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Biology 467 > TF Regulatory Mechanisms > Flashcards

TF Regulatory Mechanisms Flashcards

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1
Q

Which two morphogens act on patterning the D-V axis by secreting morphogen from the dorsal side of the neural tube?

A

BMP and Wnt

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2
Q

Once morphogen gradients are established, describe how responding cells are “locked in” to a cellular program

A

Once a cell reacts to a morphogen and its cellular fate is determined, downstream target genes of the morphogen are activated and the cell can continue on this path independently of its exposure to a morphogen

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3
Q

Define a coherent feedforward loop

A

In a pathway x, y, z, the pathway from x > y > z is the same sign as the path from x directly to z

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4
Q

Define an incoherent feedforward loop

A

The sign of path X to Z is the opposite of the sign of the path from X to Z through transcription factor Y

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5
Q

What is the functional importance of incoherent feedforward loops? (3)

A
  1. can generate temporal pulses of Z response
  2. accelerate the response time of z
  3. act as a band-pass amplitude filter providing maximal Z activity for intermediate x activity
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6
Q

What types of variables affect feedforward loops? (3)

A

concentrations of x, y and z
time
post-transcriptional mechanisms

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7
Q

what is the advantage of a double-negative gate over direct activation from x > z?

A

More locations for regulation, and more control over the overall mechanism - can directly turn Z on and off instead of indirectly turning Z off

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8
Q

Describe the fruit fly antennapedia mutation

A

Legs develop where antennae should be

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9
Q

Define a homeotic selector gene

A

A gene which determines the positional identity of a segment

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10
Q

Who coined the term homeosis. Define homeosis

A

William Bateson in 1894 - definition: a being made like, resemblance

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11
Q

Describe the chromosomal organization of hox genes

A

They appear on the chromosome ordered as they would be expressed along the AP axis (anterior genes first for head, posterior genes last for feet)

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12
Q

In flies there are two major homeotic gene complexes, what are they called?

A

Antennapedia complex, bithorax complex

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13
Q

What are the 4 very general regions of the fly larval cuticle from most anterior to most posterior

A

Head (acron), thorax, abdomen, telson

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14
Q

The anterior hox genes in flies are located at the (5’, 3’) end of the chromosome

A

5’

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15
Q

Describe the common mechanism which prevents mutations such as the antennapedia mutation

A

Normally other genes repress hox genes dedicated to other body segments

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16
Q

Homeotic selector genes are sometimes also called…

A

Realisator genes

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17
Q

All homeodomain genes have… What is this motif called?

A

A 60 aa conserved region called the homeodomain

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18
Q

The homeodomain area of a gene codes for…

A

Transcription factor

19
Q

Genes with homeodomains are called

A

Homeobox genes

20
Q

Approximately how many homeobox genes are there in humans?

A

235

21
Q

Describe the anatomy of the homeobox

A

3 alpha helix region where TFs bind

22
Q

What is the core binding sequence on DNA to which homeobox proteins bind?

A

TAAT

23
Q

Homeodomain sequence specificity is achieved at this location…

A

The 9th amino acid of helix 3

24
Q

Flies have the Hom-C cluster of homeodomain genes. How many paralogous clusters exist in mammals? Why do mammals have more of these?

A

4 clusters

Have them from random gene duplication at some point in evolution

25
Q

Of the 4 paralogous hox gene clusters that mammals have (hom-C in flies), what regions of the gene are particularly conserved among all paralogous genes in mammals?

A

10 and 11 regions - may have some regulatory role which has promoted conservation

26
Q

What hox gene inhibits the formation of the thoracic skeletal region in mice?

A

Hox10

27
Q

What hox gene inhibits the formation of the lumbar skeletal region in mice?

A

Hox11

28
Q

Describe the relationship between the sacral, lumbar, and thoracic skeletal regions and the hox genes which inhibit the formations of these regions

A

thoracic formation inhibited by hox10, lumbar inhibited by hox 11, when both are inhibited the region becomes sacral

29
Q

Describe hox gene expression within a limb: how are the genes represented along the chromosome?

A

They are ordered in sequence as they are expressed on the limb

30
Q

Mutations in Hoxa11 and Hoxd11 (the only two hox genes in the zeugopod region) in mice results in…

A

Complete loss of the ulna and radius (the bones of the zeugopod area)

31
Q

During the initial stages of development, hox genes are…

A

globally silent

32
Q

Describe the activation of hox genes

A

They are activated progressively and directionally (e.g. posterior to anterior in deuterostomes) - this sequence of activation is the same sequence as the genes appear on the chromosome

33
Q

Define temporal colinearity

A

The activation of hox genes in sequence from posterior to anterior as development progresses

34
Q

The expression pattern reflected by temporal colinearity is largely activated through changes in…

A

Epigenetic expression

35
Q

What are the 2 main ways histones are modified?

A

Modifications of histone proteins occur at lysine 27 (inactive) or lysine 4 (active) - the area in which you have trimethylation of these residues will dictate whether your transcription factor is active or inactive

36
Q

Histone proteins make up a (1)-mer

A

Octamer

37
Q

What is the role of median motor column (MMC) neurons?

A

Span the whole SC, contain MN that project to axial muscles

38
Q

What is the role of hypaxial motor column (HMC) neurons?

A

Span the thoracic levels, innervate the body wall muscles

39
Q

What is the role of lateral motor column (LMC) neurons?

A

Contain motor neurons that innervate the limbs

40
Q

What is the role of preganglionic motor column (PGC) neurons?

A

Contain visceral motor neurons which innervate sympathetic ganglia

41
Q

The PGC neurons are a division of this subset of the nervous system

A

Autonomic

42
Q

The PGC neurons regulate…

A

Bodily functions and fight or flight response

43
Q

The PGC neurons are located in this region of the SC

A

thoracic

44
Q

In the chick, the PGC neurons are also called…

A

The Column of Terni (CT) neurons

Biology 467 (20 decks)

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