Dihybrid cross, incomplete dominance, and codominance -- Lecture 11 Flashcards
true-breeding parents can only provide ___ of allele
1 type
ex. RR, rr
crossing Rr X Rr in monohybrid cross only works if:
gametic types are equally likely
gametes combine randomly
outcome in each square is equally probable
law of segregation
homologous chromosomes segregate during Anaphase I, so alleles must segregate as well
only 1 allele of a gene can be in each sperm or egg cell
dihybrid cross in pea plants:
parents (P0) only differ in ___ traits
2
ex. RRYY vs. rryy
dihybrid cross F1 X F1 ratio
9/16 : 3/16 : 3/16 : 1/16
9 : 3 : 3 : 1
9:3:3:1 ratio only possible if:
each trait in dihybrid cross is governed by a single gene
each gene only has 2 alleles
there is a clear dominant-recessive relationship b/n the alleles of each gene
incomplete dominance:
parents w/ 2 different phenotypes can produce offspring that have a 3rd phenotype
ex. of incomplete dominance:
japanese 4 ‘clocks
red flower + white flower –> pink flower
flowers can only be red if homozygous red
flowers can only be white if homozygous white
flowers will be pink if heterozygous
Japanese 4’oclocks:
color gene produces an enzyme that makes a plant pigment called ___
anthocyanin
Japanese 4’oclocks:
___ produces an enzyme that makes a plant pigment called anthocyanin
color gene
Japanese 4’oclocks:
color gene produces an enzyme that makes a ___ called anthocyanin
plant pigment
Japanese 4’oclocks:
depending on the amount of ___ produced –> flower will be white, light pink, or red
anthocyanin
Japanese 4’oclocks:
depending on the amount of anthocyanin produced –> flower will be ___
white, light pink, or red
Japanese 4’oclocks:
the R allele produces a ___
very active enzyme (high anthocyanin production)
Japanese 4’oclocks:
the W allele produces an ___
enzyme that’s not very active (almost no anthocyanin production)
incomplete dominance in japanese 4’oclocks:
CRCR are ___ for the active enzyme (lots of anthocyanin produced) (red colored flower)
homozygous
