Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

B3.0 > Hox Clusters: Changes To Gene Function And Regulation > Flashcards

Hox Clusters: Changes To Gene Function And Regulation Flashcards

1
Q

Homeosis

A

changing a structure to a different position

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Homeotic gene (Hox)

A
  • gene for position
  • 8 in drosophila (Hox)
  • homeotic mutants (e.g. bithorax)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Hox genes

A
  • A-> P axis
  • cluster: near each other in chromosomes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Hox genes

A
  • A-> P axis
  • cluster: near each other in chromosomes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Homeobox

A

Recognisable c180bp DNA region

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Homeodomain

A
  • c60aa protein region coded by Homeobox
  • helix 3 facilitates TF
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Spatial colinearity

A
  • Hox genes are expressed along the body in the same order they are found in the embryo
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Mus

A

39 Hox genes in 4 clusters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Somites

A

Form into vertebrae in the vertebral column

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Hox similarities

A
  • sequence between sp
  • expression pattern between sp
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Broken cluster?

A
  • Drosophila -> 5 and 3 separated by 100s of other gens
  • ancestrally once cluster, secondarily split
  • relaxed selection pressure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Other clades

A

Also have broken clusters, suggesting that these mutations are tolerated and not v important

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Mosquitoe

A
  • complete, unbroken cluster
  • can they tolerate cluster breakage?
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

C. elegans clusters

A

Broken into chunks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Ciona

A
  • sea squirt
  • broken + chromosome migration
  • you can still tell “which is which” from aa sequnece
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Is there anything in common between animals where Hox clusters have broken?

A
  • yes! Fast developing (model sp.)
  • e.g. Drosophila lays eggs in rotting fruit
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Slow development

A

Temporal colinearity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Fast development

A
  • no temporal colinearity
  • allows the cluster to break?
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Spatial colinearity

A
  • arthropods, annelids, molluscs, tunicates, amphioxus, vertebrates; pretty much all bilaterians
  • probably dates to the base
  • debated in Echinoderms
  • not the case for other genes
20
Q

Temporal colinearity

A
  • need a biochemical mechanism for turning them on one at a time, from A-> P during gastrulation
21
Q

Epigenetic temporal colinearity

A
  • remove complete heterochromatin over a series of days
  • transcriptional activation
  • highly descriptive evidence
22
Q

Removing heterochromatin

A
  • H3K27me3: transcriptional repression
  • gradually removed A->P
  • measured using chromatin immunoprecipitation in an ESC (mimics early development)
23
Q

Observing H3K27me3

A
  1. 8.5 days =3 active
  2. 9.5 days =more
    - time sequence
    - studying mouse hard pre8.5
24
Q

Transcriptional activation

A
  • H3K9Ac
  • gradually moves A->P (close developmental time points)
25
Q

Development

A
  • Posterior elaboration
  • progressive activation of sequence
26
Q

Temporal colinearity causes

A

Spatial colinearity

27
Q

Was temporal colinearty ancestral for Metazoa?

A

Non-conserved genes evolved for Hox activation in annelids and Crustacea

28
Q

Extra clusters?

A

Most - 1
Mice - 4 (tetrapods, sharks)
Teleosts - 7/8 (some lost); paralogy groups 13. 1 cluster went thru WGD, genes lost.
Salmonids - 16

29
Q

Identifying gene loss

A
  • Look at 39 Hox gene protein sequences to divine relations
  • number them
  • gaps; gene loss
  • 14 in vertebrates; 1 lost in mammals
30
Q

Identifying gene loss

A
  • Look at 39 Hox gene protein sequences to divine relations
  • number them
  • gaps; gene loss
  • 14 in vertebrates; 1 lost in mammals
31
Q

Cluster colinearity

A
  • in each cluster
  • overlap
  • some cluster on different chromosomes: 2, 7, 12, 17
32
Q

Is WGD selectively advantageous?

A
  • subfunctionalisation (tissue specificity)
  • spiders and horseshoe crab
  • mouse; gene KO = homeotic transformations tolerable; subtle tissue-specific expr swoon
33
Q

Drosophila

A
  • other homeoboxes not involved in segment identity
  • functional differentiation? Neofunctionalisation?
  • expressed in stripes in embryo
  • segment cascade (earlier than Hox)
  • e.g. maternally deposited bcd
34
Q

z2 and zen

A
  • roles in EEMs
  • evolved from Hox3
  • less developmental significance
  • changed functions and duplicated
35
Q

Butterflies, moths and hover flies

A
  • dozens of extra zen-like genes expressed in membranes around egg
36
Q

In insects, some hox genes have

A

Completely changed function

37
Q

How is changing role achieved without lethality?

A
  • hox mutant = homeosis
  • expression domain sliding, functional redundancy, Neofunctionalisation
38
Q

Hox TD

A

Might be just as bad as KO due to regulatory interference

39
Q

Are all 39 genes actually Hox?

A
  • KO expts
  • if you KO B4, slight changes to vertebral column; modifies axis segment; homeotic transformation
  • look for G/LOF
40
Q

LOF Hox mutation

A

Found for all

41
Q

GOF Hox mutations

A

Done for some eg a7

42
Q

B13 KO

A
  • does not change segment type (expected under homeosis)
  • makes tail longer; segment counting gene
  • spatially segregated (Mouse genome browser view)
  • broken cluster + escape
43
Q

Hoxbl3

A
  • in domestic sheep w/ long tails
  • nearby regulatory region insertion mutations; changed regulation
44
Q

Extra roles?

A
  • w/o tandem duplication
  • genital bud
  • limb bud (posterior genes of Hoxa, Hoxd)
  • blood cells (mainly Hoxb)
45
Q

Hoxb in blood cells

A
  • establish using haematopoesis in situ hybridisation
  • functional in haematopoetic stem cells
  • KO; loses multipotency
  • necessary
46
Q

Extra Hox in mollusc shells

A
  • ventral: nerve cord -> normal colinear expression
  • dorsal: no colinearity ; expressed in rings of shell formation
    Hypothesis: decoupled D/V regulation; shell development recruitment

B3.0 (23 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions