Questions: Traits such as sociability and aggressiveness are thought to be - monogenic - non-inherent - vestigial - polygenic Which of the following causes Down syndrome? - The presence of an extra chromosome on the 21st pair - The presence of only 22 pairs of chromosomes - The presence of more than 23 pairs of chromosomes - The presence of an extra chromosome on the 23rd pair

Question 11:
The answer is the last one: polygenic.
Explanation:

• Monogenic: This refers to traits controlled by a single gene. Traits like sociability and aggressiveness are influenced by multiple genes, not just one, so this is incorrect.
• Non-inherent: This term is not typically used in genetics to describe traits. Traits like sociability and aggressiveness are inherent, meaning they are influenced by genetic factors, so this is incorrect.
• Vestigial: This term refers to traits or organs that have lost their original function through evolution. Sociability and aggressiveness are not vestigial traits, so this is incorrect.
• Polygenic: This refers to traits that are influenced by multiple genes. Sociability and aggressiveness are complex traits affected by many genetic factors, making this the correct answer.

Question 12:
The answer is the first one: The presence of an extra chromosome on the 21st pair.
Explanation:

• The presence of an extra chromosome on the 21st pair: This is the correct cause of Down syndrome, also known as Trisomy 21, where there is an extra copy of chromosome 21.
• The presence of only 22 pairs of chromosomes: This would result in a different chromosomal disorder, not Down syndrome.
• The presence of more than 23 pairs of chromosomes: This is not specific enough and does not accurately describe Down syndrome, which specifically involves an extra chromosome on the 21st pair.
• The presence of an extra chromosome on the 23rd pair: This would affect the sex chromosomes and lead to a different condition, not Down syndrome.