Content Writer
X and Y chromosomes are called sex chromosomes as they are responsible for determining the sex of an individual. Chromosomes are thread-like structures that cannot be seen by our naked eyes. These are found in the nucleus of the cell and contain the genetic material that is passed from parents to offspring.
- Humans have 23 pairs of chromosomes out of which one pair is the sex chromosome, while the rest are autosomal chromosomes.
- There are various disorders that are linked to both X chromosome and Y chromosome.
In this article, we will read about what is chromosomes, X and Y chromosomes, and the difference between X and Y chromosomes.
| Table of Contents |
What are Chromosomes?
[Click Here for Sample Questions]
Chromosomes are the genetic material present in both eukaryotic and prokaryotic cells. These were discovered by scientist Walther Flemming in 1882. Each one of them is composed of a protein and deoxyribonucleic acids (DNA).
- There are 23 pairs of chromosomes in the human body of which only one pair is the sex chromosome (X and Y).
- Chromosomes play an important role in cell division ensuring that DNA is copied accurately and distributed evenly.
- The structure of chromosomes is different in prokaryotic and eukaryotic cells.
X and Y chromosomes
[Click Here for Sample Questions]
The human body consists of 23 pairs of chromosomes, which makes a total of 46 chromosomes. X and Y are the two types of chromosomes.
- X and Y chromosomes are called sex chromosomes.
- The sex of an individual is determined by sex chromosomes.
- Females have two X chromosomes (XX), while males have a single X and a Y chromosome (XY).
- Females pass only one copy to her offspring, while male pass either an X chromosome or a Y chromosome.
- When a male passes an X chromosome it is a female child, and a male child is when a Y chromosome is passed.
Figure: X and Y Chromosomes
Difference between X and Y chromosomes
[Click Here for Sample Questions]
X and Y chromosomes differ in shape, size, number of genes, etc. The table below shows the difference between X and Y chromosomes:
| Parameters | X Chromosomes | Y Chromosomes |
|---|---|---|
| Found in | These chromosomes are found both in males and females. | These chromosomes are found only in males. |
| Shape | These chromosomes are ‘X’ in shape as they are meta-centric. | These chromosomes are ‘Y’ in shape as they are acro-centric. |
| Size | Larger in size than the Y chromosome. | Smaller in size than the X chromosome. |
| Genes | They have a larger number of genes than the Y chromosome. | They have a smaller number of genes than the X chromosome. |
| DNA | They have a large number of DNA. | They have a smaller number of DNA. |
| Number of Chromosomes | Females have two copies of X chromosomes. | Males have only one copy of X and Y chromosomes. |
| Inheritance | Shows a criss-cross inheritance. | Shows a straight inheritance. |
| Euchromatin | Present in large quantity. | Present in low quantity. |
| Heterochromatin | Present in low-quantity | Present in higher quantity. |
| Roles | They play a major role in the production of eggs in females. | They play a major role in sperm production in males. |
Things to Remember
- X and Y chromosomes are called allosomes or sex chromosomes.
- The proteins present in chromosomes are called histone and non-histone proteins.
- Any change that occurs in the sex-chromosomes leads to genetic disorders.
- The point on a chromosome where the chromatids are attached is called a centromere.
- X chromosomes are metacentric, while the Y chromosomes are acrocentric.
Sample Questions
Ques. What is chromatin? Mention any two functions. (2 marks)
Ans. A type of genetic material composed of DNA and proteins is called chromatin. There are two functions of chromatin:
- Responsible for controlling gene expression.
- Helps in preventing DNA damage.
Ques. Name the scientist who discovered chromosomes. (1 mark)
Ans. Strasburger was the scientist to first discover chromosomes in the year 1815.
Ques. Define Chromatids. What are its functions? (2 marks)
Ans. The two strands that make up a chromosome are called chromatids.
Chromatids play a major role in cell division. They ensure an even distribution of chromosomes to the daughter cells.
Ques. Why is the X chromosome called metacentric and the Y chromosome is acrocentric? (2 marks)
Ans. X and Y chromosomes are distinguished as metacentric and acrocentric respectively.
- The X chromosome is known to be a metacentric chromosome, which means that the centromere is located in the center resulting in equal strands.
- The Y chromosome is called an acrocentric chromosome because the centromere is located slightly away from the center leading to one long and one short strand.
Ques. What proteins are present in chromatin? Mention any one function of each. (2 marks)
Ans. There are two types of proteins present in chromatin:
- Histone proteins
- Non-Histone proteins
Histone proteins help in gene regulation while non-histone proteins help in compacting and organizing chromosomes.
Ques. What are sex characteristics? (2 marks)
Ans. Sex characteristics are defined as the chromosomal or physical characteristics of a person that determine whether the individual is a male or a female. Sex characteristics are of two types: primary and secondary characteristics.
Ques. Explain what are primary and secondary sex characteristics with examples. (2 marks)
Ans. Primary sex characteristics are present at the time of birth and are related to the reproductive organs and hormones. For example, male and female genitals, and gametes.
Secondary sex characteristics are those that develop at the time of puberty. For example, the development of breasts in females and the growth of facial hair in males.
Ques. What is Intersex? Mention any two identifications of intersex. (3 marks)
Ans. Individuals born with a male or a female body that does not resemble their genitals or internal reproductive organs are called intersex. The following are the two identifications of intersex:
- They have ovaries and uterus but no vagina.
- Both ovaries and testicular tissues are present
Ques. What are gonads? (1 mark)
Ans. Gonads are the reproductive glands responsible for producing hormones and gametes. The male gonads are testis and female gonads are ovaries.
Ques. Are autosomes sex chromosomes? (2 marks)
Ans. No, autosomes are not sex chromosomes.
- There are 22 pairs of autosomal chromosomes, the 23rd being the sex chromosomes. Autosomes are responsible for controlling the inheritance of the organism's traits.
Ques. What are sex-linked disorders? Give examples. (2 marks)
Ans. Any abnormal change or mutation in the X chromosome is called a sex-linked disorder. Males are more prone to sex-linked disorders. Examples of sex-linked disorders are Hemophilia, Color Blindness, Rett Syndrome, etc.
Ques. What is Turner Syndrome? Mention its symptoms. (2 marks)
Ans. Turner syndrome is a genetic disorder that affects females at birth. This disease is caused due to the absence of one X chromosome in females.
Symptoms include stunted growth, no breast development, and no ovaries or uterus.
Ques. What is Klinefelter's Syndrome? Mention its symptoms. (2 marks)
Ans. Klinefelter's Syndrome is a genetic condition that affects males and is caused by the presence of an extra X chromosome. Symptoms include breast development and sparse facial hair, or no facial hair.
Comments