1. Prenatal development

what is prenatal development

• life potential begins when sperm meets the egg

• occurs when the cells divide and the zygote is formed

• cell differentiation

• human gestation = 40 week

3 stages of Pre-natal development

• Germinal stage: period of the zygote - first 2 weeks

• Embryonic stage: Period of the embryo - first 2 weeks after conception

• Foetal stage: Period of the foetus - 8-40 weeks

Germinal Stage

• from fertilisation to when cell attatches to the wall of the uterus

• Continual cell division as it travels

sometimes these cells can divide to create monozygotic (identical)

Dizygotic (fraternal) - 2 eggs released and fertilised

implantation of the zygote results in HumanChorionicGonadatrophin hormone released

Embryonic Stage

• zygote is now called the embryo

• life supports systems are developed

• Differentiation: systems are developed

5 weeks: spine begins to form

6 weeks: head, chest, eyes, ears starting to develop

8 weeks: 1inch, all internal organs, face, head enlarges

Foetal stage

• Longest phase of development

8-12 weeks: the foetus is more recognisable as a human being

pregnancy consists of 3 trimesters

12 weeks marks the end of first trimester

Genotype

an organism's complete set of genetic material or the specific set of alleles (gene variants) it carries at a particular location in its DNA

Phenotype

the set of observable characteristics or traits of an organism

Teratology

the study of causes of birth defect

Teratogen - anything that could potentially cause a birth defect or negatively affect any area of development.

examples of teratogens

• diet

• diseases suffered by the mother

• Alcohol/ Drugs

• Genetics

• Maternal age

Trisomy 21 (down syndrome)

chromosome abnormality

extra chromosome is transferred in fertilisation

3 chromosomes where there should be 2 on the 21st chromosome

Dominant Genes

a version of a gene that masks or overrides the effect of a different version of the same gene when only one copy is present

Recessive Genes

a type of gene variation that only shows a physical trait or health condition when an individual inherits two identical copies of it—one from each parent