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
incomplete dominance in japanese 4’oclocks:
CRCR are homozygous for the ___ (lots of anthocyanin produced) (red colored flower)
active enzyme
incomplete dominance in japanese 4’oclocks:
CRCR are homozygous for the active enzyme (___ anthocyanin produced) (red colored flower)
lots of
incomplete dominance in japanese 4’oclocks:
CWCW is homozygous and has only the very ___ (almost no anthocyanin) (white flower)
inactive enzyme
incomplete dominance in japanese 4’oclocks:
CWCW is ___ and has only the very inactive enzyme (almost no anthocyanin) (white flower)
homozygous
incomplete dominance in japanese 4’oclocks:
CWCW is homozygous and has only the very inactive enzyme (___ anthocyanin) (white flower)
almost no
incomplete dominance in japanese 4’oclocks:
heterozygotes (CRCW) have ___ the amount of the active enzyme (1/2 anthocyanin)
half
incomplete dominance in japanese 4’oclocks:
___ (CRCW) have half the amount of the active enzyme (1/2 anthocyanin)
heterozygotes
incomplete dominance in japanese 4’oclocks:
heterozygotes (CRCW) have half the amount of the ___ (1/2 anthocyanin)
active enzyme
incomplete dominance in japanese 4’oclocks:
heterozygotes (CRCW) have half the amount of the active enzyme (___ anthocyanin)
1/2
incomplete dominance in japanese 4’oclocks:
the R allele is ___ over the W allele
incompletely dominant
codominance (definition and example)
the heterozygote will have both phenotypes
ex. human blood types
genetics of A,B,O blood types:
glycosylation
process where different types of sugars can be added to the surface of RBCs
genetics of A,B,O blood types:
controlled by ___ alleles of the ‘I’ gene
3
genetics of A,B,O blood types:
controlled by 3 alleles of the ___ gene
‘I’
genetics of A,B,O blood types:
IA, IB, and Ii all cause different patterns of ___ on RBCs
glycosylation
genetics of A,B,O blood types:
___ all cause different patterns of glycosylation on RBCs
IA, IB, Ii
genetics of A,B,O blood types:
IA, IB, and Ii all cause ___ of glycosylation on RBCs
different patterns
genetics of A,B,O blood types:
IA (which blood type)
type A
genetics of A,B,O blood types:
IB (which blood type)
type B
genetics of A,B,O blood types:
Ii (which blood type)
type O
mechanism of action and codominance:
IA allele codes for an enzyme (a transferase) that adds ___ to the surface of RBCs
galactosamine
mechanism of action and codominance:
IB allele codes for a version of the transferase enzyme that adds ___ to the surface of RBCs
galactose
mechanism of action and codominance:
Ii allele codes for an ___
inactive version of the transferase enzyme
dominance relationships b/n IA, IB, and Ii
IA > Ii
IB > Ii
IA and IB are codominant
what is a simple Mendelian inheritance pattern?
crossing true-breeding homozygous dominant and true-breeding recessive
