1. Do Now What does the term “heredity’ mean?
Heredity is the passing of traits from parent to offspring
How can you explain that the child has blue eyes like her mom but brown hair like Dad?
Children inherit traits from both parents.

2. Heredity

3. Today’s Objectives Describe how sex of the offspring is determined.
Determine the probability of a trait being inherited using Punnett squares.

4. Genetics Cells contain a nucleus Nucleus contains paired chromosomes
Chromosomes contain genes
Gene is a section of DNA
DNA contains an organism’s information code
to make a specific protein
Proteins are needed for growth
and repair of cells

6. How is sex determined? Your chromosomes!!
The 23rd pair of chromosomes determines the sex of the fetus.

7. Tell me what I am ?????

8. What determines a boy or girl?
Humans have 23 pairs or 46 chromosomes
The 23rd pair can be either XX or XY
In mammals if the sex chromosomes are alike, XX it results in a female.
If the sex chromosomes are different, XY it results in a male.

9. Sex Determination

10. Sex Determination
Female can contribute only a X chromosome towards the sex of their offspring.
Male can contribute an X or a Y chromosome toward the sex of their offspring.
Absence of an Y chromosome results in a the embryo developing into a female.
Presence of an Y chromosome results in the embryo developing into a male.

11. So how are other traits determined?
Brown Eyes
Blue eyes

12. Gregor Mendel Austrian Monk Considered the “Father of Heredity”
He conducted pea plant breeding experiments in their monastery garden.
In 1865 he made his work public, units of inheritance.

14. Mendel’s First Experiment
Mendel crossed pure tall
Pea plants with pure short
Pea plants.
Tall X Short 
What do you predict
Happened?

15. All the Offspring Plants were Tall!
How can you explain this?
One trait is dominant over the other or covers it up.
The other trait is said to be recessive.

16. Does the recessive trait disappear?
To test if the recessive trait was still there Mendel allowed the offspring from the first experiment to reproduce.
Tall offspring X Tall offspring 
What do you think happened?

17. The short trait reappeared!
Not only did it reappear, but it was always in a three to one (3:1) ratio
Three tall to every one short.
(75% tall, 25% short)
Why was this so predictable?

18. Mathematical Probability
Lets apply letters to represent the traits
T = tall
t = short
How many letters does the offspring get from its parents?
2! One from mom and one from dad

19. We now use something called a
So the pure tall would be  TT
and the pure short would be  tt
TT X tt  ?
We now use something called a
Punnet Square to calculate the probability
of the offspring

20. T T t T t T t t T t T t Punnett Square T T x t t Tall vs. Short
Tall is Dominant over Short
Pure tall crossed with pure short
Tall allele = T
Short allele = t T T t T t T t
All Tt
100% will be Tall t T t T t

21. T t T T T t T t T t t t Punnett Square
Tall vs. Short
Hybrid Tall x Hybrid Tall
T t x T t
Tall is Dominant over Short
The Short trait only appears when pure-
Because it is Recessive
Tall allele = T
Short allele = t T t T T T t T
1TT: 2Tt: 1tt
3 Tall (75%): 1 Short (25%) t T t t t

22. DO NOW What determines if the offspring will be a male or female?
23 pair of chromosomes
What are the chromosomes for a girl?
Boy?
XX girl XY boy

23. Do we all inherit the same variation of a gene?
We do NOT inherit the same variation of the gene
The different forms a gene may have for a trait are its alleles
If the trait was ice cream, there would be 31 varieties at Baskin Robbins. Or 31 alleles.

24. How many alleles does the offspring receive for each trait?
TWO! One from mom and one from dad.
You can get same allele from each parent:
Homozygous  Pure, two of the same alleles from each parent
OR two different alleles:
Heterozygous  Hybrid, two different alleles from each parent.

