Punnett Squares Dihybrid Cross
6F: Students will predict possible outcomes of genetic combinations such as monohybrid crosses, dihybrid crosses, and non-mendelian inheritance TEKS
Each parent has TWO traits (4 alleles, 2 for each trait) Example: AaBb So each parent can give either a dominant or recessive allele for the first trait (A or a) and a dominant or recessive allele for the second trait (B or b) Determination of Gametes
This leads to 4 possible gametes (2 n ) for each parent Determination of Gametes
This leads to 4 possible gametes (2 n ) for each parent AB: dominant for both traits Determination of Gametes
This leads to 4 possible gametes (2 n ) for each parent AB: dominant for both traits Ab: dominant for trait #1, recessive for trait #2 Determination of Gametes
This leads to 4 possible gametes (2 n ) for each parent AB: dominant for both traits Ab: dominant for trait #1, recessive for trait #2 ab: recessive for trait #1, dominant for trait #2 Determination of Gametes
This leads to 4 possible gametes (2 n ) for each parent AB: dominant for both traits Ab: dominant for trait #1, recessive for trait #2 ab: recessive for trait #1, dominant for trait #2 ab: recessive for both traits Determination of Gametes
Branching Method Determination of Gametes
FOIL Method First Outer Inner Last Determination of Gametes
Dihybrid Punnett Square
Dihybrid Punnett Square
Dihybrid Punnett Square
Dihybrid Punnett Square
Dihybrid Punnett Square
A cross with two heterozygous parents always gives the same phenotypic ratio Determining Probability
A cross with two heterozygous parents always gives the same phenotypic ratio Both dominant: 9/16 Determining Probability
A cross with two heterozygous parents always gives the same phenotypic ratio Both dominant: 9/16 1 st dom; 2 nd rec: 3/16 Determining Probability
A cross with two heterozygous parents always gives the same phenotypic ratio Both dominant: 9/16 1 st dom; 2 nd rec: 3/16 1 st rec; 2 nd dom: 3/16 Determining Probability
A cross with two heterozygous parents always gives the same phenotypic ratio Both dominant: 9/16 1 st dom; 2 nd rec: 3/16 1 st rec; 2 nd dom: 3/16 Both recessive: 1/16 Determining Probability
A cross with two heterozygous parents always gives the same phenotypic ratio Both dominant: 9/16 1 st dom; 2 nd rec: 3/16 1 st rec; 2 nd dom: 3/16 Both recessive: 1/16 9:3:3:1 Determining Probability
Due to independent assortment, there is another way to determine probability The probability of two events occurring together is the product of their individual probabilities (ie: multiply the two probabilities together) Example: the odds of flipping two heads in a row on a coin toss is ½ x ½ = ¼ Another Way
If you breed two plants that are both heterozygous for being tall and yielding red flowers, what are the chances of getting an offspring that is tall and white? Tall is dominant to short Red flowers are dominant to white flowers Another Way An Example
If you breed two plants that are both heterozygous for being tall and yielding red flowers, what are the chances of getting an offspring that is tall and white? Tall is dominant to short T = tall t = short Red flowers are dominant to white flowers Another Way An Example
If you breed two plants that are both heterozygous for being tall and yielding red flowers, what are the chances of getting an offspring that is tall and white? Tall is dominant to short T = tall t = short Red flowers are dominant to white flowers R = red r = white Another Way An Example
If you breed two plants that are both heterozygous for being tall and yielding red flowers, what are the chances of getting an offspring that is tall and white? Red flowers are dominant to white flowers Tall is dominant to short Parent 1: Parent 2: Another Way An Example
If you breed two plants that are both heterozygous for being tall and yielding red flowers, what are the chances of getting an offspring that is tall and white? Red flowers are dominant to white flowers Tall is dominant to short Parent 1: Tt Parent 2: Another Way An Example
If you breed two plants that are both heterozygous for being tall and yielding red flowers, what are the chances of getting an offspring that is tall and white? Red flowers are dominant to white flowers Tall is dominant to short Parent 1: TtRr Parent 2: Another Way An Example
If you breed two plants that are both heterozygous for being tall and yielding red flowers, what are the chances of getting an offspring that is tall and white? Red flowers are dominant to white flowers Tall is dominant to short Parent 1: TtRr Parent 2: Tt Another Way An Example
If you breed two plants that are both heterozygous for being tall and yielding red flowers, what are the chances of getting an offspring that is tall and white? Red flowers are dominant to white flowers Tall is dominant to short Parent 1: TtRr Parent 2: TtRr Another Way An Example
Parent 1: TtRr Parent 2: TtRr Another Way An Example
Parent 1: TtRr Parent 2: TtRr Another Way An Example
Parent 1: TtRr Parent 2: TtRr Another Way An Example
Parent 1: TtRr Parent 2: TtRr Another Way An Example
Parent 1: TtRr Parent 2: TtRr Another Way An Example
Parent 1: TtRr Parent 2: TtRr Another Way An Example
Parent 1: TtRr Parent 2: TtRr Probability of tall: ¾ Another Way An Example
Parent 1: TtRr Parent 2: TtRr Probability of tall: ¾ Probability of white: ¼ Another Way An Example
Parent 1: TtRr Parent 2: TtRr Probability of tall: ¾ Probability of white: ¼ Probability of tall AND white: ¾ X ¼ = 3/16 = 18.75% Another Way An Example
Parent Cross: TtRr X TtRr Probability of tall AND white (T-rr) offspring? Compare
Parent Cross: TtRr X TtRr Probability of tall AND white (T-rr) offspring? Compare