Significance of Crossing Over

Q.

Define linkage.

Q. Two genes A and B present on same chromosome show $40\%$ recombination, then what will be the percentage of gamete $\left(aB\right)$ for the plant having genotype $AaBb$ in cis arrangement?

1. $40\%$
2. $70\%$
3. $20\%$
4. $15\%$

Q. During, meiosis-I, the bivalent chromosomes clearly appear as tetrads during:

1. Diakinesis
2. Diplotene
3. Leptotene
4. Pachytene

Q. If a double stranded DNA has $20\%$ Thymine, the percentage of Guanine in the DNA

1. $30\%$
2. $10\%$
3. $90\%$
4. $40\%$

Q. The exchange of corresponding parts between non-sister chromatids of homologous chromosomes producing a new combinations is called .

1. linkage
2. fusion
3. crossing over
4. conjugation

Q. What is crossing over? Give its significance.

Q. Explain two situations when Independent Assortment of genes occur, resulting in 50% recombination.

Q. What is the significance of crossing over?

Q. Which one of the following list contains the correct order of meiosis?

1. Separation of sister chromatids, recombination, formation of the synaptonemal complex, separation of homologous chromosomes
2. Separation of homologous chromosomes, formation of the synaptonemal complex, recombination, separation of sister chromatids
3. Formation of synaptonemal complex, recombination, separation of sister chromatids, separation of homologous chromosomes
4. Formation of the synaptonemal complex, recombination, separation of homologous chromosomes, separation of sister chromatids

Q. The function of crossing over is?

1. Segregation of alleles
2. Recombination of alleles
3. Segregation of chromosomes
4. Distribution of linked genes

Q. Who experimentally verified chromosomal theory of inheritance and proposed the term recombination?

1. Sturtevant
2. T.H. Morgan
3. Boveri
4. Sutton

Q.

Does recombination create variation?

Q. Blue eye colour is recessive to brown eye colour. A brown-eyed woman, whose father was blue-eyed marries a blue-eyed man. The children can be

1. Both blue and brown eyed in the ratio 1: 1
2. All brown eyed
3. All blue eyed
4. Both blue eyed and brown eyed in the ratio 3: 1

Q. Give an example of incomplete linkage.

Q. If a gene from haemolytic jaundice is dominant and 10% population carrying this gene develops disease then, what percentage of progeny from a marriage between heterozygous for haemolytic jaundice and normal individual suffers from this disease?

1. 50%
2. 5%
3. 10%
4. 1/5th

Q. A researcher was performing a cross between two individuals of a species to verify Mendel’s law of independent assortment experimentally, but every time he performs the experiment, he finds that some characters do not assort independently, this is due to

1. the crossing over between the genes
2. the linkage between the genes
3. the dominance of one trait over the other
4. the recombination between the genes

Q.

Do brothers and sisters have the same DNA?

Q. Assume that genes a and b are linked and show 40% recombination. If ++ / ++ individual is crossed with ab / ab, then types and proportions of gametes in $F_1$ will be :

1. ++ 20% : ab 20% : +b 20% : a + 40%
2. ++ 50% : ab 50%
3. ++ 25% : ab 25% : +b 25% : a + 25%
4. ++ 30% : ab 30% : +b 20% : a + 20%

Q. Two linked genes a and b show $20\%$ recombination. The individuals of a dihybrid cross between $+$ $+/+$ $+$ $\times$ ab/ab shall show gametes.

1. $++50:ab:50$
2. $++80:ab:20$
3. $++40:ab40:+a10+b:10$
4. $++30:ab30:+a20:+b:20$

Q. The diagram given below represents a certain phenomenon which occurs during meiosis, Name and explain the phenomenon by using the terms homologous chromosomes, chromatids, crossing over.

Q. Two heterozygous parents (AaBb) are crossed. If the two loci are completely linked (AB/ab), what would be the distribution of phenotypic features in resulting generation of test cross?

Q. Define centrioles.

Q. Crossing over that results in genetic recombination in higher organisms occurs between :-

1. Non-sister chromatids of a bivalent
2. Two daughter nuclei
3. Two different bivalents
4. Sister chromatids of a bivalents

Q. T.H. Morgan discovered that all the genes in Drosophila are linked to four pairs of linkage groups which correspond to 4 pairs of chromosomes. Sometimes, the linkage of some genes, present at some specific distance, is broken and they show independent assortment. The most plausible reason for break in the concept of linkage would be

1. Transposition
2. Recombination
3. Translocation
4. Sister-chromatid exchange

Q. Chromosomal theory of inheritance was based on

1. Segregation of genes
2. Diploidy and haploidy
3. Sex linkage
4. Presence of sex chromosomes

Q. Fruit colour in squash is an example of

1. Recessive epistasis
2. Dominant epistasis
3. Inhibitory genes
4. Complementary genes

Q. Phenomenon of crossing over in diploid organisms is responsible for

1. Recombination between linked genes
2. Linkage between genes
3. Segregation between genes
4. Dominance of gene

Q. The linkage map of X-chromosome of fruitfly has 66 units, with yellow body gene (y) at one end and bobbed hair (b) gene at the other end. The recombination frequency between these two genes (y and b) should be

1. < 50%
2. 100 %
3. 66%
4. >50 %

Q. How is variation bought in the progeny in the sexual reproductive organisms?

Q. Short / Long answer type questions
How do variations arise in sexually reproducing organisms? Explain very briefly.