The figure shows a karyotype prepared from cells taken during pregnancy. Chromosomes are arranged in pairs, apart from the sex chromosomes. The test is offe...
Question 1 Report
The figure shows a karyotype prepared from cells taken during pregnancy. Chromosomes are arranged in pairs, apart from the sex chromosomes. The test is offered when there is evidence that a fetus may have a chromosome condition.
(a) What is a karyotype used to show? [1]
(b) Describe the chromosome difference visible in Fig. 1. [1]
(c) Explain how meiosis can produce a sex cell with an extra chromosome. [2]
(d) Give two reasons why the result of this test should be discussed carefully with parents. [2]
Answer Details
(a) A karyotype shows the number and appearance of chromosomes in a cell. [1]
(b) One chromosome set has three chromosomes instead of a pair. [1]
(c) During meiosis, a pair of chromosomes may fail to separate. One sex cell then receives both chromosomes, so it has an extra chromosome. [2]
(d) The result may affect decisions about pregnancy, and the condition may affect the child's health or development. Parents may also need support to understand probabilities, and results are personal and confidential. Any two valid reasons gain credit. [2]
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