CH.4-Microevolution/genetic changes Flashcards
Natural selection acts on —- but —- do not evolve during their lifetime
individuals - individuals
What is a population?
A group of same species living is same area
What is the smallest unit of evolution?
A population
Natural selection can only happen if:
1) Members of a pop have variations in genetic characteristics
2) Environmental pressures to produce more
3) Lots of time
What are genes?
Section of DNA on a chromosome that has the information to make specific proteins. These proteins have a certain trait
How many pairs of chromosomes does a human have?
23 pairs (46 total) –> 23 from ch/ parent
What are homologous chromosomes?
Copies of the same chromosome (have same gene)
Are homologous chromosomes identical?
NO - they have same genes but different versions (alleles)
What are alleles?
Different version of same gene (characteristic). Will code for different trait of characteristic.
Eye color is a — and brown/blue/green eyes is a —
Gene - Alleles
Is eye color a characteristic or a trait?
Characteristic
Are blue eyes a characteristic or a trait?
Trait
How many alleles for every gene?
2 (1 allele from each chromosome from each parent)
— alleles for a gene are always expressed as a trait when present
Dominant
—- alleles for a gene are only expressed when an individual has 2 copies of it
Recessive
What’s a genotype?
Combination of alleles an individual has for a particular gene
What are the 3 possible genotypes for a gene that has 2 alleles versions (e and E)
EE, Ee, ee
What is homozygous? E and e
Individual’s genotype has 2 alleles the same EE, ee
What’s heterozygous?
Individual’s genotype has 2 different alleles Ee
What is a phenotype?
The trait that is expressed for particular characteristic (end result)
EE, Ee, ee are —
Genotypes
EE = Brown eyes, Ee = Brown eyes, ee = blue eyes are —-
Phenotypes
What is a gene pool?
A population’s genetic makeup. Quantifies how many of ch/ type of allele for a given gene can be found withing the population
How does microevolution affect the gene pool?
Changes in the ALELLE FREQUENCIES within the gen pool can occur over generations
What is the formula for GENOTYPE FREQUENCY?
of individuals with a particular genotype/Total # of individuals in the population
What’s the formula for allele frequency?
of copies of a specific allele for a gene in the population/ Total # of alleles for a gene in the population
When do we apply the Hardy-Weinberg Principle?
When the population isn’t evolving (Equilibrium)
What is Genetic Equilibirum?
1) No gene flow
2) No mutation
3) Random mating
4) No natural selection
5) Large population size
Hardy-Weinberg:
what is p and q?
p = freq of dominant allele
q = freq of recessive allele
Hardy-Weinberg:
What is p^2 and q^2? What is 2pq?
p^2 = freq of homozygous dominant genotype
q^2: = freq of homozygous recessive genotype
2pq = freq of heterozygous genotype
What causes microevolution?
1) Natural selection
2) Genetic drift
3) Gene flow
What are the 3 modes that natural selection can act on a population?
1) Directional selection
2) Disruptive selection
3) Stabilizing selection
What is directional selection?
1 extreme variant in phenotype is favored
What is disruptive selection?
2 extreme variants in phenotype are favored
What is stabilizing selection?
Intermediate variant in phenotype is favored (average phenotype)
What is Genetic drift?
Random fluctuations in allele frequencies from 1 generation to the next
Is a genetic drift more substantial to a small or large population?
Small - If large, most likely to be similar to previous population
What are the special cases of Genetic Drift?
1) Founder Effect
2) Bottle neck effect
What is the Founder effect? Is the gene pool necessarily the same?
When very few individuals get isolated and start their own population - Gene pool differs bc very few (bigger effect)
What is the Bottle neck Effect?
Population’s number lowers drastically because of disaster (surviving population)
What is Gene flow?
Transfer of alleles in/out of population bc of immigration/emigration of fertile individuals or gametes
