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Dihybrid Crosses and Different Patterns of Inheritance. Dominant/Recessive. when two different alleles are present, one is expressed (dominant) while the other is hidden (recessive). Dihybrid Cross Two Trait Punnett Squares. Dihybrid Cross Two Trait Punnett Squares. - PowerPoint PPT Presentation
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Dihybrid Crosses and Different Patterns of Inheritance
Dominant/Recessive Pattern• when two different alleles are present, one
is expressed (dominant) while the other is hidden (recessive)
Dihybrid CrossTwo Trait Punnett Squares
Dihybrid CrossTwo Trait Punnett Squares
• breeding that involves two unique traits– Seed Shape: R = round, r = wrinkled– Seed Color: Y = yellow, y = green
Dihybrid CrossTwo Trait Punnett Squares
Dihybrid CrossTwo Trait Punnett Squares
Dihybrid CrossTwo Trait Punnett Squares
Dihybrid Example• A plant that is heterozygous for seed shape
(Rr) and heterozygous for seed color (Yy) is self-pollinated. What will the genotypic and phenotypic ratios be of the offspring?
Dihybrid Example
Dihybrid Example
RY Ry rY ry
RY
Ry
rY
ry
Dihybrid Example
RY Ry rY ry
RY RRYY RRYy RrYY RrYy
Ry RRYy RRyy RrYy Rryy
rY RrYY RrYy rrYY rrYy
ry RrYy Rryy rrYy rryy
Dihybrid Example
• Genotypic Ratio:– 1 RRYY : 2 RRYy : 1 RRyy : 2 RrYY : 4 RrYy :
2 Rryy : 1 rrYY : 2 rrYy : 1 rryy• Phenotypic Ratio:
– 9 Round & Yellow : 3 Round & Green : 3 Wrinkled & Yellow : 1 Wrinkled & Green
Incomplete dominance• a condition in which a heterozygous
individual appears in-between two different phenotypes– neither allele is completely dominant
• two alleles resulting in three phenotypes
Incomplete dominance• heterozygous individuals have a phenotype
somewhere in the middle of the two alleles• Example in humans
– a straight-haired parent and a curly-haired parent will produce a wavy-haired child
• use an apostrophe (’) or superscript letters to indicate different alleles– S = straight, S’ = curly
• SS = straight, SS’ = wavy, S’S’ = curly
Incomplete dominance
Codominance• two alleles are expressed at the same time• Example in humans
– ABO blood type in humans
Codominance in Shorthorn Cattle
CWCW
CWCR
CRCR
Codominance in Camellia Flowers
CWCW
CWCP
CPCP
Codominance• use superscript letters to show
different alleles–CW = white, CR = red
• CWCW = white, CRCR = red, CWCR = roan
Multiple alleles• genes with 3 or more alleles possible for the
same character• Example in humans
– ABO blood type in humans
Multiple Alleles & Codominance
Multiple alleles• use capital and lowercase letters
and/or superscript letters to show different alleles–TA = __________, TB = __________,
t = __________• TATA = __________, TAt = __________,
TBTB = __________, TBt = __________,
TATB = __________, tt = __________
Multiple alleles• use capital and lowercase letters
and/or superscript letters to show different alleles–TA = type A blood, TB = __________,
t = __________• TATA = __________, TAt = __________,
TBTB = __________, TBt = __________,
TATB = __________, tt = __________
Multiple alleles• use capital and lowercase letters
and/or superscript letters to show different alleles–TA = type A blood, TB = type B blood, t
= __________• TATA = __________, TAt = __________,
TBTB = __________, TBt = __________,
TATB = __________, tt = __________
Multiple alleles• use capital and lowercase letters
and/or superscript letters to show different alleles–TA = type A blood, TB = type B blood, t
= type O blood• TATA = __________, TAt = __________,
TBTB = __________, TBt = __________,
TATB = __________, tt = __________
Multiple alleles• use capital and lowercase letters
and/or superscript letters to show different alleles–TA = type A blood, TB = type B blood, t
= type O blood• TATA = type A blood, TAt = __________,
TBTB = __________, TBt = __________,
TATB = __________, tt = __________
Multiple alleles• use capital and lowercase letters
and/or superscript letters to show different alleles–TA = type A blood, TB = type B blood, t
= type O blood• TATA = type A blood, TAt = type A blood,
TBTB = __________, TBt = __________,
TATB = __________, tt = __________
Multiple alleles• use capital and lowercase letters
and/or superscript letters to show different alleles–TA = type A blood, TB = type B blood, t
= type O blood• TATA = type A blood, TAt = type A blood,
TBTB = type B blood, TBt = __________,
TATB = __________, tt = __________
Multiple alleles• use capital and lowercase letters
and/or superscript letters to show different alleles–TA = type A blood, TB = type B blood, t
= type O blood• TATA = type A blood, TAt = type A blood,
TBTB = type B blood, TBt = type B blood,
TATB = __________, tt = __________
Multiple alleles• use capital and lowercase letters
and/or superscript letters to show different alleles–TA = type A blood, TB = type B blood, t
= type O blood• TATA = type A blood, TAt = type A blood,
TBTB = type B blood, TBt = type B blood,
TATB = type AB blood, tt = __________
Multiple alleles• use capital and lowercase letters
and/or superscript letters to show different alleles–TA = type A blood, TB = type B blood, t
= type O blood• TATA = type A blood, TAt = type A blood,
TBTB = type B blood, TBt = type B blood,
TATB = type AB blood, tt = type O blood
Sex-linked• a trait that is determined by a gene found
on one of the sex chromosomes– many traits are located only on the X
chromosome
Sex-linked• leads to many recessive characteristics
being common in males– males only have one copy of the X chromosome
• Examples in humans– colorblindness, hemophilia (bleeder’s disease)
Sex-linked• must use sex chromosomes as part of
Punnett Square allele identification– Ex: XN = X chromosome with a normal gene,
Xn = X chromosome with a colorblind gene, Y = no gene
Polygenic Inheritance• several genes
influencing one character
• Example in humans:– height, weight, hair
color, and skin color• won’t use a Punnett
Square with this type of inheritance
Environmental influences• conditions around organisms also influence
their phenotype
Environmental influences
Environmental influences
Environmental influences• Examples in humans:
– height and weight are influenced by nutrition