Practice Problems 1. In tomatoes, tall is dominant and short is recessive. Red f

Question

Practice Problems 1. In tomatoes, tall is dominant and short is recessive. Red fruit is dominant and yellow fruit is recessive. What is the genotype of a Choose a key for height plant heterozygous for both traits? for color of fruit What are the possble gametes for this plant? 2. Using words, what are the Ilikely parental genotypes if the results of a two-trait problem are 1:1:1:1 among the offspring? 3. In horses, black (B) and a trotting gait (T) are dominant, while brown (b) and a pacing gait (t) are recessive. If a black trotter (homozygous for both traits) is mated to a brown pacer, what phenotypic ratio is expected among the ofspring? ratio is expected among the offspring? 4. Two black trotters have a brown pacer offspring. What is the genotype of all horses involved? black trotter parents brown pacer offspring 5. The phenotypic ratio among the offspring for two corn plants producing purple and smooth kernels is 9:3:3:1. (See lab for the key.) What is the genotype of these plants? parental plants the 9 offspring the 1 offspring? 3 of the offspring the other 3 and 84 Laboratory 20 Patterns of Inheritance

Explanation / Answer

Dominant Allele for height : H

Recessive allele for height : h

Dominant allele for fruit color : R

Recessive allele for fruit color : r

Genotype of plant heterozygous for both traits: HhRr

Gametes: HR, Hr, Hr, hr

One is heterozygous and other is recessive

HhRr x hhrr

100 % black trotter

Genotype of black trotter horses : BBTT, BBTt, BbTT, BbTt, BBTt, BbTt, BbTT, bBTt, bBTt.

Genotype of brown pacer horse: bbtt.

Lets denote dominant allel for purple by P and recessive by p

Similarly, dominant allele can be represent by S and recessive by s

Genotype of parental plants : PpSs

9: PPSS, PPSs, PpSS, PpSs, PPSs, PpSs, PpSS, pPSs, pPsS

3: PPss, Ppss, pPss

3: ppSS, PPSs, ppsS

1: ppss

ggLl X Ggll (yes)

GGLI X ggLI (no)

GGLL X ggll (no)

To get heterozygosity in both traits atleast one parent should be heterozygous

The gametes produced by GgLl : GL, Gl, gl, gL

Gametes produced by Ggll : Gl, Gl, gl, gl

Genotypes produced:

Cross one : AABB X AABB

Cross two : aabb x aabb

Parents: eeGG X EEgg

Offsprings: EeGg

20.3 X linked crosses

Phenotypic ratio:

2 red females : 1 red male : 1 white male

Genotype of white eyed male (XrY) and gametes (Xr , Y)

Genotype of white eyed female (Xr Xr) and gametes (Xr , Xr)

Genotype of red eyed male (XRY) and gametes (XR , Y)

Genotype of homozygous red eyed female (XRXR) and gametes (XR , XR)

Genotype of heterozygous red eyed female (XRXr) and gametes (XR, Xr)

Phenotypic ratio

1 red eyed female : 1 white eyed female : 2 white eyed male

White eyed males inherit allele for white from their mother. This is due to the reason father produces only one X chromosome while mother produces two X chromosomes.

2 bar eyed female : 2 non-bar eyed male

                  2 bar eyed female : I non-bar eyed male : 1 bar eyed male

                  1 non-bar eyed female : 1 bar eyed female : 1 non-bar eyed male : 1 bar eyed male

                  6)

                  Genotype of father : XrY

                  Genotype of mother : XrXR or XrXr

                   

                    7)

                 Genotype of female parent: XrXr

                 Genotype of male parent: XRY

                 8)

                 Genotype of female: XRXR

                Genotype of male: XrY

              9)

          A cross between heterozygous red eyed female and white eyed male

           Offsprings: 1 red female, 1 white female, 1 red male, 1 white male

Laboratory review 20

10. XrY (male) ; XrXr (female)

11. No gender in F1 will have white eyes

12. Nothing. Father passes only Y chromosome to male offspring.

13. Heterozygous

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