Very Short Answer Question. What is crossing over? - Biology

Short Note

Very Short Answer Question.

What is crossing over?



  1. Crossing over is a process that produces new combinations (recombinations) of genes by interchanging and exchanging of corresponding segments between non-sister chromatids of homologous chromosomes.
  2. It occurs during pachytene of prophase I of meiosis.
  3. The mechanism of crossing over consists of four sequential steps such as synapsis, tetrad formation, crossing over, and terminalisation.
  4. The phenomenon of crossing over is universal and it is necessary for the natural selection because it increases the chances of variation.
  Is there an error in this question or solution?
Chapter 3: Inheritance and Variation - Exercises [Page 68]


Balbharati Biology 12th Standard HSC for Maharashtra State Board
Chapter 3 Inheritance and Variation
Exercises | Q 2.4 | Page 68

Video TutorialsVIEW ALL [1]


Which of the following is NOT an example of connecting link?

  1. Archaeopteryx
  2. fchthyostegia
  3. Seymouria
  4. Biston betularia

What is criss-cross inheritance?

Linkage and crossing-over of genes are alternatives of each other. Justify with the help of an example.

Define Linkage.

Define the following:

test cross.

A cross between a normal couple resulted in a son who was haemophilic and a normal daughter. In course of time, when the daughter was married to a normal man, to their surprise, the grandson was also haemophilic.
(a) Represent this cross in the form of a pedigree chart. Give the genotypes of the daughter and her husband.
(b) Write the conclusion you draw of the inheritance pattern of this disease.

Define complete linkage. Give an example of a cross, showing complete linkage.

Answer the following question.
British geneticist R.C. Punnett developed a graphical representation of a genetic cross called “Punnett Square”. Mention the possible result this representation predicts of the genetic cross carried.

Very Short Answer Question.

Give one example of complete sex linkage?

What is a linkage? How many linkage groups do occur in human being?

Give an example of complete linkage.

How many linkage groups are present in Drosophila melanogaster?

Write a note on sex linkage.

Give detail account of sex-linked inheritance.

______ results in separation of linkage groups during meiosis.

Which of the following refers to tendency of genes to inherit together?

What was Morgan's observation when he hybridized yellow bodied white eyed female Drosophila to brown bodied red eyed male Drosophila and inter-crossed their progeny?

Analyse the following statements with respect to complete sex linkage and select the correct option.

  1. It is exhibited by genes located on non-homologous regions of X and Y chromosomes
  2. Y-linked trait is hypertrichosis.
  3. X-linked traits are haemophilia, red-green colour blindness, myopia (near sightedness).

The genetic map distance between two genes located on the same chromosome can be analyzed by calculating ____________.

The phenomenon of ____________ is universal and it is necessary for the natural selection, because it increases the chances of variation.

The number of linkage groups of a particular species corresponds to its ______ number of chromosomes.

Linkage reduces the frequency of ______.

Which of the following will not result in variations among siblings?

Crossing over in diploid organism is responsible for ______.

A and B genes are linked. What shall be the genotype of progeny in a cross between AB/ab and ab/ab?

Mr. Kapoor has Bb autosomal gene pair and d allele sex-linked. What shall be proportion of Bd in sperms?

What will be the distribution of phenotypic features in the first filial generation after a cross between a homozygous female and a heterozygous male for a single locus?

Mendal formulated the law of purity of gametes on the basis of ______.

What is true about the crossing over between linked genes?

From a cross AABb x aaBb, the genotypes AaBB : AaBb : Aabb will be obtained in the ratio ______.

The percent crossing over is high when ______.

Linkage groups can be separated during ______ in meiosis.

When the parental gene combine with itself; termed as

The strength of linkage between two genes is ______.

Which of the following statement is correct?

The enzyme involved in the process of crossing over is ______.


      Forgot password?
Use app×