Lecture 13- Chromosomes

Question 1

What did the Chromosomal Theory of Inheritance state?

Answer 1

Genes are found at specific locations (loci) on chromosomes & the behavior of chromosomes during meiosis can explain Mendel’s laws of inheritance (law of segregation- become two daughter cells, independent assortment- alleles of two or more different genes get sorted into gametes independently of one another)

Question 2

On which chromosome is the SRY gene found? What does it code for?

Answer 2

Found on Y chromosome, codes for testes

Question 3

What does it mean for a trait to be the wild type?

Answer 3

Wild type (w+) refers to the phenotype of the typical form of a species as it occurs in nature

Question 4

What does it mean for a trait to be the mutant type?

Answer 4

Mutant type (w) refers to a phenotype that differs from the normal

Question 5

What are linked genes? What is their significance?

Answer 5

When genes are close together on the same chromosome, they are said to be linked. Due to their close proximity, linked genes will be inherited as a unit more frequently than not. Linked genes violate Mendel’s Law of Independent Assortment.

Question 6

What is a barr body?

Answer 6

Inactivated X-chromosomes in cells with more than one X-chromosome

Question 7

What is X-inactivation?

Answer 7

X-inactivation is a random process by which X-chromosomes are rendered inactive in cells with more than one X-chromosome

Question 8

What type of fruit fly did Thomas Hunt Morgan use in his experiment?

Answer 8

Droposphilia Melanogaster

Question 9

Autosomes

Answer 9

• 22 pairs, 44 total
• homomorphic (same shape)

Question 10

Sex Chromosomes

Answer 10

• 1 pair
• heteromorphic (not morphologically similar, meiosis, some regions synapse)

Question 11

Males are _________ and females are ___________

Answer 11

hetergametic, homogametic