Lecture 2: Recessive mutations File Flashcards

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1
Q

What are genetic differences created by ?

A

Sex (recombination)

Spontaneous mutation

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2
Q

How many new mutations are in a child (compared to parent) ?

A

100-200

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3
Q

Name the three main origins of spontaneous mutations

A
  1. Replication/repair errors
  2. DNA damaging agents
  3. Ionising radiaion
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4
Q

DNA damage - repair = ?

A

DNA damage - repair = Net mutation

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5
Q

How would you increase mutation rate ?

A

increase amount of DNA damage,

or decrease rate of repair

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6
Q

How do you induce mutation ?

A

Use chemical mutagens or radiation

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7
Q

how many times more mutations can be made using mutagens

A

> 1000 fold

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8
Q

Name 2 things that ALL mutagens do

A
  1. Damage DNA (cause mutation)

2. cause cancer

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9
Q

Name two unimportant regions

A
  1. Between genes

2. Between exons

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10
Q

Most mutations are silent unless ____?

A

unless they affect the protein coding part of genes (or their expression)

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11
Q

what is a silent mutation?

A

One base changes, but end protein is the same

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12
Q

Whats is a nonsense mutation?

A

One base changes and stops protein production (forms a stop codon)

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13
Q

What are the two types of missense mutation?

A

Conservative and non-conservative

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14
Q

what is conservative missense mutation?

A

The mutation causes a different final protein, but the protein is in the same group as the original (e.g. acidic)

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15
Q

What is non-conservative missense mutation?

A

The mutation causes a different final protein, but the protein is in a different group from the original (e.g. alkaline)

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16
Q

Name the two types of frameshift mutations

A
  1. Insertion

2. Deletion

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17
Q

Name base modifier chemical mutagen

A

EMS (point mutations)

18
Q

Name base analogue chemical mutagen

A

5BU (point mutations)

19
Q

Name intercalating agent chemical mutagen

A

Acridine dyes (Frame-shift)

20
Q

Thymine dimers are caused by what ?

A

UV light

21
Q

Thymine dimers lead to …..

A

Frame-shift mutations

22
Q

Give an example of ionising radiation and name the resulting mutations

A

X-rays, result in chromosomal breaks (deletion, translocation and inversion)

23
Q

What is aneuploidy?

A

The presence of an abnormal number of chromosomes in a cell

24
Q

What causes downs syndrome and what are main phenotypes?

A

Extra chromosome 21

short stature, mental retardation and susceptible to alzheimers disease

25
Q

What are the risk factors for downs syndrome ?

A

Age of mother (<30=0.04%, >35=1.25%)

26
Q

What causes Xeroderma pigmentosum ?

A

Mutations in genes for excision repair machinery

27
Q

What are phenotypes of Xeroderma pigmentosum?

A

Extreme sensitivity to UV light (exposure causes basal cell carcinoma, metastatic malignant melanoma and squamous cell carcinoma)

28
Q

What is the only way for recessive mutations to show in phenotype?

A

If two carriers mate (requires some form of inbreeding)

29
Q

What type of mutation can be cured and how ?

A

Recessive mutations can be cured by gene therapy (inserting wild type version of the gene)

30
Q

Can dominant mutations be cured by gene therapy ?

A

Nope lol

31
Q

What causes albanism ?

A

mutant tyrosinase enyzme is unable to convert tyrosine to the pigment melanin

32
Q

What is the albanism phenotype

A

Melanin absent from skin, hair and eye retinas

33
Q

What does OCA1 do ?

A

Codes tyrosinase enzyme (mutants have SEVERE albanism)

34
Q

What does OCA2 do ?

A

Codes P protein, a tyrosinase helper (Mutants have MILD albanism)

35
Q

What does OCA3 do ?

A

Tyrosine related gene (mutants have WEAK albanism)

36
Q

What does OCA4 do ?

A

Codes SLC45A2 protein, a tyrosinase helper (mutants have MILD albanism)

37
Q

What is alkaptonuria ?

A

Disorder when gene that encodes homogentisate 1,2-dioxygenase (chromosome 3) mutates

38
Q

What are alkaptonuria phenotypes?

A

Mutants cant convert homogentistic acid (black colour) to maleyacetoacetic acid, Mutants expel black urine

39
Q

What is phenylketonuria ?

A

Recessive condition, progressive brain dysfunction caused by high phenylpyruvic acid levels

40
Q

How can you treat phenylketonuria

A

Phenylpyruvic acid birth test and low phenylalanine diet

41
Q

What is cretinism ?

A

Mental retardation caused by thyroid gland not producing enough thyroxine