embryo development

Aims

• Introduction to genetics

• flow of genetic information from parent to offspring

• genetic aberrations

• development of the human and animal embryo

• embryonic development

• developmental aberrations

• development from embryo to adult

• the nature nurture debate

Development of the embryo

• Fertilised egg – single cell

• how does the information in the DNA generate

a complex structure?

• Gestation period

-Humans 266 days

-Mice 20 days

-Elephants 645 days

•happens early in the developmental cycle

stage 1:

stage 2:

stage 3:

Later development of the embryo includes:

• Neurulation

• Formation of spinal cord and brain (occurs after

gastrulation)

• Organogenesis

• Formation of organs: neurulation

problems:

Formation of limbs:

—

Organogenesis

• Cells are directed to specialise in different ways

• Controlled by genes being switched on and off

in different ways in different cells

Epigenetics

• Genetic changes not associated with changes in

the DNA sequence

• Genes permanently switched on/off

• determines cell type

Genes used in development:

• how do we know which genes are involved in

controlling development ?

• make use of mutants

• Drosophila (the fruit fly)

Homeotic mutants

• mutants that affect development

Genes which have universal role in development:

• HOX genes

• E.g. Eyeless mutant of Drosophila

Genes involved in development

Genetics vs the environment

• “nature – nurture debate”

• Clear genetic influences

• E.g. Haemophilia – presence of the defective

alleles causes the phenotype

• E.g. Ricketts – vitamin D deficiency causes

phenotype

• example of both - Rhesus blood group and pregnancy

• Blood groups Rh+ and Rh-

blood transfusion…Generates antibodies against RH+ leading to severe reaction