1. Cells and Inheritance
S7L3. Students will recognize how biological traits are passed on to successive generations.
a. Explain the role of genes and chromosomes in the process of inheriting a specific trait.

2. Essential Question:
What are the roles of genes and chromosomes in the process of inheriting a specific trait?

3. Sex Chromosomes
Reproductive (sex) Cells - Female contributes an egg & Male contributes the sperm.
23 pairs of chromosomes in each body cell.
The sex chromosomes carry genes that determine whether a person is male or female, as well as genes that determine other traits.
XX = girl XY= boy. These are called sex-linked genes.

4. The Roles of Mom and Dad
Because 23 genes come from Mom and 23 genes come from Dad, the reproductive cell division is different than somatic cells.

6. Mom
Dad

7. Using what you have learned, Test yourself.
Heterozygous?
Homozygous?
Purebred?
Hybrid?
Dominant?
Recessive?

8. What does it mean to be a carrier?
A carrier is a person who has one recessive and one dominant allele for a trait. But, why is this important?
Turn to page 148 in your textbook.

9. Punnett Square: Color Blindness
Genotype form
XX = female
XY= male
CC = Dominant normal vision
Cc= Normal vision (carrier)
cc = colorblindness
____= Colorblindness in male

10. How do genes and the environment affect each other.
Page 150 – Whole class
Diet
Physical factors such as muscle tone, hearing, eye sight, etc.

11. Briefly. What is a mutation?
This is a change in an organism’s trait or phenotype from what is normal. (The nitrogen bases are paired up wrong, completely replaced, or an extra pair is added). Remember Adenine, Thymine, Guanine and Cytosine: AT and GC.

12. What are genetic disorders?
Some genetic disorders are caused by mutations in the DNA of genes. Other disorders are caused by changes in the overall structure or number of chromosomes.
Examples: Cystic Fibrosis, Sickle-Cell Disease, Hemophilia, Down Syndrome (page 152).

13. What is a pedigree and how does it help?
A pedigree is an important tool that geneticists use to trace the inheritnace of traits in humans.
It is a chart or “family tree” that tracks which members of a family have a particular trait.

14. A closer look
A horizontal line connecting male and female represents marriage.
A circle represents a female.
A square represents a male.
A vertical line and a bracket connect the parents to their children.
A circle or square that is note shaded indicates that a person neither has the trait nor is a carrier.
A completely shaded square or circle indicates a person has a trait.
A half-shaded circle or square indicates that a person is a carrier.