1. Mendel and Heredity

2. Genetics
The study of how traits are passed from parents to offspring.

3. Traits Characteristics that are inherited controlled by genes
Attached Earlobe
Free Earlobe

4. Genes Found on the chromosomes inside the nucleus of the cell.
Made up of DNA

5. passing of traits to offspring
Heredity
passing of traits to offspring D M
pedigree

6. History of Genetics Gregor Mendel (1800’s): “Father of Genetics”
Studied traits of pea plants
Came up with 3 Laws of Inheritance

7. Alleles
Different forms of a gene for a trait
Dominant or Recessive

8. Dominant vs. Recessive Alleles
Dominant - the allele that dominates, or covers up, another allele (written with a capital letter
EX: T – tall plant Trait: Height
Recessive - the allele that is covered up, or hidden by another allele and seems to disappear (written in lowercase)
EX: t – short plant Trait: Height

9. Genotype vs. Phenotype
Genotype - the actual genetic makeup of an organism (TT, Tt, or tt)
Phenotype - the physical trait that shows as a result of the genotype
(tall, short)

10. Genotype vs. Phenotype Genotype Phenotype TT Tall plant Tt tt
Short plant

11. Homozygous vs. Heterozygous
You have 2 alleles for a trait, so there are three possible combinations you could have.
Homozygous Dominant
Homozygous Recessive
Heterozygous Dominant

12. Homozygous vs. Heterozygous
Homozygous or purebred an organism with 2 alleles for a trait that are exactly the same. There are 2 types:
Homozygous Dominant (TT, tall)
Homozygous recessive (tt, short)
Heterozygous or hybrid - an organism with 2 different alleles for a trait.
Heterozygous Dominant (Tt, tall)

13. Punnett Square
Chart used to predict genetic outcomes

14. A monohybrid cross involves inheritance of only one specific trait.
The TT and tt that were the original parents are called the P1 generation.
The four Tt are called F1 GENERATION

15. Steps for Using a Punnett Square
1. Write the genotype of one parent along the top of the square & the genotype of the other parent along the side of the square.

16. Punnett Squares 3. Bring over the alleles over from the side
2. Bring down the alleles down from the top
3. Bring over the alleles over from the side

17. Punnett Squares Genotypes: 2 Rr, 2 rr Ratio= 2:2 %= 50% Fractions= 1/2
3. Analyze the results.
Genotypes: 2 Rr, 2 rr
Ratio= 2: %= 50% Fractions= 1/2
Phenotypes: 3 red, 1 white
Ratio= 3: %= 75% & 25% Fractions= 3/4 & 1/4

18. 3 chances to get red = 3/4 or 75%
Punnett Squares
4. Answer any questions given.
What is the probability (chance) of the new plant having a red flower?
3 chances to get red = 3/4 or 75%

19. Experiment 1:
Parents = Tall x Short
Offspring = 100% tall  X

20. Experiment 2: Parents = Tall x Tall Offspring = 3 tall : 1 short
practice
Experiment 2:
Parents = Tall x Tall
Offspring = 3 tall : 1 short

21. #4 on Bikini Bottom Genetics
SpongeBob Squarepants recently met SpongeSusie Roundpants at a dance. SpongeBob is heterozygous for his square shape, but SpongeSusie is round. Create a Punnett square to show the possibilities that wouldresult if SpongeBob and SpongeSusie had children. HINT: Read question #2!
A. List the possible genotypes and phenotypes?

22. #4 on Bikini Bottom GeneticsP: Ss
& ss
&
Squarepants
Roundpants

23. #4 on Bikini Bottom GeneticsSs Ss S ss ss
B. What are the chances of a child with a square shape? ____ out of ____ or ____%
C. What are the chances of a child with a round shape? ____ out of ____ or ____% 2 4 50 2 4 50

24. Dihybrid Punnett Squares
A dihybrid cross is a cross between 2 individuals that differ in two traits of particular interest.
For example:
S = spherical seeds & s = wrinkled seeds
Y = yellow seeds & y = green seeds

25. Bring down both alleles across the top

26. Bring down both alleles down the side

27. Bring down both alleles from the top
Bring over both alleles from the side

28. Determine the PUREBRED DOMINANT phenotypes based on the genotype

29. Determine the HYBRIDS

30. Determine the PUREBRED recessive phenotypes based on the genotype

31. What is the phenotypic ratio of wrinkled green seeds?
9:3:3:1
What is the phenotypic ratio of spherical green seeds? 3
What is the phenotypic ratio of wrinkled green seeds? 1
What is the phenotypic ratio of wrinkled yellow seeds?
What is the phenotypic ratio of spherical yellow seeds? 9 3

32. DYHYBRID EXAMPLE
A father is heterozygous for black hair and heterozygous for tongue rolling. The mother is light haired and heterozygous for tongue rolling. What is the probability of having a child with light hair who is a tongue roller?

33. PARENT’S GENOTYPES FATHER: BbTt Heterozygous for black hair: Bb
Heterozygous for tongue rolling: Tt
MOTHER: bbTt
Light hair: bb

34. FATHER BbTt BT, Bt, bT, bt MOTHER bbTtbT, bt, bT, bt
POSSIBLE GAMETES
FATHER BbTt BT, Bt, bT, bt
MOTHER bbTtbT, bt, bT, bt

35. Punnett Square
BT Bt bT bt bT Bt bt

36. Black hair/Tongue Roller - 6 Black hair/non-roller - 2
BT Bt bT bt bT Bt bt
BbTT
BbTt
bbTT
bbTt
BbTt
Bbtt
bbTt
bbtt
BbTT
BbTt
bbTT
bbTt
BbTt
Bbtt
bbTt
bbtt
Black hair/Tongue Roller - 6
Black hair/non-roller - 2
Light hair/Tongue Roller - 6
Light hair/non-roller - 2