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Uni year 1 > IMEG > Flashcards

IMEG Flashcards

1
Q

Autosomal dominant inheritance characteristics

A
  • at least one affected parent
  • no skipping of generations
  • males and females equally likely to be affected
  • transmitted by either sex
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2
Q

Examples of autosomal dominant disorders

A
  • achondroplasia, mutations in FGFR3
  • Marfan syndrome - which is a connective tissue disorder, mutations in FBN1
  • Huntingdon’s disease is a progressive neurological disease, increased length of CAG triplet repeat
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3
Q

Autosomal recessive characterisitics

A
  • both males and females affected
  • if both parents affected, children usually will be
  • usually affected children will have parents who are carriers but not affected
  • affected individuals with normal partners usually have normal children
  • both copies of gene have to be mutated for phenotype to be abnormal
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4
Q

Autosomal recessive example and what it affects

A

cystic fibrosis

affects the lungs, pancreas, sweat glands and sometimes other organs

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5
Q

What is the mutation in cystic fibrosis and what does it do?

A

CF gene is on chromosome 7 which encodes a transmembrane protein that transports chloride ions. The mutation disrupts normal chloride transport.

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6
Q

Treatment for cystic fibrosis

A
  • intake of digestive enzymes
  • postural drainage or lungs
  • inhalation of medicines
  • gene therapy
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7
Q

X-linked recessive inheritance characteristics

A
  • mainly males affected
  • affected males are born to unaffected parents
  • no male to male transmission
  • only one mutant allele required on the X chromosome
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8
Q

X-linked dominant inheritance characteristics

A
  • either sex affected
  • usually at least one affected parent
  • for an affected male, all daughters but no sons will be affected
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9
Q

Y-linked inheritance

A
  • only males affected
  • affected males always have affected father
  • all sons of affected father are affected
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10
Q

What is translocation?

A

A segment of DNA on one chromosome breaks and moves onto another chromosome. This forms a larger abnormal chromosome. There are still 46 chromosomes. Usually, part of chromosome 21 moves onto chromosome 14

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11
Q

What are satellite regions?

A

bits of DNA that stick up above the chromosome

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12
Q

What is a hydatidiform mole?

A

When all chromosomes are of paternal origin

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13
Q

Give 2 example of a loss of function mutations

A

a-thalassaemia - deletion of a-globin gene

ATM - ataxia telangiectasia mutated

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14
Q

Give 2 examples of gain of function mutations

A

FGFR3 mutation in achondroplasia

Down syndrome - increases production of normal protein

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15
Q

What happens in the FGFR3 mutation?

A

causes independent activation of the tyrosine kinase domain
causes innapropriate inhibition of chondrocyte proliferation
leads to shortening of bones - achondroplasia

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16
Q

What is the mutation in sickle cell anaemia?

A

Single base change that changes the amino acid from glutamine to valine
It decreases the solubility of deoxygenated Hb
forms stiff fibrous polymers that distort RBC giving it a sickle shape

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17
Q

What is a multigenic trait and give two examples

A

multiple genes involved
digenic disorder
retinitis pigmentosum

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18
Q

What is ataxia tenlangiectasia?

A

Autosomal recessive disorder
progressive cerebellar degeneration
immunodeficinecy
unusual sensitivity to ionising radiation

It is a recessive disorder so individuals are either homozygous for the ATM mutation of heterozygous with two different mutations

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19
Q

How could you test for AT?

A

X-ray induced chromosome damage due to exposure to radiation - AT patients are extra sensitive to ionising radiation
Increased radiation sensitivity means there will be increased DNA double strand breaks

20
Q

Would a carrier of the ATM gene be expected to show heightened sensitivity to radiation?

A

No

21
Q

What can be used to detect the ATM protein and what will it tell you?

A

Western blot
Will show the presence/absense of protein but won’t give an indication of how ,much protein is present
Even if protein is present, Western blot will not give information about whether it is functional

22
Q

What does an absense of the ATM protein show?

A

It is a feature of AT caused by a nonsense mutation

23
Q

What could the presence of the ATM protein show?

A
  • patient doesn’t have AT
  • patient could have AT but the protein has been mutated by a missense mutation - protein will be present but not functioning properly
24
Q

Analysis in patients with no ATM function

A

expectation would be to find two null mutations

Two nonsense mutations leading to truncated proteins leads to total loss of protein

25
Q

Analysis of mutations in patients with reduced level of protein

A

expectation would be that at least one of the two mutations would be missense
It is possible that this protein retains some degree of function

26
Q

When is a missense mutation more likely to be pathogenic?

A

If the mutation affects a functionally important part of the protein
If the amino acid is conserved over evolution
If the amino acid substitutions are non-conservative eg polar for non-polar or acidic for basic

27
Q

What are phosphospecific antibodies?

A

Antibodies that will recognise the phosphorylated protein but not the unphosphorylated

28
Q

What is haploinsufficiency?

A

The phenotype when a diploid organism has lost one copy of a gene and is left with a single functional copy of that gene
For some gene products, half the amount of normal protein is sufficient for normal function. For others 50% is not enough and an abnormal phenotype is produced.

29
Q

What is a dominant negative effect?

A

A mutation who gene product affects the normal gene in the same cell
p53 is a common example

30
Q

What is locus heterogeneity?

A

Where the same disease is caused by a mutation in a different gene

31
Q

Which genes cause AT?

A

ATM

hMRE11 - MRE11 is required for full activation of ATM

32
Q

What is nonsense mediated mRNA decay?

A

Reduces error in gene expression by eliminating mRNA transcripts that contain premature stop codons

33
Q

What are the two recognition sites to remove an intron?

A

GT and AG

34
Q

How many genes are there in the human genome?

A

22000

35
Q

How many base pairs are there in the human genome?

A

3x10^9 base pairs

36
Q

Alternative splicing (4 examples)

A
  • Alternative selection of promoters
  • Alternative selection of cleavage/polyadenylation sites
  • intron retaining mode
  • exon cassette mode (exons retained or removed)
37
Q

Intron retention

A

If an intron is retained it can be treated like normal mRNA and a larger protein could be made.
It may undergo nonsense mediated mRNA decay due to presence of premature stop codons.
The intron may be treated like the end of the mRNA so a poly A tail is added and a shorter protein made.

38
Q

prophase

A

Chromosomes condense and become visible
Bipolar spindle develops
Centrioles move to poles

39
Q

Prometaphase

A

Nuclear envelope dissolves

Chromosomes migrate to equator - seen to have two chromatids

40
Q

Metaphase

A

Chromosomes fully condensed and located at equator

Spindle connects to the kinetochore at the centromere

41
Q

Anaphase

A

Each centromere splits

Two chromatids pulled to opposite poles

42
Q

Telophase

A

Chromosomes reach poles and start to decondense
Nuclear membrane reforms
Cytoplasm starts to divide

43
Q

Name 2 chromosome breakage disorders

A

Bloom syndrome

Faconi anaemia

44
Q

How do mutations arise?

A
  1. Copying errors during DNA replication
  2. Spontaneous depurination
  3. Exposure to background ionising radiation
45
Q

What is depurination?

A

Spontaneous hydrolysis of the N-glycosyl linkage

46
Q

How is apoptosis initiated?

A

Signalling to bcl-2 protein (on mitochondrial membrane) mediated by p53

Uni year 1 (19 decks)

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