17.2 — dihybrid inheritance Flashcards
covers: what a dihybrid cross is; an example of dihybrid in pea plants; reasons for deviations from expected ratios.
what is a dihybrid cross? (compare to monohybrid)
unlike monohybrid crosses, which show the inheritance of one gene with two alleles, dihybrid crosses show the simultaneous inheritance of two genes controlling separate characteristics.
what can dihybrid crosses help to do? (3)
- determine whether genes are linked
- locate genes of specific chromosomes
- calculate expected phenotypic ratios in subsequent generations
what does meiosis ensure?
meiosis ensures that each gene still has just one allele in a dihybrid cross
what does the law of assortment mean?
the law of assortment means that alleles for different genes segregate independently during gamete formation in meiosis, unless they are linked
what traits does a true/pure breeding organisms have?
homozygous for the traits being studied
what does selecting homozygous parents ensure?
predictable allele transmission during meiosis
all F1 offspring identical phenotypes and identical genotypes in a. dihibrid cross between homozygotes. what does this show?
this shows that the two gene pairs have undergone independent assortment (has occurred during meiosis) and indicated that the genes are not linked
what ratio is typical of a dihybrid cross with both parents heterozygous at both gene loci and what does this illustrate?
9:3:3:1; this illustrates the independent segregation of alleles.
what do dihybrid crosses predict?
specific phenotypic ratios
what are the two main reasons of deviation from expected phenotypic ratios?
