Ch.23 Flashcards
Define alleles
A particular version of a gene
Define genotype
 Refers to the genetic material past between generations
Define phenotype
The Observable traits of an individual
What does nonrandom mating only change
It onlychanges genotype frequencies NOT allele frequencies
What does inbreeding do to alleles
Homozygosity of alleles increase but heterozygosity of alleles decrease
Result in less fitness and recessive alleles will represent loss of function in an organism
Define inbreeding depression
Is a decline in avg, fitness that takes place when homozygosity decreases in a population
What evolutionary process only produces adaptation?
Natural selection
Define directional selection
Changes avg. Phenotype in pop. In one direction
Effect on phenotype: cause change in avg phenotype of a pop.
Genetic variation is reduced
Define stabilizing selection
Form of natural selection where individuals with moderate or avg phenotypes are more fit
Define disruptive selection
A type of natural selection that actively selects against the intermediate in a population favoring both extremes of the spectrum
Define balancing selection
This type of natural selection that maintains genetic variation for longer than expected
Define sexual selection
Is a form of nonrandom mating that occurs when females choose certain males or males competition
It leads to change in allele frequencies
Define intersexual selection
Is a type of sexual selection inwhich an individual of one sex chosen a particular individual of other sex for matching
Define intrasexual selection
A type of sexual selection driven by competition among members of one sex (male v male)
Define founder effect
Occurs when a group establishes a new pop. In a new area. This change alleles frequencies
Define population Bottle necks
Sudden decrease in pop-size in a once large pop., that are caused by disease or natural catastrophes
What does gene flow do?
Is the random movement of alleles between pop.
That then equalized allele frequencies
gene flow occurs when
Individuals leave one population join another and breed
Define mutation
Any permanent change in the hereditary material of an organism and is the only source of new alleles in a population and modifies allele frequencies by continually introducing new alleles
Does a mutation occur by chance?
Yes, and only by chance
what is the ultimate source of genetic variation ?
Mutations
Are mutations random?
Yes
Does genetic drift decrease genetic diversity?
Yes, over time
Does gene flow increase genetic diversity? Is there any exceptions?
Yes it does, but it can also decrease variation of the source of population if alleles leave with the moving population
Define point mutation
Before chromosome level mutation
Key points of genetic drift
- Genetic drift is random with respect to fitness
- genetic drift is most pronounced in small populations
- overtime genetic daft can lead to the random loss or fixation of alleles
Define sexual dimorphism
Refers to any trait that differs between males and females of same species include:
-Weaponry deer ex antlers on males
- ornamentation and behavior in courtship ex
peacocks colorful male feathers - body size
What is heterozygote advantage?
Pattern of natural selection that favors heterozygous individuals compared to homozygous individuals.
Promotes genetic variation forming balancing selection
Define deleterious alleles
Allele that reduces an individuals fitness
What does inbreeding increase?
Homozygosity which makes offspring have lower fitness
The assumptions of the Hardy- Weinberg principle
- Random mating- no mate choice; gametes combine randomly
- No natural selection- all individuals contribute equally to gene pool
- No genetic drift- random allele frequency changes)
- No gene flow - no new alleles added or lost from gene pool
- No mutations - no new alleles introduced into gene pool
Define gene pool
alleles from all gametes and each generation go into a single group then combine randomly This concept was first brought up by Hardy and Weinberg
What four processes is known to drive evolution?
- natural selection
- Genetic drift
- Gene flow
- Mutation
Alleles that reach a frequency of 1.0 are said to be
Fixed
Deleterious alleles are said to be
Lost at a 0.0
Natural selection
Increases the frequency of alleles that contribute to reproductive success in a particular environment
Genetic drift
causes allele frequencies to change randomly
The 5 important assumptions of the hardy Weinberg principle
- Random mating- no mate Choice gametes combine randomly
-  No natural selections- all individuals contribute equally to gene pool
- No genetic drift - (random allele frequency changes) - alleles not picked by chance because it assumes population is large
- No gene flow - no new alleles added or lost from gene pool
- No mutations- no new alleles introduced into gene pool
Given a population Of 100 individuals where 15 AAand 25 Aa and 60 aa what is the frequency of allele “A” and the frequency of alleles ”a”
The Hardy Weinberg equation
P^2+2pq+q^2=1
4 processes of evolution
Natural selection
Genetic drift
Gene flow
Mutation
Natural selection
Increases the frequency of alleles that contribute to reproductive success in a environment
Genetic drift
Causes allele frequencies to change randomly
Can lead to random loss or fixation of alleles
Thy can result to decrease in genetic variation
Gene flow
Occurs when individuals leave one pop., join another, and breed
Mutation
Modifies allele frequencies by continually introducing new alleles
Natural selection occurs in what 4 patterns?
- Directional selection
- Stabilizing selection
3.disruptive selection
- Balancing selection
4 processes of evolution
- Natural selection
- Genetic drift
- Gene flow
- Mutation
