Developmental genetics - lecture 10

Question 1

What is superficial cleavage in Drosophila?

Answer 1

rapid nuclear divisions without forming separate cells

Question 2

How are gametes formed in Drosophila?

Answer 2

When some nuclei move to the posterior end

Question 3

What happens to Drosophila Melanogaster to form the blastoderm?

Answer 3

nuclei move to the edge of the blastoderm , to form syncytial blastoderm . Cell membranes form around cells to create a cellular blastoderm

Question 4

what does Invagination in Drosophila do, during gastrulation ?

Answer 4

A ventral furrow appears on the ventral surface and cellular movements begin to occur.

Future mesodermal cells move into the middle , this tube will then dissociate to form a layer internally

Question 5

When does Germ- band occur?

Answer 5

At the same time as gastrulation.

Question 6

What is Germ- band extension?

Answer 6

Movement of ventral tissue around the posterior end and onto the dorsal side . These cells invaginate in and become the midgut

Question 7

Forming neuroblasts

Answer 7

After invagination of future mesodermal cells, the ventral furrow closes.

Ectodermal cells move in between external ectoderm and internal mesoderm , forming the neuroblasts

Question 8

What is a genetic screen?

Answer 8

technique used to identify and study an interesting phenotype within a mutated genotype

Question 9

Forward genetics

Answer 9

Scientists start the mutation, then determine which genes are involved

Question 10

what are the three steps involved in forward genetics?

Answer 10

• Generate the mutants
• Identify genes that are mutated
• Find where the genes are expressed

Question 11

Why is Drosophila well suited to genetic screens?

Answer 11

• Quick generation time
• simple genome
• small and cheap
• easy to determine phenotype

Question 12

What are homeotic genes?

Answer 12

genes that control body plan axis and growth

▪transcription factors
▪control the pattern of body formation
▪contain a homeobox domain (HOX)
▪activate or repress other genes

Question 13

Collinearity

Answer 13

The order of expression in the embryo matches the order on the chromosome

Question 14

What genes control head development in Drosophila

Answer 14

Labial (Lab) and Deformed (Dfd)

Question 15

What genes control thorax development?

Answer 15

• sex combs reduced (SCR)
• Antennapedia (Antp)
• Ultrabithorax (Ubx)

Question 16

What genes control abdomen development?

Answer 16

• Abdominal A (abdA)

- Abdominal B (Abd B)

Question 17

Who won Nobel prize in 1995 for discoveries concerning early embryonic

Answer 17

Eric Wiecschaus and Christiane Nusslein - Volhard?

Question 18

What gives the antennae in the head?

Answer 18

Labial and Deformed give antennae

Question 19

What gene give the legs in the thoracic segment 1?

Answer 19

Sex combs reduced

Question 20

What gene gives legs and wings in thoracic segment 2?

Answer 20

Antennapedia

Question 21

What genes gives a pair of legs and halteres in thoracic segment 3?

Answer 21

Ultrabithorax and antennapedia

Question 22

What genes give no outgrowth in abdominal segment 4

Answer 22

UbaA Ubx and Antp

Question 23

What is syncytial blastoderm?

Answer 23

all the cleavage nuclei are contained within a common cytoplasm.

Question 24

What is the common form of Drosophila melanogaster?

Answer 24

• 1 pair of wings
• halteres
• 3 pairs of legs

Question 25

How do you generate mutants in forward genetics?

Answer 25

• male mutated
• Breed coproduce F1; producing some mutated animals and some normal
• F1 offspring mutated with more wild animals to produce F2 . Then F3.
• only 1/16 of the offspring will be homozygous recessive and therefore be mutated

Question 26

What begins gastrulation?

Answer 26

Appearance of a ventral furrow , then cellular movements can begin