Nondisjunction and Chromosomal Disorders

The video tutorial explains nondisjunction, a failure in chromosome separation during meiosis, leading to conditions like Down syndrome. It covers nondisjunction in both meiosis I and II, showing how it results in abnormal chromosome numbers in daughter cells. The tutorial also discusses the link between parental age and increased risk of nondisjunction.

What is nondisjunction in the context of meiosis?

• The successful separation of chromosomes

• The failure of homologous pairs or sister chromatids to separate

• The duplication of chromosomes

• The deletion of chromosomes

During which phase of meiosis does nondisjunction occur if homologous pairs fail to separate?

• Anaphase one of meiosis one

• Anaphase two of meiosis two

• Prophase one of meiosis one

• Metaphase two of meiosis two

What is the result of nondisjunction during anaphase two of meiosis two?

• All daughter cells have the same number of chromosomes

• One daughter cell has an extra chromosome, one is missing one, and two are normal

• All daughter cells are missing chromosomes

• All daughter cells have extra chromosomes

Which of the following is NOT a result of nondisjunction?

• Normal distribution of chromosomes

• Extra chromosome in a daughter cell

• Missing chromosome in a daughter cell

• All daughter cells having identical chromosomes

If nondisjunction affects chromosome 21, what condition might result?

• Klinefelter syndrome

• Patau syndrome

• Down syndrome

• Turner syndrome

How many copies of chromosome 21 are present in a person with Down syndrome?

• Two

• Four

• Three

• One

What is the term used to describe three copies of chromosome 21?

• Tetrasomy 21

• Disomy 21

• Monosomy 21

• Trisomy 21

How can Down syndrome be identified through a karyotype?

• By counting the number of chromosomes

• By identifying three copies of chromosome 21

• By checking for missing chromosomes

• By looking for extra chromosomes in all pairs

What factor increases the risk of nondisjunction as it rises?

• The number of chromosomes

• The age of the parents

• The amount of genetic material

• The number of cell divisions

At what age does the risk of nondisjunction significantly increase?

• 45

• 40

• 35

• 30