Heredity Chapter 5, Day 4 Child 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