Week 5: Development of the Nervous System & Our Genes

Question 1

Stages of CNS development

Answer 1

1.Gastrulation
2.Primary Neurulation
3.Secondary Neurulation
4.Neurogenesis

Question 2

Gastrulation

Answer 2

development of germ layers

Question 3

Germ layers

Answer 3

layers of tissue formed during early development

Question 4

Types of germ layers

Answer 4

–Endoderm (inner tissue) →internal linings, organs
–Mesoderm (middle tissue) →skeletal system, muscles, connective tissue, organs
–Ectoderm (outer tissue) →skin and nervous system

Question 5

Primary neurulation

Answer 5

~ 3-4 weeks formation of the neural tube
–Development of neuroectoderm→becomes the neural plate →folds inwards to become neural groove →folds fuse to become neural tube

Question 6

Secondary neurulation

Answer 6

~4th week, the neural tube differentiates into 3 interconnected chambers
*Primary vesicles: Prosencephalon, Mesencephalon, Rhombencephalon

Question 7

Neurogenesis

Answer 7

~ 11 weeks: structures of the CNS are formed, but amount of cells and tissue rapidly increases… through NEUROGENESIS

Question 8

5 stages of neurogenesis:

Answer 8

✓Proliferation
✓Migration
✓Differentiation
✓Myelination
✓Synaptogenesis

Question 9

Proliferation stage

Answer 9

production of new cells

Question 10

ventricular zone

Answer 10

layer of cells that line the inside of the neural tube

Question 11

progenitor cells

Answer 11

Undifferentiated cells of the ventricular zone that divide and give rise to the CNS

Question 12

Progenitor cells undergo 2 types of division:

Answer 12

1. symmetrical division
2. Asymmetrical division

Question 13

symmetrical division

Answer 13

each cell division gives rise to two identical cells; increases the size of the ventricular zone and the brain that develops from it

Question 14

asymmetrical division

Answer 14

cell division that gives rise to another progenitor cell and one differentiated cell which gives rise to a glia cell OR neuron, which migrates away from the ventricular zone towards its final resting place in the brain

Question 15

Asymmetrical division gives rise to:

Answer 15

▪Radial glia cells = glia that offer scaffolding to migrating neuroblasts (and intermediate progenitor cells)
▪Cajal-Retzius(CR) cells = migrate to the end of radial glia, just inside pia, important for radial migration of neurons
▪Neuroblasts = undifferentiated neurons

Question 16

Inside-out development

Answer 16

Each new cell to be produced must pass through all the cells that came before it

Question 17

Migration

Answer 17

via chemicals
▪Reelin &Immunoglobulins (CR cells)

Question 18

differentiation

Answer 18

▪Differentiation of cells begin once migrated to resting place and express their genes to make proteins
▪Enables the cell to acquire distinctive characteristics ( appearance and function) within their particular region
▪Fate of the cell depends on where it “lands”

Question 19

Myelination

Answer 19

Myelin sheaths are produced from caudal to rostral development

Question 20

Synaptogenesis

Answer 20

Formation of synapses

Question 21

Lamina of the cortex

Answer 21

*Cortex contains up to 6 layers
*Cell structure and organization varies between different regions of the cortex
*Morphological differences relate to functional differences
*Presence and thickness of lamina depend on section of cortex–Example: Layer V (motor) vs. Layer IV (sensory)

Question 22

Is development random or programmed?

Answer 22

Roger Sperry’s experiments with newts proved it is not random (1943).

Question 23

Laws of inheritance

Answer 23

–1) Law of Segregation
–2) Law of Independent Assortment
–3) Law of Dominance

Question 24

law of segregation

Answer 24

Each inherited trait is defined by a gene pair; offspring inherit one genetic allele from each parent when sex cells unite in fertilization.

Question 25

Law of Independent Assortment

Answer 25

Genes for different traits are sorted separately from one another so that inheritance of one trait is not dependent on inheritance of another

Question 26

Law of dominance

Answer 26

An organism with alternate forms of a gene will express the form that is dominant.

Question 27

4 bases of DNA

Answer 27

adenine
guanine
cytosine
thymine

Question 28

4 bases of RNA

Answer 28

adenine
guanine
cytosine
uracil

Question 29

autosomal genes

Answer 29

genes on autosomes

Question 30

Sex-linked genes

Answer 30

genes on sex chromosomes (e.g., recessive gene on X chromosome, red-green colourdeficiency)

Question 31

sex-limited genes

Answer 31

genes on autosomes influenced by sex hormones (e.g., autosomal genes influenced by hormonal conditions –e.g., bearded men)

Question 32

Genetic mutation

Answer 32

Alterations in genetic code –there is change in DNA molecule

Question 33

Epigenetics

Answer 33

–Changes in the expression of a gene without changing the genetic code –turning a gene on or off
–Turned on or off by Tags: acetyl groups and methyl groups

Question 34

concordant

Answer 34

When both twins carry the disease

Question 35

discordant

Answer 35

When only 1 twin carries the disease

Question 36

candidate gene approach

Answer 36

examination of a single gene and it’s association with a behaviour based on theory
–APOEe4 of the APOE gene as a risk factor for Alzheimer’s disease

Question 37

Genome Wide Association studies (GWAS)

Answer 37

examine all genes and determine differences between two groups with a particular behavior of interest
–Discover mutations at several loci for a particular phenotype