more genetics Flashcards
epistasis
refers to when one gene is dominant (overrides) a whole ‘nother gene
locus
location on chromosome
polyploidy
abnormal condition such as trisomy
prophase I
nucleus dissolves; chromatin condenses into chromosomes (at this point, diploid as well as replicated )
synapsis
arrangement of chromosomes during prophase I, where homologous chromosomes are paired in the center. A pair is called a BIVALENT or TETRAD
crossing over/recombination
the exchange of alleles btw homologous pairs during prophase I
synaptonemal complex
protein structure that mediates synapsis, forming as early as prophase. These proteins keep the neighbouring chromatids bound close so as to facilitate recombination
nondisjunction
when either homologous chromosomes fail to separate, or, when sister chromatids fail. Can result in trisomy or monosomy
law of segregation
two alleles in an organism are separated and passed on SINGLY to offspring
law of independent assortment
alleles of one gene do not follow other alleles - not always true though
codominance
heterozygous situation where two alleles are both expressed but aren’t blended; AB blood type is example
incomplete dominance
heterozygous situation where phenotype is a blend (e.g. pink flowers)
pleiotropism
gene that alters many seemingly unrelated parts of the phenotype
polygenism
traits that are under influence of several genes, e.g. height
penetrance
likelihood that a person with given genotype will express the expected phenotype (e.g. breast cancer gene doesn’t always result in cancer)
recessive lethal alleles
alleles which cause death when they are homozygous recessive
linkage
when genes defy law of independent assortment
frequency of recombination
= number of recombinant phenotypes / total number of offspring
when genes are further apart on chromosome, recombination frequency is higher
Hardy weinberg law
the frequencies of alleles in a population will NOT change over time, given
no mutation
no migration
no natural selection
random mating
population sufficiently large to prevent random drift
Where homozygotes = pp or qq; heterozygotes = 1pq
Takes 2 generations to restore equilibrium after disrupted
artificial selection
e.g. humans control animal mating
sexual selection
selection via mate choice
kin selection
e.g. a chimpanzee protects cousins and relatives in its troupe
prezygotic barriers
one of the barriers to different species reproducing
types: ecological (location), temporal, behavioral (courtship ritual), mechanical, gametic (egg and sperm can’t connect)
postzygotic barriers
barriers to hybridization that occur after fertilization.
Types: hybrid inviability (may die as embryo), hybrid sterility (mules are sterile), hybrid breakdown (hybrid’s offspring sterile)
allopatric isolation
speciation occuring due to geographical isolation; whereas sympatric speciation is speciation in same area
anagenesis
one species simply becomes another through drift, such that it couldn’t mate with its own ancestors
homologous structure
structures shared by common descendants (bat wings and monkey hands)
analogous structure
similar looking structures that converged from different species (whale flipper and shark fins)
parallel evolution
two species go through similar changes due to same pressures (e.g. in ice age, all animals grow to tolerate cold)
order of taxonomy
domain, kingdom, phylum, order, family, genus, species
reducing environment
Earth’s early atmosphere had no O2
proteinoids
proteins made from abiotic synthesis
protobionts
earliest forms of ‘life’
microspheres - droplets of proteinoids
liposomes - lipid layer surrounding microsphere
coacervates - have proteins, polysaccharides, nucleic acids
back cross
simply the breeding of F1 generation with one of its parents
all test crosses are back crosses; they are just a specific type where you cross a suspected heterozygous F1 with a homozygous recessive parent to determine if they are indeed heterozygous
hemizygotic
synonym for homozygous
