Topic 2: Development Flashcards
(113 cards)
1
Q
What is development?
A
A series of progressive changes in form and function that occurs during an organism’s life cycle and continues until death.
2
Q
What are the 5 key stages of development?
A
- Fertilisation
- Cleavage
- Gastrulation
- Organogenesis
- Morphogenesis
3
Q
Where do the cytoplasm and mitochondria in the zygote come from?
A
The egg (not the sperm, all maternal)
4
Q
Where is the nucleus located in the zygote?
A
Animal pole
5
Q
Where are the nutrients concentrated in the zygote?
A
Vegetal pole
6
Q
What is the grey crescent?
A
Portion of cortical cytoplasm is amphibian embryos which is exposed after fertilisation. Proteins in the grey crescent control what form cells will take during development.
7
Q
What is cleavage?
A
Division of cells to form a blastula
8
Q
What is a blastula?
A
Hollow ball of cells (blastomeres)
9
Q
What are the 3 patterns of cleavage?
A
- Complete
- Incomplete-discoidal
- Incomplete-superficial
10
Q
What determines which cleavage pattern will happen?
A
- Amount of yolk
- Orientation of mitotic spindles
11
Q
What is complete cleavage?
A
- Cells are separated completely
- Cells with no/some yolk
12
Q
What happens in cleavage of cells with no yolk?
A
Cells are completely separated and are equal in size
13
Q
What happens in cleavage of cells with some yolk?
A
- Yolk impedes the formation of a cleavage furrow
- Cells divide completely but asymmetrically
14
Q
What happens in cleavage of cells with lots of yolk?
A
- Incomplete-discoidal
- Cleavage furrows don’t penetrate the yolk (incomplete)
- Blastodisc forms on top of the yolk
15
Q
What kind of cleavage occurs in birds?
A
Discoidal incomplete cleavage
16
Q
What kind of cleavage occurs in insects?
A
Superficial incomplete cleavage
17
Q
What happens in superficial incomplete cleavage?
A
- Nucleus divides inside egg
- Nuclei migrate to the edges of the cell and the membrane grows inwards which partitions the nuclei into separate cells
18
Q
What are the 3 cleavage patterns caused by mitotic spindle orientation?
A
- Radial cleavage
- Spiral cleavage
- Rotational cleavage
19
Q
What is radial cleavage?
A
- Mitotic spindles form at right angles or parallel to animal–vegetal axis
- Regular pattern of cells
20
Q
What is spiral cleavage?
A
- Mitotic spindles are diagonal to a–v axis
- Causes spiral patternq
21
Q
What is rotational cleavage?
A
- First division is parallel to a–v axis, second is at right angles, third is a right angle to that etc.
- Seemingly random pattern of cells
22
Q
What is gastrulation?
A
When a blastula becomes and embryo with 3 tissue layers and body axes
23
Q
What are the 3 tissue layers?
A
- Endoderm
- Mesoderm
- Ectoderm
24
Q
What forms from endoderm?
A
- Gastrointestinal tract (+ liver and pancreas)
- Respiratory system (lungs)
25
What forms from the mesoderm?
Bone, muscle, heart, kidneys, bladder, ovaries/testes and inner layer of skin
26
What forms from the ectoderm?
- Outer layer of skin
| - Nervous system
27
What is the blastocoel?
Cavity inside the blastula
28
How does gastrulation occur in sea urchins?
- Vegetal pole of blastula invaginates
- Cells migrate into blastocoel and form primary mesenchyme cells (mesoderm)
- Invagination forms archenteron (gut)
- Secondary mesenchyme cells connect archenteron to animal pole
- Mouth forms where blastopore was
29
How does gastrulation occur in birds?
- Hensen's node moves from anterior to posterior of blastodisc, leaving the primitive streak
- Primitive streak becomes blastopore: cells migrate through it into the blastocoel forming endoderm and mesoderm
30
What are the elements of the blastodisc?
- Epiblast
- Hypoblast
- Blastocoel (in between)
31
What forms from the epiblast?
Embryo
32
What forms from the hypoblast?
Extraembryonic membranes
33
How does gastrulation occur in mammals?
- Primitive groove forms in epiblast
| - Cells migrate through groove to form endoderm and mesoderm
34
What are the 2 elements of the mammalian blastula?
- Inner cell mass
| - Trophoblast (placenta)
35
What are the 2 elements of the mammalian inner cell mass?
- Epiblast (embryo)
| - Hypoblast (extraembryonic membranes)
36
What is a blastocyst?
Mammalian blastula in which some differentiation of cells has occurred
37
What is organogenesis?
Formation of organs and organ systems
38
What is neurulation?
