Ans: The mechanism that establishes the sex of an individual as it begins life is called sex determination.
2. Make gametes a sperms are responsible for the birth of a baby boy, why?
Ans: It is because sperms contain both the X as well as Y chromosomes and Y chromosome is essential to form a male zygote whereas in female Y chromosomes are not found. Thus, males are responsible for the birth of a baby boy.
3. What is crossing over?
Ans: The exchange of hereditary materials between non-sister chromatids of each homologous pair is known as crossing over.
4. What is chiasma?
Ans: Chiasma is a point of overlap of paired chromatids on which crossing over takes place.
5. Define homologous chromosome.
Ans: A pair of chromosomes which is similar in shape, size and function containing a maternal and paternal chromatids joined together at the centromere is called homologous chromosome.
6. Define bivalent.
Ans: Each pair of homologous chromosomes in synapsis is called a bivalent.
7. Define tetrad.
Ans: Each chromosome in a homologous pair splits lengthwise into two chromatids so that there are four threads in a pair which is known as tetrad.
8. Define chromosomes.
Ans: Chromosomes are the genetic materials present in the nucleus of a cell.
9. Write the full form of DNA and RNA.
Ans: The full form of
DNA is Deoxyribonucleic acid and
RNA is ribonucleic acid.
10. What is meant by karyotype?
Ans: A complete set of chromosomes in a species or in an individual organism is called karyotype.
11. Write the number of chromosomes found in somatic cell of human being and potato.
Ans: A human being has - 46 (23 Pairs)
Potato has - 28 (14 Pairs)
12. Write any two examples of sex chromosomal disorder.
Ans: The examples of sex chromosomal disorder are klinefelter syndrome and Turner's syndrome.
13. What are homologous chromosomes?
Ans: The paired paternal (father) and maternal (mother) chromosomes which are similar in structure are called homologous chromosomes.
14. What makes chromosomes to be fitted inside the nucleus of cell?
Ans: A protein known as histones makes chromosomes to be fitted inside the nucleus of the cell.
15. Write one function of gene.
Ans: The function of the gene is to give traits like eye colour, hair colour, height etc to the organism by synthesizing proteins.
16. What is meant by genetic disorder?
Ans: Genetic disorder is a disease / condition that is caused by an abnormality in a person's DNA.
17. Differentiate between autosomes and sex chromosomes.
Ans:
| Autosomes | Sex chromosomes |
1. These are responsible for | 1. These are responsible for the determination of sex. |
| 2. There are 22 pairs of autosomes in human body cells. | 2. There are 1 pairs of sex chromosomes in the human body cell. |
18. What is haemophilia? Write ant two symptoms of it.
Ans: Haemophilia is a genetic disorder which is caused by one of the clotting factor detective genes on the X chromosome.
The two symptoms are;
i. Excessive internal and external bleeding in any small cut, wound, bite, etc.
ii. Spontaneous nose bled.
19. Differentiate between klinfelters syndrome and Down's syndrome.
Ans:
| Klinfelters Syndrome | Down's Syndrome |
1. It is the sex chromosomal disorder.
| 1. It is an autosomal disorder.
. |
| 2. An additional copy of the X chromosome is present in the class of the affected persons. | 2. An additional copy of a 21st autosomal chromosome is present in the cells of the affected persons |
20. Haemophilia mostly affects men and women's are carrier, why?
Ans: Haemophilia is a genetic disorder associated with 'X' chromosome, the defective genes can be passed from mother to son. Males typically lack a second 'X' chromosomes so they are unable to make up for the defective gene. But, the females are unlikely to have the disorder as the chances of abnormal genes on both the 'X' chromosome are very rare. Therefore, haemophilia mostly affects man and women are carriers.
21. Chromosomes are called hereditary materials, why?
Ans: Chromosomes contain DNA which contains several genes. These genes are responsible for determining the characteristics such as eye colour, hair colour, height etc. During the formation of zygote chromosomes of father and mother combine so; the chromosomes transfer the genetic characters from parents to offspring from generation to generations. Therefore, chromosomes are called hereditary materials.
22. Define aneuploidy. How does aneuploid arise/result?
Ans: It is the abnormal condition in which there are more or fewer numbers of chromosomes than the normal set (i.e.23pairs in human) of chromosomes. Aneuploids are the organisms resulted from aneuploidy. Aneuploids arise due to a failure of separation of the homologous chromosomes during meiosis (during gamete formation).
23. Which syndrome is called 21 trisomy and why?
Ans: Down's syndrome is called 21 trisomy. It is because the cells of such person contain an additional 21st copy of chromosome number 21 instead of a normal two 21st chromosomes.
