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Two-character genetic inheritance (problems solved). (Page 11)

Genetics problem 79

In a tropical variety of pepper, white flowers and large fruit are dominant characters (alleles B and G) compared to yellow flowers and small fruit. What phenotypic offspring will be obtained in F2 from a cross between a plant with a white flower and large fruit and another with a yellow flower and small fruit, if both are homozygous for the two characters? What is the probability of obtaining a diheterozygous plant from  parental plants of BbGg and bbGg genotypes?

Genetics problem 80

Two pure lines of chickens are crossed, one with brown feathers (B) and a serrated crest (a) with another with white feathers (b) and a rosette crest (A), the brown and rosette characters being dominant over the white and in saw. What is the probability of having white plumage and rosette crest hens in the second generation F2?

Genetics problem 81

In pumpkin, the white color of the fruit is due to the dominant allele (B), and the yellow color to the recessive allele  (b). A dominant allele at another locus is responsible for the disk shape of the fruit (F), and  its recessive allele (f) is responsible for the spherical shape. If we cross a disk-shaped white homozygous variety  (BBFF) with a spherical-shaped yellow homozygous variety (bbff)  in F1 all the offspring are (BbFf). What phenotypic ratios are expected in F2?

Genetics problem 82

The fruit of the watermelon can be smooth or striped, and elongated or flattened. A homozygous plant with smooth and elongated fruit is crossed with another homozygous plant with striped and flattened fruit. The F1 is smooth and flattened fruit. In F2, the following are obtained: 9 of smooth and flattened fruit, 3 of striped and flattened fruit, 3 of smooth and elongated fruit and 1 of elongated and striped fruit.

a) Indicates how many pairs of characters are involved in this inheritance.

b) What are the dominant factors and why?

Geneticz problem 83

In mice, a dominant allele (B) determines black hair color and a recessive allele (b) determines white hair. On the other hand, a dominant allele (L) determines the long tail while another recessive (l) determines the short tail. Both genes are found in autosomes. A dihybrid mouse with black hair and long tail is crossed with a female with white hair and short tail.

a. Indicate the genotypes of the mice in the cross.

b. What are the genotypes and phenotypes obtained in F1?

c. In what proportion will these genotypes and phenotypes occur in F1?

Genetics problem 84

The red color of the tomato pulp depends on the presence of a dominant R factor over its r allele for yellow. The normal size of the plant is due to a dominant N gene over the dwarf size n.
A plant with red pulp and normal size is crossed with another yellow and normal one and the following are obtained:30
normal red plants, 31 normal yellow, 9 dwarf red and 10 dwarf yellow.

a. What are the genotypes of the plants that are crossed? Check the result by crossing.
b. What are the genotypes of the offspring?

Genetics problem 85

In the mouse, curly hair (R) dominates over straight hair (r), and black hair (N) dominates white hair (n). We crossed a mouse with curly hair and black color with another with smooth hair and white color, both homozygous for these characters. Indicate:

a) What will be the genotypic and phenotypic ratios of F1 and F2? (1,5)
b) What proportion of individuals with curly hair and black color can be expected to be homozygous for both characters? (0.4)
c) Define the terms autosome, sex-linked inheritance, and independent characters. (0.6)

Genetics problem 86

The white color of certain herbivores is an autosomal recessive trait and the split claw is an X-linked recessive trait. A white male with entire hoof is crossed with a dark-colored female whose father was white and hoofed divided, and whose mother was split-hoofed. 

Determine the genotypes of the animals that are crossed, and the genotype and phenotypic frequencies of their offspring. (Use N and n for the color and E and e for the hoof shape). (1 point)

Genetics problem 87

Two heritable conditions in man, cataracts and brittle bones, are due to dominant alleles. A man with cataracts and brittle bones, whose father had normal eyes and bones, married a woman without cataracts and brittle bones, whose father had normal bones. Please indicate:

a) the genotypes of the parents;

b) the genotypic and phenotypic proportions of their offspring.

Genetics problem 88

In tomato, the red color of the fruit is dominant (R) over the yellow color (r) and the biloculated form (B) dominates over the multiloculated (b). If it is desired to obtain a line of plants of red and multiloculated fruits from the cross between pure red and biloculated races with yellow and multiloculated races, what proportions of the F2 will have the desired phenotype? What proportions of this will be homozygous for the two characters? (1 point)