glucose is in the blood and release insulin when glucose is high (fed state)

29
Q

What is a key enzyme in glucose sensing?

A

Glucokinase

30
Q

What does glucokinase do?

A

It determines how much glucose is broken down and therefore how much insulin is produced

31
Q

What does a mutation in one glucokinase gene (heterozygous) result in?

A

Persistent mild hyperglycaemia, a type of diabetes called MODY2 (maturity onset diabetes of the young, type 2)

32
Q

What is the MODY2 mutation?

A

Dominant so presence of the wild type can’t mask the effect of the mutant

33
Q

What do homozygous MODY2 individuals have?

A

Sever diabetes and very high blood glucose levels

34
Q

What is the mutation that causes MODY2?

A

Base changes from G to A so amino acid changes from glutamate to lysine

35
Q

What is the first part needed for genetic testing?

A

Obtain some cells (such as form the mouth)

36
Q

What happens after some cells are obtained?

A

Isolate DNA

37
Q

What happens after isolate DNA?

A

PCR amplify a specific gene sequence

38
Q

What happens after PCR amplify a specific gene sequence?

A

Detect genetic difference of interest

39
Q

What goes in the test tube for PCR?

A

DNA from cells, DNA nucleotides, primers with sequences that can base pair with the region of DNA that you want to amplify and Taq DNA polymerase

40
Q

What is the first step of PCR?

A

Heat DNA to 95 degrees to break the hydrogen bonds and separate DNA

41
Q

What is the second step of PCR?

A

Cool to approximately 60 degrees to anneal (base pair) a DNA primer (a short sequence approximately 20 nucleotides that is chemically synthesised)

42
Q

What is the third step of PCR?

A

Heat DNA to 72 degrees to allow Taq DNA polymerase to copy the DNA (add complementary nucleotides)

43
Q

What happens when the PCR cycle is repeated?

A

It doubles the amount of DNA present each time

44
Q

What is used to detect sequence differences?

A

Enzymes

45
Q

What is HIndlll?

A

A restriction enzyme that specifically cuts the sequence AAGCTT to recognise the mutation

46
Q

What does Hindlll cut?

A

The mutated version to give two fragments

47
Q

What does Hindlll not cut?

A

The wild type

48
Q

What does the wild type show up as on gel electrophoresis?

A

One band

49
Q

What does the MODY2 show up as on gel electrophoresis?

A

Fragments

bioc192 (38 decks)

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