What is the result of homologous chromosomes failing to separate ...

[sc00by25]

What is the result of homologous chromosomes failing to separate during meiosis?
 
  a. Neurofibromatosis
  b. Nondisjunction
  c. Polyploidy
  d. Conjoined twins

Question 2

The condition in which an extra portion of a chromosome is present in each cell is called:
 
  a. reciprocal translocation.
  b. partial trisomy.
  c. inversion.
  d. Down syndrome.

[amy.lauersdorf90]

Answer to Question 1

ANS: B
Nondisjunction is an error in which homologous chromosomes or sister chromatids fail to sepa-rate normally during meiosis or mitosis. Neurofibromatosis is not due to chromosome failure dur-ing meiosis. Polyploidy occurs when a euploid cell has more than the diploid number of chromo-somes. Conjoined twins are not due to chromosome failure during meiosis.

Answer to Question 2

ANS: B
Partial trisomy is a condition in which only an extra portion of a chromosome is present in each cell. A reciprocal translocation occurs when breaks take place in two different chromosomes and the material is exchanged. An inversion occurs when two breaks take place on a chromosome, followed by the reinsertion of the missing fragment at its original site, but in inverted order. Down syndrome is an aneuploidy of the twenty-first chromosome.