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
What is the difference between paracentric and pericentric inversion in chromosomal mutation?
Paracentric they flip over the centromere Pericentric doesn’t involve the centromere
26
What is a Robertsonian translocation?
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
What are Isochromosomes?
When 2 arms on a chromosomes fuse and another is lost
28
What are ring chromosomes?
When the cell tries to fix a break in a chromosome and ends up fusing it into a ring shape.
29
What are marker chromosomes?
Not real chromosomes. | Extra bits of DNA floating around
30
What is polyploidy?
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
What is aneuploidy?
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
What is Mosaicism?
The presence of 2 or more cell lines in an individual (throughout body or tissue specific) Caused by non-disjunction in mieosis
33
Why do we use cytogenetic testing to look for abnormalities?
Accurate diagnosis and prognosis of clinical problems Better clinical management Asses future reproductive risks Prenatal diagnosis
34
Why would you refer someone for cytogenetic tests?
``` Prenatal diagnosis Birth defect Abnormal sexual development Infertility Recurring foetal loss Leukaemia Solid tumour Prognostic I for for translocations ```
35
When considering the consequences for a persons germ line and somatic cell mutations what do “balanced” and “unbalanced” mean?
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