Chapter 12 - Mutations & Gene Pools Flashcards
What is a species?
A group of individuals that share many characteristics and are able to interbreed to produce fertile offspring.
What are alleles?
Alternative forms of a gene.
What is a population?
A group of organisms of the same species living together in a particular place at a particular time.
What is a gene pool?
The sum of all the alleles carried by the members of a population.
What is allele frequency?
How often each allele of a gene occurs in a population.
What does it mean when different populations differ in the characteristics they possess?
They are likely to have different frequencies of various alleles of a gene in their respective gene pools.
The composition of the gene pool of a population ______________
May change over time
What is a mutation?
A change on a gene or a chromosome leading to a new characteristic in an organism.
How do mutations occur?
Suddenly and by chance
What is a mutant?
An organism with a characteristic resulting from a mutation
What are the two main types of mutations?
- gene mutations
- chromosomal mutations
What are gene mutations?
Changes in a single gene so that the traits normally produced by that gene are changed or destroyed
What are chromosomal mutations?
A change to the structure and/or number of chromosomes in an organism.
When do gene mutations occur?
During the replication of DNA before cell division.
DNA is a __________ and ___________
Complex molecule, any subtle alteration in its structure can produce changes in the usual characteristics of a species
What are mutagens?
An agent that is known to increase the rate at which mutations occur
What are some examples of mutagens?
- mustard gas
- formaldehyde
- Sulfur dioxide
- some antibiotics
What are examples of ionising radiation mutagens?
- UV light
- X-rays
- cosmic rays
Why do doctors try to avoid using X-rays early in pregnancy?
Because if a woman is treated with large doses of X-rays during the first trimester the child may be born with mental retardation, skeletal deformations, or a smaller head in relation to the rest of its body.
What is a somatic mutation?
A change occurring in a gene in a body (somatic) cell
Who does a somatic mutation effect?
Only the individual with the mutation
What is a germ line mutation?
A change in the hereditary material in the egg or sperm that becomes incorporated into the DNA of every cell in the body of the offspring.
What are the differences between somatic and germline mutations?
- occur in different cells
- germline are passed on to new generations
What do the sequence of bases with in a gene code for?
Amino acids
What is a point mutation?
A change in one of the bases in a DNA molecule.
What can a point mutation do?
Alter a protein, have no effect at all, or prevent the protein from being produced.
What are some examples of diseases caused by point mutations?
- albinism
- Cystic Fibrosis
- the Duchenne form of muscular dystrophy
What are lethal recessive?
Recessive alleles, that inherited in the homozygous condition, result in the death of the embryo, foetus or child.
How do lethal recessive cause changes in the gene pool?
People who inherit two such alleles would die before their alleles could be passed on to the next generation, so the proportion of lethal recessive sin the gene pool would generally reduce.
What are chromosomal mutations?
A change to the structure and/or number of chromosomes in an organism.
What are the types of chromosomal mutations?
- deletion
- duplication
- inversion
- translocation
- non-disjunction
What is deletion?
Part of a chromosome is lost.
What is duplication?
Part of a chromosome occurs twice. This may happen is part of a chromatid breaks off and joins into the wrong chromatid.
What is inversion?
Breaks occur in a chromosome and the broken piece joins back, but the wrong way around. This changes the order of the genes on a chromosome and may disrupt the pairing of homologous chromosomes during meiosis.
What is translocation?
Part of a chromosome breaks off and is re-joined to the wrong chromosome.
What is non-disjunction?
During meiosis, a chromosome pair does not separate and so one daughter cell has one extra and one daughter cell has one less than the normal number.
What is an aneuploidy?
A change in the chromosome number
What is trisomy?
When there is 3 of one chromosome
What is an example of trisomy?
Down syndrome, trisomy 21
What is partial trisomy?
When part of an extra copy of a chromosome attaches to one of the other chromosomes.
