# Dihybrid Crosses Unit 4 – Lecture 6.

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Dihybrid Crosses Unit 4 – Lecture 6

Dihybrid Cross a 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 Dihybrid Determine the genotypes of each parent
Given to you, or you have to solve for them Given: Parent #1 AABB Given: Parent #2 aabb

Solving a Dihybrid Create your dihybrid cross [4x4]

Solving a Dihybrid Determine Gametes:
pair first allele of first trait with first allele of second trait A A B B first gamete = AB

Solving a Dihybrid Determine Gametes:
pair first allele of first trait with second allele of second trait A A B B second gamete = AB

Solving a Dihybrid Determine Gametes:
pair second allele of first trait with first allele of second trait A A B B third gamete = AB

Solving a Dihybrid Determine Gametes:
pair second allele of first trait with second allele of second trait A A B B fourth gamete = AB

Solving a Dihybrid Determine Gametes:
pair first allele of first trait with first allele of second trait a a b b first gamete = ab

Solving a Dihybrid Determine Gametes:
pair first allele of first trait with second allele of second trait a a b b second gamete = ab

Solving a Dihybrid Determine Gametes:
pair second allele of first trait with first allele of second trait a a b b third gamete = ab

Solving a Dihybrid Determine Gametes:
pair second allele of first trait with second allele of second trait a a b b fourth gamete = ab

Solving a Dihybrid Label cross w/ parent gametes above / to left AB ab

Solving a Dihybrid Fill in boxes:
fill DOWN each column w/ whatever’s there AB ab AB ab A B

Solving a Dihybrid Fill in boxes:
fill ACROSS each column with whatever’s there AB ab A B AB ab AaBb

Solving a Dihybrid Determine Genotype Ratios
record all genotypes you have count and record number of each genotype AaBb: 16/16 [or 100%] AB ab AaBb

Solving a Dihybrid Determine Phenotype Ratios
count how many of each phenotype you have record # of phenotypes represented purple, round: 16/16 [or 100%] AB ab AaBb

Solving a Dihybrid #2 Determine 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 QqRr Given: Parent #2 QqRr

Solving a Dihybrid Create your dihybrid cross [4x4]

Solving a Dihybrid Determine Gametes:
pair first allele of first trait with first allele of second trait Q q R r first gamete = QR

Solving a Dihybrid Determine Gametes:
pair first allele of first trait with second allele of second trait Q q R r second gamete = Qr

Solving a Dihybrid Determine Gametes:
pair second allele of first trait with first allele of second trait Q q R r third gamete = qR

Solving a Dihybrid Determine Gametes:
pair second allele of first trait with second allele of second trait Q q R r fourth gamete = qr

Solving a Dihybrid Label cross w/ parent gametes above / to left QR Qr

Solving a Dihybrid Fill in boxes: Q R Q r q r
fill DOWN each column w/ whatever’s there QR Qr qR qr Q R Q r q r

Solving a Dihybrid Fill in boxes: QQRR QQRr QqRR QqRr QQrr Qqrr qqRR
fill ACROSS each column with whatever’s there QR Qr qR qr QQRR QQRr QqRR QqRr QQrr Qqrr qqRR qqRr qqrr QR Qr qR qr Q R Q r q r

Solving a Dihybrid Determine Genotype Ratios
record all genotypes you have count and record number of each genotype [not going to make you do it for this one.. just know how to] QR Qr qR qr QQRR QQRr QqRR QqRr QQrr Qqrr qqRR qqRr qqrr

Solving a Dihybrid Determine Phenotype Ratios
count how many of each phenotype you have record # of phenotypes represented 9/16 - purple, round 3/16 - purple, wrinkled 3/16 - white, round 1/16 - white, wrinkled QR Qr qR qr QQRR QQRr QqRR QqRr QQrr Qqrr qqRR qqRr qqrr