Animal development

Question 1

Define homeosis?

Answer 1

The replacement of part of one segment of an insect or other segmented animal by a structure characteristic of a different segment, especially through mutation.

Question 2

Characteristics of homeotic mutations?

Answer 2

Affects segment type not segment number.

Those affecting T2, T3, and A1-A8 map close to each other are the Bithorax Complex. (3 BX-C genes)

Those affecting the head are the Antennapedia complex. (5 ANT-C genes).

Each gene affects a certain segment.

Question 3

What are the ANT-C (Antennapedia Complex) and the BX-C (Bithorax Complex)?

Answer 3

Clusters/complexes of Hox genes. Hox genes tell cells where they are along head to tal axix. Expect
them to say they are in Drosophila.

Question 4

How do Homeotic genes work?

Answer 4

All 8 of the fly homeotic genes have a special motif - a 60 aa chunk within the protein called the homeodomain.

The DNA sequence that codes for this is called the homeobox

Genes get switched on in regions. Can tell the cells that they are in those regions. Can switch other genes on or off.

Question 5

General rules about vertebrate Hox gene expression?

Answer 5

Expressed in spatial domains along Anterior Posterior axis.

Domains overlap, unlike flies.