24. Which disease is also known as bleeder's disease, why? How can it be identified?
Ans: Haemophilia is also known as bleeder's diseases.
Haemophilia is a sex-linked chromosomal disorder caused due to the defective gene on X-chromosome which cannot produce or synthesize clothing factor i. e factor. People with haemophilia tend to bleed for a long time after an injury due to the lack of clotting factor. So, haemophilia is called bleeders diseases.
It can be identified by performing a special blood test to detect clotting factor.
25. What is the role of chromosome for living beings? Write any three functions of chromosomes.
Ans: The functions of chromosomes are;
1. Chromosomes are keys for a cell division.
2. Chromosomes are responsible for the inheritance of hereditary characteristics from parents to their offspring.
3. Chromosomes help in growth and metabolism by synthesizing structural as well as enzymatic proteins.
26. What is Turner's syndrome? Write any two symptoms of Turner's syndrome.
Ans: It is a sex chromosomal disorder in which one copy of X chromosome is missing.
The symptoms of Turner's syndrome are;
1. Females with poorly developed ovaries, underdeveloped breast, Small uterus, lack of menstrual cycle, infertility, etc.
2. Short stature or height, broad chest, narrow hips etc.
27. In which genetic disorder there is one additional copy of 21st chromosome. How can such disorder be identified?
Ans: In Down's syndrome or Mongolism, there is one additional copy of a 21st chromosome.
Down's syndrome is a genetic disorder, it can be identified by the following methods;
1. Blood test to examine the chromosomes.
2. Amniocentesis: In this method, amniotic fluid is drawn from the amniotic sac of the womb of the mother which is then examined. This test is done before the birth of a child.
3. Chest X-rays, echocardiography to check for the heart's problem and by looking at the appearance of a child at birth.
28. Write short notes on
a. Chromosomes b. Chromosomal disorders
Ans: a. Chromosomes:Chromosomes are thin hair like structure which is responsible for the inheritance of hereditary characters from parents to the offspring. Each human body cell consists of (diploid) 46 numbers of chromosomes whereas the germ cells i.e gametes consist of 23 numbers of chromosomes (haploid).
Chromosomes are located inside the nucleus of the cell and are composed of DNA and proteins called histones. The electron microscopic structure of each chromosome shows chromonema, centromere, secondary constructions nucleolar organiser, telomeres and satellites.
b. Chromosomal disorder:
A disorder that occurs in the human body due to change in the number and structure of chromosomes is called chromosomal disorder. It results from the change in number and structure of chromosome during cell division. The chromosomal disorder can take place either in sex chromosome or an autosome. Examples of sex chromosomal disorders are Klinefelter syndrome and Turner's syndrome. Examples of an autosomal disorder are Down's syndrome and Eduard's syndrome (18 trisomies). Not only that chromosomal disorder can also be resulted due to the mutation in chromosomes. Examples of such type of disorders are haemophilia and muscular dystrophy.
29. Define gametogenesis.
Ans: The process by which animals produce gametes is known as gametogenesis.
30. What is zygote?
Ans: Zygote is a diploid cell formed after the fusion of male and female gamete.
31. Write any two differences between gamete and Zygote.
Ans:
| Gamete | Zygote |
| 1. It is haploid. | 1. It is diploid. |
| 2. It is formed the reproductivecell after meiosis. | 2. It is formed by the fusion of male and female gamete. |
32. Differentiate between male gamete and female gamete.
Ans:
| Male gamete | Female gamete |
| 1. It is motile and smaller in size. | 1. It is non-motile and larger in size. |
| 2. It is produced by the male sex organ. i.e. testes. | 2. It is produced by female sex organ ie. alaries. |
33. A zygote is a diploid (Rn) structure, why?
Ans: A zygote is formed by the fusion of male and female gametes. Each male and female gamete contains haploid in the chromosome. When such haploid gametes fuse together, a diploid cell or structure i.e. Zygote is formed.
Male gamete (n) + Female gamete (n) □(→┴(Fertilization ) ) Zygote (2n)
34. What is karyokinesis?
Ans: The division of nucleus is called karyokinesis.
35. Write four examples of haploid cells?
Ans: Four haploid cells are Sperm cells, Egg cells, Pollen grains and Ovules.
36. Define cell division.
Ans: The process of formation of new cells, from pre-existing cells, is called cell division.
37. Write a significance of mitosis cell divisions.
Ans: It is essential for growth and development of the organism.
