Question

1. What are homeotic genes? Provide two examples of such genes.

2. Describe the roles in patterning of the following genes in Drosophila: A)Bicoid B)Oskar C)Nanos D)Hunchback E)Eve F)Kruppel G)Giant H)Knirps

Answer 1

Homeotic genes are genes which regulate the development of anatomical structures in various organisms such as insects, mammals, echinoderm etc.These genes encode proteins known as transcription factors that direct cells to form various parts of the body.
Example of Homeotic gene
1) Hox gene in fruit fly
2) ParaHox gene of Mouse

A) Bicoid gene is a maternal effect gene whose protein concentration gradient patterns the anterior-posterior axis during Drosophila embryogenesis.

B) For Drosophila embryo development Oskar gene required.It defines the posterior pole during early embryogenesis.

C) Nanos gene help through establishment of the anterior-posterior body pattern and for the migration of primordial germ cells.

D) Hunchback gene help by the establishment of an anterior-posterior gradient of gene activity in the transition from unfertilized egg to developing zygote. it also help during thorax development in Drosophila.

E) For the development of both odd- and even-numbered parasegments Eve gene required.

F) Kruppel gene involved in the control of development of the thoracic and abdominal segments of the fly. Expression forms a single broad band, like a belt, around the middle of the embryo.

G) Giant gene of Drosophila encodes a b-ZIP DNA-binding protein that help in the expression of other segmentation gap genes.Gene giant is a segmentation gene that affects anterior head structures .

H) For Patternig Drosophila embryo by mean of short range repression knirps gene required.

Hope it clear your doubt. Thank you