Did You Know These About Science?

There are many things we don't know about science, So, today we are going to learn some of theme.

Q. How is variation produced in a species?

Ans. During meiosis, the exchange of genetic material between non-sister chromatids occurs resulting in new combinations. These combinations give rise to variation resulting in the evolution of species.

Q. Why is the first division of meiosis called a reductional division?

Ans. The first division of meiosis is called a reductional division because in this division the chromosome number is reduced to half.

Q. What are chromosomes?

Ans. The chromosomes are fine thread-like structures found in the nucleus of both plant and animal cells.

Q. What is a gene?

Ans. A gene is a unit of heredity composed of DNA.

Q. What are the two forms of genes known as?

Ans. The two forms of genes are called alleles.

Q. Why do gametes have a haploid number of chromosomes?

Ans. Gametes have a haploid number of chromosomes in order to maintain the 2n chromosome of the diploid zygote when they fuse together to form the zygote.

Q. Name the cell division that takes place during gametogenesis. What is its significance?

Ans. Meiosis occurs during gametogenesis. Its significance is that it helps to restore the number of chromosomes of the species.

Q. What are the two divisions that follow during cell division?

Ans. Karyokinesis and cytokinesis.

Q. How many meiotic divisions are necessary to produce 100 pollen grains?

Ans. 25 meiotic divisions. 

Q. Why is variation seen in progeny?

Ans. The exchange of the chromosome material during crossing over provides innumerable recombinations because of which the offsprings of the same parents however similar are different from each other in some respects. The variations are one of the important causes of evolution.

Q. What is the difference between monohybrid and dihybrid cross (Phenotypic ratio)? (2011)

Ans. Monohybrid phenotypic ratio = 3:1

Dihybrid phenotypic ratio = 9:3:3:1

Q. What are autosomes?

Ans. The chromosomes that do not have genes for sex determination are called autosomes.

Q. What is a phenotype?

Ans. The observable characteristics of an organism that are genetically controlled are called the phenotype.

Q. Define variations.

Ans. The differences which occur in closely related organisms are called variations.

Q. If a colorblind man marries a woman with normal vision, what will be the nature of their children?

Ans. Their daughter will be a carrier of color blindness but their son will have normal vision.

Q. What is the name of the disorder caused by humans due to chromosome mutation?

Ans. It is Downs's syndrome.

Q. What is a pure strain and how it is different from a hybrid strain?

Ans. The self-pollinated progeny of a homozygous plant is a pure strain while the offspring of genetically dissimilar parents is a hybrid strain. These offsprings are obtained by artificial pollination.