1. Practice with Punnett Squares

2. Review P1 generations= Parental generation
F1 generation= first offspring
F2 generation= second generation of offspring

3. Laws of Segregation Each organism contains:
2 factors for each trait ( one from both parents)

4. Law of independent assortment
Factors for different characteristics are distributed to the gamete (egg or sperm) independently.

5. More REVIEW
A segment of DNA on a chromosome that controls heredity is a ___________
Genes occur in pairs, WHY?
Alternative forms of a gene is an________
CAPITAL letter refer to a ________________
Will be expressed
Hides the recessive trait
lower case letter refer to a ______________
Only is expressed in a homozygous recessive organism

6. Review continued…
When both alleles in a pair are alike (AA or aa), the organism is ________________
When the two alleles are different, the organism is __________________

7. What the point? PREDICT the likely outcome of genetic crosses.
What happens when you breed two organisms together?
What do we get?
Genetic engineering
Genetic diseases/disorders

8. HOW DO WE PREDICT
PUNNETT SQUARES- aid in predicting the probability that certain traits will be inherited
TYPES:
MONOhybrid-cross between individuals that involves one pair of contrasting traits= different

9. PRACTICE Example 1: Cats S= Dominant for spots s= Recessive no spots
Homozygous X homozygous
What is the probability that the offspring will have the GENOTYPE Ss?

10. Homozygous x homozygous SS X ss

11. Example 2: homozygous X heterozygous
Rabbits: B= dominant black b=recessive brown
Genotypes: ______ x ______
What are the predicted genotypes?
What is the probability of each genotype?

12. Example 3: heterozygous x heterozygous
Flies: L= dominant for Long wings l = recessive for short wings
Genotypes: _______x________
What is the genotypic ratio?
What is the phenotypic ratio

13. Ratios
Genotypic ratio: ratio of the genotypes that appear in offspring
Phenotypic ratio: ratio of the ________ that appear in offspring

14. Test Crosses Determines the genotype of an ____________
Cross an unknown individual with a HOMOZYGOUS RECESSIVE individual.
Why?
A testcross can determine the genotype of any individual with a dominant phenotype (BB or Bb)

15. What????
If the unknown genotype is homozygous black (BB)what will all the offspring be?
If the genotype is heterozygous black (Bb) what will all the offspring be?

16. More confusion: Complete and incomplete dominance
When one allele has complete dominance over another = ___________________
EXCEPTION- sometimes the offspring will result in a phenotype that is mixed between the dominant and recessive traits
THIS IS INCOMPLETE DOMINANCE

17. 4 O’clocks Rr x Rr
In snap dragons, both the allele for red flowers (R) and the allele for white flowers ( r) will influence the phenotype
Neither allele is completely dominant over the other….which one will be expressed?

18. Red mixed with White = ???? Rr Cross RR with rr WHAT??
ALL Rr = pink flowers
Now cross Rr X Rr
What happens
The parent traits return! Rr

19. Wait….there is more
What is neither allele is Domainant or Recessive, nor do the alleles blend in the phenotype?
___________________
Calico Cats, painted horses, spotted cows

20. Dihybrid crosses
Predict the possible genotypes and phenotypes for two traits
Example:
R= dominant round
r= recessive wrinkled
Y= Dominant yellow
y= recessive green

21. Example: Homozygous x homozygous Genotypes________x _______
Cross these individuals

22. Example 2 Heterozygous X heterozygous Genotypes ______x_______
Why do you pair R and Y together instead of RR and YY on the punnett square?
Independent assortment

23. What is the genotypic and phenotypic ratios
_______ with round, yellow seeds
Genotypes:
_______with round green seeds
_______with wrinkled, yellow seeds
_______ with wrinkled green seeds

24. What is the phenotypic ratio
____ : ____ : ____ :____

25. Sex Determination
Sex in Humans, and other organisms is determined by X and Y CHROMOSOMES

26. FEMALE
Have two X Chromosomes
(XX)

27. Males Have one X and one Y (XY)

28. 23 is the magic Number
Sex of offspring is determined by chromosome pair number 23
Sex linked traits in humans are determined by genes carried ONLY on the X chromosome

29. Too bad boys  These rarely appear in FEMALES
Because…a dominant gene mask them
BUT: if there is a recessive allele, it will always show up in the male since he has only ONE X chromosome
Example: Hemophilia and colorblindness

30. More punnett Squares… In sex linked traits:
The Letters will Always be and X and Y
Superscripts represent the dominant or recessive trait
Capital superscript= Dominant
Lowercase superscript= Recessive
XBXB OR XbY

31. Lets Practice
John and Mary have 4 Girls. John wants a 5th child to be a boy.
What is the probability of John and Mary having a son?
Always 1:1 or a 50% chance

32. More Practice
Shauna is hybrid for colorblindess. She Marries Jake who is NOT colorblind.
What are the chances their son will be Colorblind?

33. WHAT???? Shauna’s Genotype: Jake’s Genotype: There is a 50% chance
* The chances of having a colorblind child is 1:4 or 25%

34. You TRY…Just give it a try
On a separate Sheet of paper
Victoria is heterozygous for hemophilia, a recessive sex-linked trait. Her husband is not a hemophiliac. What percentage of their children will have hemophilia?
Describe what each child genotype.
TURN IN WHEN FINISHED