Genetic and Environmental Foundation We are made up of cells Each cell has a nucleus The nucleus contains chromosomes There are 23 pairs of chromosomes One chromosome is inherited from the mother and one from the father

Genetic Code Each cell in your body contains chromosomes. Each chromosome contains a long molecule of DNA. Each DNA molecule contains many genes Chromosomes are made up of a chemical substance called deoxyribonucleic acid (DNA) A gene is a segment of DNA along the length of the chromosome Genes can be of different lengths The DNA can duplicate itself through a process called mitosis

The Sex Cells There are two types of sex cells: male and female. The male sex cells are sperm, while the female sex cells are ovum. Meiosis is the cell division process When the sperm and ovum unite at conception, it results in a zygote

Determining whether it is a boy or girl 22 of the 23 pairs of chromosomes are matching pairs (this is known as autosomes-they are not sex chromosomes) The 23rd pair consist of sex chromosomes In females, this pair is called XX In males it is called XY The X is a large chromosome The Y is a short chromosome The sex of the new organism is determined by whether an the sperm is bearing an X or Y chromosome which fertilizes the ovum

Multiple Offspring Twins are created when a zygote that has started to duplicate separates into two clusters of cells that develop into two individuals These are called identical or monozygotic twins because they have the same genetic makeup

Chromosomal Abnormalities Down syndrome is the most common chromosomal disorder It occurs 1 out of every 770 live births In 95% of the cases, it results a failure of the 21 pair of chromosomes to separate during meiosis As a result, the individual receives three of these chromosomes rather than the normal two The effects of Down syndrome include: mental retardation, memory and speech problems Limited vocabulary Slow motor development

Chromosomal Abnormalities Individuals who are affected may have distinct physical features short, stocky build A flattened face A protruding tongue Almond shaped eyes Infants with down syndrome are often born with eye cataracts, hearing loss and heart and intestinal defects Affected individuals who live past age 40 show symptoms of Alzheimer’s disease The risk of bearing a child with down syndrome rises with maternal age

Matching Activity The goal of this activity is to match the correct answer to the correct phrase. On your tables you have a set of card with a sentence written on it. Read each sentence and match each sentence to the correct word You have three minutes to do this activity After three minutes, we will go over each sentence and determine what the correct answer is.