Sex-linked inheritance, Mendelian and chromosomal disorders
- With the help of given pedigree, find out the probability for the birth of a child having no disease and being a carrier (has the disease mutation in one allele of the gene) in F3 generation. Answer: 1. 1/4 Key idea: The legend shows carriers only among females, so the trait is X-linked recessive. The F2 mother is a carrier: X^AX^... 1
- Match List I with List II :List I:A. Down's syndromeB. α-ThalassemiaC. β-ThalassemiaD. Klinefelter's syndromeList II:I. 11^th chromosomeII. 'X' chromosomeIII. 21^st chromosomeIV. 16^th chromosomeChoose the correct answer from the options given below… Answer: 4. A-III, B-IV, C-I, D-II Down's syndrome - trisomy of chromosome 21 (A-III). α-Thalassemia - chromosome 16 (B-IV). β-Thalassemia -... 1
- Broad palm with single palm crease is visible in a person suffering from- Answer: 2. Down's syndrome Key idea: Down's syndrome (trisomy 21) has typical physical features. These include a short stature, a small roun... 1
- Which one of the following symbols represents mating between relatives in human pedigree analysis? Answer: 3. [pedigree symbol: square joined to circle by double line] Key idea: In a human pedigree, a double horizontal line between the mal... 1
- Which of the following statements are correct about Klinefelter's Syndrome?A. This disorder was first described by Langdon Down (1866).B. Such an individual has overall masculine development. However, the feminine development is also expressed.C. The… Answer: 4. B and E only Key idea: Klinefelter's syndrome has the karyotype 47, XXY. A is wrong: Langdon Down described Down syndrome. B is c... 1
- If a colour blind female marries a man whose mother was also colour blind, what are the chances of her progeny having colour blindness ? Answer: 1. 100% Key idea: Colour blindness is X-linked recessive. The female is colour blind: X^cX^c . The man's mother was colour blind, so... 1
- Which of the following occurs due to the presence of autosome linked dominant trait ? Answer: 3. Myotonic dystrophy Myotonic dystrophy is an autosomal dominant disorder. Thalassemia and sickle cell anaemia are autosomal recess... 1
- In a cross between a male and female, both heterozygous for sickle cell anaemia gene, what percentage of the progeny will be diseased ? Answer: 3. 25% Both parents are heterozygous carriers (Hb ^A Hb ^S ). Cross: Hb ^A Hb ^S × Hb ^A Hb ^S gives 1 Hb ^A Hb ^A : 2 Hb ^A Hb ^S :... 1
- Mutations in plant cells can be induced by : Answer: 3. Gamma rays Mutations are induced by mutagens such as gamma rays, which are ionising radiation and damage DNA. Kinetin and zeatin... 1
- Select the correct match. Answer: 3. Sickle cell anaemia - Autosomal recessive trait, chromosome-11 Key idea: Recall the mode of inheritance of each disorder. Haemoph... 1
- What is the genetic disorder in which an individual has an overall masculine development, gynaecomastia, and is sterile ? Answer: 2. Klinefelter's syndrome Key idea: Klinefelter's syndrome is XXY. The individual is male with overall masculine development but als... 1
- A woman has an X-linked condition on one of her X chromosomes. This chromosome can be inherited by Answer: 4. Both sons and daughters Key idea: A woman has two X chromosomes and passes one at random to each child. Each child (son or daught... 1
- A disease caused by an autosomal primary non-disjunction is : Answer: 4. Down's Syndrome Key idea: Non-disjunction of an autosome gives a trisomy or monosomy of an autosome. Down's syndrome is trisomy 2... 1
- Thalassemia and sickle cell anemia are caused due to a problem in globin molecule synthesis. Select the correct statement. Answer: 2. Thalassemia is due to less synthesis of globin molecules. Key idea: The two disorders differ in the type of globin defect. Thalas... 1
- If a colour-blind man marries a woman who is homozygous for normal colour vision, the probability of their son being colour-blind is Answer: 4. 0 Colour blindness is X-linked recessive. Let the normal allele be X and the defective allele X^c. Father: X^cY. Mother (homozygo... 1
- Pick out the correct statements :(a) Haemophilia is a sex-linked recessive disease.(b) Down's syndrome is due to aneuploidy.(c) Phenylketonuria is an autosomal recessive gene disorder.(d) Sickle cell anaemia is an X - linked recessive gene disorder. Answer: 4. (a), (b) and (c) are correct. Key idea: Check each statement. (a) Haemophilia is X-linked recessive: correct. (b) Down syndrome i... 1
- Which of the following most appropriately describes haemophilia ? Answer: 2. X - linked recessive gene disorder Key idea: Haemophilia is caused by a recessive gene on the X chromosome, so it is the most pre... 1