1. GENETICS The study of heredity
Where do you get the traits that people see in you?

2. Sexual reproduction Sperm + egg = zygote  embryo
At fertilization, homologous chromosomes match up and pair in the zygote

3. Chromosomes Chromosomes are segments of DNA.
Genes are segments of a chromosome that codes for one particular trait.
Eye Color
Attached ear lobes
Straight hair vs Curly hair
Gene

4. What are homologous chromosomes?
Homologous=Same
Size
Homologous chromosomes are 2 paired chromosomes (one from each parent)

5. What is a trait? Characteristics about an organism.
You get your traits from your parents

6. Gregor Mendel The Father of Genetics
researched and experimented using pea plants (peas are self-fertilizing, easily cultivated and cross pollinated)

7. Mendel’s Experiments
He crossed a Yellow Pea plant with a Green Pea plant.
ALL offspring were Yellow
He determined that YELLOW color must be DOMINANT over Green

8. Mendel’s Principles and the Punnett Square

9. Essential questions 1. What are homologous chromosomes?
2. What is a gene?
3. How do we get traits from our parents?
4. Who is Gregor Mendel?
5. What were Mendel’s contribution to Genetics?

10. Principle of Dominance
Dominant genes hide the recessive genes
Alleles: Different forms of a gene represented by different letters
Phenotype: Physical expression of a trait. (what you see)
Genotype: Gene combinations for a particular trait/characteristic. (the letters)
Homozygous dominant (YY)
Heterozygous (Yy)
Homozygous recessive (yy)

11. Dominant vs. Recessive Dominant- stronger gene
Upper case letter
Recessive –weaker gene; hidden
Lowercase letter

12. Principle of Segregation
The pair of alleles must separate in the parent and ONE gets passed onto the child

13. Principle of Independent Assortment
One trait’s expression does not affect another’s when chromosomes separate during meiosis.

14. How can we predict genetic offspring?
Punnett squares
A diagram used to predict the genotype and phenotype ratios of different organisms when specific gametes join together

15. Monohybrid Cross
Involves one trait

16. Example Key= Y=yellow y = green
Cross: 2 heterozygous yellow pea plants
Punnett Square:
Yy x Yy (parents)
Parents Y
Y y y
Offspring YY Yy Yy yy

17. Phenotypes:
yellow=3/4=75%
Green=1/4=25%

18. How can we predict genetic offspring?
Punnett squares
A diagram used to predict the genotype and phenotype ratios of different organisms when specific gametes join together

19. Monohybrid Cross
Involves one trait

20. Monohybrid Cross Example
B b b
A heterozygous black dog (Bb) mates with a homozygous recessive tan dog (bb).
What is the probability that these two dogs will have a tan offspring?
Genotype ratio
2 Bb : 2 bb
Phenotype ratio
2 Black : 2 Tan Bb bb
50%

21. Essential questions 1. What are Mendel’s 3 principles of genetics?
2. What is meant by Homozygous and Heterozygous?
3. How can you predict genetic outcomes?
4. What are genotypes and phenotypes?

22. Non-Mendelian Genetics
Essential Questions:
1. What happens when you have two alleles for a trait that are dominant?
2. What is a blended phenotype?
3. If two alleles are dominant, how do I identify which letter to use in the punnett square?

23. (homozygous tall) (homozygous short)
1.    Cross a homozygous tall (T) with a homozygous
short plant (t). (Draw the Punnett Sqaure and fill it in!)
Genotypic Ratios:
How many are TT?_____ 
How many are Tt? _____
How many are tt? _____
0 TT: 4 Tt : 0 tt
Phenotypic Ratios:
How many are Tall?
How many are short?
4 Tall : 0 Short
T T
Key:
Tall: TT or Tt
Short: tt
Parents:
TT x tt
(homozygous tall) (homozygous short) t

24. (heterozygous tall) (heterozygous tall)
2. Cross together two of the offspring from #1.
(Draw the Punnett Sqaure and fill it in!)
Genotypic Ratios:
How many are TT?_____ 
How many are Tt? _____
How many are tt? _____
__ TT: __ Tt : __ tt
Phenotypic Ratios:
How many are Tall?
How many are short?
____ Tall : ____ Short
Key:
Tall: TT or Tt
Short: tt
Parents:
Tt x Tt
(heterozygous tall) (heterozygous tall)

25. 2 Yellow: 2 White 0 YY: 2 Yy: 2 yy
3. In flowers, yellow (Y) is dominant to white (y).
Cross a heterozygous yellow flower plant with a white flower plant.
(Draw the Punnett Sqaure and fill it in!)
Genotypic Ratios:
How many are YY?_____ 
How many are Yy? _____
How many are yy? _____
Phenotypic Ratios:
How many are Yellow?
How many are White?
0 YY: 2 Yy: 2 yy
__ YY: __ Yy: __ yy
2 Yellow: 2 White
____ Yellow: ____ White
Key:
Yellow: YY or Yy
White: yy
Parents:
____ x _____
(heterozygous yellow) (homozygous white)
Remember,
HOMO = Same (YY, yy)
HETERO = Different (Yy)

26. Incomplete Dominance Neither allele is completely dominant
When the offspring is heterozygous, a third blended phenotype appears

27. Incomplete Dominance Example
If red flowers (RR) are incompletely dominant to white flowers (R’R’), show the offspring of a cross between 2 pink flowers (RR’)
Q: What is the probability that these two parents will produce pink offspring?
50%
R R’ R R’

28. Codominance Both alleles are equally dominant
When the genotype is heterozygous, both phenotypes are represented in an almost equal ratio
Example:
A black cow and a white cow may produce a black and white cow

29. Codominance Example BW BB
If black chickens (BB) are co-dominant to white chickens (WW), show a cross between a black chicken (BB) and a black and white chicken (BW).
What is the probability that these two chickens will have a white offspring? 0% BW BB W B
Phenotype ratio:
Black 2, black and white 2, white 0

30. Pedigrees Pedigrees: Diagrams used to look at multiple generations
Allows you to follow a specific trait through a family history.
Shows who is affected, normal and a carrier for a trait