MCQ’S ON LINKAGE AND CROSSING OVER
1. Crossing over takes place in the
(a) Diakinesis stage
(b) Anaphase stage
(c) Pachytene stage
(d) Leptotene stage
Answer: (c)
2. There are 4 pairs of chromosomes in a Drosophila. The linkage groups present in it are
(a) one more than the pair of chromosomes
(b) one less than the pair of chromosomes
(c) four
(d) eight
Answer: (c)
3. Percentage of crossing over is more when
(a) genes are located in a different cell
(b) genes are not linked
(c) linked genes are located close to each other
(d) linked genes are located far apart from each other
Answer: (d)
4. If the percentage of crossing over between two genes is 10, then the distance between two genes will be
(a) 5 morganoid
(b) 10 centimorgans
(c) 20 centimorgans
(d) 40 map units
Answer: (b)
5. Alleles of different genes that are on the same chromosome can occasionally be separated by a phenomenon called
(a) crossing over
(b) continuous variation
(c) epistasis
(d) pleiotropy
Answer: (a)
6. Repulsion and coupling are two faces of
(a) mutation
(b) chiasmata
(c) linkage
(d) crossing over
Answer: (c)
7. If gene frequency between genes a and c is 2%; b and c is 13%; b and d 4%; a and b 15%; c and d 17 and a and d 19%. The sequence of genes in a chromosome is
(a) a,d,b,c
(b) d,b,a,c
(c) a,b,c,d
(d) a,c,b,d
Answer: (d)
8. This is the reason why Mendel did not recognize linkage phenomenon in his experiments
(a) he studied only pure plants
(b) he did not have a powerful microscope
(c) characters he studied were situated on different chromosomes
(d) many chromosomes to handle
Answer: (c)
9. In a linear chromosome map distance between 4 loci is as follows a-b is 10%, a-d is 3%, b-c is 4% and a-c is 6%. The crossover frequency between c and d is
(a) 4-12%
(b) 3-6%
(c) 9%
(d) 3%
Answer: (d)
10. Where does this evidence come from? – crossing over takes place at a four-stranded stage and not at two stranded stages of chromosomes.
(a) studies on linkage maps of chromosomes in Drosophila
(b) studies of meiosis in maize
(c) 4:4 organization of ascospores in Neurospora
(d) 2:2:2:2 organization of ascospores in Neurospora
Answer: (d)
11. Crossing over occurs between
(a) Non-sister chromatids of non-homologous chromosome at zygotene stage of prophase-I
(b) Non-sister chromatids of homologous chromosome at pachytene stage of prophase-I
(c) Non-sister chromatids of non-homologous chromosomes at pachytene stage of prophase I
(d) Non-sister chromatids of homologous chromosome at zygotene stage of prophase I
Answer: (b)
