Chapter 12 Flashcards
(25 cards)
Two key parts to Mendel’s methods:
- cross true-breeding strains having alternate forms of a trait (e.g. flower color) to produce hybrids
- allow hybrids to self-fertilize and count the number of offspring showing each form of the trait.
Monohybrid cross:
crossing of single traits
F1 generation
hybrids produced by crossing two true-breeding (parent) strains
dominant
the form of each trait seen in the F1s
recessive
the form of the trait that was “lost” in the F1s
F2 generation
offspring resulting from the self-fertilization of F1 plants (F1 X F1 = F2)
gene
section of a chromosome that codes for a particular trait
locus
location of a gene on a chromosome
alleles
alternate forms genes that occur on homologous chromosomes
homozygous
having the same allele
heterozygous
having different alleles
genotype
the genes that produce phenotypes
phenotype
outward appearance – the result of many different genes, interactions among those genes, and environmental effects
principle of segregation
- alleles separate during meiosis
- If an individual is homozygous for a trait, all gametes will have the same allele.
- If an individual is heterozygous for a trait, half of its gametes will be dominant and half will be recessive.
- Chromosomes carrying the alleles join randomly during fertilization to produce offspring genotypes. One allele from father, one allele from mother.
pedigrees are used to …
track inheritance patterns in families
dihybrid cross
examines two different traits in a single cross
principle of independent assortment
- examines two different traits in a single cross
- This only happens if the alleles for the two traits are on different chromosomes or are far apart on the same chromosome.
- If alleles are close together on the same chromosome they are said to be linked and therefore do NOT assort independently.
testcross
determines the genotype of an individual with a dominant phenotype, always cross with homozygous recessive
Mendel’s model of inheritance assumes that:
- each trait is controlled by a single gene
- each gene has only two forms (2 alleles)
- there is a clear dominant-recessive relationship between the alleles
polygenic inheritance
many different genes control phenotype
pleiotropy
one allele has more than one effect on the phenotype
incomplete dominance
heterozygote is intermediate in phenotype between the 2 homozygotes, blending of traits
codominance
the heterozygote shows aspects of both homozygous phenotypes but separately
epistasis
One set of genes can modify the expression of another set of genes
