problem 2 Flashcards
(33 cards)
allele
Variant form of a given gene. Different alleles can result in different observable phenotypic traits
homozygous
having 2 copies of the same allele (AA/ aa)
heterozygous
having 2 copies of different alleles (Aa)
blending inheritance
Inheritance of traits from 2 parents (black and blond hair) produces offspring with characteristics that are intermediate / a mixture between those of the parents (brown hair)
single-gene characteristic
any characteristic where allelic variation in a single gene accounts for differences in the phenotype
one gene –> one effect
polygenetic trait
Traits are polygenic when there is wide variation in them and each (dominant) allele “adds up” to the expression of the trait (i.e. if you have many alleles that code for height they add up and contribute to the overall big height)
co-dominance
heterozygotes fully express the phenotype of both of their homozygous parents (i.e. blood groups like AB)
incomplete dominance
phenotype of the heterozygote is intermediate in form between those of the two homozygotes (i.e. red homozygote + white homozygote = pink flower), the third phenotype is a combination of the phenotypes of both alleles
linkage
Tendency of DNA sequences that are close together on a chromosome to be inherited together during meiosis. The closer together on a chromosome, the less the chance of recombination between them
law of segregation
mendel
Allele pairs randomly separate / segregate during gamete formation and randomly unite at fertilization, each gamete carries only one allele for each gene
law of dominance
mendel
Recessive alleles will always be masked by dominant ones, therefore only the dominant phenotype will be expressed, while still having a heterozygote genotype
law of independent assortment
mendel
When 2 or more characteristics are inherited, individual hereditary factors assort independently during gamete production, giving different traits and equal opportunity of occurring together (wrinkles or smooth and yellow or green)
Hardy-Weinberg equilibrium
states that allele + genotype frequencies in a (perfect) population will remain constant from generation to generation in absence of other evolutionary inferences
- large population, no mutations, random mating, no natural selection, no gene flow
p+q=1; p2+2pq+q2=1
independent segregation
happens when genes for two characteristics lie on different chromosomes – if on same chromosome, they exhibit linkage (travel together until broken apart by recombination)
e.g. color + texture
neutral theory of molecular evolution
holds that at the molecular level most evolutionary changes and most of the variation within and between species is not caused by natural selection but by genetic drift of mutant alleles that are neutral
genetic amplification
an increase in the number of copies of a gene without proportional increase in other genes
quantitative genetics
Branch of population genetics that deals with continuously varying phenotypes as opposed to discretely identifiable phenotypes and gene products (predicting phenotypes which are not either/or)
polygenetic inheritance
a sum of genes can be inherited differently but the single alleles that contribute follow the mendelian laws
inbreeding
production of offspring
genetic drift
Variation in the relative frequency of different genotypes in a small population, due to the chance of disappearance of genes as individuals die or don’t reproduce
heritability
estimation of the degree of variation in a phenotypic trait in a population that is due to genetic variation between individuals in that population
coefficient of relatedness = r
Probability that 2 individuals share an allele due to common ancestry, ranges from 0 (unrelated) to 1 (clones)
behavioral genetics
Research that uses genetic methods to investigate the nature + origins of individual differences in behavior
monozygotic twins
dizygotic twins
identical twins (100%)
non-identical twins (50%)
