Lecture 6 Chromosomal Theory of Inheritance Part I

What were Mendel's 'hereditary factors' identified as today?

Genes.

What does the Boveri-Sutton Chromosome Theory of Inheritance state?

Genes have specific loci on chromosomes, and chromosomes undergo segregation and independent assortment.

What is the Law of Segregation?

The two alleles for each gene separate during gamete formation.

What was the phenotypic ratio observed in the F2 generation from an F1 x F1 cross for dihybrid plants, according to Mendel?

9:3:3:1.

What organism did Thomas Hunt Morgan study to provide evidence for chromosomal linkage?

The fruit fly, Drosophila melanogaster.

What are wild-type phenotypes?

Traits that are common in the fly populations.

What does it mean for an allele to be 'hemizygous'?

A male needs only one copy of the allele due to having one X chromosome.

What type of genes are located on the Y chromosome?

Y-linked genes.

What does genetic recombination involving linked genes refer to?

The production of offspring with combinations of traits differing from either parent due to crossing over.

How does Sturtevant construct a genetic linkage map?

Using recombination frequencies to determine the distances between genes along a chromosome.

What is the expected recombination frequency for genes that are far apart on the same chromosome?

Near 50%.

Give an example of a disorder caused by recessive alleles on the X chromosome.

Color blindness.

Why are X-linked recessive disorders more common in males than females?

Males only need one copy of the allele, while females need two copies to express the trait.

What are the offspring called that have a phenotype matching one of the parental phenotypes?

Parental types.

What phenomenon occurs when genes on the same chromosome are inherited together?

Genetic linkage.

What is the term for genes that tend to assort independently due to being on different chromosomes?

Unlinked genes.