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Flashcards in Hox Genes Deck (70):
1

what forms the axial skeleton?

somites

2

what induces sclerotome to migrate around the notochord and neural tube?

SHH from the notochord

3

what is endochondrial ossification?

when sclerotome cells differntiate the cartilage (and subsequently bone) of the vertebrae and ribs

4

which vertebrae are fused?

the sacral vertebrae and the coccygeal vertebrae

5

the adult drosophila has how many segments in the head?

7

6

the adult drosophila has how many segments in the thorax?

3

7

the adult drosophila has how many segments in the abdomen?

8

8

what does each segment of the thorax produce?

a pair of legs ventrally

9

what do the second and third thoracic segments produce?

wings dorsally

10

what does the second thoracic segment have a pair of?

wings

11

what does the third thoracic segment have a pair of?

halteres

12

who came up with the term homeosis?

william bateson

13

who first identified a mutation (bithorax) caused homeosis?

calvin bridges

14

what did bithorax (bx) cause?

it transformed the rostral half of the haltere into rostral wing

15

what did bithoraxiod cause?

it transformed the caudal half of the haltere into caudal wing

16

who discovered ultrabithorax?

wf hollander

17

what did ultrabithorax cause?

it weakly transformed halteres into wings when heterozygous but killed the embryo when homozygous

18

what type of mutation are bithorax, bithoraxiod and ultrabithorax?

loss-of-function

19

on which chromosome will you find the bithorax complex?

chromosome 3

20

how many chromosomes do drosophila have?

4

21

who carried out detailed genetic studies of bithorax mutations?

edward lewis

22

what do infra-abdominal (iab) mutations do?

cause homeotic transformations in the abdomen

23

how did the bithorax complex evolve?

its member genes had been formed during evolution by gene duplication

24

what does a homozygous deletion of the bithorax complex cause?

it transforms the third thoracic segment and all abdominal segments into a second thoracic segment

25

how many genes are in the bithorax complex?

3 protein coding genes

26

what are the genes in the bithorax complex called?

Ulltrabithorax (Ubx), abdominal-A (abdA) and abdominal-B (AbdB)

27

what affects Ubx?

all bithorax mutations

28

what affects abdA and AbdB?

infra-abdominal mutations

29

which regions do Ubx mutations affect?

3rd thoracic segment and 1st abdominal segment

30

which regions do abdA mutations affect?

the 2nd through 5th abdominal segments

31

which regions do AbdB mutations affect?

the 5th through 8th abdominal segments

32

what is colinearity?

the correlation between a genes chromosomal position and the segments it affects

33

What do gain-of-fuction Antennapedia mutations cause?

antennae to be transformed into legs with a bristle pattern that corresponds to that of the 2nd thoracic legs

34

where is Antp normally expressed?

in the thorax, but the dominant mutation causs it to be expressed in the head as well

35

what type of mutation is Antp?

gain-of-function

36

what do loss-of-function Antennepedia mutations cause?

they disrupt second leg development

37

where is the Antp gene located?

on chromosome 3 in the antennapedia complex

38

what other genes does the antennepedia complex contain?

labial (lab), proboscipedia (pb), Deformed (Dfd) and Sex combs reduced (Scr)

39

which regions do lab, pb and Dfd affect?

progressively more caudal regions of the head

40

which regions does Scr affect?

the first thoracic segment

41

which region does Antp affect?

the second thoracic segment?

42

which genes are transcribed in the head?

lab, pb and Dfd

43

which genes are transcribed in the thorax?

Dfd, Scr, Antp and Ubx

44

which genes are transcribed in the abdomen?

Ubx, abdA and AbdB

45

homeotic genes combine to make what?

a hox code

46

how long is the homeobox?

180bp

47

how long is the homeodomain?

60 amino acids

48

what are homeotic proteins?

transcription factors

49

what do homeotic proteins bind to?

the regulatory regions of different target genes in the genome

50

what are selector genes?

transcription factors that make important cellfate decisions

51

who discovered that there were similar homeobox genes in vertebrates?

walter gehring

52

what was the first vertebrate homeobox to be discovered?

HoxC6

53

how many homeobox genes do most vertebrates have?

39

54

what are vertebrate homeobox genes called?

hox genes

55

what do hox genes encode?

sequence-specific DNA binding proteins - transcription factors

56

where are the 39 vertebrate hox genes found?

in hox complexes

57

how many complexes do vertebrates have?

4 - all on different chromosomes

58

what are vertebrate hox genes called?

HOXA (human chromosome 7), HOXB (human chromosome 17), HOXC (human chromosome 12) and HOXD (human chromosome 2)

59

what are parologues?

genes at the same location in each complex and show the greatest degree of sequence similarity

60

along which axis are hox genes expressed?

rostral-caudal

61

what is the HOX code?

a unique combination of expressed HOX genes in each somite

62

hox genes specify a somites position along the rostral-caudal axis. true or false?

false - they specify the type of vetebrae the somite will differentiate

63

has homeosis been seen in humans?

yes - some people (1/200) have an extra rib attached to the seventh 'cervical' vertebra

64

what can having cervical rib cause?

a form of thoracic outlet syndrome due to compression of the lower trunk of the branchial plexus or subclavian artery

65

which HOX genes are found in all 3 complexes?

HOX4, HOX9 AND HOX13

66

which HOX genes are expressed in cervical somites?

HOX4 AND HOX5

67

which HOX genes are expressed in thoracic vertebrae?

HOX6-9

68

where are HOX9-11 expressed?

in the lumbar region

69

what does a mutation in one of HOX9-11 cause?

a transformation of the first 4 lumbar vertebrae into rib bearing thoracic vertebrae

70

what does the expression of one of HOX9-11 in the thoracic region cause?

a transformation of the thoracic vertebrae into rib-less lumbar vertebrae