1. Warm-up Get out your Vital Vocabulary packet
Add the following words to your dictionary:
-allele -recessive
-genotype -homozygous
-phenotype -heterozygous
-trait -dominant
You can start adding definitions by looking in your textbook, but leave the example box blank

2. Genetics
An Introduction

3. Gregor Mendel
An Austrian monk who worked with pea plants to develop our basic understanding of genetics
Genetics – the scientific study of how traits are passed down from parents to offspring (heredity)

4. Mendel’s Experiments Mendel studied 7 different traits in pea plants
Trait – a specific characteristic that varies from one individual to another
Examples:
Green seeds vs. Yellow seeds
Tall plants vs. Short plants

5. Mendel’s Experiments cont’d
Mendel crossed plants with different traits and studied their offspring
The offspring are called hybrids
Mendel saw that the hybrids had the character of only one of the parents. The character of the other parent disappeared

6. Mendel’s Experiments cont’d

7. Mendel’s Experiments cont’d
Mendel then made a cross of the two hybrids and saw that the characteristic that disappeared in the first cross came back

8. Mendel’s Experiments cont’d

9. Results of Mendel’s Experiments
Genes are passed from parent to offspring
Genes – the genetic information that controls one trait
There are different forms of a gene that create specific traits. These are called alleles
Example: One allele of the gene for plant height makes it tall, the other allele makes it short

10. Describing Genes and Traits
Most organisms have 2 copies of a gene (1 from mom, 1 from dad)
Genotype – shows what type of alleles the 2 genes are
Phenotype – what the organism looks like (what trait is being expressed)

11. Principle of Dominance
Some alleles are dominant, some are recessive
An organism with a dominant allele will always exhibit that form of a trait
Recessive – only shows that form when there is no dominant form present

12. Dominance Represented with Upper and lower case letters:
T – dominant trait for tall plants
t – recessive trait for tall plants
TT = tall plant Homozygous Plant
Tt = tall plant Heterozygous Plant
tt = short plant Homozygous Recessive Plant
phenotype
genotype

13. What were those words again?
Homozygous Dominant – 2 dominant alleles
Homozygous Recessive – 2 recessive alleles
Heterozygous – 1 dominant and 1 recessive

14. Incomplete dominance
Heterozygous phenotype is intermediate between the two parental homozygotes.

15. Incomplete dominance It takes 2 doses of the red allele to get red
If you cross true breeding red and white snapdragons
F1 are all pink flowers
F2 - 1:2:1 red:pink:white
It takes 2 doses of the red allele to get red
RR- red Rr – pink rr - white