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A Level Biology > 6.1 Body Plans & apoptosis > Flashcards

6.1 Body Plans & apoptosis Flashcards

1
Q

What is morphogenesis?

A

Regulation of the pattern of anatomical development

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2
Q

What controls development of all organisms?

A

The same group of genes

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3
Q

The genes were discovered by scientists investigating what?

A

Fruit flies with strange mutations e.g. Legs in the place of antennae

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4
Q

Why are fruit flies easy to study?

A

Small
Short life cycle
Easy to keep

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5
Q

(Homeobox genes) what is a homeobox?

A

Section of DNA 180bp coding for part of a protein of 60 amino acids

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6
Q

(Homeobox genes) what is the part of the protein called and what is it similar in?

A

Homeodomain

Similar in plants animals and fungi

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7
Q

(Homeobox genes) why are homeobox genes regulatory genes?

A

Responsible for switching genes on and off

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8
Q

(Homeobox genes) how have the homeobox genes been linked to humans and mice?

A

Common ancestor
Mutations led to very different organisms
Many homeobox genes present in both have same nucleotide sequence

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9
Q

(Homeobox genes) what happens when the pax6 homeobox gene is mutated?

A

It causes a form of blindness in humans, mice and fruit flies

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10
Q

(Hox genes) what are hox genes?

A

Group of homeobox genes only present in animals

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11
Q

(Hox genes) what are hox genes responsible for?

A

Ensuring correct positioning of body parts

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12
Q

(Hox genes) mammals have how many clusters of hox genes?

A

4 on different chromosomes

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13
Q

(Hox genes) in what order are hox genes expressed?

A

In the order they appear on chromosomes

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14
Q

(Hox genes)how many hox genes do humans have?

A

39

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15
Q

(Body plans) how are body plans represented ?

A

Cross sections through the organisms showing arrangement of body tissue

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16
Q

(Body plans) what do diploblastic animals have?

A

2 primary tissue layers

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17
Q

(Body plans) what do triploblastic animals have?

A

3 primary tissue layers

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18
Q

(Body plans) what is a body plan?

A

Cross section through an animal showing arrangement of tissue layers

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19
Q

(Body plans) what is radial symmetry?

A

Animals having symmetry around a central axis (diploblastic)

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20
Q

(Body plans) what is bilateral symmetry?

A

Body can be divided into 2 mirror image halves

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21
Q

(Body plans) what is a coelom?

A

Fluid filled cavity within the mesoderm

22
Q

(Body plans) the coelom enables independent movement of what?

A

The gut wall and body wall

23
Q

(Body plans) the coelom provides space of what?

A

Enlargement and development of internal organs

24
Q

(Body plans) what does the coelom act as?

A

Circulatory medium for transport

Storage area for excess or waste materials

25
Q

(Body plans) give an example of how animals are segmented?

A

Rings of a worm

Vertebrates backbones

26
Q

(Body plans) what do hox genes in the head control?

A

Development of mouth parts

27
Q

(Body plans) segments are multiplied over time and specialise to do what?

A

Perform different functions

28
Q

(Body plans) what do hox genes in the thorax control development of?

A

Wings
Limbs
Ribs

29
Q

(Body plans) individual vertebrae have developed from segments in the embryo called what?

A

Somites

30
Q

(symmetry) where is radial symmetry seen?

A

diploblastic animals like jellyfish which have no left or right side only a top and bottom

31
Q

(symmetry) where is bilateral symmetry seen?

A

most animals

they have sides, a head and a tail

32
Q

(symmetry) where is asymmetry seen?

A

sponges which have no lines of symmetry

33
Q

what does mitosis do?

A

increases cell number for growth

34
Q

what does apoptosis do?

A

programmed cell death - removes unwanted cells and tissues shaping body parts

35
Q

what can cells undergoing apoptosis release?

A

chemical signals stimulating mitosis leading to remodelling of tissues

36
Q

which genes regulate mitosis and apoptosis?

A

hox genes

37
Q

(apoptosis) what are the stages of apoptosis?

A

cell shrinks
DNA & proteins degraded
mitochondria degraded
blebs containing broken down organelles form of cell surface
engulfed by phagocytes
phagocytes release signals to inhibit inflammation

38
Q

(apoptosis) why do cells commit suicide?

A

defence against pathogens or damaged cells

or as part of normal development

39
Q

(apoptosis) when cells are infected by viruses why do they undergo apoptosis?

A

cytotoxic t lymphocytes kill them by making them undergo apoptosis

40
Q

(apoptosis) how do cells with DNA damage undergo apoptosis?

A

cells with damage to the DNA produce large amounts of the p53 protein which induces apoptosis

41
Q

(apoptosis) what do some forms of radiotherapy and chemotherapy do?

A

set off apoptosis in cancer cells

42
Q

(apoptosis) during synapse formation in the development of the NS what does apoptosis do?

A

removes extra synaptic connections so the right connections can be made to form a particular pathway

43
Q

(apoptosis) how is apoptosis involved in trimming and shaping?

A

removes excess tissue between fingers and toes

44
Q

(factors) what is stress and what is it due to?

A

condition when homeostatic balance in an organism is upset

die to external factors e.g. temperature or internal factors e.g. release of hormones

45
Q

(factors) what can drugs do?

A

affect activity of regulatory genes

46
Q

(factors) what did thalidomide do?

A

prevented normal expression of particular hox genes resulting in babies having shortened limbs

47
Q

(factors) why is thalidomide sometimes used in cancer treatment?

A

stops development of tumours by preventing the networks of capillaries essential for tumours to grow and develop

48
Q

what does it mean that oncology recapitulates ontology?

A

genes expressed in development of an embryo are expressed again by cancerous cells

49
Q

(apoptosis) apoptosis depends on positive signals such as what?

A

growth factor for neurones

interleukin for mitosis of lymphocytes

50
Q

(apoptosis) aptosis also depends on negative signals such as what?

A

high levels of oxidants e.g. peroxide ions

harmful radiation

A Level Biology (102 decks)

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