1. Genetics & Heredity
Psst, pass it on…

2. Predicting Inherited Characteristics
Gregor Mendel
Studied heredity using pea plants
His work is the foundation of modern Genetics

3. Peas were used because:
1. Many traits in peas exist in 2 forms
*Tall or Short
*Wrinkled or Non Wrinkled
*Green or Yellow
2. Many offspring are produced in one generation.
3. They Self-Pollinate: this ensured pure breeding.

5. Mendel’s Conclusions:
Individual Factors (later known as genes) control inherited characteristics.
These factors are inherited from parents.
3. These Factors exist in pairs
4. One Factor can mask or hide another (known as dominance).

6. Gene A segment of a DNA molecule
Contains information about a specific trait

7. Asexual reproduction One parent
Parent divides to produce a copy of itself
Offspring is genetically (Identical) the same as parent

8. Sexual reproduction Two parents Offspring has genes from both parents
Offspring is genetically (Diverse) DIFFERENT from parents

9. Alleles Different forms of a gene
An organism gets one allele from each parent for a gene
**It takes two alleles to make a complete gene for a trait**

10. Dominant allele
This is the allele for a trait that always shows up in the offspring.
Shown with a capital letter when working genetics problems
DD – would be a pure form of this dominant trait (Homozygous)
Dd – would be a hybrid (One capital letter and one lowercase letter) form of this dominant trait (Heterozygous)

11. Recessive allele
Hidden when a dominant allele (Capital Letter) is present
Only shows when offspring has two alleles (Two lowercase Letters) for the recessive trait
Shown with a lower case letter when working genetics problems
dd – would be how this pure recessive (Homozygous) trait is shown

12. Homozygous This means the trait is pure DD or dd
The organism has two dominant or recessive alleles for this trait

13. Heterozygous This means the trait is hybrid
The organism has a dominant and a recessive allele for this trait
Dd – is how this is shown
** the dominant trait will always show in this case **

14. Genotype This is the GENETIC makeup of a trait (The Letters)
The genetic expression Example: DD or Dd or dd

15. Phenotype This is the PHYSICAL EXPRESSION of a trait
You CAN see the phenotype (Dark hair, Blue eyes ect…)
The dominant allele will ALWAYS show in a phenotype

16. Monohybrid Punnet Squares
(Only one characteristic)
Tall plant-TT or Tt
Short plant- tt
Mother plant-(Tt) heterozygous tall
Father plant-(Tt) heterozygous tall T t
Example: Garden Pea Plant- height

17. TT Tt Tt tt Monohybrid Punnet Squares T t T t Match the letters:
(Only one characteristic)
Example: Garden Pea Plant- height
Mother plant- heterozygous tall
Father plant- heterozygous tall
Tall plant-TT or Tt
Short plant- tt
Match the letters:
Red- across
Blue- down T t T TT Tt Tt tt t

18. TT Tt Tt tt Monohybrid Punnet Squares The result is:
(Only one characteristic)
Mother plant- heterozygous tall
Father plant- heterozygous tall
Tall plant-TT or Tt
Short plant- tt
The result is:
2 of the offspring will be heterozygous tall
1 Will be homozygous tall
1 Will be homozygous short TT Tt Tt tt

19. The sex of an animal is determined by chromosomes…
Female – XX
Male – XY
What are the chances of an offspring being male? (hint – do the cross on a Punnett square)

20. Let’s try some more…
Long fur (L) is dominant over short fur (l) in cats.
Cross a heterozygous dominant male with a short furred female.
Your cross should be between the male (Ll) with the female (ll)