1. Mendelian Genetics
Chapter 10 and 12

2. Gregor Mendel (a little history)
“Father of Genetics”
Conducted experiments on heredity with pea plants.

3. Mendel’s Work With Pea Plants
Garden Peas

4. Mendel’s Work With Peas

5. Example cross: What do you think the offspring will look like?

6. The Results (F1 generation)

7. The Results (F2 generation)

8. Generations Notice that Mendel looked at 3 generations in his crosses.
P = the original Parents (the first ones he crossed
F1= the offspring of the P generation
F2 = the offspring of the F1 generation

9. Important Vocabulary
Heredity—the passing on of characteristics from parents to offspring
Genetics—study of heredity
Traits– inherited characteristics
Gametes
Fertilization
Zygote

10. Do you recall… Answer the following:
Gregor _______ is the Father of ______.
Heredity is the passing of ______.
Genetics is the study of ________.

11. More Vocabulary:
Gene= section of DNA on a chromosome that controls a specific trait.
Allele: alternate form of a gene
Ex. tall allele vs. short allele for the “height gene”

12. Vocab…
Dominant—the trait that is observed (masks the other allele) in a hybrid.
Upper case letter
Recessive—the trait that gets masked (not observed) in a hybrid
Lower case letter

13. Is the trait dominant or recessive?
This is a ______ trait.

14. Is the trait dominant or recessive?
This is a ______ trait.

15. Vocab… Phenotype Vs. Genotype
Genotype—The gene combination of the organism (i.e. BB, Bb or bb.)
Phenotype – the way an organism looks and behaves as a result of its genotype (i.e brown)

16. Vocab… Homozygous vs. heterozygous
Homozygous—has two of the SAME alleles for a trait
Ex.
Heterozygous—has two DIFFERENT alleles for a trait
Carrier = a carrier is heterozygous.
In a heterozygous creature, which trait will show up as the organism’s phenotype?

17. Genetics Vocab Assignment
Vocab Word
Explanation (your own words)
Example/Drawing
Gene
Allele
Dominant
Recessive
Genotype
Phenotype
Homozygous
Heterozygous
Carrier

18. How to Solve Genetics problems
READ and Make a Key
ex. B= black fur, b= white fur
Parent genotypes (Write them down)
ex. BB x Bb
Gametes (Figure out what the gametes would be & put them on Punnett square)
Fill in Punnett square to get offspring
Phenotypes/Genotypes of offspring (Write them out)– Best if written as a reduced fraction!
Example…

19. B BB Bb Monohybrid Cross Punnett Square Cross for one characteristic
Example:
Hair color
B b
B BB Bb
Punnett Square
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20. Practice Problems
1. In pea plants, tall (T) is dominant to dwarf (t). Show the cross between a heterozygous tall and a dwarf plant.
a. What are the expected genotypes and phenotypes and in what proportion?
b. Show the cross between two heterozygous tall plants. What are the expected genotypes and phenotypes and in what proportion?

21. In goats, a recessive gene causes the goats to "faint" when they are startled. A farmer breeds two goats (that have never fainted) and their first offspring faints two days after its birth. What must the parent's genotypes have been? Show the cross to prove it.
uJg FAINTING GOATS VIDEO CLIP

22. Dihybrid Cross Cross with two characteristics at the same time
Example:
Seed Color AND
Seed shape
2 types of genes

23. DIHYBRID crosses (how to perform them)
Exm. Parents = RrYy x RrYy
Make a key
Write out parents.
Use FOIL method to determine gametes
FOIL = first, outer, inner, last
Write out possible gametes.
Place the father’s gametes on the side and the mother’s on the top.
Use a 16 square Punnett square (4x4)

24. Practice Problems
In guinea pigs, short hair is dominant to long hair. Also in guinea pigs, black eyes are dominant to red eyes. A male guinea pig that is heterozygous for both traits is crossed with a female that is long haired and red eyed.
a. What are the expected phenotypes of their offspring and in what proportion?
b. If both parents are heterozygous for both traits, what are the expected phenotypes of their offspring and in what proportion?

25. Mendel’s Laws Law of Segregation
When gametes are made, allele pairs segregate (separate).
Then alleles randomly recombine at fertilization (with the alleles of the other parent).

26. Law of Independent Assortment
Genes for different traits (ex. Height and seed color) are inherited independently of each other.
(i.e. how tall you are will NOT affect what color your seeds are)

27. Genetics Problems Review
On a separate piece of paper, make up three genetics problems as follows:
1. an easy monohybrid problem
2. a difficult monohybrid problem
3. a dihybrid cross
You can make up any traits you like. Feel free to be creative.
ex. Unibrows are dominant in snorkeloos. If a homozygous dominant snorkeloo marries a homozygous recessive snorkeloo, what are the expected genotype and phenotype ratios for their babies?

28. Other Inheritance Patterns
Incomplete Dominance
Codominance
Multiple Alleles
Polygenic
Sex-Linked (X linked)

29. Pink Carnation Incomplete dominance Hybrid is a blend of traits
Example:
RR=red
RR’ =pink
R’R’=white
Pink Carnation

30. Practice problem
A cross between red snapdragons and white snapdragons produces all pink offspring.
Show the cross of the F1 generation (cross two pink ones.)
What is the genotype ratio?
What is the phenotype ratio?

