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Rio Hondo BIO125spencer Genetics

1 gene on the Y chromosome plays a crucial role

on the development of testis (SRY)


is a form of dwarfism (aa = normal; Aa = dwarf; AA = death of embryo), dominant

All eggs contain

a X chromosome


alternative forms of genes ex: flower color has purple or white alleles

All sperm contain

either and X or a Y chromosome


chromosomes other than the sex chromosomes (X and Y)

chromosome theory of inheritance

states that (1) genes are located on chromosomes (2) the behavior of chromosomes during meiosis and fertilization accounts for inheritance patterns


(expression of both alleles)

cross-fertilization = hybridization

fertilization of one plant by pollen from another plant

dihybrid cross

mating of two individuals with differing characteristics


a gene that is expressed when multiple alleles are present; capital letter, ex: P for purple

F1 generation

filial ((Latin for son or daughter)) = offspring

F2 generation

offspring of F1 generation

family pedigree

family tree representing occurance of genes in parents and offspring across generations) shows the history of a trait in a family and allows researchers to analyze human traits

Females must receive 1 copy from each parent (2 total) to phenotypically acquire a recessive trait and males need

only 1 recessive gene on the X chromosome to phenotypically acquire a recessive trait

For each characteristic, each organism has

two genes; one from each parent


(egg and sperm) carry only one allele for each inherited characteristic because allele pairs separate in the production of gametes (meiosis)


units that determine heritable traits


an organism's genetic makeup

Gregor Mendel

Was the first person to scientifically analyze patterns of inheritance (studied garden peas which self-fertilize)
Found that genetic characteristics followed a few simple rules and deduced the fundamental principles of genetics

Homologous chromosomes have genes at specific

loci (locations of specific genes on a chromosome) and alleles of a gene at the same locus


offspring of two different true breeding varieties


mating of close relatives; ↑chances of offspring being homozygous for harmful recessive traits

Incomplete dominance

when the phenotype of heterozygote (Aa) is intermediate between the phenotypes of homozygotes (AA and aa)

Independent assortment

Each pair of alleles segregates independently of the other pairs during gamete formation; the inheritance of one characteristic has no effect on the inheritance of the other


locations of specific genes on a chromosome

Many human characteristics result from a combination of

heredity and environment, including skin color

Mendel's principle of segregation

pairs of alleles segregate (separate) during gamete formation; the fusion of gametes at fertilization creates allele pairs again

monohybrid cross

is a cross between parent plants that differ in only one characteristic ex. flower color

Most human genetic disorders are


P generation

parent generation


an organism's physical traits


is the impact of a single gene on more than one characteristic, sickle-cell disease is an example

Polygenic inheritance

the additive effects of two or more genes on a single phenotype

Punnett square

tool for predicting results of a genetic result


a gene that is not expressed when multiple alleles are present; lower case letter, ex: p for white flower

Rule of multiplication

probability of a compound event is the product of the separate probabilities of the independent events.

Sex chromosomes influence the inheritance of

certain traits

Sex-linked genes

any genes located on a sex chromosome
Were discovered during studies on fruit flies while studying eye color (gene found to be on X chromosome)


is a mating between an individual of unknown genotype (P_) and homozygous recessive individual (pp)


when self fertilization produces only offspring identical to parents

Wild type

traits are traits most commonly found in nature

The Y chromosome of human males is only about

one-third the size of the X chromosome and has only 1/100 the # of genes carried by X chromosomesgenes

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