1. Genetics & Heredity What is genetics?
The scientific study of heredity

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

3. Born in 1822 in Czechoslovakia.
Became a monk at a monastery in 1843.
Taught biology and had interests in statistics.
Also studied at the University of Vienna

4. Mendel continued
After returning to the monastery he continued to teach and worked in the garden.
Between 1856 and 1863 he grew and tested over 28,000 pea plants

5. 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.

7. 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).

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

9. Asexual reproduction One parent
Parent divides to produce a copy of itself
Offspring is genetically the same as parent

10. Sexual reproduction Two parents Offspring has genes from both parents
Offspring is genetically DIFFERENT from parents

11. 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**

12. Dominant allele
This is the allele for a trait that always shows up in the organism
Shown with a capital letter when working genetics problems
DD – would be a pure form of this dominant trait
Dd – would be a hybrid form of this dominant trait

13. Recessive allele Hidden when a dominant allele is present
Only shows when offspring has two alleles for the recessive trait
Shown with a lower case letter when working genetics problems
dd – would be how this pure recessive trait is shown

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

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

16. Genotype This is the GENETIC makeup of a trait
You can’t see the genotype

17. Phenotype This is the PHYSICAL EXPRESSION of a trait
You CAN see the phenotype
The dominant allele will ALWAYS show in a phenotype

18. Punnett Square

19. 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

20. 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

21. 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

22. 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)

23. 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)