module 6 - 19.3 & 19.4 genetic control of body plans

Question 1

what is a body plan?

Answer 1

observable, spatial arrangement of an organisms body parts

Question 2

what are homeobox genes?

Answer 2

• a gene that controls the initial development of an organisms body plan
• highly conserved by natural selection

Question 3

what is the DNA like in homeobox genes?

Answer 3

double helix

Question 4

what do homeobox genes code for?

Answer 4

• code for transcription factors which control the expression of structural genes
• when these genes are expressed they ensure body plan is developed correctly

Question 5

what type of gene is a homeobox gene?

Answer 5

a regulatory gene

Question 6

what is a homeodomain?

Answer 6

the binding site of a transcription factor (produced by homeobox)

Question 7

what codes form a homeodomain?

Answer 7

• a specific DNA sequence within the homeobox gene
• binding site for transcription factors DNA

Question 8

what do all human homeobox genes contain?

Answer 8

the exact same homeobox, exact same sequence of 180 base pairs

Question 9

what happens if mutations occur in an organisms homeobox genes?

Answer 9

• its unlikely to survive
• so mutations in homeobox genes are selected against by natural selection

Question 10

what do structural genes do in DNA?

Answer 10

ensure development of a body plan

Question 11

why are homeboxes and homeobox genes highly conserved by natural selection?

Answer 11

because the homeobox found in animals, plants and fungi are remarkably similar

Question 12

what are hox genes?

Answer 12

• type of homeobox gene only found in animals
• gene that is involved in the symmetry of an animal

Question 13

what is a homeobox?

Answer 13

DNA sequence inside a homeobox gene

Question 14

what does a homeobox (not homeobox genes) code for?

Answer 14

transcription factors homeodomain

Question 15

when do body plans develop?

Answer 15

in an organisms embryonic stage

Question 16

which processes control the development of an organisms body plan?

Answer 16

• mitosis
• apoptosis

Question 17

how does mitosis control the development of an organisms body plan?

Answer 17

during cell cycle, mitosis causes cells to divide which produces new cells for growth, repair and reproduction

Question 18

how does apoptosis control the development of an organisms body plan?

Answer 18

causes cells to die which removes old cells or cells that are no longer needed

Question 19

what are mitosis and apoptosis controlled by?

Answer 19

• hox genes, which respond to internal and external stimuli
• depending on stimulus hox genes either initiate mitosis or apoptosis

Question 20

what are master control genes?

Answer 20

genes that control development

Question 21

what are the 2 types of DNA affected by transcriptional factors?

Answer 21

• promoters (stimulate transcription)
• enhancers (increase/decrease likelihood of transcription)

Question 22

what is a typical mechanism used by transcriptional factors to regulate gene expression?

Answer 22

stabalise or blo1ck binding of RNA polymerase to DNA