Development 2: What controls development? Flashcards

1
Q

What are the 3 control factors in development?

A

Cytoplasm (epigenetic)
External environment (epigenetic)
Genes (genetic)

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2
Q

During embryonic development, what normal DNA process is ‘turned off’?

A

Transcription

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3
Q

What is the cytoplasm’s role in embryonic development?

A

Controls metabolic cycles and instructions for driving cell division

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4
Q

Early development is controlled by which parent?

A

Maternally controlled, cytoplasm comes from mother

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5
Q

What is genomic activation?

A

change from maternal control to embryo control

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6
Q

Describe what happens once genomic activation has occurred.

A
  • Embryonic DNA starts transcription = cell division
  • Cell division slows down (because transcription & translation take time) = how this stage is identified
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7
Q

What does cell differentiation result from?

A

differential gene expression (certain genes are switched off = cell function)

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8
Q

What is differential gene expression influenced by?

A

the cytoplasm and the extracellular environment

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9
Q

Describe the results of the Experiment on frogs to test the role of cytoplasm on differentiation

A

Genomic equivalence = No info is lost in the early stages of development (every nucleus in every somatic cell contains all the genes for creating a whole new individual)

= Shows the cytoplasm controls the fate of a nucleus

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10
Q

Describe cytoplasmic segregation in development

A

when a factor is unequally distributed in the cytoplasm and ends up in some daughter cells but not in others, or in greater conc.s than in others
= cause differentiation of cells due to animal and vegetal poles differing in their developmental potential

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11
Q

Define induction in development

A

When a factor is secreted by some cells to induce others to differentiate

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12
Q

Describe primary induction in birds and amphibians

A
  • In amphibians, cells moving over the dorsal lip of the blastopore (Spemann organiser) induce overlying ectoderm to form neural tissue
  • In birds, cells moving over Hensen’s node are induced to form the CNS
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13
Q

The development of which sensory organ is an example of secondary induction?

A

the vertebrate eye

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14
Q

How do cells ‘know’ where they are in an animal?

A

By interpretating positional info = conc. gradient of a morphogen

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15
Q

A signal is a morphogen if …

A
  • It directly affects target cells (does not work through an intermediary)
  • Diff conc.s cause different effects
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16
Q

What is genomic imprinting?

A

in mammals some development genes are active only if they come from a sperm OR egg

17
Q

What are segmentation genes?

A

they influence the number, boundaries, and polarity of the body segments

18
Q

What do gap genes do in body segmentation?

A

organise large areas along the anterior large areas along the anterior-posterior

19
Q

What do pair rule genes do in body segmentation?

A

divide the embryo into units of 2 segments each

20
Q

What do segment polarity genes do in body segmentation?

A

determine segment boundaries

21
Q

What do homeotic (hox) genes do in body segmentation?

A

are expressed along the length of the body and determine what the segments will become

22
Q

Describe how body segmentation is controlled in mice

A
  • 4 families of homeotic genes (hox genes) control differentiation along the axis
  • Temporal and spatial pattern of expression of hox genes is tied together → also follows the linear order on the chromosome
23
Q

How do hox genes control segmentation? What do mutations result in?

A

they specify the properties of each segment, mutations in these can change a segments identity

24
Q

What is apoptosis?

A

programmed cell death, caused by the activation of ‘death’ genes

25
Q

Give an example of apoptosis in human development

A

In development, we have webbed hands and feet - the enzyme caspase stimulates apoptosis of this extra skin

26
Q

Give en example showing why environmental factors can be necessary for successful development

A

House mice raised in microbe-free environments lack gut bacteria
- Gut bacteria induce gene expression in the intestine which is essential for normal capillary development

27
Q

Give an example of environmental factors disrupting development

A

Cyclopamine inhibits the action of the Sonic Hedgehog protein, which is involved in the formation of the neural system

28
Q

Give an example of a developmental stage that is under both genetic and environmental control

A

Neurulation: primarily under genetic control, but environ derived material e.g vitamins and minerals are also needed
= neural tube defects can be reduced if the pregnant person receives enough folic acid