RBSE Solutions For Class 12 Biology Chapter 36: Chromosomal Aberrations in Humans | Textbook Important Questions & Answers

RBSE Class 12 Biology Chapter 36- Chromosomal Aberration in Humans. In this chapter, students can learn in detail about chromosomes, types of chromosomes, autosomes, sex chromosomes, human chromosomal aberrations, linkage, types of linkage, crossing over, types of crossing over, sex-linked inheritance, and characteristics of crossing over. It also deals with autosomal abnormalities, abnormalities related to the sex chromosomes, Down syndrome, Turner syndrome, Klinefelter syndrome, additional chromosomes in male and females, colour blindness, phenylketonuria, haemophilia, sickle cell anaemia and much more.

These important questions help students to perform exceptionally well in their exams. By practising these important questions, students can analyze their preparation, get a thorough knowledge about all the important terminologies and perform their best in the examinations.

RBSE Solutions for Class 12 are the best study material for both class assignments and other board examinations. By practising these important questions, students can gain deep knowledge about the topics explained in this chapter and also help them to be well prepared for their upcoming examinations.

RBSE Class 12 Biology Chapter 36 Important Questions

RBSE Biology Chapter 36: MCQ Type Questions

Q.1.Which of the following diseases is called sex-linked diseases?

(a) Diarrhoea

(b) Haemophilia

(c) Mongolism

(d) Edward Syndrome

Sol: (b) Haemophilia.

Q.2. Which of the following diseases is caused by the numerical changes in autosomes?

(a) Down syndrome

(b) Turner’s syndrome

(c) Triple female

(d) Klinefelter’s syndrome

Sol: (a) Down syndrome.

Q.3. The total number of autosomes found in man are _________.

(a) 42

(b) 44

(c) 46

(d) 48

Sol: (b) 44.

Q.4. The progeny of a normal female and colour-blind father will be_________.

(a) All children are colourblind

(b) Colour blind boys and normal girls

(c) Girls are the carrier but boys are normal

(d) Normal vision in all children and no carrier

Sol: (c) Girls are the carrier but boys are normal.

Q.5. A number of chromosomes in Turner’s Syndrome are_________.

(a) 44

(b) 45

(c) 46

(d) 47

Sol: (b) 45.

Q.6.Which offspring will a haemophilic father and disease carrier mother produce?

(a) All haemophilic sons

(b) All haemophilic daughter

(c) Half normal sons and half haemophilic sons

(d) Half normal daughters and half haemophilic daughters

Sol: (c) Half normal sons and half haemophilic sons.

Q.7. What happens when the linkage is found in a group of genes?

(a) Cannot show independent assortment

(b) Stimulates cell division

(c) Do not show chromosomal mapping

(d) Show recombination during the meiosis

Sol: (a) Cannot show independent assortment.

Q.8. In which of the following the hereditary recombination is found in the higher animals as the result of crossing over?

(a) Between the two daughter nuclei

(b) Between the two different bivalents

(c) Between the sister chromatids of any bivalent

(d) Between the non-sister chromatids of any bivalent

Sol: (d) Between the non-sister chromatids of any bivalent.

Q.9. Which of the following enzymes cannot be synthesized in phenylketonuria diseases?

(a) Phenylalanine hydroxylase

(b) Phenyl oxygenase

(c) Phenyl hydroxylase

(d) Phenylalanine dehydrogenase

Sol: (a) Phenylalanine hydroxylase.

Q.10. Sickle cell anaemia is caused by _________.

(a) Polyploidy of sex chromosome

(b) Aneuploidy of sex chromosome

(c) Mutation of the autosomal gene

(d) None of the above

Sol: (c) Mutation of the autosomal gene.

RBSE Biology Chapter 36: Short and Long Answer Type Questions.

Q.1.When and which type of cell division crossing over occurs?

Sol: Meiosis is the type of cell division, which occurs during the Pachytene phase of Meiosis-1.

Q.2.Which type of mutation occurs in the haemoglobin of the sickle cell anaemia?

Sol: Point mutation: At the sixth position of the B chain of the haemoglobin glutamic acid is replaced by valine amino acid.

