1. A student examining a stained root tip of a fern species noted that the a roo

Question

1. A student examining a stained root tip of a fern species noted that the a root cell contains a total of 36 chromosomes. In addition, these cells were diploid. Gender in this fern is not determined by sex chromosomes, rather a pheromone released by sexually mature individuals determines gender of young plants (i.e. in the presence of the pheromone, young individuals develop as ‘males’; in the absence of the pheromone, young individuals develop into hermaphrodites). How many linkage groups does the genome of this fern have?

a. 144

b. 72

c. 36

d. 18

e. This cannot be determined, for the number of genes in the genome is not given.

2. What phenotypic ratio is expected when a double heterozygote in the cis configuration is crossed with a double heterozygote in the trans configuration and the gene are tightly linked (i.e. exhibit complete linkage)?

a. 3:1

b. 1:1

c. 2:1:1

d. 1:1:1:1

e. 9:3:3:1 3.

Explanation / Answer

Answer:

1) d. 18

Explanation : Number of linkage group is equal to total number of haploid chromosomes

2n=36 therefore n=18

2) a. 3:1

Explanation :A dihybrid cross of linked genes theoretically gives a phenotypic ratio of . 3:1.

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