6.1 Body Plans & apoptosis Flashcards
What is morphogenesis?
Regulation of the pattern of anatomical development
What controls development of all organisms?
The same group of genes
The genes were discovered by scientists investigating what?
Fruit flies with strange mutations e.g. Legs in the place of antennae
Why are fruit flies easy to study?
Small
Short life cycle
Easy to keep
(Homeobox genes) what is a homeobox?
Section of DNA 180bp coding for part of a protein of 60 amino acids
(Homeobox genes) what is the part of the protein called and what is it similar in?
Homeodomain
Similar in plants animals and fungi
(Homeobox genes) why are homeobox genes regulatory genes?
Responsible for switching genes on and off
(Homeobox genes) how have the homeobox genes been linked to humans and mice?
Common ancestor
Mutations led to very different organisms
Many homeobox genes present in both have same nucleotide sequence
(Homeobox genes) what happens when the pax6 homeobox gene is mutated?
It causes a form of blindness in humans, mice and fruit flies
(Hox genes) what are hox genes?
Group of homeobox genes only present in animals
(Hox genes) what are hox genes responsible for?
Ensuring correct positioning of body parts
(Hox genes) mammals have how many clusters of hox genes?
4 on different chromosomes
(Hox genes) in what order are hox genes expressed?
In the order they appear on chromosomes
(Hox genes)how many hox genes do humans have?
39
(Body plans) how are body plans represented ?
Cross sections through the organisms showing arrangement of body tissue
(Body plans) what do diploblastic animals have?
2 primary tissue layers
(Body plans) what do triploblastic animals have?
3 primary tissue layers
(Body plans) what is a body plan?
Cross section through an animal showing arrangement of tissue layers
(Body plans) what is radial symmetry?
Animals having symmetry around a central axis (diploblastic)
(Body plans) what is bilateral symmetry?
Body can be divided into 2 mirror image halves
(Body plans) what is a coelom?
Fluid filled cavity within the mesoderm
(Body plans) the coelom enables independent movement of what?
The gut wall and body wall
(Body plans) the coelom provides space of what?
Enlargement and development of internal organs
(Body plans) what does the coelom act as?
Circulatory medium for transport
Storage area for excess or waste materials
(Body plans) give an example of how animals are segmented?
Rings of a worm
Vertebrates backbones
(Body plans) what do hox genes in the head control?
Development of mouth parts
(Body plans) segments are multiplied over time and specialise to do what?
Perform different functions
(Body plans) what do hox genes in the thorax control development of?
Wings
Limbs
Ribs
(Body plans) individual vertebrae have developed from segments in the embryo called what?
Somites
(symmetry) where is radial symmetry seen?
diploblastic animals like jellyfish which have no left or right side only a top and bottom
(symmetry) where is bilateral symmetry seen?
most animals
they have sides, a head and a tail
(symmetry) where is asymmetry seen?
sponges which have no lines of symmetry
what does mitosis do?
increases cell number for growth
what does apoptosis do?
programmed cell death - removes unwanted cells and tissues shaping body parts
what can cells undergoing apoptosis release?
chemical signals stimulating mitosis leading to remodelling of tissues
which genes regulate mitosis and apoptosis?
hox genes
(apoptosis) what are the stages of apoptosis?
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
(apoptosis) why do cells commit suicide?
defence against pathogens or damaged cells
or as part of normal development
(apoptosis) when cells are infected by viruses why do they undergo apoptosis?
cytotoxic t lymphocytes kill them by making them undergo apoptosis
(apoptosis) how do cells with DNA damage undergo apoptosis?
cells with damage to the DNA produce large amounts of the p53 protein which induces apoptosis
(apoptosis) what do some forms of radiotherapy and chemotherapy do?
set off apoptosis in cancer cells
(apoptosis) during synapse formation in the development of the NS what does apoptosis do?
removes extra synaptic connections so the right connections can be made to form a particular pathway
(apoptosis) how is apoptosis involved in trimming and shaping?
removes excess tissue between fingers and toes
(factors) what is stress and what is it due to?
condition when homeostatic balance in an organism is upset
die to external factors e.g. temperature or internal factors e.g. release of hormones
(factors) what can drugs do?
affect activity of regulatory genes
(factors) what did thalidomide do?
prevented normal expression of particular hox genes resulting in babies having shortened limbs
(factors) why is thalidomide sometimes used in cancer treatment?
stops development of tumours by preventing the networks of capillaries essential for tumours to grow and develop
what does it mean that oncology recapitulates ontology?
genes expressed in development of an embryo are expressed again by cancerous cells
(apoptosis) apoptosis depends on positive signals such as what?
growth factor for neurones
interleukin for mitosis of lymphocytes
(apoptosis) aptosis also depends on negative signals such as what?
high levels of oxidants e.g. peroxide ions
harmful radiation