Occurs early in organogenesis and begins the formation of the nervous system in vertebrates.
39
How does neurulation occur?
- Thickening of ectoderm above notochord (forms neural plate)
- Edges of neural plate grow to form ridges around a groove
- Ridges close over the top forming the neural tube
- Brain forms at anterior end of neural tube
40
What happens during body segmentation?
- Somites produce vertebrae, ribs, muscles
| - Neural crest cells break off and form peripheral nerves
41
What are the 4 extraembryonic membranes in bird eggs?
- Yolk sac
- Amniotic sac
- Chorion
- Allantois
42
What is the function of the yolk sac?
Nutrient transfer
43
What is the function of the amniotic sac?
Protection
44
What is the function of the chorion?
Gas/water exchange
45
What is the function of the allantois?
Waste storage
46
What is morphogenesis?
Cell differentiation and growth to form the complex adult shape
47
What are the 3 controlling factors of development?
- Cytoplasm
- Genes
- External environment
48
What is the genetic factor of devlopment?
Genes
49
What are the epigenetic factors of development?
- Cytoplasm
| - External environment
50
What does DNA do in very early embryos?
- Replicates
| - Does not make proteins (transcription switched off)
51
What controls early embryo development?
- Cytoplasm
- All enzymes and proteins produced by cytoplasm
- Metabolism and cell division controlled by cytoplasm
- MATERNAL CONTROL
52
What is genomic activation?
- Transition from maternal control to genomic control in early development
- Causes cell division to slow down (transcription and translation take time)
53
What is determination?
- The commitment of a cell to a particular fate
| - Cells are totipotent before this
54
When does gastrulation occur?
After determination, before differentiation
55
How does cell differentiation occur?
- Differential gene expression (switch on/off)
| - Influenced by cytoplasm and extracellular environment
56
What is genomic equivalence?
All cells in an organism contain the same entire set of DNA
57
What are the 2 forms of chemical signalling involved in development?
- Cytoplasmic segregation
| - Induction
58
What is cytoplasmic segregation?
- When a factor is unequally distributed in the cytoplasm of dividing cells and ends up in some daughter cells but not others (nutrients in the vegetal pole)
- These differences in cytoplasmic make-up cause differentiation of cells
59
What is induction?
When a factor is secreted by some cells to induce other cells to differentiate
60
How does primary induction occur in amphibians?
Cells moving over the dorsal lip of the blastopore (Spemann organiser) induce overlying ectoderm to form neural tissue
61
How does primary induction occur in birds?
Cells moving over Hensen’s node are induced to form the Central Nervous System
62
Where does secondary induction occur in vertebrates?
Series of induction events lead to development of the eye
63
What gives positional information to developing cells?
The concentration gradient of morphogens
64
What makes a signal a morphogen?
- It directly affects target cells
| - Different concentrations cause different effects
65
What is the role of BMP2?
- Morphogen produced at the base of limb buds
| - Highest dose forms thumb, lowest dose forms little finger
66
What is genomic imprinting?
- In mammals, some development genes are active only if they come from a sperm, others only if they come from an egg
- Why mammals can't reproduce by parthenogenesis
67
Which syndrome is caused by a deletion on paternal chromosome 15?
Prader-Willi Syndrome
68
Which syndrome is caused by a deletion on maternal chromosome 15?
Angelman Syndrome
69
What are the 4 types of segmentation genes?
- Gap genes
- Pair rule genes
- Segment polarity genes
- Homeotic genes
Act one after the other
70
What are gap genes?
Organise large areas along the anterior-posterior axis
71
What are pair rule genes?
Divides the embryo into units of 2 segments each
72
What are segment polarity genes?
Determine segment boundaries
73
What are homeotic genes?
They are expressed along the length of the body and determine differentiation of the segments
74
What are Hox genes?
- Type of homeotic genes
- Control differentiation
- Expressed along the body in the order they appear on the chromosome
75
What does the homeotic gene mutation antennapedia cause in flies?
Legs where antennae should be
76
What does the homeotic gene mutation bithorax cause in flies?
Extra thorax so extra set of wings (2)
77
How many cells are programmed to die in C.elegans development?
131
78
What happens when a mouse is raised in a microbe-free environment (environmental control of development)?
- Lacks normal gut bacteria
| - Gut bacteria induce gene expression in the intestine, which is essential for normal capillary development
79
What is folic acid needed for in human development (environmental control of development)?
Preventing neurulation defects
80
What does iodine deficiency cause in humans?
- Goitre in adults (hyperthyroidism)
- Cretinism in babies
Body can't make iodine, must get it from environment
81
What is cyclopamine?
- Chemical in corn lily plant which causes birth defects in lambs
- Inhibits Sonic Hedgehog protein which is involved in formation of the neural system
82
What is a clone?
An individual which is genetically identical to another individual
83
What are the 4 methods of cloning?
- Natural
- Embryo splitting
- Reprogramming somatic cells
- Nuclear transfer
84
What are 2 examples of natural cloning?
- Asexual reproduction
| - Monozygotic twins
85
What is cloning by embryo splitting?
- Spemann experiment
| - Artificial version of monozygotic twins
86
What is cloning by reprogramming somatic cells?
- Reverse differentiation of adult cells
| - Grow clone of donor
87
Why is cloning by nuclear transfer controversial?
- Invasive
- Technical problems
- Ethical dilemma
88
How is cloning by nuclear transfer done?
Nucleus from donor cell is injected into an enucleated fertilised egg
89
How were Megan and Morag cloned?
- EMBRYO donor cells put into G0 by removing growth factors
| - Nuclei from donor embryos injected into enucleated egg cells and grown in surrogate
90
How was Dolly cloned?
- Arrested the development of ADULT cells and fused with enucleated egg cells
- Transplanted into surrogate
91
Who is Polly?
- First transgenic mammal clone
| - Genetically modified to have Human Factor 9 protein in milk which is used to treat haemophilia
92
What are some uses of cloning?
- Medical research
| - Conservation
93
What are 2 problems associated with cloning for conservation?
- Who decides which species should be cloned?
| - Doesn't address issue of habitat loss
94
What is a misunderstanding about cloning?
Can't bring back a loved one:
- Only DNA is cloned- not cytoplasm
- Clones have own mutations
- Environment is important
95
What are the problems associated with cloning?
- Clone has the telomeres of its parent so is born with shorter telomeres than usual which causes age-related diseases at a young age
- Large foetus syndrome and prolonged gestation
- Low success rate
- Lack of genetic variation
- Ethical issues with human cloning
96
What is therapeutic cloning?
- Somatic cell nucleus injected into enucleated egg and grown to form embryonic stem cells
- Treat stem cells with growth factors to induce them into forming different types of stem cells
- Use to replace damaged cells
97
What do stem cells produce?
- More stem cells
| - Differentiated progeny cells
98
What does Dopamine deficiency cause?
Parkinson's disease
| Dopamine-producing cells die over time
99
How does the environment influence development in clown fish?
Can change from male to female if the number of females drops below a certain level
100
What 3 things do Evo Devo biologists study?
- How changes in the genes that regulate development affect the adult forms of organisms
- How those genes have changed during the course of evolution
- How these changes have influenced evolution
101
In what 3 ways can changes in developmental genes change morphology?
- Mutations in genes that regulate development
- Changes in the spatial expression of developmental genes (where it's expressed)
- Changes in the temporal expression of developmental genes (timing of expression)
102
What is modularity?
Sections of the body can change independently of eachother
103
Why don't insects have legs on their abdomens?
They all carry a mutation of the Ubx gene which is expressed in the abdomen. This means it represses the dll gene which is essential for leg formation.
104
What change led to ducks having webbed feet?
- BMP4 morphogen promotes apoptosis and destroys webbing in chicken feet
- Gremlin is a BMP4 inhibitor which protects the toes
- Gremlin began to be expressed in the webbing which causes webbed feet to remain in ducks
- Spatial change
105
What is heterochrony?
When the timing of developmental processes shift independently of eachother
106
What are the 2 types of environmental cues that determine development?
- Cues necessary for normal development
| - Signals closely correlated with future conditions
107
What protein is necessary for mosquito egg production?
Vitellogenin
108
How are environmental cues important for normal development in mosquitos?
A blood meal stimulates production of vitellogenin
109
How are environmental cues important for normal development in leafhoppers?
Require specialised bacteria symbiotes for normal gut formation
110
How do developing Squinting Bush Butterflies use environmental cues to adapt to future conditions?
The temperature when they're in larval form determines whether they'll grow into the dry or wet season form by changing dll gene expression
111
What is polyphenism?
When 2 or more phenotypes can be produced from the same genotype (e.g. wet/dry season butterflies dll)
112
How do developing Nemoria moths use environmental cues to adapt to future conditions?
- Spring form larvae feed on oak flowers so resemble oak flowers
- Summer form feed on oak leaves so resemble oak leaf stems (better for camouflage because no flowers left)
113
How do spadefoot toads change development in response to environment?
- If pond starts to dry up, tadpoles develop a wider mouth, powerful jaw muscles and a modified intestine
- They eat other tadpoles to speed up their development so they're fully formed when the pond dries up
