Question

The diploid garden pea plant has 14 chromosomes. The haploid fungus Neurospora crassa has 7 chromosomes. Neither organism has separate male and female individuals. Therefore, the number of linkage groups in these two organisms is: (A) Garden pea has 14 linkage groups, and Neurospora has 7. (B) Garden pea has 7 linkage groups, and Neurospora has 7. (C) Garden pea has 8 linkage groups, and Neurospora has 8. (D) Garden pea has 15 linkage groups, and Neurospora has 8.

Answer 1

Answer:

(B) Garden pea has 7 linkage groups, and Neurospora has 7.

Explanation:

Number of linkage group is always equal to type of chromosomes. In garden pea which is a diploid organism, there are 7 linkage groups because the homologous chromosomes of a pair are alike so even though the total number of chromosomes are 14 yet no. of linkage group will be 7.

Here, it may also be noted that there is no separate male or female chromosomes i.e. no allosomic pair in this organism which are usually different for males and lead to the increase in linkage groups. For example in human males out of the 23 pairs, we have 23rd pair which leads to the increase in linkage groups as compared to number of diploid sets of chromosomes. In human males, 22 pairs of chromosomes are alike but the 23rd pair is different which has 1 X chromosome and 1 Y chromosome which leads to a total of 22+1+1 = 24 linkage groups. In contrast to this, human females have only 23 linkage groups because in females 23rd pair of chromosome is XX in which both the X chromosomes are alike so it does not lead to an increase in linkage groups.

Neurospora crassa has 7 haploid chromosomes so the type of chromosomes and total number of chromosomes both are 7. Since type of chromosomes are 7, the linkage groups will also be 7 in this organism.