19.3 Body Plans

Question 1

What is a homeobox gene? (1 mark)

Answer 1

A group of genes which all contain a homeobox.

Question 2

What is a homeobox? (2 marks)

Answer 2

A sequence of 180 pairs found within genes that are involved in regulating anatomical development.

Question 3

If the homeobox gene Pax6 mutates, what can it cause? (1 mark)

Answer 3

Blindness

Question 4

What is a hox gene? (2 marks)

Answer 4

Only found in animals.
help make sure body parts are in the right place.

Question 5

What is the difference between a diploblastic and a triploblastic animal? (2 marks)

Answer 5

A diploblastic animal has two primary tissue layers, whereas a triploblastic animal has three tissue layers.

Question 6

What does radial symmetry in an animal mean? (1 mark)

Answer 6

Only symmetry via the top and bottom.

Question 7

What does bilateral symmetry in an animal mean? (1 mark)

Answer 7

The animal has a left and right side, and a head and tail.

Question 8

What does asymmetry mean in an animal? (1 mark)

Answer 8

The animal has no lines off symmetry.

Question 9

What is apoptosis, give an example? (2 marks)

Answer 9

Programmed cell death, e.g., in the development of fingers.

Question 10

Hox genes regulate m_____ and a_______. (1 mark)

Answer 10

Hox genes regulate mitosis and apoptosis.

Question 11

Describe the process of apoptosis. (3 marks)

Answer 11

The cell shrinks and the nucleus condenses.
Apoptotic bodies break away from the main body of the cell, and get engulfed by phagocytes.
The nucleus fragments.

Question 12

Name two factors that can affect the expression of regulatory genes. (1 mark)

Answer 12

Stress
Drugs

Question 13

Give an example of a drug that affects the expression of regulatory genes, and describe how. (3 marks)

Answer 13

Thalidomide- given to pregnant women to prevent morning sickness.
Prevented the expression of a certain hox gene.
the babies had shortened limbs.