Heredity

Chapter 5, Day 4Child Development

The Basic Rules of Heredity Heredity is the passing on, or transmission, of

biological traits from parent to child

A child’s hair color, eye color, skin color as well as their height or the way they look are all determined, in part, from the genetic information inherited from the parents.

Chromosomes Chromosomes are tiny structures found within

cells that contain the genetic information that is passed on from one generation to the next

Most of the cells in your body contain 23 pairs of chromosomes

A fertilized egg contains 46 chromosomes, 23 from the sperm(dad) and 23 from the ovum (mom)

Genes A gene is a section of a chromosome that

determines or affects a characteristic or trait

Genes come in pairs

The 46 chromosomes form the person’s DNA

DNA is the complex molecule that makes-up genes. DNA contains the genetic code DNA molecule has a specific gene for height, another

for weight, another for eye color, etc.

Dominant and Recessive Traits Individuals carry two genes for each trait

When the genes are the same, that characteristic automatically shows Two Dominant genes – characteristic automatically shows Two Recessive genes – characteristic automatically

shows

When the genes are different, the characteristic is controlled, or dominated by the Dominant gene One Dominant + one Recessive – Dominant shows

Dominant Hierarchy Dominant hierarchy

Tall dominates short Brown eyes dominate blue eyes Dark hair dominates blonde hair

Sex Chromosomes The gender of the child is determined at

conception

Each egg carries an X-chromosome

Each sperm carries either an X- or a Y-chromosome

Sex Determination Sperm (X) + Egg (X) = Girl (XX) Sperm (Y) + Egg (X) = Boy (XY)

Multiple Births The delivery of more than one baby (i.e., twins,

triplets, quadruplets) is called a multiple birth

Multiple births carry greater risk to the mother and the fetus’

Identical Twins Identical twins develop from a single fertilized

egg or zygote Have the same inherited traits Are the same sex (because they develop from identical

embryos)

Fraternal Twins Fraternal twins develop from two eggs released

at the same time from the ovary and are fertilized by two sperm No more alike than any other siblings May or may not be the same sex

Other Multiple Births Triplets, quadruplets, and other multiple births

are less common than twins

Caused by more than one egg being released and some of those eggs splitting.

Could result in a combination of Identical and Fraternal twins

Infertility Infertility is the inability to become pregnant.

Options for Infertile Couples Adoption Artificial Insemination – the father’s sperm is injected

into the mother’s uterus In vitro Fertilization – egg is extracted and egg and

sperm are combined in the lab. The fertilized egg is then inserted into the mother’s uterus

Ovum Transfer – donated egg plus in vitro fertilization Surrogate Mother – fertilized egg is inserted into

surrogate or artificial insemination process

Individual Activity

Heredity In the Works – Follow the instructions on the handout. Will Discuss as a Class

Culture Matters Essay – Follow the instructions on the handout. TURN IN TODAY!

HOMEWORK – What Is In My Genes? DUE NEXT CLASS