1. Gene Mutations Flashcards
What is a genetic mutation?
a random change to the DNA which may be the structure or number of chromosomes, occur spontaneously during DNA replication
What are somatic mutations?
a random change in DNA associated with mitotic division and are not passed to offspring, commonly associated with cancerous tumours
how can mutations be passed down to offspring?
a random change in DNA before meiosis and gamete formation
what are the two types of DNA mutation?
point mutation
insertion or deletion
what is a point mutation?
when one base pair is substituted for another
what are the three types of point mutation?
silent
missense
nonsense
what is a silent mutation?
a change to the base triplet, where the base triplet still codes for the same amino acid and so the primary, secondary and tertiary structure is not affected
what is a missense mutation
a change to the base triplet that leads to the change in the amino acid sequence in a protein
this alters the primary and therefore tertiary structure which changes it shape and prevents it from carrying out its function
what is an example of a missense mutation?
sickle cell anaemia which is a missense mutation on the sixth base triplet of the gene for B-polypeptide chains of haemoglobin
the amino acid valine is placed instead of glutamic acid
haemoglobin become sickle-shaped blocking capillaries and depriving tissues of oxygen
what is a nonsense mutation?
mutation may occur that the base triplet becomes a stop codon which results in a truncated protein that will not function, this protein will most likely be degraded within the cell
what is an insertion/deletion mutation?
when nucleotides are inserted or deleted from the gene a frameshift occurs as the code is non-overlapping and read in groups of three so all subsequent base triplets are altered
primary structure and tertiary structure is altered so protein can not carry out its function
what happens if a triplet of base pairs is inserted or deleted from the gene?
the addition or loss of an amino acid and not in a frameshift
what are neutral mutations?
commonly silent mutations or the change in base sequence alters the gene to become a different version of the same allele
what are examples of neutral mutations?
differently shaped ear lobes
rolling your tongue
what are beneficial mutations?
mutations that drive evolution through natural selection
examples of beneficial mutations
paler skin where there is less sunlight as vitamin D to be made with a lower intensity of sunlight and vitamin D protects us from rickets, heart disease and cancer
black skin with high concentrations of melanin protect people from sunburn and skin cancer which would be an advantage in a hotter climate with more sunlight
what are harmful mutations?
mutations that have negative effects on an organisms
what is an example of a harmful mutations?
blue eyes as the lack of iris pigmentations could lead to lens cataracts but in more temperate zones it could allow people to see better in less bright light
also cystic fibrosis