31. Codominance Codominance—showing both alleles at the same time
Ex. *Checkered chicken (Black and white at same time)
B= Black W= White
So BB= Black, WW =white, and BW = black and white checkered.
Another example is Blood Type!
Type AB

32. Codominance x BB WW BW

33. Practice problem
Background: A black rooster and a white hen have offspring that are all checkered.
What inheritance pattern is this?
Cross a heterozygous chicken with a white chicken.
Give genotype and phenotype ratios.

34. Multiple Alleles TYPES: A = IAIA, IAi B = IBIB , IBi AB = IAIB O = ii
Multiple alleles: more than 2 possible alleles for a gene. Ex: human blood types
3 Alleles: IA, IB, i
TYPES:
A = IAIA, IAi
B = IBIB , IBi
AB = IAIB
O = ii

35. Practice problem
Show the cross of a man heterozygous for type B blood with a woman that has type O blood
Describe genotypes and phenotypes of the offspring.

36. Polygenic traits
Polygenic trait = a trait that is influenced by more than one gene.
Ex. Eye color, skin color, hair color, height…
What do all of these characteristics have in common that can help you to recognize that the trait is polygenic?

37. Determining Sex (gender)
Look at sex chromosomes (X and Y)
XX = female
XY = male

38. Sex-Linked Gene is found on a sex chromosome (usually X)
Trait more commonly seen in males. Ex. Colorblindness, hemophilia
Possible genotypes
Female=
XRXR
XRXr
XrXr
Male=
XRY
XrY
“Y” is empty
Fruit Flies C:\Documents and Settings\BBAUGHMAN\Desktop\bio powerpoints\Chapter 12 BDOL IC

39. Practice problem
A female carrier of colorblindness marries a normal male who is not colorblind. Describe their potential offspring in terms of genotype an phenotype probabilities.

41. Pedigree Charts Male = Female= Sexual Union= Offspring=
Shaded= has the trait (the phenotype)

42. Pedigree Chart -Cystic Fibrosis

43. end

44. Mendel’s Monohybrid Crosses
1st Generation: All plants were tall
2nd Generation: Mendel allowed tall plants of first generation to self-pollinate
1000 plants produced in second generation
What do you think Mendel saw in the
F2 generation?
1000 plants produced
750 were tall
250 were short
3:1 ratio
The Short Trait Reappeared!!!

45. Mendelian Genetics WHAT DOES THIS MEAN?????
Mendel did several similar crosses looking at various traits of the pea plant
Each trait had similar results
One pair of the trait disappeared in the F1generation
The trait would reappear in the F2 generation
WHAT DOES THIS MEAN?????

46. Rule of Unit Factors 2 factors control each traits of an organism
These factors are genes located on chromosomes
Different gene forms called Alleles
Ex: tall allele (T), short allele (t)
Plant can have allele (TT), (tt) or (Tt)
Each allele is inherited from each parent; one from mom and one from dad

47. Rule of dominance
When Mendel crossed tall plants with short plants he observed only tall plants were produced in the F1 generation.
Dominant: observed trait
Mendel concluded allele for tall plants is dominan to allele for short plants
Dominant trait seen when allele is (TT) or (Tt)
Recessive: trait that dissappeared
Recessive trait only seen when allele is (tt)

48. Rule of dominance
Dominant trait is always written with an uppercase letter
Ex: tallness (T)
Recessive trait is always written with a lowercase letter (t)

49. Law of Segregation Mendel’s Law of Segregation
Recall, where there any short plants when Mendel crossed a tall plant with a short plant?
All plants in the F1 generation were Tall
When F1 tall plants were bred the shortness trait reappeared
Mendel concluded each tall plant in the F1 generation carried one dominant allele for tallness and one unexpressed recessive allele for shortness

50. Law of Segregation
Law of segregation: because each plant has two different alleles, it can produce two different types of gametes.
During fertilization, male and female gametes randomly pair so there can be a combination of four different alleles
(T1 T2) (T1 t2) (t1 T2) (t1 t2)

51. Law of Segregation

52. Phenotypes and Genotypes
Two organisms can look alike but have different allele combinations
Ex: tall plants can have allele combination (TT) two dominant alleles or (Tt): one dominant and one recessive allele.
Short plants have allele combination (tt) two recessive alleles. TT Tt

53. Phenotypes and Genotypes
Phenotype: the way an organism looks and behaves
The outward physical appearance of an organism
Ex: brown hair, green eyes, tall, short, etc.
Genotype: The allele combination an organism contains
Ex: (BB) (Bb) (bb)

54. Phenotypes and Genotypes
You cannot always see the organism’s genotype when you know the phenotype
A dominant trait can have a (Tt) or (tt) genotype but still display the dominant trait
Homozygous: when the two alleles for the same trait are the same. (TT) or (tt)
TT – homozygous dominant
tt – homozygous recessive
Heterozygous: when two of its alleles differ for the same trait
Tt - heterozygous

55. Next Week….. Mendel’s Dihybrid Crosses Punnett squares
Mendel’s law of independent assortment