Genetic Variation Flashcards
Genes
Regions of DNA that contain sequences coding for RNA and protein products; humans have around 22,000 genes
Genome
The complete set of DNA in an organism where genes are structured in; humans have a genome of 23 pairs of chromosome
Exons
Coding regions
Introns
Non coding regions
Are non coding regions more prevalent in the genome compared to coding regions?
Non coding regions make up most of the genome (exons make up 1.5%); many of these non coding (intergenic) elements are nonfunctional
Mutation
A change in DNA sequence relative to some standard or previously existing sequence
Mutant
An individual whose genome contains a mutation at some location of interest
Mutations occur randomly and does not respond to an organism’s “needs”. T or F?
True
Where do new mutations come from?
- Errors during DNA replication
- Errors during chromosomal separation during meiosis (nondisjunction)
- Mutagens
Mutagens
Accelerates mutation; Ex: reactive oxygen species, UV light, ionizing radiation that can damage DNA and increase the rate of errors
Mutations arise…
Randomly from errors in chromosomal segregation
Non-randomly from errors in replication or in chromosomal segregation
Non-randomly when they are caused by mutagens
Randomly from errors in DNA replication
A and D
A and D
Point mutation
If one nucleotide pair changes; also called substitution
Nondisjunction
Chromosomes fail to correctly separate during meiosis
Aneuploidy
Duplicate or missing chromosome causes unequal numbers of chromosomes
Which statement is NOT true about mutation?
Mutations occur randomly
Each individual has at least some new mutations
Mutation rates can differ between species
Natural selection causes useful mutations to arise
Natural selection causes useful mutations to arise
Somatic mutations
Occur in body tissues of an organism and are not transmitted to the next generation
Germline mutations
Occur in gametes and are transmitted to offspring; these mutations matter for evolution
How many new mutations occur in each individual?
Approx. 34 new mutations
How many mutations are deleterious, neutral, or beneficial?
70% deleterious
20% neutral
10% beneficial
Silent mutation
No effect because the amino acid is the same
Missense mutation
Changes one amino acid to another one
Nonsense mutation
The change creates a STOP codon
Frameshift mutation
Caused by insertions or deletions, which changes the reading frame during transcription (shifts the whole sequence)
If a silent mutation occurs in the germ line, the next generation…
Will have the mutation but it will not affect the amino acid production
Phenotypic variation
Variation in phenotypes such as morphology, behavior, physiology, etc. among members of a group of organisms
Genetic variation
Variation in mutations/alleles among members of a group of organisms
Error correction mechanisms
Cellular/molecular mechanisms that correct most errors in DNA replication/meiosis
Fitness
The contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals in the population
