Genetics

Question 1

How are chromosomal abnormalities caused during meiosis?

Answer 1

• Misaligned pairing during chromosomal recombination

- Non-disjunction during meiosis- a cause of numerical abnormalities (aneuploidy)

Question 2

Define deletion with regards to genetics

Answer 2

A loss of a segment of a chromosome

Question 3

Define duplication with regards to genetics

Answer 3

A part of the chromosome is duplicated

Question 4

Define translocation with regards to genetics

Answer 4

A segment of a chromosome breaks off and attaches to another chromosome

Question 5

Define inversion with regards to genetics

Answer 5

Two-break rearrangement in a chromosome in which a segment is reversed

Question 6

State the central dogma of genetics

Answer 6

DNA is transcribed into mRNA, which is translated into an amino acid chain, which is folded into a protein

Question 7

How is pre-mRNA edited before it leaves the nucleus?

Answer 7

It gets spliced. Introns are removed and exons are rearranged, depending on which proteins are needed.

Question 8

Which direction is DNA coded in?

Answer 8

5’ –> 3’

Question 9

Describe some of the post-translational modifications proteins undergo

Answer 9

Phosphorylation- the addition of a phosphate group
Acetylation- the addition of an acetyl group
Methylation- the addition of a methyl group
Palmitoylation- the addition of a fatty acid
Glycosylation- the addition of glycans (sugar chains)
Polyubiquitination on Lys- targets proteins for degradation

Question 10

Why are post-translational modifications required?

Answer 10

• regulating the folding of proteins
• targeting of proteins to specific subcellular compartments
• help with protein’s interaction with ligands or other proteins

Question 11

Define the term ‘transcriptome’

Answer 11

The whole population of mRNA and non-coding RNAs in a cell, tissue or organ at one time

Question 12

Define the term ‘proteome’

Answer 12

Population of proteins in a cell, tissue or organ at one time

Question 13

Why is genetic stability important?

Answer 13

It maintains organisms and species by:
• Ensuring accurate DNA replication
• Providing a mechanism to repair accidental DNA damages

Question 14

Define the term ‘homozygote’

Answer 14

An organism in which the two alleles of a given gene are the same

Question 15

Define the term ‘heterozygote’

Answer 15

An organism in which the two alleles of a given gene are the different

Question 16

Define the term ‘locus’

Answer 16

The position of a gene on the chromosome

Question 17

Define the term ‘allele’

Answer 17

One of the two homologous genes on the same locus

Question 18

What letters are give to the arms of chromosomes, separated by the centromere?

Answer 18

P (short arm) and q (long arm)

Question 19

In a heterozygous pair of alleles, what phenotype will be shown?

Answer 19

The dominant allele will have more influence over the phenotype displayed. In other words, one allele (the dominant one) may “mask” the other allele

Question 20

What does autosomal dominant inheritance mean?

Answer 20

When a single affected allele is sufficient to cause the phenotype (heterozygote). There’s no generational skip

Question 21

What does autosomal recessive inheritance mean?

Answer 21

When you need both affected alleles to cause the phenotype. Only recessive homozygote (aa) is affected

Question 22

Give the most likely genes of the parents for autosomal recessive inheritance

Answer 22

Father: Aa
Mother: Aa

Question 23

What causes variation in genetic information?

Answer 23

DNA mutation, which gets passed on to offspring if the mutation is in the gametes

Question 24

Why don’t mutations matter much for most of the genome?

Answer 24

Only 25-33% of the whole genome encodes for genes

Question 25

What does X-linked dominant inheritance mean?

Answer 25

The dominant allele for a condition is located on the X chromosome

Question 26

What does X-linked recessive inheritance mean?

Answer 26

The allele for a condition is located on the X chromosome. In girls, only homozygotes are affected. Having the mutated allele is sufficient for boys to be affected.

Question 27

Define the term ‘genotype’

Answer 27

An individual’s genetic constitution at a locus

Question 28

Define the term ‘phenotype’

Answer 28

A characteristic that’s actually observed, either physically or clinically.

Question 29

What is meant by genomic imprinting?

Answer 29

When some genes/alleles are silenced (transcriptionaly inactive). Imprinting is an epigenetic modification, such as DNA methylation

Question 30

When is methylation beneficial?

Answer 30

It stabilises established patterns of gene expression in differentiated cells
It silences lethal genes such as onco-viral genes
Dosage compensation in X-chromosome inactivation
Long-term memory storage

Question 31

What has hypermethylation of promoter regions been linked to?

Answer 31

Carcinogenesis

Question 32

Describe the structure of chromosomes

Answer 32

DNA double helix → Loose chromatin → Chromatin fibre of packed nucleosome → Section of chromosome in extended form → Condensed section of chromosome → Chromosome

Question 33

What are exons?

Answer 33

Exons are coding regions of DNA

Question 34

What are introns?

Answer 34

Introns are non-coding regions of DNA

Question 35

What two things, in combination with each other, lead to DNA mutation?

Answer 35

DNA damage + repair system not functioning