Match List-I with List-II: Choose the correct answer from the options given below.List-I List-II (A) Down's Syndrome (I) Absence of a copy of X chromosome (B) Klinefelter's Syndrome (II) Presence of additional copy of X chromosome (C) Turner's Syndrome (III) Mutation of X chromosome (D) Colour blindness (IV) Trisomy of 21st chromosome
(A)-(IV), (B)-(II), (C)-(I), (D)-(III)
Understanding Genetic Disorders and Chromosome Abnormalities
The question asks us to match a list of genetic conditions and disorders with their underlying causes or chromosomal abnormalities. Let's analyze each item in List-I and find its correct match in List-II.
Matching Down's Syndrome with its Cause
Down's Syndrome is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. This condition is also known as Trisomy 21.
- From List-II, option (IV) states Trisomy of 21st chromosome.
Therefore, (A) Down's Syndrome matches (IV).
Matching Klinefelter's Syndrome with its Cause
Klinefelter's Syndrome is a genetic condition that results when a boy is born with an extra copy of the X chromosome. This leads to a karyotype of XXY instead of the typical XY.
- From List-II, option (II) states Presence of additional copy of X chromosome.
Therefore, (B) Klinefelter's Syndrome matches (II).
Matching Turner's Syndrome with its Cause
Turner's Syndrome is a chromosomal disorder that affects only females. It results when one of the X chromosomes is missing or partially missing. The typical karyotype is XO instead of XX.
- From List-II, option (I) states Absence of a copy of X chromosome.
Therefore, (C) Turner's Syndrome matches (I).
Matching Colour Blindness with its Cause
Colour blindness, or colour vision deficiency, is most commonly an inherited condition. It is typically an X-linked recessive trait, meaning it is caused by a mutation on the X chromosome.
- From List-II, option (III) states Mutation of X chromosome.
Therefore, (D) Colour blindness matches (III).
Summary of Matches
Based on the analysis:
- (A) Down's Syndrome matches (IV) Trisomy of 21st chromosome.
- (B) Klinefelter's Syndrome matches (II) Presence of additional copy of X chromosome.
- (C) Turner's Syndrome matches (I) Absence of a copy of X chromosome.
- (D) Colour blindness matches (III) Mutation of X chromosome.
Let's organize these matches in a table:
| List-I (Condition) | List-II (Cause) | Match |
|---|---|---|
| (A) Down's Syndrome | (IV) Trisomy of 21st chromosome | A - IV |
| (B) Klinefelter's Syndrome | (II) Presence of additional copy of X chromosome | B - II |
| (C) Turner's Syndrome | (I) Absence of a copy of X chromosome | C - I |
| (D) Colour blindness | (III) Mutation of X chromosome | D - III |
The correct matching is (A)-(IV), (B)-(II), (C)-(I), (D)-(III).
Revision Table: Genetic Disorders and Causes
| Genetic Condition | Genetic Basis/Cause |
|---|---|
| Down's Syndrome | Trisomy of chromosome 21 (extra copy of chromosome 21) |
| Klinefelter's Syndrome | Presence of an additional X chromosome (XXY karyotype) |
| Turner's Syndrome | Absence or partial absence of one X chromosome (XO karyotype) |
| Colour blindness | Mutation in genes located on the X chromosome (X-linked recessive) |
Additional Information: Chromosomal Abnormalities and Genetic Mutations
Understanding the terms used in the question is key to matching the genetic disorders correctly.
What is Trisomy?
Trisomy is a type of aneuploidy (an abnormal number of chromosomes). Trisomy occurs when a cell contains three copies of a particular chromosome instead of the normal two copies. For example, Trisomy 21 means there are three copies of chromosome 21.
\(\text{Normal human karyotype has 23 pairs of chromosomes (46 total): 22 pairs of autosomes and 1 pair of sex chromosomes.}\)
\(\text{Trisomy 21 karyotype: 47, XX or XY, +21}\)
Sex Chromosome Abnormalities
The sex chromosomes are X and Y. Females typically have XX and males typically have XY. Abnormalities involving the number of sex chromosomes can lead to conditions like Klinefelter's and Turner's syndromes.
- Klinefelter's Syndrome (XXY): An extra X chromosome in males.
- Turner's Syndrome (XO): Absence of one X chromosome in females. This is a type of monosomy (presence of only one chromosome from a pair).
Genetic Mutations
A mutation is a change in the DNA sequence of an organism. Mutations can occur in genes located on any chromosome (autosomal or sex chromosome). Colour blindness is an example of a condition caused by a gene mutation on the X chromosome. Since it is X-linked recessive, males are more frequently affected because they have only one X chromosome.
Important Questions from Heredity and Variation
Down’s syndrome is caused by:
The probability of having a haemophilia carrier daughter by a haemophilia carrier mother and a normal father is:
Which of the following statements are correct about Thalassemia?
A. In β-Thalassemia, production of β-globin chain is affected, and in α-Thalassemia, production of α-globin chain is affected.
B. α-Thalassemia is controlled by two closely linked genes HBA1 and HBA2.
C. The genes HBA1 and HBA2 are located on chromosome 11 of each parent.
D. β-Thalassemia is controlled by a single gene HBB.
Choose the correct answer from the options given below:
Match List-I with List-II:
List-I List-II (A) Phenylketonuria (I) Incomplete dominance (B) Haemophilia (II) 9:3:3:1 (C) Snapdragon (III) Pleiotropy (D) Dihybrid cross (IV) Sex-linked Choose the correct answer from the options given below:
Chromosomes in meiocytes of butterflies are:
