3B1 Causes of Genetic Variation Flashcards
Describe how genetic variation is introduced and the benefits of sexual reproduction.
What is genetic variation in biology?
The differences in the nucleotide sequence of DNA between individuals of a species. It is also known as the difference in allele frequencies between populations of a species.
This variation provides the fuel for evolution and, sometimes, speciation.
What are genes made up of?
Specific sequences of DNA, or locations on chromosomes, that provide the necessary information for a trait.
What are alleles?
Variations of a gene.
Examples: Brown hair or lactose intolerance.
What is gene frequency, or allele frequency?
Refers to how often a particular form of a gene - an observable trait - shows up in a population.
What lead to natural selection?
Genetic variation.
Organisms with more positive traits will go on to reproduce.
What are the sources of genetic variation?
- Mutation
- Genetic recombination
What is the main type of genetic variation?
Mutation.
What are germline mutations?
Mutations that occur in gametes - sperm and egg cells - and can be passed on to offspring.
What is a frameshift mutation?
An alteration in the reading frame of the DNA.
What are the two types of traits for identifying genetic variation?
- Discrete traits
- Continuous traits
What is a discrete trait?
A trait that is controlled by a small amount of genes.
Examples: Flower color in pea plants.
What is genetic recombination?
It occurs when chromosome pairs exchange genetic information during meiosis.
How does sexual reproduction contribute to genetic variation?
Sexual reproduction increases genetic diversity by allowing for more and different combinations of alleles than found in either parent.
What is independent assortment in sexual reproduction?
Chromosomes assort themselves without respect to one another during the formation of gametes.
What is crossing over?
The exchange of genetic material between sister chromatids during meiosis.
What is the importance of crossing over in terms of genetic variation?
It increases genetic variation.
What are gametes and their role in crossing over?
Reproductive cells (eggs in females, sperm in males) that have only half the normal chromosomes and undergo crossing over to create genetic variation.
How does crossing over lead to unique DNA sequences in chromatids?
Chromatids undergo crossing over by exchanging segments of DNA with their homologs, resulting in unique DNA sequences.
What is the result of crossing over in meiosis?
The creation of four new gametes, each with half the number of chromosomes as the precursor had, and containing brand new gene sequences.
What is a continuous trait?
A trait that shows a lot of variation among a population. They are controlled by many genes.
Examples: Human skin color, hair color, or height.
What is gene flow?
The movement of individual organisms and genetic information into and out of a population.
What is the founder effect?
A phenomenon where a small group of organisms leaves a larger group to colonize a new area, carrying a reduced amount of the variation found in the original species.
What is a population bottleneck?
A large population reduced in size, leading to a reduced subset of the original population’s genetic variation.
What is vertical gene transfer?
The transfer of genetic material between a parent cell and daughter cells.
