Genetics

Question 1

What is a transposon?

Answer 1

Transposon are sequences that transpose from one part of DNA to another.

Question 2

In what order is protein synthesised?

Answer 2

Protein is synthesised from amino end to carboxy end

Question 3

Compare the sequences found in the coding strand and template strand of DNA,

Answer 3

DNA:
Coding strand has codons
Template strand has anti-codons

Question 4

In what order is DNA synthesised?

Answer 4

DNA and RNA is synthesised from 5’ to 3’

Question 5

What is the difference between exons and intron in mRNA?

Answer 5

mRNA:
Exons sequences: coding
Intron sequences: function less clear

Question 6

Describe the interaction between mRNA and tRNA

Answer 6

mRNA had codons that attach to the anti-codons of tRNA:

mRNA:codons:anti-codons:tRNA

translations of protein

Question 7

What is ‘epigenetic’ alteration?

Give an example.

Answer 7

Enduring change in gene expression that does NOT alter DNA sequence.

May be cause for somatic alterations in cancer.

Example: Methylation of promoter regions leading to gene inactivation.

Question 8

Which genetic changes are most likely to lead to cancer?

Answer 8

Loss of Heterogeneity.

Question 9

What is the difference between allelic and no-allelic heterogeneity?

Answer 9

Allelic: lots of mutations in the ONE gene (e.g. CFTR1 gene)

Non-allelic: mutations in TWO different genes

Question 10

What is genomic imprinting?

Answer 10

Imprinting is an epigenetic phenomena.

Imprinted alleles are SILENCES by METHYLATION such that the gene expressed is only from the one parent who has the non-imprinted allele.

Question 11

What is mosaicism?

Answer 11

Mosaicism is when an individual has 2 or more cell lines that differ in genotype but are from a single zygote/chtomosome.

Can be chromosomal or single gene disorders.

Question 12

Describe gonadal mosaicism. Give an example.

Answer 12

Gonadal mosaicism:

There is a mix of normal and mutated germ cells but only in the germ cells.

Explains why some families have 2 or more children affected despite both parents being normal.

Example: Duchenne muscular dystrophy, Tuberous Sclerosis.

Question 13

Describe somatic mosaicism. Give an example.

Answer 13

Somatic mosaicism:

Mix of normal and mutated cells (some tissues carry mutations whereas others don’t)

Example: Turner’s syndrome, Mosaic Down Sydrome