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BMS1062 Molecular Biology > Mutations > Flashcards

Mutations Flashcards

1
Q

What is the difference between inherited and non-inherited genes?

A

Inherited mutations: germline mutations

  • Present in all cells of the body
  • Transmitted from parents to offspring.
  • Responsible for single gene disorders, e.g. cystic fibrosis
  • May or may not be present in multifactorial disorders, e.g. cancer, heart disease, diabetes, Alzheimer’s disease.
  • Cause predispositions

Non-inherited: somatic mutations

  • Affect cells that descend form cell with mutation
  • not transmitted to offspring
  • Contribute to multifactorial disorders
  • Accumulate in age-related processes so the earlier in life the mutation occurs, the greater its effect as the cell in which the mutation occurred will give rise to more cells
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2
Q

What are the major classes of mutations?

A
  • Point mutation
  • Trinucleotide repeat expansion (CAG in Huntington’s disease)
  • Deletion/insertion
  • Inversion
  • Duplication
  • Translocation
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3
Q

What are the types of point mutations?

A

Base substitution:

  • Missense: different amino acid
  • Nonsense: stop codon
  • Silent: last base of codon affected and due to degenerative nature of DNA no effect.

Deletion/insertion: frame shift

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4
Q

What are Duchenne and Becker Muscular Dystrophies?

A

DMD (severe) causes an “out of frame” frameshift, where the protein synthesis is terminated much earlier then it should.One base less lost than is BMD.

BMD (mild) causes an inframe frameshift, where only part of the amino acid is lost and the remaining are normal.

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5
Q

What is the difference between balanced translocation and insertion of large DNA segments?

A

Balanced translocation occurs when genes swap chromosomes. Insertions occur when genes from one chromosome move to another.

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6
Q

True or false? Mutations in the non-coding parts of DNA will never have an affect.

A

False, the mutation may be in a regulatory site, etc.

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7
Q

What is the difference between base excision repair and nucleotide excision repair?

A

Base excision repair: when a wrong base is inserted, glycolase cuts the backbone, removing the nucleotide. DNA polymerase adds a new nucleotide, which is sealed off by a ligase.
Nucleotide excision repair: when two bases are bound together (caused by UV), the entire section is removed and fixed.

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8
Q

What portion of genes is polymorphic (more than one allele)

A

At least one third.

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9
Q

Why do some disease-causing mutations persist through evolution?

A

They may provide heterozygous advantage.

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10
Q

How can gene duplication lead to origin of new genes?

A

The original gene well function as normal while the duplicate is able to evolve, giving rise to new members of its gene family.

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11
Q

What is a gene family?

A

A family of genes that encode for proteins with related structure and function.
E.g. globin genes.

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12
Q

Why are heterozygotes for a disease-causing recessive gene able to live healthy?

A

The correct allele is able to make sufficient protein.

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13
Q

What is restriction fragment length polymorphism (RFLP)?

A

Identifies disease-causing mutations.
- Get normal DNA sample and the sample. Subject both to a restriction enzyme that cuts at the site of the normal gene. Run gel electrophoresis. If the sample is not cut (less strands are produced), then the person has a mutation.

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14
Q

Which nucleotides does depurination affect?

A

Adenide and guanine (the purines)

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15
Q

How many depurinations occur each day in each cell? In the body?

A

10^4 in each cell

10^17 in the body

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16
Q

How many dimers does UV light cause per second in one cell?

A

50

17
Q

Why is having dark skin advantageous in terms of UV damage?

A

Prevents degradation of folate, a vitamin B complex.

18
Q

How many genes control the size of a dog?

A

A single gene

19
Q

Out of the 3,000,000,000 nucleotide pairs that make up the human genome, how many are different between individuals?

A

1,000,000

20
Q

What is an allele?

A

A different form of a gene- result of mutation.

21
Q

Why do some disease causing mutations persist through evolution?

A

They may produce heterozygous advantage, e.g. sickle cell anaemia.

22
Q

True or false; mutations in non-coding regions of DNA are important for identification?

A

True- mutations in the non-coding regions accumulate.

23
Q

The tree of life is based on comparing which molecule between species?

A

rRNA as its sequences are highly conserved through evolution.

24
Q

Which mutation gives protection against HIV? When did it evolve?

A

Deletion of a gene that allows entry of the virus into the cell.
CCR5 –> CCR5^32
(^- triangle)
Evolved during the black plague.

25
Q

The beta and alpha globin genes were once on the same chromosomes. What chromosome is each located on now

A

Alpha- chromosome 16

Beta- chromosome 11.

26
Q

Which globin genes are dominant during infancy and are suppressed after birth, being replaced by beta globin?

A

Epslon globin due to its high affinity for oxygen.

27
Q

What is the gene kit responsible for?

A

Skin pigmentation (boy and rat similarity).

28
Q

What are frog models useful for studying?

A

Development

29
Q

What is the heterozygous advantage provided by beta-thalassaemia?

A

Malaria

30
Q

What is the heterozygous advantage provided by cystic fibrosis?

A

Diarrheal diseases (cholera)

31
Q

What is the heterozygous advantage provided by phenylketonuria (PKU)?

A

Spontaneous abortion

32
Q

What is the heterozygous advantage provided by tay-sachs disease?

A

Tuberculosis

33
Q

What is the heterozygous advantage provided by sickle cell anaemia?

A

Malaria

34
Q

What change to protein causes muscular dystrophies?

A

Incorrect protein folding

35
Q

What change to protein causes haemophilia?

A

Reduced protein quantity

36
Q

What change to protein causes sickle cell anaemia?

A

Reduced protein efficiency due to base substitution

37
Q

What change to protein causes Huntington’s disease?

A

Changes in protein function due to CAG repeats in DNA causing extra amino acids.

38
Q

What is restriction length polymorphism?

A

Technique used to detect mutations.

  1. Subject DNA to digestion by specific restriction enzymes. The normal allele will be cut but the mutated will not.
  2. Run gel electrophoresis and compare number and size of bands.
39
Q

What are the mutation sources for evolution?

A

Intragenic mutation: single bases
Gene duplication: during DNA replication, a bit of DNA or the entire chromosome can be replicated. The original gene is able to carry on with its original function in the cell. The duplicated gene can accumulate mutations and gain a new function.
DNA segment shuffling: new variations caused by gene recombination.

BMS1062 Molecular Biology (15 decks)

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