Q.3. What is Down syndrome?

Sol: It is an autosomal abnormality, which is caused due to one extra 21st chromosome (45 + 2 = 47). It is also called 21st trisomy or mongolism.

Q.4. What is the function of Phenylalanine hydroxylase?

Sol: This enzyme catabolizes phenylalanine into the tyrosine.

Q.5. How many chromosomes are present in Klinefelter’s syndrome?

Sol: A person suffering from the Klinefelter’s syndrome has 47 or 48 or 49 chromosomes in their cells.

Q.6. What is a linkage group?

Sol: The group of genes found on one chromosome, which has a tendency to be inherited together is called the linkage group.

Q.7. What do you mean by haemophilia?

Sol: Haemophilia is a sex-linked hereditary disease. There is a delay or no blood clottings. Its recessive defective gene is found on the X-chromosome.

Q.8. What is a number of chromosomes found in a man and woman?

Sol: The number of chromosomes found in a man is – 44 + XY

The number of chromosomes found in a woman is – 44 + XX.

Q.9. What is aneuploidy?

Sol: The condition in which there is a loss or gain of chromosomes due to abnormal segregation of genes during cell division is called aneuploidy.

Q.10. What is polyploidy?

Sol: The condition in which the count of the entire set of chromosomes increases due to the failure of cytokinesis in cell division is called the polyploidy. It is mostly observed in plants.

Q.11. What are the examples of chromosomal abnormalities?

Sol: The examples of chromosomal abnormalities are :

  • Down syndrome
  • Klinefelter syndrome
  • Turner syndrome

Q.12. What are chromosomes?

Sol: Chromosomes are thread-like structures present in the nucleus, which plays an important role in carrying the hereditary information in the form of genes, which is passed from parents to offspring.

Q.13. What is Haemophilia?

Sol: This is a type of sex-linked recessive disorders. According to the genetic inheritance pattern, the unaffected carrier mother passes on the haemophilic genes to sons. Haemophilia is a very rare type of disease among females because for a female to get the disease, the mother should either be hemophilic or a carrier but the father should be haemophilic.

Haemophilia is a disorder in which blood doesn’t clot normally as the protein which helps in clotting of blood is affected. Therefore, a person suffering from this disease usually has symptoms of unexplained and excessive bleeding from cuts or injuries. This type of genetic disorder is caused when the affected gene is located on the X chromosomes. Therefore, males are more frequently affected.

Q.14. What is Down syndrome? What are the symptoms of Down syndrome?

Sol: The Down syndrome is a type of trisomy as there is an extra copy of chromosome 21. It is named so after the person who discovered this chromosomal disorder – Langdon Down.

The symptoms in a person include the following:

  • Broad palm.
  • Furrowed tongue and partially open mouth.
  • Physical and mental development is retarded.
  • The person is short and has a small and round head.

Q.15. What is Sickle-cell anaemia?

Sol: This is a type of autosomal recessive genetic disorder. Its inheritance pattern follows inheritance from two carrying parents.

Sickle-cell anaemia is caused when the glutamic acid in the sixth position of the beta-globin chain of the haemoglobin molecule is replaced by valine. The mutant haemoglobin molecule undergoes a physical change which changes the biconcave shape into the sickle shape.

This reduces the oxygen-binding capacity of the haemoglobin molecule.

Q.16. What is Phenylketonuria?

Sol: This is a type of autosomal recessive genetic disorder. Phenylketonuria is an inborn error caused due to the decreased metabolism level of the amino acid phenylalanine. In this disorder, the affected person does not have the enzyme to convert phenylalanine to tyrosine. As a result, phenylalanine accumulation takes place in the body and is converted into many derivatives which result in intellectual disability or mental retardation.

Q.17. What are chromosomal abnormalities?

Sol: Every species has a characteristic structure and number of chromosomes. The slightest alteration in the chromosomes can lead to various abnormalities. The chromosomal abnormalities are a type of genetic disorders that are seen in an individual when there is a :

  1. Alteration in the chromosomal structure.
  2. Variations in the number of chromosomes.
  3. Changes of chromosomes irregularities at the time of cell division.
  4. In some rare cases, the whole chromosome is gained or lost, this type of disorder usually results in a fatality or affects many other genes.

