Non-Disjunction Disorders

Question 1

What is Non-Disjunction?

Answer 1

• The failure of homologous chromosomes or sister
  chromatids to separate properly during cell division
• Can happen during meiosis I or meiosis II
• Results in extra or missing chromosomes

Question 2

What does aneuploidy mean?

Answer 2

Abnormal chromosome number.

Question 3

How can Non-Disjunction occur during Anaphase 1?

Answer 3

• When homologous chromosome pairs fail to separate

Resulting in two gametes with an extra copy of one chromosome (n + 1) or gametes that have fewer chromosomes (n - 1)

Question 4

How can Non-Disjunction occur during Anaphase 2?

Answer 4

• When one pair of sister chromatids fail to separate

Resulting in two gametes with normal
number of chromosomes, and two gametes with an abnormal number of chromosomes
(one with n+1 and the other with n-1)

Question 5

What is Monosomy?

Answer 5

One missing chromosome. In humans, the zygote
will have only 22 pairs of chromosomes instead of
23 pairs.

Question 6

How can Non-Disjunction occur during Anaphase 1?

Answer 6

• When the homologous chromosome pairs fail to separate

Resulting in two gametes with extra (n + 1) chromosome or one less (n - 1) chromosome

Question 7

What are the three types of Aneuploidy?

Answer 7

Monosomy, Trisomy, Polysomy

Question 8

What is Monosomy?

Answer 8

One missing chromosome. The zygote will have only 22 pairs of chromosomes instead of 23 in humans.

Question 9

What is Trisomy?

Answer 9

One extra chromosome. The zygote will have 24 pairs of chromosomes instead of 23 in humans.

Question 10

What is Polysomy?

Answer 10

More than one extra chromosome.