1. What is Genetics? Objectives: 1. Explain the history of genetics.
2. Explain how genetics works. 1

2. Genetics is the study of heredity.
Heredity is the passing of traits from parent to offspring.
Your eye color, hair color, shape of your nose, etc...

3. Traits A trait is a characteristic that you receive from your parents
Traits A trait is a characteristic that you receive from your parents. For example: brown hair, blue eyes
Alleles
Different forms of a gene.
Dominant alleles- traits that cover up or masks other traits
Recessive alleles- traits that are masked and seem to disappear

4. What controls our traits?
Genes are found on our chromosomes.
Genes are made up of DNA.
Human body cells have 23 PAIRS of chromosomes…our sex cells have only 23 (total).
Why?

5. Gregor Mendel - Father of Genetics
Lived in 1800’s in Eastern Europe
Was taught about plants by Father
Became a monk
Famous experiment with plants.
Died without ever knowing his work would become famous

6. Dominant and Recessive Factors
Dominant traits appear to dominate or cover up other traits.
Recessive traits appear to disappear…but do they?

7. Alleles Homozygous Heterozygous
Two alleles for a trait that are exactly the same.
Example: TT or tt
Heterozygous
Two alleles for a trait that are different.
Written as Tt

8. Genotypes The inherited combination of alleles Represented by letters
Ex. The letter P might stand for purple flowers in peas

9. Phenotypes
Are physical traits that show as a result of a particular genotype.
Examples
Red is the phenotype for red flowering plants
Brown hair
Blue eyes
Tall
Short

10. Species Trait Individual Trait
Traits that are carried by all members of a species.
Example: The ability to walk upright in humans.
Individual Trait
Traits that make the individual different from others
of the same species.
Example: color of eyes, hair color, body build

11. Incomplete Dominance Can you explain how colors in flowers, for example, are blended? (For example, red and white alleles make pink flowers)
When both alleles are expressed in offspring, the condition is called incomplete dominance…in other words, no allele is dominant.
Read pages Draw within a Punnett Square Mendel’s experiments with red and white flowers.

12. Multiple Alleles
Many traits have more than 2 alleles that control them.
Blood is an example of a multiple allele.
Blood has 3 alleles.
3 major blood types: A B O

13. Punnett Squares y y Yy Y Yy Yy Yy Y
*A tool used to predict results in genetics.
*Uses your knowledge of dominant and recessive alleles. y y Yy Y Yy Yy Yy Y

14. Punnett Squares Shows genetic makeup or genotype of an organism.
A capital letter (G) stands for a dominant allele.
A small letter (g) stands for a recessive allele.
Every cell in body has 2 alleles for a trait.

15. Practice using Punnett Squares
Now let’s practice using Punnett squares!