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Question
If the female gamete carries 22+XX chromosomes, while male gamete is normal, predict the probable defects in the baby formed as a result of fusion between these gametes.
i. Triple X syndrome
ii. Klinefelter’s syndrome
iii. Turner’s syndrome
iv. Edward’s syndrome
If the female gamete carries 22+XX chromosomes, while male gamete is normal, predict the probable defects in the baby formed as a result of fusion between these gametes.
i. Triple X syndrome
ii. Klinefelter’s syndrome
iii. Turner’s syndrome
iv. Edward’s syndrome
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Solution
The correct option is A i and ii
Gametes are haploid cells. The number of chromosomes in gametes in case of human beings is 23.
The normal male gametes (sperms) in humans have 22 autosomes and either X or Y chromosomes.
The normal female gametes (eggs) in humans have 22 autosomes and X chromosome.
The female gamete mentioned in the question carries two copies of X chromosome instead of a single copy. The probable reason for this might be nondisjunction (failure of separation of homologous chromosomes during meiosis I or failure of separation of sister chromatids during meiosis II).
If the sperm fertilising the egg (22+XX) carries an X chromosome, then the zygote formed would carry 44 autosomes and XXX sex chromosomes. This will lead to triple X syndrome in the female offspring.
If the sperm fertilising the egg (22+XX) carries a Y chromosome, then the zygote formed would carry 44 autosomes and XXY sex chromosomes. This will result in Klinefelter’s syndrome in the offspring. The affected offspring will develop into sterile males.
This has been explained via the following cross:-
The individuals affected with Turner's syndrome have a single copy of X chromosome. The offspring with Turner's syndrome is not possible as a result of the fusion of the gametes given in the question.
The individuals affected with Edwards syndrome have three copies of 18th chromosome instead of two copies per cell. The offspring with Edward's syndrome is not possible as there is no abnormality with respect to autosomes in the gametes mentioned in the question.
Gametes are haploid cells. The number of chromosomes in gametes in case of human beings is 23.
The normal male gametes (sperms) in humans have 22 autosomes and either X or Y chromosomes.
The normal female gametes (eggs) in humans have 22 autosomes and X chromosome.
The female gamete mentioned in the question carries two copies of X chromosome instead of a single copy. The probable reason for this might be nondisjunction (failure of separation of homologous chromosomes during meiosis I or failure of separation of sister chromatids during meiosis II).
If the sperm fertilising the egg (22+XX) carries an X chromosome, then the zygote formed would carry 44 autosomes and XXX sex chromosomes. This will lead to triple X syndrome in the female offspring.
If the sperm fertilising the egg (22+XX) carries a Y chromosome, then the zygote formed would carry 44 autosomes and XXY sex chromosomes. This will result in Klinefelter’s syndrome in the offspring. The affected offspring will develop into sterile males.
This has been explained via the following cross:-
The individuals affected with Turner's syndrome have a single copy of X chromosome. The offspring with Turner's syndrome is not possible as a result of the fusion of the gametes given in the question.
The individuals affected with Edwards syndrome have three copies of 18th chromosome instead of two copies per cell. The offspring with Edward's syndrome is not possible as there is no abnormality with respect to autosomes in the gametes mentioned in the question.
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