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MCBG > Mutations > Flashcards

Mutations Flashcards

1
Q

Define mutation.

A

A change of the nucleotide sequence

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2
Q

Define Mutagenesis.

A

The processs of mutation generation

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3
Q

Describe spontaneous deamination

A

DNA base is spontaneously changed structure by removing an amine. Cytosine becomes Uracil and 5-Methylcytosine becomes Thymine.

After the first replication this incorrect DNA strand is now used as a template. By the second replication this mistake is now “fixed’ in the DNA.

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4
Q

What is a Transposon?

A 
A tranposable element.
As specific DNA sequence 
It’s supernumerary (many copies)
It’s contained in a DNA molecule (sits within chromosome) 
Moves (transposed) as a discrete unit 
Moves to random sites 
Ubiquitous (all species have them) 
May insertion-ally inactivate genes or change gene expression

CAN JUMP IN OR OUT OF SEQUNCES

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5
Q

What effect may the movement of a transposable element cause?

A

May mean produced protein is active
May mean produced protein is inactive
May activate transcription by jumping into regulatory sequence
May have no-effect as it may enter an intron

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6
Q

What may a mutation cause?

A 
May or may not cause phenotypic change
May be “good” or “bad”
Source of genome variation 
Driving force of evolution 
May cause disease
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7
Q

What is an SNP?

A

A single nucleotide polymorphism

One nucleotide change

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8
Q

What are the 3 types of SNP?

A

Anonymous SNP = no known effect

Non-coding SNP= outside a gene

Coding SNP= inside a gene

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9
Q

What is micro mutation?

A

Small scale mutation, ie on a base level

Deletion, insertion, substitution etc

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10
Q

What is a macro mutation?

A

A mutation happens on a large scale, eg at the chromosome level. They are also called chromosome abnormalities,

May occur in meiosis.

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11
Q

Give some examples of macro mutations. (Chromosome abnormalities)

A 
Deletion 
Duplication 
Inversion 
Substitution 
Translocation
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12
Q

How does the non-overlapping triplet code effect mutations?

A

It means that if a base is added/deleted the whole frame is shifted changing the way the sequence is read.

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13
Q

What is a Transition mutation? (In bases)

A

Changes to the same type of base
Purine goes to Purine (A and G)
Pyrimidine goes to Pyrimidine (C and T)

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14
Q

What is a transversion mutation? (In bases)

A

Change to a different type of base
Purine to pyrimidine (A/G to C/T)
Pyrimidine to purine

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15
Q

What may a single nucleotide mutation cause?

A

Change in the gene product (RNA or polypeptide)

Change the amount of gene product

Change the polypeptide length

No effect

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16
Q

What is a missense mutation?

A

Changes the amino acid produced

17
Q

What is a synonymous mutation?

A

A silent mutation (no effect)

18
Q

What could cause a change in polypeptide length?

A 
Frameshift mutation 
Mutation of STOP codon 
Nonsense mutation (when a normal codon becomes a STOP codon)
19
Q

What can mutations that effect regulatory sequences do?

A

Alter promotor activity
Alter translation initiation (AUG)
Prevent mRNA splicing (introns remain)
Reduce mRNA stability

20
Q

What could deletions in multiples of 3 base pairs do?

A

May remove some info but the code might still make sense-could still have functional polypeptide

May remove key codon (eg the active site)-so non-functional polypeptide is made

21
Q

What is an inversion chromosomal mutation?

A

Part of the chromosome is inverted (swapped top to bottom,flipped over)

22
Q

What is a substitution chromosomal mutation?

A

When a loci on both chromosomes swaps

23
Q

What is a translocation chromosomal mutation?

A

When a piece of one chromosome leaves and joins another

24
Q

What is a micro deletion on a chromosome?

A

When something is deleted but in imaging the bands on the chromosomes don’t appear to change

25
Q

What is the difference between paracentric and pericentric inversion in chromosomal mutation?

A

Paracentric they flip over the centromere

Pericentric doesn’t involve the centromere

26
Q

What is a Robertsonian translocation?

A

When 2 different chromosomes break at the centromere. Their Q arms fuse. The small P arms are lost as accentric fragments. (2 chromosomes become one). Often due to the small size of the P arms they don’t contain much info so no phenotypic signs appear

27
Q

What are Isochromosomes?

A

When 2 arms on a chromosomes fuse and another is lost

28
Q

What are ring chromosomes?

A

When the cell tries to fix a break in a chromosome and ends up fusing it into a ring shape.

29
Q

What are marker chromosomes?

A

Not real chromosomes.

Extra bits of DNA floating around

30
Q

What is polyploidy?

A

A numerical chromomes abnormality.
The person gains a haploid set as well as the normal diploid set. (69 pairs)

Most common cause is polyspermy

Triploidy occurs in 2-3% pregnancies and causes 15% of miscarriages

31
Q

What is aneuploidy?

A

The loss or gain of a whole chromosome
Cause by non-disjunction in meiosis
Trisomies (gain of chromosome)-Downs syndrome
Monosomies (loss of chromosomes)-Turner syndrome

32
Q

What is Mosaicism?

A

The presence of 2 or more cell lines in an individual (throughout body or tissue specific)
Caused by non-disjunction in mieosis

33
Q

Why do we use cytogenetic testing to look for abnormalities?

A

Accurate diagnosis and prognosis of clinical problems
Better clinical management
Asses future reproductive risks
Prenatal diagnosis

34
Q

Why would you refer someone for cytogenetic tests?

A 
Prenatal diagnosis 
Birth defect 
Abnormal sexual development 
Infertility
Recurring foetal loss
Leukaemia 
Solid tumour 
Prognostic I for for translocations
35
Q

When considering the consequences for a persons germ line and somatic cell mutations what do “balanced” and “unbalanced” mean?

A

Balanced-no genetic info lost, no phenotypic change apparent (may still have a mutation but doesn’t cause issue)

Unbalanced-loose major inf0, phenotypic changes

MCBG (16 decks)

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