DNA and Chromosomal Mutations

Question 1

What is a mutation?

Answer 1

a heritable alteration in a gene or chromosome
- a change in the sequence of nucleotides

it is also the process that produces the alteration

Question 2

what is mutagenesis

Answer 2

the process of mutation generation

Question 3

name a spontaneous mutation

Answer 3

chemical change that can happen spontaneously where are cytosine become a uracil due to deamination

Question 4

what are transposable elements

Answer 4

specific repetitive DNA sequences that move randomly

• AKA jumping genes or transposons
• ubiquitous
• cause mutations

Question 5

what effect can transposable elements have

Answer 5

• no effect
• inactivate
• reactivate
• alter gene expression

Question 6

what is SNP

Answer 6

single nucleotide polymorphism

• no known effect- anonymous SNP
• outside a gene- non-coding SNP
• inside a gene- coding SNP

Question 7

single nucleotide changes - transition

Answer 7

change to the same type of base

Question 8

transversion

Answer 8

change to a different type of base

Question 9

effects of single nucleotide changes

Answer 9

change gene product
change the amount of gene product
change the polypeptide length
do not have an effect

Question 10

missense

Answer 10

change in amino acid which changes the gene product and the amount

AKA nonsynonymous

Question 11

frameshift

Answer 11

change in the polypeptide length

• mutation of the stop codon
• nonsense

Question 12

silent or neutral

Answer 12

AKA synonymous

do not have an effect

Question 13

what does insertion or deletion of multiples other than 3bp lead to

Answer 13

frameshifts

Question 14

what are balanced abnormalities

Answer 14

no genetic information lost and or no phenotypic changes apparent

Question 15

unbalanced abnormalities

Answer 15

not balanced genetic info lost

Question 16

what is polyploidy

Answer 16

gain a haploid set of chromosomes

e. g. triploidy 3n=69
- most common cause is polyspermy
- occurs in 2-3% of pregnancies

Question 17

Aneuploidy

Answer 17

loss or gain of whole chromosome
trisomies and monosomies
caused by meiotic non-dysjunction

Question 18

mosaicism

Answer 18

presence of 2 or more cell lines in an individual
throughout the body or tissue-specific
caused my mitotic non-disjunction

Question 19

paracentric inversion

Answer 19

same swaps around not involving the centromere

Question 20

pericentric inversion

Answer 20

inversion over the centromere

Question 21

reciprocal translocation

Answer 21

chromosome abnormality caused by exchange of parts between non-homologous chromosomes. Two detached fragments of two different chromosomes are switched.

• can be balanced or unbalanced
• if all the info is there may not cause a problem

Question 22

meitotic consequences of reciprocal translocation

Answer 22

• quadrivalent will form
• segregation will have 3 possible ways
• 3:1 non-disjunction

Question 23

Robertsonian translocation

Answer 23

2 acrocentric chromosomes fuse

-acts as one chromosome

Question 24

meiotic consequences of robertsonian translocation

Answer 24

• trivalent will form
• segregation with 6 possible outcomes
• 2 balanced 4 unbalanced

-aneuploidy risk

Question 25

cytogenetic testing

Answer 25

• cytogenetic analysis
• fluorescent in situ hybridisation
• microarray hybridisation
• DNA sequencing

Question 26

why do cytogenetic testing

Answer 26

• accurate diagnosis and prognosis of clinical problems -better clinical mangagement
• assess future reproductive risk
• prenatal diagnosis