Question

1. a) What types of chromosome abnormality can occur if there is a failure of chromosome separation in meiosis? Discuss the severity of these chromosome abnormalities.

b) What types of chromosome abnormality can occur if there is a failure of chromosome separation in mitosis? Discuss the severity of these chromosome abnormalities.

Answer 1

1. a) Chromosome separation failure can occur at two stage during meiosis, that at meiosis I and meiosis II .

Separation failure at Meiosis I - If homologous chromosomes fails to separate during meiosis I then two copies of gamete lack that paricular chromosome and two copies of gamete are with two copies of chromosomes. If a gamete with two copies of the chromosome combines with a normal gamete during fertilization, the result is trisomy (2n+1). Severity of this chromosome is that it can leads to Klinefelter syndrome (a trisomy genetic disorder) in males caused by the presence of one or more X chromosomes.

When separation failure occurs during meiosis II, the consequence is, one gamete that lacks that chromosome, two normal gametes with one copy of the chromosome, and one gamete with two copies of the chromosome. if a gamete with no copies of the chromosomes combines with a normal gamete during fertilization, the result is monosomy (2n-1). In this case sverity can be seen in Turner syndrome, a monosomy in which females may contain all or part of an X chromosome.

b) Failure of chromosomes to separate during mitosis Nondisjunction. This give rise to new cells with either extra or missing chromosomes, this condition is called aneuploidy. Human embryos with aneuploidy have a rare chance to survive development. About only 0.3 percent of human aneuploidy pregnancies are able to give a live birth. The children born with aneuploidy have severe genetic problems such as Down Syndroms, Turner syndrome, Edward’s Syndrome, Patau Syndrome and Kleinfelter’s Syndrome( aneuploidy disorders ).