body plans

Question 1

define body plan

Answer 1

general structure each individual organism assumes as it develops

Question 2

define morphogenesis

Answer 2

regulation of the pattern of anatomical development

Question 3

define homeobox genes

Answer 3

group of genes that regulate the development of anatomical structures in animals, fungi and plants
- contain very similar sequence of nucleotides - homeobox sequence

Question 4

define homeodomain

Answer 4

section of protein coded by homeobox that binds to DNA and switches other genes on/off

Question 5

define hox genes

Answer 5

group of homeobox genes that are only present in animals
- responsible for correct positioning of body parts

Question 6

describe how homeobox genes are similar across life and how they differ.

Answer 6

• 180 base pairs long, coding for 60 amino acids for homeodomain
• many organisms share similar homeobox gene nucleotide sequences
  Eg - Pax6 mutation causes blindness in humans and fruit flies

Question 7

describe the role of Hox genes in controlling the body plan of animals.

Answer 7

• order they appear in is order in which their effects are expressed in the organism
• responsible for the correct positioning of body parts

Question 8

define apoptosis

Answer 8

programmed cell death

Question 9

describe the process of apoptosis

Answer 9

• cell contents breaks up
• cell membrane shrinks into projections called blebs

Question 10

how is apoptosis controlled

Answer 10

by hox genes

Question 11

when does apoptosis occur

Answer 11

• if the cell is old
• if an error in the cell cycle is detected

Question 12

describe the role of mitosis in growth and development

Answer 12

increases the number of cells leading to growth

Question 13

describe the role of apoptosis in growth and development

Answer 13

shapes different body parts by removing unwanted cells and tissues

Question 14

describe the factors that may influence the rate of mitosis or apoptosis.

Answer 14

• external - change in temperature or light intensity
• internal - change due to release of hormones or psychological stress
• drugs eg: thalidomide

Question 15

Describe how the rates of mitosis and apoptosis are maintained at the correct level and what might occur if there is too much or too little apoptosis.

Answer 15

• regulated by Hox genes
• too much apoptosis = neurodegenerative diseases
• too little apoptosis = cancer