Genetics and Evolution Flashcards
What are chromosomes composed of
DNA and protein
Griffith experiment
used two strains of S. pneumonie to show that there was a transforming factor.
Heat killed S + live R strains killed the mice, meaning that the cell extract of the dead S conferred virulence to the R strain.
Avery, MacLeod, McCarty,
Destroyed DNA and saw that the virulence wasn’t conferred to R, showing that DNA is the molecule of inheritance.
Hershey and Chase
used two phage cultures, one labeled with P and one labeled with S, to confirm what Avery, MacLeod, and McCarty found.
gene
fundamental unit of inheritance
homologous chromosomes
two nonidentical copies of a chromosome from a mother and a father
alleles
different versions of a gene
genotype/phenotype
DNA sequence a person carries/ the physical expression of genotype
dominant/recessive
dominant - allele that is expressed no matter what other allele is
recessive - allele that is silent unless present in homozygous state
What does meiosis do?
Reduces number of copies of each chromosome from two to one, producing gametes
males - occurs in testes with haploid spermatozoa
females - in ovaries it produces ova
difference between meiosis and mitosis
meiosis has two rounds and recombination/crossing over occurs between homologous chromosomes
synapsis
when homologous chromosomes pair with each other during prophase I
synaptonemal complex
mediates synapsis
metaphase I
tetrads are aligned at the center of the cell
anaphase I
homologous chromosomes separate and sister chromatids remain together
telophase I
cell divides into two haploid cells with a single set of chromosomes
meiosis II vs mitosis
movement of chromosomes are identical
nondisjunction
failure of chromosomes to separate correctly during meiosis, can cause trisomy or monosomy
law of segregation
two alleles of an individual are separated and passed on to the next generation as singles
law of independent assortment
alleles of one gene will separate into gametes independently of alleles for another gene
incomplete dominance vs codominance
phenotype of heterozygote is a mix of both alleles vs the two alleles are both expressed but not blended (ex blood type)
linkage
failure of genes to display independent assortment
genes located close together will probably not be independently inherited
What does recombination do to allele assortment?
It produces new combinations of alleles not found in the parent
mitochondrial traits
affected females have all affected offspring
autosomal recessive vs autosomal dominant
recessive - can skip generations
dominant - doesn’t skip generations
y linked
only affects males
x linked recessive vs dominant
recessive - affects males more, affected female has all affected sons
dominant - rare, affected females have all affected daughters
population meaning
members of a species that mate and reproduce with each other
gene pool
sum total of all genetic info in a population
Hardy Weinberg assumptions
no mutation, no migration, no natural selection, random mating, large population
not possible for a population to meet all these conditions
hardy Weinberg formulas
p+q = 1
p^2 +2pq + q^2 = 1
hardy Weinberg equilibrium
allele frequencies no longer change
natural selection effects
differential reproduction of different phenotypes
fitness
how many offspring an individual can have
modes of natural selection
directional, divergent, stabilizing, artificial, sexual, kin
reproductive isolation
keeps existing species separate, includes pre zygotic and post zygotic mechanisms
homologous structures
shared by two different species as a result of a common ancestor
analogous structures
serve same function in two different species
convergent evolution
two different species come to possess many analogous structures due to similar selective pressures
principal taxonomic categories
domain, kingdom,phylum, class, order, family, genus, species
