Trisomy Disorders and Chromosome 21

The video discusses trisomy, focusing on Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and Patau syndrome (trisomy 13). It explains why Down syndrome is more common due to fewer genes being affected by dosage compensation disruption. The video also covers the impact of chromosome size on gene expression and the lethality of each trisomy type. Chromosome 21 is the smallest, leading to fewer affected genes, while chromosome 13 is the largest, affecting more genes and making Patau syndrome rare.

Which trisomy disorder is the most common among humans?

• Edwards syndrome

• Patau syndrome

• Turner syndrome

• Down syndrome

What is the frequency of Edwards syndrome in the population?

• 1 in 1,000

• 1 in 10,000

• 1 in 5,000

• 1 in 16,000

What is the genetic cause of Down syndrome?

• Three copies of chromosome 21

• Two copies of chromosome 21

• Three copies of chromosome 18

• Three copies of chromosome 13

Which syndrome is associated with trisomy 13?

• Klinefelter syndrome

• Down syndrome

• Edwards syndrome

• Patau syndrome

How does dosage compensation affect trisomy disorders?

• It reduces chromosome size

• It increases the number of chromosomes

• It balances gene expression

• It disrupts gene expression

Why is Down syndrome less lethal compared to other trisomies?

• It affects fewer genes due to a smaller chromosome

• It affects more genes due to a larger chromosome

• It has no effect on gene expression

• It is not a genetic disorder

Which chromosome is the smallest among the autosomes?

• Chromosome 18

• Chromosome 21

• Chromosome 13

• Chromosome 22

How many protein-coding genes are present on chromosome 21?

• 256

• 622

• 285

• 343

What is the primary reason for the rarity of Patau syndrome?

• It affects a small number of genes

• It affects a large number of genes

• It is not a trisomy disorder

• It is not a genetic disorder

Why was chromosome 21 initially thought to be larger than chromosome 22?

• Due to its larger size

• Due to historical naming conventions

• Due to incorrect base pair count

• Due to incorrect gene count