Lecture Exam 2 Flashcards
Law of Segregation
sperm and egg cells contain only one allele for each gene b/c allele pairs separate from one another during meiosis
Law of Independent Assortment
each pair of alleles segregate independently of other pairs of alleles during gamete formation
Heterzygous
Aa (different alleles)
Homozygous
AA or aa (same alleles)
Genotype
genetic variation
Phenotype
physical characteristic variation
Complete Dominance
dominant allele completely overtakes the recessive allele (black or brown)
Incomplete Dominance
heterozygotes phenotype expression is an intermediate to that of both homozygotes (red, white, or pink)
Codominance
heterozygotes express both alleles at the same time (stripes, blood types)
X linked genes
2 copies on women
1 copy on men
Y linked genes
0 copies on women
1 copy on men
Recessive, sex linked disease alleles will most often be expressed in …
MEN
Pleiotrophy
One gene will effect multiple aspects of an organism’s phenotype (albinism)
Polygenetic
traits appear to exibit continous variation and are often under the influence of a large number of genes (skin color)
Epistasis
expression of one gene influences the phenotypic expression of another one (coat color in labs)
Besides, pleiotropy, polygenetic, and epistasis, what can influence gene expression
environment
How many crosses does mendelian inheritance employ
a single cross
Population genetics allows us to estimate the allele and genotype frequency of how many crosses
many
Hardy-Weinberg Equillibrium
a population’s allele and genotype frequencies are constant, unless there is some type of evolutionary force acting on them
What five truths must be true to preserve Hardy-Weinberg
no mutation, no genetic drift, no gene flow, no selective mating, no selection
mutation introduces
new alleles
what is the source of all new genetic variation
mutation
mutation is
random
on its own, mutation is
weak
in combination, mutation is
powerful
natural selection produces
adaptations
fitness =
survival, reproductive success, mating success
traits are subject to natural selection if they are
heritable, variable, and associated with variation in lifetime reproductive success
genetic drift leads to
random change
what are the two ways genetic drift occurs
- some gametes participating in fertilization at the expense of others
- unpredictable events that remove some alleles at greater frequencies (bottlenecking events)
genetic drift is more pronounced in _______ populations
smaller
gene flow _______ populations
homogenizes
gene flow works counter to
selection
non random mating
alters genotypes
what is assortive mating
individuals choosing mates that are phenotypically similar
what are produced as a product of assortive mating
excessive homozygotes
biological species classification
species based on reproductive isolation
-pro: clear criteria for defining
-con: difficult to apply to certain populations
morphospecies
defines species on same or different phenotypic /morphological features
-pro: easy to apply to a wide range of organisms
-con: subjective, may miss cryptic species, may split up polymorphic species
phylogenetic
defines species based on monophly
-pro: easy to apply to a wide range of organisms
-con: requires good phylogeny, can over estimate a number of species
how do new species originate?
genetic isolation -> genetic divergence
diploidy
2 sets of chromosomes
polyploidy
more than 2 sets of chromosomes
allopatric speciation
populations are genetically isolated via geographic border
sympatric speciation
populations are genetically isolated by non random mating
autopolyploid
duplication of the same genome; requires one genome; produces a tetraploid
alloployploid
combination of 2 distinct genomes; requires 2 distinct species; produces a polyploid
outcomes of secondary contact
1) populations diverge successfully, cannot interbreed -> reproductive isolation complete
2) populations interbreed successfully, gene flow continues -> differences between populations eliminated
3) populations interbreed successfully, offspring are not viable -> reinforcement occurs
4) populations interbreed successfully to product viable and fertile offspring -> hybrid zone forms
