Chromosome and Sex Determination: Class 10 Science Notes
Chromosome and Sex Determination Class 10 Science Complete Notes. This note include all the excercise given in Chromosome and Sex Determination chapter of science book such as question answer, numericals, give reason, diagrammatic questions and define the following. This note is published for helping students to solve their problems.
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Chapter - 17
Chromosome and Sex Determination
📚EXERCISES
2. Answer the following questions:
a. What is sex determination ? Introduce homogametic organism.
Ans: The mechanism that fixes the sex of an individual as it begins life is called sex determination.
The organisms having two similar sex chromosomes (XX) are called homogametic organism.
b. What are chromosomes and chromatids ?
Ans: Chromosomes are thread-like structures located inside the nucleus of animal and plant cells. Chromatids is one of the two identical halves of a replicated chromosome.
c. What is gene ? Where is it located ? Write its function.
Ans: Gene is the smallest segment of DNA of chromosome that takes part in transmission of genetic characters of an organism to their offsprings. It is located in chromosomes. The main function of gene is to transfer the genetic characters from parents to offsprings.
d. How is a son or daughter determined?
Ans: If a zygote is formed with X chromosome by the sperm and X chromosome by ovum then female child is produced.
If an egg having X chromosome is fertilized by the sperm having Y chromosome then male child is produced.
e. What is chromosome ? Write in brief about the structure of chromosome.
Ans: A chromosome is a long linear double standed DNA molecule with a protein coat that is responsible for the transmission of hereditary characters from parents to the offspring.
Each cell has a pair of each kind of chromosome known as a homologous chromosome. They are made up of chromatin, which contains a single molecule of DNA and associated proteins. Each chromosome contains hundreds and thousands of genes that can precisely code for several proteins in the cell.
f. What is chromosome made up of ?
Ans: Chromosome is made up of proteins and DNA organized into genes.
g. What is chromosome disorder? write any three example.
- Down's syndrome
- Klinefelter's Syndrome
- Turner's Syndrome
h. How many chromosomes are there on the basis of the position of centromere in the chromosomes?
Ans: There are 5 type types of chromosome on the basis of the position of centromere in the chromosome.
i. Define
i. Diploid cell
Ans: It is a cell or organism that has pair of chromosome, one from each parent.
ii. Haploid cell
Ans: It is a cell having a single set of chromosome.
iii. Homologous chromosome
Ans: Homologous chromosome are pair of chromosom made up of two homologs.
iv. Maternal Chaomosome
Ans: Maternal chromosome are the chromosome in the nucleus with maternal origin.
v. Aneuploidy
Ans: It is a type of chromosomal aberration where there is one extra chromosome or one missing chromosome.
j. What type type of disease is Klinefelter's Syndrome? Write any two symptoms.
- Less muscular body
- Under developed testes
k. What do you mean by Down's Syndrome? Write any two symptoms.
- Round Face
- Short Neck
l. What is Turner's Syndrome? Write any two Symptoms of it.
- Abnormal intelligence
- Broad Chest
3. Differentiate between:
a. Chromosome and Chromatids
Ans: The difference between chromosome and chromatid are as follows;
| Chromosome | Chromatids |
|---|---|
| It is the most condensed form of DNA. | It is less condensed than a chromosome. |
| It involve in the distribution of genetic material. | It involve in metabolism and other activities of cell. |
| It consist of a single, double-stranded DNA molecule. | It consist of two DNA strands joining by their centromere. |
b. Autosome and sex chromosomes
Ans: The difference between autosome and sex chromosomes are as follows;
| Autosomes | Sex Chromosomes |
|---|---|
| Male and female contain the same copy of autosome. | Male and female contain different sex chromosomes. |
| Position of centromere is identical. | Position of centromere is not identical. |
| Autosome determine somatic traits. | Sex chromosome determines the gender. |
c. Ova and Sperm
Ans: The difference between ova and sperm are as follows;
| Ova | Sperm |
|---|---|
| They are produced in the ovaries. | They are produced in testes. |
| It has large amount of cytoplasm. | It has very small amount of cytoplasm. |
| It is stationary. | It is motile. |
d. Homogametic and Heterogametic
| Homogametic | Heterogametic |
|---|---|
| It is a condition in which similar type of gamets are formed. | It is the condition in which two types of gamets are formed. |
| Itself, it can't decide the sex of the progeny. | They play a very important role in deciding the sex of the off spring. |
4. Give reasons:
a. In the formation of a baby boy or baby girl, mother does not have the main role.
Ans: In the formation of a baby boy or baby girl, mother does not have the main role because the mother only has X chromosomes to give, it should be obvious that it is the father's chromosome that determine whether the baby will genetically be a boy or a girl.
b. Down's syndrome is autosomal chromosomal disorder.
Ans: Down's syndrome is autosomal chromosomal disorder because it is caused by a random error in cell division that results in the presence of an extra copy of chromosome 21.
c. Turners' syndrome is found in girls only not in boys.
Ans: Turners' syndrome is found in girls only not in boys because it is caused when one of the X chromosomes (sex chromosomes) is missing or partially missing.
d. Klinefelter's syndrome occurs in boys only not in girls.
Ans: Klinefelter's syndrome occurs in boys only not in girls because it is caused when extra copy of the X chromosome (XXY) is present. Here the X chromosome is not a "female" chromosome and is present in everyone.
e. Haemophilia is a Mendelian disease.
Ans: Haemophilia is a Mendelian disease because it is a genetic disorders caused by alterations or mutations in a single gene as in haemophilia and thalassemia.
f. Haemophilia does not occur in females usually even though they have genes with defected clotting factors.
Ans: Haemophilia does not occur in females usually even though they have genes with defected clotting factors because women have to be homozygous, which is fatal.
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