HUBS1403 Lecture Notes - Lecture 17: Gene Flow, Natural Selection, Genetic Drift
8 Jun 2018
School
Department
Course
Professor
Mutations, Population Genetics and Evolution
Mutations
• Caused by errors during DNA replication
• Caused by mutagens
o UV and ionising radiation
o Carcinogens
o Viruses
o Free radicals '
o Etc
• Without mutations we would not have any variation
Types
• Alteration to the genome (DNA)
• Single gene mutation (affects protein product) - if it doesn’t affect product = silent mutation
o Substitution
o Deletion
o Insertion/Addition
• Change in chromosome number
o Aneuploidy - unusual number of chromosomes
• Change in chromosome structure
o Rearrangements
Substitution
• Change in a single nucleotide is a major source of variation within the population
• If a specific nucleotide is varied >1% of the population it considered a 'single
nucleotide polymorphism' (SNP)
• Less frequent = mutation
• Detrimental = mutation
• >1 nucleotide altered = mutation
Deletion
• Can alter the triplet code and therefore protein sequence
• Entire genes or even chromosomes could be deleted
• --> 1 copy if those genes in the genome - typically embryonic lethal
• Even a single nucleotide deletion can have a major effect on the sequencing
structure of the protein
Addition/Insertion
• Can alter the triplet code and therefore protein sequence
• Entire genes or even chromosomes could be added
• Excess information and 'syndromes' - many genes are affected so may
traits/symptoms present - most are lethal
• Eg down syndrome; addition of chromosome 21 (trisomy 21)
• Even a single addition can be detrimental as it changes the frame that the codons are
read in
Rearrangements
• No loss of information - it is shuffled
• Typically don’t affect the individual - because the information is there
• Can have severe consequences for offspring - because of the process of
gamete formation
• Inversion - inverts the sequence
• Translocation - information is taken to a different chromosome, changes lengths of
chromosomes
• Reciprocal translocation - swapping of areas of chromosomes
Document Summary
Mutations: caused by errors during dna replication, caused by mutagens, uv and ionising radiation, carcinogens, viruses, free radicals , etc, without mutations we would not have any variation. Single gene mutation (affects protein product) - if it does(cid:374)"t affect product = sile(cid:374)t (cid:373)utatio(cid:374: substitution, deletion. Insertion/addition: change in chromosome number, aneuploidy - unusual number of chromosomes, change in chromosome structure, rearrangements. Substitution: change in a single nucleotide is a major source of variation within the population. If a specific nucleotide is varied >1% of the population it considered a "single nucleotide polymorphism" (snp) Less frequent = mutation: detrimental = mutation, >1 nucleotide altered = mutation. Deletion: can alter the triplet code and therefore protein sequence, entire genes or even chromosomes could be deleted. -> 1 copy if those genes in the genome - typically embryonic lethal: even a single nucleotide deletion can have a major effect on the sequencing structure of the protein.
