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MCBG * > S13 Mutations > Flashcards

S13 Mutations Flashcards

1
Q

What is Robertsonian translocation?

A

When p arms of acrocentric are lost and two q arms join together - to 2 sets of genetic info on one chromosome (p arms are so small, contain no/v little genetic info) - leads to 45 chromosomes rather than 46

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2
Q

Can a person still be healthy with robertsonian translocation?

A

Yes

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3
Q

What is aneuploidy?

A

Occurs due to non-disjunction of chromosomes (triosomy or monosomy)

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4
Q

Give an example of triosomy

A

Down’s syndrome

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5
Q

Give an example of monosomy.

A

Turner syndrome

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6
Q

What is mosaicism? When does it occur?

A

Cells have a variation of chromosomes that are normal, monosomy or triosomy.

Occurs if non-disjunction happens after the 1st zygotic division.

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7
Q

What are microscale mutations?

A

Deletion
Substitution
Addition

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8
Q

What are macroscale mutations?

A 
Duplication
Inversion
Deletion
Translocation
Substitution
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9
Q

What is polyploidy? Give an example.

A

When a cell gains a haploid set of chromosomes so it becomes 3n (69 chromosomes rather than 46).

Polyspermy - when two sperm fuse with one egg cell.

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10
Q

Give examples of exogenous causes of mutations.

A

Ionising radiation
Free radicals
Mutagenic chemicals
Anti-cancer agents

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11
Q

Give examples of endogenous causes of mutations.

A

DNA replication defects

Transposable elements

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12
Q

What is a non-exogenous/non-endogenous cause of mutation?

A

Spontaneous events

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13
Q

What are spontaneous events that lead to mutations?

A

E.g. Spontaneous deamination - conversion of C to U - affects DNA replication - strands of same DNA will have different sequences

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14
Q

What are transposable elements?

A

DNA sequences that can change location (either into a gene, at the start of a gene or outside a gene)

May or may not have an affect on a gene

Affect could be not expressed or changes the start/stop codon

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15
Q

If a person is heterozygous, is the recessive allele still expressed?

A

Yes, it is justoverridden by the dominant allele expression

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16
Q

What is a SNP?

A

A single nucleotide polymorphism.

A change in a single nucleotide base to another base.

17
Q

What are the two types of substitution?

A
  1. Transition - change to same base type

2. Transversion - change to different base type

18
Q

What is a missense mutation?

A

A change in base that leads to a change in amino acid

19
Q

What is a synonymous mutation?

A

A change in base that leads to no change in the amino acid

20
Q

What is a nonsense mutation?

A

A mutation that results in a premature stop codon forming

21
Q

What are 4 regulatory sequence mutations?

A
  1. Prevention of mRNA splicing
  2. Reduction in mRNA stability (linked to capping and polyadenylation)
  3. Alteration of promotor activity
  4. Alteration of translation initiation (change to AUG codon)
22
Q

What molecular techniques can be used for cytogenic testing?

A
  1. FISH (fluorescence in situ hybridisation)
  2. Microarray hybridisation
  3. Karyotyping
  4. DNA sequencing
23
Q

What is cytogenic testing?

A

Examining chromosomes to identify structural abnormalities

24
Q

What are the advantages of cytogenic testing?

A
  1. Leads to accurate diagnosis and prognosis
  2. Allows for better clinical management
  3. Allows assessment of reproductive risks
  4. Allows for prenatal diagnosis
25
Q

What do balanced and unbalanced mean in terms of mutations?

A

Balanced - no genetic info is lost/no phenotypic changes are apparent

Unbalanced - not balanced

26
Q

Give 7 reasons for cytogenic testing referral.

A
  1. Prenatal diagnosis
  2. Birth defects
  3. Abnormal sexual development
  4. Infertility
  5. Recurrent fetal loss
  6. Leukaemias
  7. Solid tumours
27
Q

What is the difference between an oncogene and proto-oncogene?

A

Oncogene - a gene that causes cancer

Proto-oncogene - a gene that, if mutated, cause cancer (becomes an oncogene)

28
Q

What is a mutation?

A

A heritable alteration in a gene or chromosome and the process that produces the alteration

29
Q

What type of mutation causes sickle cell anaemia?

A

A missense base substitution mutation that results in one amino acid change. Glu to Val

MCBG * (12 decks)

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