Which one of the following statements regarding sex chromosomes in the human body is correct?
Chromosome X is included in Group C of the autosomal chromosomes.
Under the Denver classification (1960), the 46 human chromosomes are arranged into seven groups A to G by size and centromere position. Group C comprises chromosomes 6 to 12, medium-sized submetacentric chromosomes; the X chromosome closely resembles them in size and centromere position and is therefore placed in Group C. The Y chromosome, being small and acrocentric, is classified with Group G (chromosomes 21 and 22).
Y in Group E is wrong: Group E holds chromosomes 16 to 18, short submetacentrics. X in Group G reverses the correct assignment, since Group G carries the Y, not the X. Y in Group F is wrong: Group F contains chromosomes 19 and 20, short metacentrics.
Key point: A (1-3), B (4-5), C (6-12 plus X), D (13-15), E (16-18), F (19-20), G (21-22 plus Y). Mnemonic: X sits with C, Y sits with G.
Important Questions from Genetic Disorders & Public Health
- Which one of the following conditions is NOT inborn error of metabolism?
- Amniocentesis is called for in all of the following circumstances EXCEPT:
- Consider the following pairs of genetic diseases that show Mendelian inheritance. Each of the following pairs represents a genetic disease and it has been matched with a type of inheritance :How many of the pairs given above are correctly matched?
1 Cystic fibrosis Autosomal recessive 2 Huntington's chorea Autosomal dominant 3 Marfan's syndrome Recessive sex-linked Consider the following statements :
Statement I:
Signs of thalassemia major usually develop after 6 months of age.
Statement II:
This is the time when haemoglobin synthesis switches from haemo-globin F to haemoglobin A.
Which one of the following is correct in respect of the above statements?
- Cystic fibrosis involves which of the following organs?
1. Lungs
2. Liver
3. Pancreas
4. Kidney
Select the correct answer using the code given below.