Q.18. What is Klinefelter Syndrome? What are the causes and symptoms of Klinefelter Syndrome?

Sol: Klinefelter syndrome is one of the genetic disorders in males. It occurs when a male baby is born with more than required or extra X chromosomes. A person suffering from this disease is always a man.

Causes of Klinefelter Syndrome

Men with Klinefelter may have:

  • An extra X chromosome in every cell.
  • More than one extra X chromosome.
  • An extra X chromosome in only some cells called mosaic Klinefelter.

Symptoms of Klinefelter Syndrome

There are no obvious symptoms in men with Klinefelter syndrome. Some of the most common symptoms of Klinefelter Syndrome are:

  • Thinly dispersed hair body
  • Wide hips, and enlarged breasts.
  • The testicles in every man stay small while in some the penis does not grow to adult size.

Q.19. What is Turner’S Syndrome?

Sol: Turner’s Syndrome:

A person suffering from this disease is always a woman. Such a woman has only one X chromosome instead of two and hence a total number of chromosomes found are only 45 (44 + 0). It is called Turner’s Syndrome. This is a rare disorder, which occurs in 1 out of every 3,000 live births.

The symptoms of Turner’s Syndrome include:

  • Intellectual disability (mental retardation).
  • Women with this disorder are short in stature.
  • Short neck, underdeveloped mammary glands.
  • Broad chest and lack of secondary sexual characteristics and sterile.

Q.20. Explain the changes in chromosomal numbers in a Klinefelter Syndrome with a diagram.

Sol: Klinefelter Syndrome is mainly seen in males. Their cells may have 47, 48 or 49 chromosomes rather than 46. This additional number may be of X or Y chromosomes. Klinefelter males may have the following type of chromosomes:

44 + XXY (one additional X chromosome) = 47 chromosomes.

44 + XXXY (Two additional X chromosomes) = 48 chromosomes.

44 + XXXXY (Three additional X chromosomes) = 49 chromosomes.

44 + XXYY (One additional X and one additional Y chromosome) = 48 chromosomes.

44 + XXXYY (Two additional X and one additional Y chromosome) = 49 chromosomes.

Klinefelter Syndrome

Q.21. What is colour blindness?

Sol: Colour blindness:

It is a hereditary disease. In this disease, the person is unable to differentiate different colours.

Th colour blindness is of two types:

  1. Blue colour blindness.
  2. Red- Green colourblindness.

The colour blindness disease is mainly found in men because males have only one X chromosome. If X chromosome contains a recessive allele of pigment formation gene then no cone formation takes place and man suffers from colour blindness.

Women may be carriers of this disease or they may suffer from this disease. This is mainly because two x-chromosomes are found in a woman.

Q.22. What are sex-linked character and their inheritance?

Sol: Sex-linked inheritance:

The human females have XX chromosomes and the human male has XY chromosome along with 44 autosomes in both the sexes.

The genes present on the X chromosome may express in both the male and female gender and hence it is called criss-cross heredity. While genes present on the Y-chromosome are found only in the males.

Genes of approximately 20 characters, found on the X-chromosome of humans are sex-linked characters. A son cannot receive sex-linked traits (of the X chromosome) from his father, whereas, a father can transmit or pass sex-linked traits (of the X chromosome)

to his daughters only.

Some of the sex-linked hereditary diseases found in human beings are as follows:


Colour Blindness

Q.23. Explain the types of linkage?

Sol: Linkage is of two types:

Complete linkage

When certain genes are located so nearly on the same chromosomes and tend to remain linked together while passing from one generation to another without any new combination are termed as the complete linkage.

Incomplete linkage

Linked genes are not inherited always in their combination. In the homologous chromosomes or at the time of meiosis, the exchange of such genes may be found due to the crossing over. The genes located at the distance on the chromosomes are also incompletely linked because of the more chances of isolation by the crossing over.

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