1. Genetics and Heredity

2. Deoxyribonucleic Acid (DNA)
DNA is an organism’s genetic material.
Large molecule with a shape similar to a twisted ladder (double helix).

4. Chromosomes – made of coiled DNA.
Gene – a section (pair) of a chromosome that has genetic information for 1 trait.
Allele – 1 copy of a gene. Each characteristic (trait) has two alleles, one from each parent.

5. Topic: Traits
EQ: why are genes important?

7. Traits are controlled by genes
Genes are located on your chromosomes
Individuals inherit genes from their parents
Your cells contain 23 chromosome pairs

8. What is a trait? Trait – a physical characteristic that can be seen.
Example of traits – eye color, freckles, number of legs, thumb on top, rolling tongue.
Each trait is represented by two letters (ex: Tt).

9. Heredity and Genetics
Heredity – passing of traits from parents to offspring.
Genetics – the study of how traits are passed from parent to offspring.

10. The Father of Genetics Gregor Mendel Austrian Monk Gardener, bee
keeper, scientist
Experimented on
plants, especially
known for his
work on pea plants.

11. Mendel studied 30,000 common pea plants over 8 years and many generations. Mendel found that traits show up without any blending.

12. Dominant vs. Recessive
Dominant trait – the allele that masks the appearance of another allele. Represented by a capital letter.
Recessive trait – the allele that is blocked by a Dominant allele. Represented by a lower case letter.

13. Dominant Traits Recessive Traits
Broad lips
Hazel or green eyes
Second toe longest
Widow’s peak hairline
Crossing thumbs – left on top
Unattached earlobe
Rolling tongue
Dimples
Freckles
Straight thumb when extended
Curly hair
Thin lips
Blue or grey eyes
Big toe longest
Straight hairline
Crossing thumbs – right on top
Attached earlobe
Non-rolling tongue
No dimples
No freckles
Bent thumb when extended
Straight hair

14. Genotype & Phenotype
Genotype – The specific two alleles inherited for a particular trait (example TT, Ss, oo, Gg, etc.)
Phenotype – The physical characteristic that appears.

15. The Punnett Square Reginald Punnett created the Punnett Square
A tool used by scientists to predict the genotypes of offspring.

16. Using the Punnett Square
Draw the square

17. Using the Punnett Square
Write the genotypes of the parents on the outside of the box.
T t T t

18. Using the Punnett Square
Fill in the boxes with the alleles down and across
T t T t
T T
T t
t T
t t

19. Using the Punnett Square
Each box represents 1 offspring. In the above Punnett Square, how many different genotypes are there? How many different phenotypes are there? How can you represent those number in a percent (%)

20. Answers The genotypes are 1 or 25% BB , 2 or 50% Bb, and or 25% bb
The phenotypes are 3 or 75% purple and or 25% white

21. Different types of Genotypes
Heterozygous genotype – a genotype in which the two alleles are different. (example Tt)
Homozygous genotype – a genotype in which the two alleles are the same. (example TT or tt)

22. Different types of Genotypes
Hybrid – a heterozygous genotype and is the result of 2 genetically different parents.
Example: TT + tt = Tt
Pure Bred – a homozygous genotype and is the result of 2 genetically same parents
Example: TT + TT = TT or tt + tt = tt

23. What is a pedigree?
A pedigree is a chart of the genetic history of family over several generations.
Show the phenotypes of genetically related family members.

24. Constructing a Pedigree
Female
Male
You must learn the symbols of the pedigree charts before you can start to learn how to interpret it. These are the symbols that represent a male and a female.

25. Connecting Pedigree Symbols
Married Couple
Children
These symbols also represent relationships between people. some may have to each other.

26. A heterozygous genotype such as Hh or Bb
What is a carrier?
A heterozygous genotype such as Hh or Bb

27. Example What does a pedigree chart look like?
This is just an example of a pedigree and there can be many more different types.

28. Symbols in a Pedigree Chart