Review of Mutations and Genetic Code

Flashcards about mutations and genetic code

What is a gene?

A part of DNA that codes for the synthesis of one protein.

What determines the sequence of amino acids in a polypeptide?

The sequence of nucleotides in a gene.

What is a mutation?

Any change in the nucleotide sequence of DNA.

What are the factors that cause mutations called?

Mutagenic or carcinogenic agents.

What is the genetic code?

A dictionary that recognizes the correspondence between the nucleotide sequence in a gene and the sequence of amino acids in a polypeptide chain.

What are codons?

Three-letter words present on the mRNA that make up the genetic code.

How many nucleotides code for one amino acid in the polypeptide chain?

Three

How many codons have been formed using the four nucleotide bases?

64

What are termination codons?

Codons that do not code for any amino acids and terminate the process of protein synthesis.

What is the initiation codon and what amino acid does it code for?

AUG, codes for methionine.

What happens if one of the bases is changed in the codon?

A different amino acid becomes incorporated into the polypeptide chain, potentially making it non-functional.

What does it mean that the genetic code is specific?

One codon always codes for the same amino acid.

What is degeneracy of the genetic code?

One amino acid may be coded by more than one codon.

What are point mutations?

Mutations that result from changes in a single base or nucleotide in the codon.

What is a transition mutation?

A pyrimidine is changed into another pyrimidine or a purine is changed into another purine.

What is a transversion mutation?

A pyrimidine is replaced by a purine or vice versa.

What is a silent mutation?

The new codon made after mutation codes for the same amino acid, so it has no effect on the protein structure.

What is a missense mutation?

The new codon resulting from the mutation codes for a different amino acid, a different amino acid is mistakenly incorporated into the protein structure.

What is a nonsense mutation?

The mutated codon is a termination codon, causing early termination of protein synthesis.

Give an example of a point mutation.

Sickle cell anaemia, where glutamic acid is replaced by valine.

What are frameshift mutations?

Mutations that occur when one or two nucleotides are deleted or inserted into the DNA.

What is the effect of a frameshift mutation on the reading frame?

The mRNA formed from a gene with a deleted or inserted nucleotide has an altered reading frame.

What are splice-site mutations?

Mutations that occurs at a splice site, affecting the way introns are removed.

What are introns?

non-coding intervening sequences