BIS2B Midterm 2 Flashcards
Blended inheritance
hereditary determinants in the egg and sperm are irreversibly blended (e.g. red + white flowers= pink flowers)
Particulate inheritance
hereditary determinants in the egg and sperm are passed to its offspring through genes, which keep their ability to be expressed while not always being physically seen in a descending generation
Segregation (Mendel’s 1st law)
When an individual produces gametes, the two copies of its gene segregate, so that each gamete receives only one copy (one maternal haploid + one paternal haploid= one offspring diploid)
Alleles
different variations of a gene (e.g. R, r)
Genotype
diploid individual’s combination of alleles (RR, rr, Rr)
Homozygous
similar combination of alleles (RR, rr)
Heterozygous
different combination of alleles (Rr)
Phenotype
trait expressed by organism (PHenotype= PHysical appearance)
Dominant
phenotype expressed in heterozygotes
Recessive
phenotype expressed in homozygotes only
Incompletely dominant
intermediate heterozygote phenotype (white+red=pink)
Codominant
both allele phenotypes are expressed in heterozygotes
Dihybrid cross
test cross done when different loci assort independently
Test cross
done in order to determinate genotype(whether heterozygous or homozygous) when a dominant phenotype appears
Independent assortment
alleles of different genes assort independently during gamete formation
Additive effect
phenotypic effects at one locus are independent of genotype at the other locus
Locus
the physical location of a gene in the chromosome
Polygenic traits
traits that are controlled by many genes of small effect
Pleiotropy
allelic variation at one locus affects multiple traits
Antagonistic pleiotropy
occurs when a single allele has both positive and negative effects
Epistasis
phenotypic effect of allele at one locus depends upon genotype of allele at another locus
Genotype x environmental interaction
phenotypic effect of allele or genotype depends on environment (temperature dependent allele, mutations depending on dietary factors)
Genotype frequency
proportion of individuals with a genotype in a population
Allele frequency
proportion of an allele across all individuals in the population or in the gametes produced by those individuals
Gene pool
all of the alleles present in members of the population
Hardy Weinberg Equilibrium assumptions
- No new mutations
- Large population
- No genetic flow (no migration)
- No natural selection
- Random mating
Genetic drift
random changes in allelic frequencies due to sampling error from generation to generation (sampling error much more significant in smaller populations)
Bottleneck
occurs when population size is reduced for at least one generation (e.g. hunting)
Founder effects
occurs when a new colony is started by a few members from the original population (e.g. Dutch settlers in South Africa- Huntington’s disease)
Non-random mating
occurs when individuals choose mates w particular phenotypes or genotypes
Assortative mating
mating b/n similar genotypes
Disassortative mating
mating b/n dissimilar individuals
Outbreeding
avoidance of mating b/n relatives
Interbreeding
mating b/n relatives
Gene flow
migration of individuals and/or gametes from one population to another resulting in transfer of their alleles b/n populations
Disease resistance (heterozygote advantage)
disease resistance alleles may confer resistance vs. different pathogens
Antagonistic pleiotropy (heterozygote advantage)
heterozygote balances costs and benefits of each allele
Metabolic pathways (heterozygote advantafe)
heterozygotes may have broader environmental tolerance than “specialist” homozygotes
Interspecific competition
competition between members of two or more different species
Intraspecific competition
competition between members of the same species
Competition
both species harmed by the interaction (in interspecific interactions)
Ammensalism
one species harmed, one species unaffected
Antagonistic interactions
one species benefits and the other is harmed
Competition
occurs when individuals harm one another; leads to decreased growth, survival, or reproduction; results in lower population growth rates
R* rule
for two species competing for a single-limiting resource, the species that can suppress the resource to the lower equilibrium value (R*) will competitively exclude the other species
Exploitative mechanism
when one individual uses a resource, one cannot; not encounter each other
Interference mechanism
competitors confront each other and harass, chase, or prohibit others from using resources
Niche utilization curve
frequency at which a species uses a range of resource types; performance of a species for a range of environmental conditions (e.g. reproduction)
Niche overlap
corresponds to the region of overlap b/n resource use curves for two competing species (shaded region b/n curves)
Character displacement
difference b/n similar species are greater in places where they co-occur and minimal in places where their distributions do not overlap
