L20 - Hox genes

Question 1

what is hox gene

Answer 1

establishes orientation of body parts in embryo

Question 2

what is homeotic mutation

Answer 2

transformation of one body part to another,
so correct tissue but in wrong place

Question 3

example of homeotic mutation in fruit fly

Answer 3

3rd thoracic segment mutates into another 2nd thoracic segment
so another set of wings is made

Question 4

typical characteristics of hox genes

Answer 4

evolutionary conserved

transcription factors

homeodomain: acts as a dna binding motif

found clustered in genome

Question 5

by what mechanism to genes initially duplicated

Answer 5

tandem gene duplication

Question 6

paralogous genes

Answer 6

duplicated genes within a single genome

Question 7

orthologous genes

Answer 7

same gene in diff organisms

Question 8

2 mechanisms subfunctionalisation can occur

Answer 8

change in protein sequence

cahnge in the time/place of expression

Question 9

what happens if duplicated gene isnt subfunctionalised

Answer 9

ends up getting removed

Question 10

what is segmental duplication

Answer 10

vry big tandem duplication
like a whole chunk of chromosome is duplicated

Question 11

what are two ways whole genome duplication events can occur

Answer 11

allotetrapolidy
autotetraploidy

Question 12

allotetraploidy

Answer 12

hybridisation between two seperate species that causes 4n cell

Question 13

autotetraploidy

Answer 13

improper meiosis resulting in 2n germ cells
a 2n combines with another 2n germ cell
to give 4n

Question 14

how would u distinguish between autotetraploidy and allotetraploidy

Answer 14

allo has more differences in the genome
naturally cuz it’s two diff species

auto has less differences

Question 15

2R hypothesis

Answer 15

basically says that vertebrates went through 2 whole genome duplication events in their ancestry

each with some gene loss events after

eventually resulting in the gene clusters we see today

Question 16

how many hox genes in human

Answer 16

39
same as mouse
we acc share the same orthologous genes as mice

4 clsuters on 4 diff chromosomes

Question 17

why deos chick have 14 cervical vertebrate but mouse has 7

Answer 17

in their hox genes
C5 and C6 fall at the boundary of where cervical ends and thoracic begins

and in a chick, the boundary is at position 14

in a mouse its at position 7

hence hox genes determine positioning and boundaries of anatomical features

Question 18

what body part is affected by mutations in hox genes that control proximal-distal identities

Answer 18

limbs
so a mutation can get rid of femurs or ur radius

these genes originally pattern body axis, but during duplication, evolved to pattern limb orientation

Question 19

general rules about vertebrate hox genes:
how are hox genes generated

Answer 19

tandem and segmental duplication events

Question 20

general rules about vertebrate hox genes:
what do the ‘spacial domains’ of hox genes indicate

Answer 20

anterior posterior orientation
so as you go along, the genes will pattern for more posterior body parts

Question 21

general rules about vertebrate hox genes:
what does it mean when we say hox genes have spatial and temporal colinearity

Answer 21

their spatial collinearity is relation between ordering of Hox genes along the chromosome and their expression patterns along the head-tail axis

temporal colinearity is the relaition between the spatial ordering of the cluster and the time that they’re expressed