TRANSITION Class 10th (Science)

1. What is meant by characteristics? It is the detail of appearance or behaviour; in other words, a particular form or a particular function. Example: Four limbs of human beings is a characteristic and that plant can perform photosynthesis is also a characteristic. 2. Who is known as the father of genetics? Gregor Johann Mendel is known as the father of genetics. 3. Define chromosome. Chromosome is a thread-like structure that bears genes and are enclosed within a nucleus. It is composed of DNA and protein. 4. Define variation. The occurrence of differences among the individuals of a species is called variation. 5. Define a gene. Gene is a segment of a DNA molecule which carries the code for the synthesis of a specific protein. 6. Define alleles. Genes which code for a pair of contrasting traits are known as alleles, i.e., they are the different forms of the same gene. 7. Write the expanded form of DNA. Deoxyribonucleic acid 8. Where is DNA found in a cell? [CBSE (AI) 20...

Why do all the gametes formed in human females have X chromosome?                    [NCERT Exemplar] Human females have two X chromosomes called sex chromosomes. During meiosis at the time of gamete formation, one X chromosome enters each gamete. Hence all the gametes possess an X chromosome. In human beings, the statistical probability of getting either a male or female child is 50 : 50. Give a suitable explanation. [NCERT Exemplar] The sex of an infant is determined by the type of sex chromosome contributed by the male gamete. Since the ratio of male gametes containing X chromosome and those containing Y chromosome is 50 : 50, the statistical probability of male or a female infant is also 50 : 50. Why did Mendel choose pea plant for his experiments?                       ...

1. Explain with reason why giraffe has long neck. According to Lamarck’s theory of use and disuse, giraffes had to stretch their necks and forelimbs for feeding on leaves of tall trees because of which these organs were elongated. But this theory has been completely discarded. It is now proposed that, the giraffe’s neck evolved with time because of ‘necking’ battle with time and natural selection. only giraffes with long necks survived. 2. Give the basic features of the mechanism of inheritance.                                        [NCERT Exemplar] (i) Characters are controlled by genes. (ii) Each gene controls one character. (iii) There may be two or more forms of gene. (iv) One form may be dominant over the other. (v) Genes are present on chromosomes. (vi) An individual has two forms...