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ANAT1003 test 2 > Hox Genes > Flashcards

Hox Genes Flashcards

1
Q

what forms the axial skeleton?

A

somites

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2
Q

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

A

SHH from the notochord

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3
Q

what is endochondrial ossification?

A

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

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4
Q

which vertebrae are fused?

A

the sacral vertebrae and the coccygeal vertebrae

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5
Q

the adult drosophila has how many segments in the head?

A

7

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6
Q

the adult drosophila has how many segments in the thorax?

A

3

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7
Q

the adult drosophila has how many segments in the abdomen?

A

8

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8
Q

what does each segment of the thorax produce?

A

a pair of legs ventrally

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9
Q

what do the second and third thoracic segments produce?

A

wings dorsally

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10
Q

what does the second thoracic segment have a pair of?

A

wings

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11
Q

what does the third thoracic segment have a pair of?

A

halteres

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12
Q

who came up with the term homeosis?

A

william bateson

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13
Q

who first identified a mutation (bithorax) caused homeosis?

A

calvin bridges

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14
Q

what did bithorax (bx) cause?

A

it transformed the rostral half of the haltere into rostral wing

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15
Q

what did bithoraxiod cause?

A

it transformed the caudal half of the haltere into caudal wing

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16
Q

who discovered ultrabithorax?

A

wf hollander

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17
Q

what did ultrabithorax cause?

A

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

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18
Q

what type of mutation are bithorax, bithoraxiod and ultrabithorax?

A

loss-of-function

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19
Q

on which chromosome will you find the bithorax complex?

A

chromosome 3

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20
Q

how many chromosomes do drosophila have?

A

4

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21
Q

who carried out detailed genetic studies of bithorax mutations?

A

edward lewis

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22
Q

what do infra-abdominal (iab) mutations do?

A

cause homeotic transformations in the abdomen

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23
Q

how did the bithorax complex evolve?

A

its member genes had been formed during evolution by gene duplication

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24
Q

what does a homozygous deletion of the bithorax complex cause?

A

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

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25
Q

how many genes are in the bithorax complex?

A

3 protein coding genes

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26
Q

what are the genes in the bithorax complex called?

A

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

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27
Q

what affects Ubx?

A

all bithorax mutations

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28
Q

what affects abdA and AbdB?

A

infra-abdominal mutations

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29
Q

which regions do Ubx mutations affect?

A

3rd thoracic segment and 1st abdominal segment

30
Q

which regions do abdA mutations affect?

A

the 2nd through 5th abdominal segments

31
Q

which regions do AbdB mutations affect?

A

the 5th through 8th abdominal segments

32
Q

what is colinearity?

A

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

33
Q

What do gain-of-fuction Antennapedia mutations cause?

A

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

34
Q

where is Antp normally expressed?

A

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

35
Q

what type of mutation is Antp?

A

gain-of-function

36
Q

what do loss-of-function Antennepedia mutations cause?

A

they disrupt second leg development

37
Q

where is the Antp gene located?

A

on chromosome 3 in the antennapedia complex

38
Q

what other genes does the antennepedia complex contain?

A

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

39
Q

which regions do lab, pb and Dfd affect?

A

progressively more caudal regions of the head

40
Q

which regions does Scr affect?

A

the first thoracic segment

41
Q

which region does Antp affect?

A

the second thoracic segment?

42
Q

which genes are transcribed in the head?

A

lab, pb and Dfd

43
Q

which genes are transcribed in the thorax?

A

Dfd, Scr, Antp and Ubx

44
Q

which genes are transcribed in the abdomen?

A

Ubx, abdA and AbdB

45
Q

homeotic genes combine to make what?

A

a hox code

46
Q

how long is the homeobox?

A

180bp

47
Q

how long is the homeodomain?

A

60 amino acids

48
Q

what are homeotic proteins?

A

transcription factors

49
Q

what do homeotic proteins bind to?

A

the regulatory regions of different target genes in the genome

50
Q

what are selector genes?

A

transcription factors that make important cellfate decisions

51
Q

who discovered that there were similar homeobox genes in vertebrates?

A

walter gehring

52
Q

what was the first vertebrate homeobox to be discovered?

A

HoxC6

53
Q

how many homeobox genes do most vertebrates have?

A

39

54
Q

what are vertebrate homeobox genes called?

A

hox genes

55
Q

what do hox genes encode?

A

sequence-specific DNA binding proteins - transcription factors

56
Q

where are the 39 vertebrate hox genes found?

A

in hox complexes

57
Q

how many complexes do vertebrates have?

A

4 - all on different chromosomes

58
Q

what are vertebrate hox genes called?

A

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

59
Q

what are parologues?

A

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

60
Q

along which axis are hox genes expressed?

A

rostral-caudal

61
Q

what is the HOX code?

A

a unique combination of expressed HOX genes in each somite

62
Q

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

A

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

63
Q

has homeosis been seen in humans?

A

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

64
Q

what can having cervical rib cause?

A

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

65
Q

which HOX genes are found in all 3 complexes?

A

HOX4, HOX9 AND HOX13

66
Q

which HOX genes are expressed in cervical somites?

A

HOX4 AND HOX5

67
Q

which HOX genes are expressed in thoracic vertebrae?

A

HOX6-9

68
Q

where are HOX9-11 expressed?

A

in the lumbar region

69
Q

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

A

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

70
Q

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

A

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

ANAT1003 test 2 (8 decks)

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