38. Differentiate between diploid and haploid cells.
Ans:
| Diploid cells | Haploid cells |
1. Diploid cells consist of a complete set i.e. 2n number of chromosomes. | 1. It consists of half the number i.e. number of chromosomes. |
| 2. Somatic cells are diploid cells. | 2. Gametes are haploid cells. |
40. What is sex determination?
Ans: The mechanism that establishes the sex of an individual as it begins life is called sex determination.
43. Gametes i.e Sperm are haploid, why?
Ans: Gametes are haploid because these are formed from the reproductive cells by meiosis cell divisions. So, gametes contain only one set of chromosome i.e in human gametes contain 23 numbers of chromosomes.
44. What is sex-linked disease? Describe with example.
Ans: The diseases which are present in sex chromosomes and which transfer from one generation to another generation are called sex linked diseases. Colour blindness, haemophilia are the examples of sex-linked disease.
45. How is son or daughter determined? Explain with illustration.
Ans: The eggs of females contain “X” chromosome. In male two different types of gametes are produced, they are denoted by “X” and “Y”. During fertilization, if the male gamete of “X” chromosome fuses with the egg of the female, it produces the female zygote. Similarly, if the male gamete of “Y” chromosome fuses with the egg of the female, it produces the male zygote. The female zygote contains “XX” chromosome and male zygote contains “XY” chromosomes. The male zygote develops into a boy and female zygote develops into a girl. In this way, son or daughter is determined.
46. On the basis of position of centromere, how many types of chromosomes are there?
Ans: On the basis of position of centromere there are four types of chromosomes.
They are:
i. Metacentric chromosome: The chromosome in which the centromere is present in the centre of the chromosomes making equal arms is called metacentric chromosomes.
ii. Sub-metacentric chromosome: The chromosome in which the centromere is present slightly at one side from the centre making unequal arms is called sub-metacentric chromosome.
iii. Acrocentric chromosome: The chromosome in which the centromere is present towards the end of the chromosome is called acrocentric chromosome.
iv. Telocentric chromosome: The chromosomes in which the centrosome is present at the tip of the chromosome is called telocentric chromosomes.
47. Write short notes on:
a.Down’s syndrome
b.Turner’s syndrome
Ans: b.Turner’s syndrome
Down’s syndrome
Each cell of human body contains 23 pairs of chromosomes. The disorder in the human body, which occurs due to one extra copy of chromosome in 21 pair of chromosomes in called Down’s syndrome. It alters the course of development.
Turner’s syndrome
The disorder in the human body which occurs due to deletion of “X” chromosome in sex chromosomes of the girls is called Turner’s syndrome. It is a condition that affects only girls and women. It results when a sex chromosome is missing or partially missing in 23 pair of chromosomes.
48. Mention the name of any one chromosomal disorder due to change in number of autosomes. Describe the causes and symptoms of the disorder.
Ans: Down’s syndrome is the chromosomal disorder due to change in number of autosomes.
It is caused due to one extra copy of chromosome in 21 pair of chromosomes.
The major symptoms of Down’s syndrome are:
i. Affected individual has small head, ears and mouth.
ii. They have small stubby fingers and Mongolian-type eyelids.
iii. They have underdeveloped gonads, congenital heart disease and mental retardation.
49. Mention the name of any one chromosomal disorder due to change in number of sex chromosome. Describe the causes and symptoms of the disorder.
Ans: Turner’s syndrome is chromosomal disorder due to change in number of sex chromosome.
Turner’s is caused in the offspring by the fertilization of an abnormal egg and a normal sperm or an abnormal sperm and normal egg. It is caused by the absence of one “X” chromosome, i.e. 44 instead of 46. Females are affected by this syndrome.
The major symptoms of Turner’s syndrome are:
i. They are sterile with poorly developed ovaries and underdeveloped breasts, small uterus and abnormal intelligence.
ii. They have webbed neck, broad chest and they possess many male characteristics like heavy neck muscle and narrow hips.
50. Describe the role of sex determination by sex chromosome of male with diagram.
Ans: The eggs of females contain “X” chromosome. In male two different types of gametes are produced, they are denoted by “X” and “Y”. During fertilization, if the male gamete of “X” chromosome fuses with the egg of the female, it produces the female zygote. Similarly, if the male gamete of “Y” chromosome fuses with the egg of the female, it produces the male zygote. The female zygote contains “XX” chromosome and male zygote contains “XY” chromosomes. The male zygote develops into a boy and female zygote develops into a girl. In this way, the sex chromosome of male plays the role in the sex determination.
