1. Genetics Dominant Vs. Recessive

2. Genetics
Genetics: The study of the passing on of traits from parents to offspring.
When we are tracking or writing out traits we use 2 letters

3. Dominant Genes
The stronger of the 2 genes for a trait is called the dominant gene.
Dominant genes are always written using a capital letter.
For the trait of height we will use the letter “t “
Dominant - Capital Letter T=tall

4. Recessive Genes The weaker gene is called the recessive gene.
Recessive genes are always written as a lower case letter.
For the trait of height we will use the letter “t “
Recessive - lowercase letter t=short

5. Recessive = non-roller
Tongue Rolling
Recessive = non-roller
Dominant = roller

6. Dimples
Dominant = Dimples
Recessive = no dimples

7. Hair
Dominant = Curly/wavy
Recessive = straight

8. How many letters are needed for each trait? 2
Dominant genes are? Stronger or Weaker
Which gene is dominant? t or T
Recessive genes are? Stronger or Weaker
Which gene is recessive? t or T

9. PURE tt Genotype= type of genes that you inherit
if an organism has 2 of the same genes for a trait it is homozygous or pure -examples: TT tt

10. HYBRID
if an organism has 2 DIFFERENT genes for a trait it is considered heterzygous or hybrid example: Tt

11. Phenotype= the physical trait an organism has
Phenotype= the physical trait an organism has. It depends on the gentoype
-examples
TT= Tall
Tt= Tall
tt= Short

12. Gregor Mendel The Father of Genetics Gregor Mendel was a monk who taught at a monastery school in Czechoslovakia. He spent a lot of time in the garden observing pea plants. He noticed that all the tall plants produced seeds that grew into tall plants. He also noticed that all the short plants produced seeds that grew into short pea plants. Both the tall plants and the short plants that Mendel observed were considered pure or homozygous. Offspring of pure lines have the same traits as the parent plant.
*Based on the information above, what is the genotype of the both the tall plants and the short plants. (use the letter “T”)
Pure Tall Plant: T T Pure Short Plant: tt

13. Mendel enjoyed studying the pea plant because it was easy to see the different characteristics. For example, the texture of the pea seed was either smooth or wrinkled. The color of the seed was either yellow or green. The height of the pea plant was either tall or short.
Mendel wondered what would happen if he crossed one of the pure tall plants (TT) with a pure short plant (tt).
He hypothesized that he would get all medium sized plants. Instead, Mendel got all tall plants! He called these plants…hybrid (heterozygous). This confused Mendel. He wondered if the short trait was gone forever. He decided to cross two of the hybrid pea plants, to see what he would get. (Tt X Tt)
*What do you think happened? ________________________________________________________________________________________________

14. Math Connection!
Mendel’s experiment produced mostly tall plants. However, some of the plants were short. As any good scientists would do, Mendel repeated this experiment many, many times, just to make sure it wasn’t a mistake. Mendel concluded that when crossing hybrids, one out of every four pea plants would be short. (1/4 short) *MATH CONNECTION-What percentage of pea plants was short? What is ¼ as a percent? __________%.

15. Who was R.C. Punnett?
From his results, Mendel hypothesized that there were two factors that controlled the height of the pea plant. One factor that produced tall plants and the other factor produced short plants. Mendel also found that the gene for shortness did not disappear when a pure short plant was crossed with a pure tall plant. He found that the short gene was just hidden by the tall gene. Mendel called the tall gene dominant, and the short gene recessive. He found that for every trait, there was both a dominant and recessive gene!
After Mendel died, a man named R.C. Punnett verified (checked) Mendel’s results mathematically through the use of a Punnett Square.

16. Summary of Mendel’s findings
Traits
Letter
Dominant
Recessive
Height T
Tall
Short
Flowers F
At the side of stem
At the end of stem
Seed Texture A
Smooth
Wrinkled
Seed Color B
Yellow
Green
Seed Coat D
Colored
White
Pea Pods G
Wide
Narrow
*Use your knowledge of genetics and the table above to complete the missing Genotypes and Phenotypes.
Genotype
Phenotype Tt
Narrow Pea Pods Ff
Yellow Seed Color
AA, Aa
Flowers at the Side of Stem dd

17. Flowers at the Side of Stem
Check your answers!
Genotype
Phenotype Tt
Tall gg
Narrow Pea Pods Ff
At the side of the stem
BB, Bb
Yellow Seed Color
AA, Aa
Smooth Seed
FF,Ff
Flowers at the Side of Stem dd
White Seed Coat