Cornell BIOG 1140 Chapter 9: Patterns of Inheritence

heredity

the transmission of traits from one generation to the next

genetics

the study of heredity

character

heritable feature that varies among individuals

trait

each variant for a character

true-breeding

over many generations of self-pollination, produced only the same variety as the parent plant

hybrids

offspring of two different varieties

P generation

true-breeding parents

F1 generation

hybrid offspring

F2 generation

offspring of F1 generation

dominant allele

determines appearance

recessive allele

no noticeable effect on appearance

law of segregation

a sperm or egg only carries one allele for each inherited character because allele pairs segregate from each other during the production of gametes

phenotype

observable traits

genotype

genetic makeup

gene locus

a specific location of a gene along the chromosome

monohybrid cross

cross between two individuals that are heterozygous for one character

dihybrid cross

a cross between two organisms that are each heterozygous for two characters being followed

dependent assortment

the alleles for seed color and shape inherited together from the P generation. genes assort together

independent assortment

genes inherited independently

testcross

a mating between an individual of unknown genotype and a homozygous recessive individual

rule of addition

the probability that an event can occur in two or more alternative ways can be determined from the sum of the separate probabilities of the alternatives

pedigree

family tree that describes the traits of parents and children across the generations

mutant trait

refers to a trait that is less common in nature

complete dominance

the dominant allele has the same phenotypic effect whether present in one or two copies

incomplete dominance

when genes "mix". red and white form pink flower

codominant

both alleles expressed in heterozygous individuals

pleiotropy

one gene influences multiple characters. ex. sickle cell disease

polygenic inheritance

many genes effecting a single phenotype

chromosome theory of inheritance

genes occupy specific loci on chromosomes, the chromosome undergoes segregation and independent assortment during meiosis. the behavior of chromosomes during meiosis and fertilization that accounts for inheritance patterns

wild-type

traits most common in nature

mutant

traits that are less common

recombination theory

17%

genetic map

ordered list of the genetic loci along a chromosome. based on the assumption that the chance of crossing over is approximately equal at all points along a chromosome.

linkage map

genetic map based on recombinant frequencies

sex-linked genes

a gene located on either sex chromosome. majority are x-linked