12/10/23: Development I

Zygote

An egg cell that has been fertilized by a sperm cell. It contains 23 pairs of chromosomes, with half of the chromosomes coming from the mother and half from the father. It lasts for approximately 2 weeks.

Chromosomes

Structures within cells that contain thousands of genes. They carry the hereditary information from both parents.

Genes

Units of hereditary information that are passed down from parents. They are located on chromosomes and determine various traits and characteristics.

Heterozygous

Gene pairs are different. For example, if an individual has a brown eye gene from one parent and a blue eye gene from the other parent, they would be heterozygous for eye color.

Homozygous

Gene pairs are the same. For instance, if an individual has two copies of the brown hair gene, they would be homozygous for hair color.

Sex-Limited Genes

genes present in males + females but, activated more in one sex due to hormones (facial hair, breasts)

Types of Genes

dominant or recessive

Dominate Gene

when paired w/ a recessive, you take on its trait

23rd pair of chromosomes

sex chromosomes

XX

female sex chrmosomes

XY chromosome

male sex chromosome

Males

determine the sex of a baby

Monozygotic (Identical) Twins

Rare; one egg is fertilized by one sperm, then divides into two; must be the same sex

Dizygotic (Fraternal) Twins

Most common; two eggs are released and fertilized by two separate sperm; can be same/opposite sex, hereditary via the mother