# DBT JRF 2020 — Question 146

Exam: DBT JRF 2020 · Section: B · Topic: Genetics · Difficulty: Hard

## Question

How many linkage groups would be there in a plant with 2n = 20?

## Options

- **A.** 5
- **B.** 40
- **C.** 10
- **D.** 20

## Answer

Option C

## Explanation

Linkage groups = chromosomes. Each chromosome constitutes one linkage group (all genes on the same chromosome are linked, albeit with variable recombination between distant genes). The number of linkage groups = the HAPLOID chromosome number ( $n$ ), because each linkage group is one chromosome, and there are $n$ different chromosomes. For a plant with $2n = 20$ : haploid number $n = \dfrac{20}{2} = 10$ . Therefore there are 10 linkage groups. Classic example: Drosophila melanogaster has $2n = 8$ → 4 linkage groups (4 chromosomes); humans have $2n = 46$ → 23 linkage groups.

Source: https://mypyqbuddy.com/questions/how-many-linkage-groups-would-be-there-in-6a05a8a02adafec4702932aa