Lecture 15

Question 1

Gene that can act like a switch between alternate gene fates

Answer 1

Selector gene

Question 2

Antennapedia complex contains how many genes and does what

Answer 2

5 genes. For head and thoracic segments.

Question 3

Bithorax complex has what genes?

Answer 3

Ultrabithorax (ubx), AbdominalA (AbdA), AbdominalB (AbdB)

Question 4

What does Ultrabithorax do?

Answer 4

Required for identity of the third thoracic segment (T3)

Question 5

AbdA and AbdB do what?

Answer 5

Responsible for the segmental identities of the abdominal segments.

Question 6

Homeotic genes in flies do what?

Answer 6

Give segment identities. ie, form features that are generally different to parts from other segments

Question 7

Example of segment identity if T2 and T3

Answer 7

In T2, the normal wing is present, but in T3 a primitive wing that serves as a balancer, Halteres.

Question 8

Loss of function mutation in Ultrabithorax that does what?

Answer 8

Eliminates differences between T2 and T3. T3 develops into normal wings. HOMEOSIS

Question 9

Homeosis

Answer 9

Mutation that makes difference into similarity

Question 10

Homeosis gain of function mutation in Antennapedia

Answer 10

Mutation mislocalizes T2 gene for legs and places them in the head.

Question 11

Each of the 8 homeotic genes in the cluster is expressed in different regions of the AP axis therefore

Answer 11

Different patterns of Hox genes emerge, giving segment identity.
Fly exhibit colinearity.

Question 12

Colinearity

Answer 12

Physical ordering of the homeotic genes on the chromosome correlates precisely with the anterior-to-posterior ordering of their in- dividual gene expression domains in the embryo

Question 13

Do homeotic/Hox genes function maternally or zygotically?

Answer 13

Zygotically

Question 14

abdA and abdB is repressed by the products of

Answer 14

Hunchback and Krüppel, which restricts expression to abdomen and prevents expression in head and thorax.

Question 15

Ubx is activated by certain levels of

Answer 15

Hunchback so that it is first transcribed in a broad band in the middle embryo

Question 16

Frequently posterior homeotic repress anterior homeotic

Answer 16

Ubx mutant, Antp expresses back til abdA.

T3 forms T2-like wings if Ubx is deleted

Question 17

How is their expression locked in?

Answer 17

Alterations of chromatin mediated by the polycomb and trithorax genes, crucial for development

Question 18

Realisator genes

Answer 18

Genes that express the proteins responsible for constructing structures.

Question 19

Homeodomain is encoded by whom

Answer 19

Homeobox

Question 20

Bicoid and Ftz proteins are what transcription factors?

Answer 20

Homeodomain

Question 21

In T2 wingless does what?

Answer 21

Growth promoter and morphogen responsible for wing development. Ubx not expressed here.

Question 22

Homothorax is a transcription factor required for what?

Answer 22

Antennae development. Antp represses it in T3 by binding to enhancer of the gene.

Question 23

Distal-less is repressed in the abdomen by

Answer 23

Ubx and abdA, which keeps limbs from coming out of abdominal segments.

Question 24

Orthologous genes are

Answer 24

Same gene in different species.