Genetics

Question 1

Missense mutation

Answer 1

A missense mutation is a type of point mutation that results in a single amino acid change in the protein sequence. This happens when a single nucleotide change causes a codon to encode a different amino acid.

Sickle cell anemia is caused by a missense mutation in the HBB gene, where the amino acid glutamic acid is replaced by valine.

Question 2

In frame mutation

Answer 2

deletion type

An in-frame mutation is a genetic mutation where the number of nucleotides inserted or deleted is a multiple of three (i.e., 3, 6, 9, etc.). This ensures that the reading frame of the mRNA is not shifted, meaning the downstream codons (and thus the amino acids they code for) remain the same. However, some amino acids may be added or deleted depending on the mutation.

e.g. Cystic fibrosis can be caused by an in-frame deletion of three nucleotides in the CFTR gene, leading to the loss of a single amino acid (phenylalanine at position 508).

Question 3

out of frame mutation

Answer 3

deletion type

An out-of-frame mutation (also known as a frameshift mutation) occurs when the insertion or deletion of nucleotides is not a multiple of three. This shifts the reading frame of the genetic code, changing the grouping of codons and often leading to the production of an entirely different and nonfunctional protein.

Question 4

promotors

Question 5

premature stop

Question 6

promoter

Answer 6

the beginning of the gene

The starting point of a gene is determined by a promoter region, which is a repetitive non-coding sequence of nucleotides - for example, T A T A T A T A sequence is one very famous promoter, called the TATA box - that marks where to begin transcribing.

A few dozen proteins and enzymes come together to form what’s called a pre-initiation complex around the promoter, also featuring an enzyme called RNA polymerase.

Question 7

GENETIC code that encodes for a stop codon

Answer 7

UAA
UAG

Question 8

POINT MUTATIONS

Answer 8

single nucleotide base in the DNA sequence has changed.

could be insertion/deletion/substitution

• Silent mutations: The mutation does not change the amino acid due to the redundancy of the genetic code.
• Missense mutations: The mutation changes the amino acid in the protein sequence.
• Nonsense mutations: The mutation introduces a premature stop codon, truncating the protein.

Question 9

purine

Answer 9

A / G

Question 10

pyrimidine

Answer 10

C / T

Question 11

how do you describe a mutation, where a stop codon has been introduced? (notation)

Answer 11

TER
or *