Mutations Flashcards
What are gene pools?
sum of all alleles in a population
What are Mutations? where can it occur
a change in the DNA that can affect a single gene (gene mutations) or all/part of a chromosome (chromosomal mutations)
- occur in body or sex cells
What are somatic mutations?
- occurs in body cells
- often involved in cancerous grwoths
- not inherited
What are germinal mutations?
- occur in gametes
- don’t usually affect individual but may be passed onto next generation
Two main types of mutations? and describe
- Gene mutations
- Changes in a single gene so that traits normally produced by that trait are changed.
- Occur during DNA replication - Chromosomal mutations
- all or part of a chromosome is affected.
What are causes of mutations?
- Agents known to increase rate of mutation called mutagenic agents or mutagens. called induced mutations
- Spontaneous mutations – random error in biological process
What is a type of gene mutation?
Point mutation
What is point mutation?
– change in only one base that could alter a protein, have no effect at all, or prevent the protein being produced
What are the 3 mechanisms of point mutation?
- Inserted – new nucleotide added to DNA strand
- Substituted – existing nucleotide is replaced with a different base
- Deleted – a nucleotide is removed from the DNA strand
2 Examples of point mutation?
Albinism – mutation in gene for melanin production
- Effects: absence of pigment from hair, skin, eyes
Duchene muscular dystrophy – arises from mutation in mother which can be passed onto sons, or in male zygote
- Effects: wasting of leg muscles and later arms, shoulders and chest.
- Death occurs within failure of respiratory muscles
What is a Lethal recessive allele? what do they cause? and example
- Most gene mutations produce a recessive allele called Lethal Recessive
- They are recessive mutations which are lethal if not masked by dominant allele
- Cause death of embryo or foetus, or early death of child
- Eg. Tay Sachs Disease - lipid metabolism disorder in which missing enzyme results in accumulation of fatty substance in nervous system and eventually deterioration of mental and physical condition in early childhood.
What are chromosomal mutations?
Involve all or part of chromosome and affect a number of genes
- Cause abnormalities so severe, miscarriage often occurs in early pregnancy.
5 Types of chromosomal mutations
Deletion: part of chromosome lost
Duplication: section of chromosome occurs twice.
- Can happen when part of chromatid breaks off and joins to wrong chromatid.
Inversion: break occurs and broken piece joins back on wrong way around.
- Change order of gene and may disrupt pairing of homologous pairs in meiosis.
Translocation: part of chromosome breaks off and re-joined to wrong chromosome.
Non-disjunction: chromosome pair does not separate during meiosis and one daughter cell has extra chromosome while the other has one less.
- Aneuploidy – change in chromosome number
What is evolution?
- the change in characteristics of a species over time.
- It is gradual and occurs over a number of generations.
- reflects the changes in allele frequencies in populations, not individuals
Changes in alleles may be due to…
- New alleles forming due to mutation or introduced due to migration
- frequency of alleles changing due to selective pressures in natural selection or by chance in genetic drift.
