Biological and Environmental Foundations

Textbook Ch 2

The beginnings of Ontogeny

Everyone began life as a single fertilized cell (zygote) which contained our entire genetic code
Each of us carries a “genetic code” from our parents
This single cell then begins to divide…

Mitosis

All body cells (except the sperm and egg)
- 46 chromosomes in 23 pairs
Body cells reproduce by a process called mitosis
- (except sperm & egg - meiosis)
During mitosis, the cell’s nucleus -including the chromosomes—duplicates itself and the cell divides
2 new cells are formed, each containing the same chromosomes, genes, and DNA as the original cell

Deoxyribonucleic acid (DNA)

Chromosomes: thread-like structures made up of deoxyribonucleic acid (DNA)
DNA is a complex molecule that has a double helix shape, like a spiral staircase, and contains genetic information
Any 2 humans are 99.6% identical in their DNA!
- Vanishing influence of ancestry

"Adam" and "Eve"

Genes & DNA

Genes are segments of DNA
- ~20,000 genes in the humans
Genes direct cells to
- reproduce themselves
- assemble proteins (100,000 in the body)
Proteins: the building blocks of cells and life
- Regulators that direct the body’s processes (Mader, 2008)

Proteins, bro💪

These 100,000 proteins, once produced, determine many physical characteristics
Genotype is translated into the Phenotype
- Environment
Natural Selection: the phenotype which “fits” the environment will successfully reproduce, passing on the genotype

Patterns of Inheritance

Dominant and Recessive genes
- Punnett square
- Carriers
- Incomplete Dominance

Sex and intersex

23rd pair known as "sex chromosomes". XX/XY
- Y chromosome has sex-determining region Y (SRY) protein
- X-linked and y-linked
XXY: Klinefelter syndrome
XO: Turner’s syndrome
XXX: Triple X syndrome
XYY: XYY syndrome
XX SRY-positive karyotype
XY: Androgen insensitivity

Autosomal (Non-Sex) Chromosome Diseases

Phenylketonuria (PKU): individual cannot properly metabolize phenylalanine, an amino acid
- Recessive
Sickle-Cell Anemia: impairs the body’s red blood cells
- Recessive (not typical D-R expression)
Huntington Disease: central nervous system degeneration
- Dominant

Studying impact of heritability

How do Genes interact with the Environment?

Theories

Theories

What if I told you, the environment can change genetic expression and inheritance regardless of genotype?

Tune in next time for epigenetics and prenatal development!