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Principles of Inheritance and Variation · Question 136

AIPMT 2004MCQEasy📈 Topic in 50% papers+4−1
1

The recessive genes located on X-chromosomes in humans are always -

  1. Expressed in females
  2. Sub-lethal
  3. Expressed in males
  4. Lethal

Answer

(3) Expressed in males

Solution

Human males are XY, so they have only one X chromosome (hemizygous for X-linked genes).

⇒ The Y chromosome has no corresponding allele to mask an X-linked recessive gene.

∴ An X-linked recessive gene is always expressed in males, while females (XX) show it only when homozygous (e.g. haemophilia, colour blindness).

Answer: (3)

AIPMT 2004

Keep practising — Principles of Inheritance and Variation

2

After a mutation at a genetic locus the character of an organism changes due to the change in :-

  1. Protein synthesis pattern
  2. RNA transcription pattern
  3. DNA replication
  4. Protein structure
AIPMT 2004
3

In a mutational event, when adenine is replaced by guanine, it is a case of -

  1. Frameshift mutation
  2. Transition
  3. Transversion
  4. Transcription
AIPMT 2004
4

Which one of the following traits of garden pea studied by Mendel was a recessive feature?

  1. Green seed colour
  2. Green pod colour
  3. Axial flower position
  4. Round seed shape
AIPMT 2003
5

The genes controlling the seven pea characters studied by Mendel are now known to be located on how many different chromosomes?

  1. Six
  2. Seven
  3. Five
  4. Four
AIPMT 2003
6

Two crosses between the same pair of genotypes or phenotypes in which the sources of the gametes are reversed in one cross, is known as:

  1. Reciprocal cross
  2. Reverse cross
  3. Test cross
  4. Dihybrid cross
AIPMT 2003
7

Pattern baldness, moustaches and beard in human males are examples of:

  1. Sex limited traits
  2. Sex influenced traits
  3. Sex determining traits
  4. Sex linked traits
AIPMT 2003
8

Which one of the following conditions though harmful in itself, is also a potential saviour from a mosquito borne infectious disease?

  1. Pernicious anaemia
  2. Thalassaemia
  3. Leukemia
  4. Sickle cell anaemia
AIPMT 2003
9

Down's syndrome is caused by an extra copy of chromosome number 21. What percentage of offspring produced by an affected mother and a normal father would be affected by this disorder?

  1. 50%
  2. 100%
  3. 75%
  4. 25%
AIPMT 2003
10

In Drosophila, the sex is determined by:

  1. X and Y chromosomes
  2. Whether the egg is fertilized or develops parthenogenetically
  3. The ratio of number of X-chromosomes to the sets of autosomes
  4. The ratio of pairs of X-chromosomes to the pairs of autosomes
AIPMT 2003
11

Christmas disease is another name for :-

  1. Hepatitis B
  2. Sleeping sickness
  3. Haemophilia B
  4. Down's syndrome
AIPMT 2003

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