Week 5 - Genetics Flashcards
What is DNA?
Deoxyribonucleic acid
Why do genes come in pairs?
They are generally aligned along chromosomes (strands of genes).
What does RNA do?
Ribonucleic acid is synthesised from the blueprint of DNA.
What does messenger RNA do?
servse as a template for the syntehsis of protein molecules.
What are the four “bases” of DNA?
Adenine, Guanine, Cytosine and Thymine.
How do bases pair up?
Guanine - Cytosine
Adenine - Thymine
What determines one amino acid?
A sequence of RNA (3 bases) determine one amino acid.
When does the central nervous system begin to develop?
Around 2 weeks after conception.
What does the embryo look like at 2 weeks?
Like an elongated plate
Does the embryo have neural tissue at 2 weeks?
No.
When does the neural plate invaginate?
at around 20 days.
When do ganglia form?
24 days.
By what time do the hindbrain, midbrain and forebrain diffeerentiate?
by 7 weeks.
By what time is the basic layout of the brain developed?
11 weeks.
At birth, how much does the brain weigh?
About 350 grams.
At the end of the first year, how much does the brain weigh?
Around 1kg (close to adult weight of 1200-1400 grams).
What are the 5 distinct stage in the development of neurons?
Proliferation, Migration, Differentiation, Myelination, Synaptogenesis.
What happens during Proliferation?
Cells in ventricles divide - some become primite neurons and glia that go to new destination.
What happens during Migration?
cells follow chemical path toward final destination.
What happens during Differentiation?
axons and dendrites are formed while migrating
What happens during Myelination?
addition of insulating sheath that speeds transmission.. Doesn’t apply to all neurons. Improves speed and efficiency of transmission. This can take up to 20 years of age.
What happens during Synaptogenesis?
Formation of synapses, continues throughout life.
What determines the survival of a neuron?
Two conditions:
- must form synapse with target cell and receive a nerve growth factor (a neurotrophin) from that cell
- must also be stimulated to release neurotransmitters into synapse
What is Apoptosis?
programmed cell death that occurs when synapses receive little nerve growth factor (NGF). This happens if a neuron doesn’t meet both requirements.
What happens during migration?
The neuron plate sinks down to form invagination. Epidermus cells are at the ends of the plate. Stem cells are in the neural crest. Some remain there and divide to form new stem cells, others migrate away and become neurons or glia. The neural tube sinks beneath the epidermal cells.
What develops first?
The axon.
The dendrites typically develop when…
the cell reaches its destination.
What is the chemoaffinity hypothesis of synaptogenesis?
Neurons find specific target locations and are guided by chemical gradients.