Lecture 2

Question 1

What is Mendel’s second law?

Answer 1

Mendel’s Second Law states that not only are the characters of each factor inherited randomly but the inheritance of each gene is independent of all other genes. This is the law of independent assortment.

Question 2

What is a test cross?

Answer 2

Mating something with a homozygous recessive individual

Question 3

What is the relationship between gene distance on a chromosome and probability of crossing over?

Answer 3

The closer the two genes are to each other, the fewer crossing over events are going to occur to give you recombinants.

Question 4

How do you measure gene distance?

Answer 4

% recombinants = #recombinant offspring / #total offspring = genetic distance. For example, In Morgan’s experiment, he got 305 recombinants and 2839 offspring. 305/2839 = 0.107 or 10.7 %. This is measured as 10.7 cM (centiMorgans) between two genes

Question 5

What is positional cloning?

Answer 5

Positional cloning is a laboratory technique used to locate the position of a disease-associated gene along the chromosome. This approach works even when little or no information is available about the biochemical basis of the disease. Positional cloning is used in conjunction with linkage analysis. It involves the isolation of partially overlapping DNA segments that progress along the chromosome toward a candidate gene.