BIOC15H3 Lecture Notes - Lecture 5: Dihybrid Cross, Genotype, Lentil

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30 Sep 2016

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F2: genotypic ratio - 1[aa]: 2[aa]: 1[aa, phenotypic ratio. [aabb (1/16); aabb (2/16); aabb (2/16); aabb (4/16)] 9:3:3:1 phenotypic ratio: if 2 genes are sorting independently, & 2 gene"s products give 2 different traits, & genes do not interact, Fact: phenotypic ratio can be affected by whether or not 2 genes studied affect 2 different traits or work together to find 1 trait. Looking at dihybrid crosses more systematically for situation where 2 genes are affecting the same trait. Looking at impact of gene interaction on phenotypic ratios & number of different phenotypes observed. Assuming on gene interaction: [not always the case in nature] Many traits are multi-factorial [affected by more than 1 gene] Multi-factorial inheritance [involves more than 1 gene] is different from multiple alleles [of same 1 gene] Multiple genes affecting same trait are different genes that influence 1 trait [1 phenotype]

Related Questions

Please show work! thanks

6. Brown hair (A) is dominant over blond hair (a), and browneyes (B) are dominant over blueeyes (b).

6a. Using a single dihybrid Punnett Square show a

ll the possible genotypes of the offspring from a

father with the genotype AaBb and a mother with the genotypeAaBB.

6b. What is the expected phenotypic ratio of the F1offspring?

7. ANSWER THE FOLLOWING QUESTIONS USING THE RULES OFPROBABILITY

7a. In the cross AaBb x AaBb what proportion of the F1 areexpected to have the genotype AAbb?

7b. In the cross AaBb x Aabb what proportion of the F1 areexpected to have the dominant phenotype for BOTH traits?

7c. In the cross AaBbCc x AabbCc what proportion of the F1 areexpected to have the genotype aa?

7d. In the cross AaBbCc x AabbCc what proportion of the F1 areexpected to have the genotype AabbCC?

8. A black and white mouse mate and have 8 healthy grey mice.What would be the expected

phenotypic ratio of the offspring resulting from two greyparents?

9. Bob has blood type A. Frank has blood type AB. Mary has bloodtype B. Mary's child

(Sabrina) has blood type O.

9a. If Mary and Frank have children would be the possible bloodtypes of their children?

9b. Which male (Bob or Frank) could possibly be the father ofSabrina?

10. Hemophilia is a recessive sex-linked human blood diseasethat leads to the failure of blood to clot

normally. What proportion of the sons are expected to havehemophilia if the mother is a carrier

and the father has hemophilia? What proportion of the daughterare expected to have

hemophilia?

yellowmanatee510

. In rye grass, seed color is a polygenic trait (additivemodel). If true-breeding red and white varieties are crossed, theF1 are intermediate in color. If the F1 are self-fertilized, about1 in 64 have white seeds. If the F1 are testcrossed, how manydifferent genotypic categories will be produced?

A. one

B. two

C. three

D. eight

E. 64

7. In rye grass, seed color is a polygenic trait (additivemodel). If true-breeding red and white varieties are crossed, theF1 are intermediate in color. If the F1 are self-fertilized, about1 in 64 have white seeds; approximately how many of the F2 shouldbe similar in color to the F1?

A. 1/64

B. 4/64

C. 6/64

D. 15/64

E. 20/64

8. A tall parent and a short parent produce intermediate F1offspring that, when self-fertilized, produce a range of offspringheights, some taller than the tall P1 and some shorter than theshort P1. Which set of parental genotypes could account for thesedata?

A. AABBCC x aabbcc

B. AABB x aabb

C. AABBcc x aabbC

D. AA x aa

E. AA x bb

9. Six additive loci control body weight in hamsters. Twoextreme strains are crossed; the F1 are interbred to produce theF2. An F2 crop of hamsters that covers the complete range ofweights (in a bell-shaped curve) is for sale. If a hamster costs $2to raise, what did it probably cost to produce this F2 crop?

A. $64

B. $2,048

C. $4,096

D. $8,192

E. $16,384 or more

10. Six additive loci control body weight in hamsters. Twoextreme strains are crossed; the F1 are interbred to produce theF2, which cover the complete range of weights (in a bell-shapedcurve). If each allele that contributes to hamster weight adds 5grams above a base weight of 100 grams, how much does the averageF2 hamster weigh?

A. 100 g

B. 105 g

C. 125 g

D. 130 g

E. 150 g

11. Long- and short-eared strains of corn are crossed to produceoffspring (F1) of intermediate ear length. When the offspring areself-fertilized, a wide range of ear lengths appears in theiroffspring (F2). About 1 in 1,000 of these F2 have ears as long asthe parental long-eared race. Given an additive model ofinheritance, how many loci are involved in ear length?

A. three

B. four

C. five

D. 6-10

E. >10

greenworm666

In rats, several independently assorting autosomal genes affectcoat color. Gene A controls the distribution of yellow pigment inhair, and gene B causes black pigmentation. The two genes interactas follows: AâBâ (gray), Aâbb (yellow), aaBâ (black), and aabb(cream). These genotypes are only expressed in the presence of thedominant allele of a third gene, C; rats with genotype cc arealbino.

a. Deduce the genotype of each albino mice, to the extent thatis possible, in the following table. Explain your answers.

True-breeding parents	F₁	F₂ offspring
Gray x albino-1	All gray	3/4 gray : 1/4 albino
Gray x albino-2	All gray	9/16 gray : 3/16 yellow : 4/16 albino

b. Deduce the genotype and phenotype of each parent in thefollowing table. Explain your answers.

Parents	Numbers of offspring
Cross 1	135 gray, 83 albino, 47 yellow, 44 black, 16 cream
Cross 2	103 albino, 74 black, 25 cream

c. A gray-colored rat is mated with one that is yellow. Theoffspring include an albino rat and a cream-colored rat. Diagramthis cross. Be sure to include the Punnett square and thephenotypic ratio in the offspring.

ivorysquirrel791

BIOC15H3 Lecture Notes - Lecture 5: Dihybrid Cross, Genotype, Lentil

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