ch 12 bio101

Josef Kölreuter (1760)

crossed tobacco strains to produce hybrids

T.A Knight

crossed two varieties of garden pea (1st gen resembled only 1 parent strain, 2nd gen= both)

Gregor Mendel

research showed that pea hybrids could be produced, many pea varieties were available, peas are small plants and easy to grow, peas can self-fertilize or be cross-fertilized

monohybrid cross

used to study only two variations of single trait

Mendel’s seven traits for pea strains

flower color, seed color, seed texture, pod color, pod shape, flower position, plant height (each trait has 2 variants)

F1 generation (filial)

offspring produced by crossing two true-breeding strains

dominant

referred to visible trait

recessive

alternative trait

F2 generation

produced from the self-fertilization of F1 plants

3:1 (1:2:1)

the dominant to recessive proportion of the traits observed in a F2 generation of a monohybrid cross

F2 plants

dominant= 3/4, recessive=1/4

actual ratio (3:1) discovered by Mendel

1 true-breeding dominant plant (homo.), 2 not-true breeding dominant plants (het.), 1 true-breeding recessive plant

Mendel’s five-element model

1.) Parents transmit discrete factors (genes), 2.) Each individual receives one copy of a gene from each parent, 3) Not all copies of a gene are identical, 4.) alleles remain discrete-no blending, 5.) presence of allele does not guarantee expression

allele

alternative form of a gene

homozygous

two of the same allele

heterozygous

different alleles

dominant allele

expressed

recessive allele

hidden by dominant allele

genotype

an individual’s complete set of alleles

phenotype

an individual’s physical appearance