Post on 27-Mar-2015
Unit 4 – Lecture 6
Dihybrid Crossa 4x4 representation of crossing TWO traits
monohybrid = 1 trait w/ 2 alleles= 1 allele gamete each for 2x2 box
dihybrid = 2 traits w/ 2 alleles EACH = 4 alleles
= 2 allele gametes each for 4x4 box[one allele for each trait in each
gamete]
Solving a DihybridDetermine the genotypes of each parent
Given to you, or you have to solve for them
Given: Parent #1 AABBGiven: Parent #2 aabb
Solving a DihybridCreate your dihybrid cross [4x4]
Solving a DihybridDetermine Gametes:
pair first allele of first trait with first allele of second trait
A A B B
first gamete = AB
Solving a DihybridDetermine Gametes:
pair first allele of first trait with second allele of second trait
A A B B
second gamete = AB
Solving a DihybridDetermine Gametes:
pair second allele of first trait with first allele of second trait
A A B B
third gamete = AB
Solving a DihybridDetermine Gametes:
pair second allele of first trait with second allele of second trait
A A B B
fourth gamete = AB
Solving a DihybridDetermine Gametes:
pair first allele of first trait with first allele of second trait
a a b b
first gamete = ab
Solving a DihybridDetermine Gametes:
pair first allele of first trait with second allele of second trait
a a b b
second gamete = ab
Solving a DihybridDetermine Gametes:
pair second allele of first trait with first allele of second trait
a a b b
third gamete = ab
Solving a DihybridDetermine Gametes:
pair second allele of first trait with second allele of second trait
a a b b
fourth gamete = ab
Solving a DihybridLabel cross w/ parent gametes above / to left
AB AB AB AB
ab
ab
ab
ab
Solving a DihybridFill in boxes:
fill DOWN each column w/ whatever’s there
AB AB AB AB
ab A B A B A B A B
ab A B A B A B A B
ab A B A B A B A B
ab A B A B A B A B
AB AB AB AB
ab
ab
ab
ab
Solving a DihybridFill in boxes:
fill ACROSS each column with whatever’s there
AB AB AB AB
ab AaBb AaBb AaBb AaBb
ab AaBb AaBb AaBb AaBb
ab AaBb AaBb AaBb AaBb
ab AaBb AaBb AaBb AaBb
AB AB AB AB
ab A B A B A B A B
ab A B A B A B A B
ab A B A B A B A B
ab A B A B A B A B
Solving a DihybridDetermine Genotype Ratios
record all genotypes you havecount and record number of each genotype
AaBb: 16/16[or 100%]
AB AB AB AB
ab AaBb AaBb AaBb AaBb
ab AaBb AaBb AaBb AaBb
ab AaBb AaBb AaBb AaBb
ab AaBb AaBb AaBb AaBb
Solving a DihybridDetermine Phenotype Ratios
count how many of each phenotype you have
record # of phenotypes represented
purple, round: 16/16[or 100%]
AB AB AB AB
ab AaBb AaBb AaBb AaBb
ab AaBb AaBb AaBb AaBb
ab AaBb AaBb AaBb AaBb
ab AaBb AaBb AaBb AaBb
Solving a Dihybrid #2Determine the genotypes of each parent
Given to you, or you have to solve for them
Given – both parents are heterozygous for both traits.
Given: Parent #1 QqRrGiven: Parent #2 QqRr
Solving a DihybridCreate your dihybrid cross [4x4]
Solving a DihybridDetermine Gametes:
pair first allele of first trait with first allele of second trait
Q q R r
first gamete = QR
Solving a DihybridDetermine Gametes:
pair first allele of first trait with second allele of second trait
Q q R r
second gamete = Qr
Solving a DihybridDetermine Gametes:
pair second allele of first trait with first allele of second trait
Q q R r
third gamete = qR
Solving a DihybridDetermine Gametes:
pair second allele of first trait with second allele of second trait
Q q R r
fourth gamete = qr
Solving a DihybridLabel cross w/ parent gametes above / to left
QR Qr qR qr
QR
Qr
qR
qr
Solving a DihybridFill in boxes:
fill DOWN each column w/ whatever’s there
QR Qr qR qr
QR Q R Q r qR q r
Qr Q R Q r qR q r
qR Q R Q r qR q r
qr Q R Q r qR q r
Solving a DihybridFill in boxes:
fill ACROSS each column with whatever’s there
QR Qr qR qr
QR Q R Q r qR q r
Qr Q R Q r qR q r
qR Q R Q r qR q r
qr Q R Q r qR q r
QR Qr qR qr
QR QQRR QQRr QqRR QqRr
Qr QQRr QQrr QqRr Qqrr
qR QqRR QqRr qqRR qqRr
qr QqRr Qqrr qqRr qqrr
Solving a DihybridDetermine Genotype Ratios
record all genotypes you havecount and record number of each genotype
[not going to make you do it for this one..just know how to]
QR Qr qR qr
QR QQRR QQRr QqRR QqRr
Qr QQRr QQrr QqRr Qqrr
qR QqRR QqRr qqRR qqRr
qr QqRr Qqrr qqRr qqrr
Solving a DihybridDetermine Phenotype Ratios
count how many of each phenotype you have
record # of phenotypes represented
9/16 - purple, round3/16 - purple, wrinkled3/16 - white, round1/16 - white, wrinkled
QR Qr qR qr
QR QQRR QQRr QqRR QqRr
Qr QQRr QQrr QqRr Qqrr
qR QqRR QqRr qqRR qqRr
qr QqRr Qqrr qqRr qqrr