25. More terms…
The alleles received from each parent is called the genotype
What is expressed (shows up) is called the phenotype
Ex: TT is the genotype
Tall is the phenotype

26. Homozygous Tall x Heterozygous Tall
Punnett Square
Tall vs. Short
Homozygous Tall x Heterozygous Tall
T T x T t
Tall is Dominant over Short
Tall allele = T
Short allele = t T T T T T T T
2TT:2Tt
All Tall t T t T t

27. Homozygous Short x Heterozygous Tall
Punnett Square
Tall vs. Short
Homozygous Short x Heterozygous Tall
t t x T t
Tall is Dominant over Short
Tall allele = T
Short allele = t t t T t T t T
2Tt:2tt
2 Tall: 2 Short t t t t t

28. Homozygous Tall x Homozygous Tall
Punnett Square
Tall vs. Short
Homozygous Tall x Homozygous Tall
T T x T T
Tall is Dominant over Short
Tall allele = T
Short allele = t T T T T T T T
All TT
All Tall T T T T T

29. Homozygous Short x Homozygous Short
Punnett Square
Tall vs. Short
Homozygous Short x Homozygous Short
t t x t t
Tall is Dominant over Short
Tall allele = T
Short allele = t t t t t t t t
All tt
All Short t t t t t

30. Dominant
Dominant
Dominant
Dominant
Dominant
Dominant
Dominant

31. Homozygous Green x Homozygous Yellow
Punnett Square
Green Pea Pod vs. Yellow Pea Pod
Homozygous Green x Homozygous Yellow
G G x g g
Green is Dominant over Yellow
Green allele = G
Yellow allele = g G G g G g G g
All Gg
All Green g G g G g

32. Homozygous Green x Heterozygous Green
Punnett Square
Green Pea Pod vs. Yellow Pea Pod
Homozygous Green x Heterozygous Green
G G x G g
Green is Dominant over Yellow
Green allele = G
Yellow allele = g G G G G G G G
2 GG: 2Gg
All Green g G g G g

33. Heterozygous Green x Heterozygous Green
Punnett Square
Green Pea Pod vs. Yellow Pea Pod
Heterozygous Green x Heterozygous Green
G g x G g
Green is Dominant over Yellow
Green allele = G
Yellow allele = g G g G G G g G
1 GG: 2Gg: 1gg
3 Green: 1 Yellow g G g g g

34. Homozygous Yellow x Heterozygous Green
Punnett Square
Green Pea Pod vs. Yellow Pea Pod
Homozygous Yellow x Heterozygous Green
g g x G g
Green is Dominant over Yellow
Green allele = G
Yellow allele = g g g G g G g G
2 Gg: 2 gg
2 Green: 2 Yellow g g g g g

37. Law of Segregation
Allele pairs separate during gamete formation and randomly unite at fertilization.
If there are 2 alleles for a trait the probability is always 50% for each allele.

39. Law of Independent Assortment
Traits are transmitted to offspring independently of one another.
Ex: Eye color and hair color sort independently. They are not connected.

40. Incomplete Dominance
A form of inheritance in which one allele for a specific trait is not completely dominant over the other allele resulting in a combined phenotype (blending together)
EX: Red and White snapdragon plants

42. Alleles are equally dominant
What is co dominance?
Alleles are equally dominant
Both genes express themselves resulting in each color showing up separately.

43. Roan Cow

44. Multiple Alleles A trait that is controlled by more than 2 alleles
Ex: Blood type
A,B,O

46. Polygenic Inheritance
More than one gene pair acts together to produce a single trait.
Creates many variations
Ex: Eye color, fingerprints

47. Who’s Baby is it? Mrs. Bright – AB Mrs. Light - A
Mr. Bright O Mr. Light - A
Baby – O Baby – A
She got the wrong baby!!

48. The resulting plant will over White Flowers
Chromosome from one plant
Chromosome from the other plant
The resulting plant will over White Flowers

49. What is a Mutation?
Dramatically different from what is expected genetically
Any permanent change in a gene or a chromosome of a cell
Many are harmful, often causing death
Some may be beneficial
Some appear not to have an effect

50. Practice Quiz Mendel

51. Practice quiz probability

52. What is a pedigree chart?
Pedigree charts show a record of the family of an individual
They can be used to study the transmission of a hereditary condition
They are particularly useful when there are large families and a good family record over several generations.

53. Symbols used in pedigree charts
A marriage with five children, two daughters and three sons. The eldest son is affected by the condition.
Eldest child  Youngest child
Normal male
Affected male
Normal female
Affected female
Marriage

54. Example of Pedigree Charts
Dominant or Recessive?
Is this pedigree dominant or recessive?

55. Answer
Dominant
It is dominant because a parent in every generation have the disorder. Remember if a parent in every generation has the disorder, the disorder has not skipped a generation. If the disorder has not skipped a generation the disorder is dominant.

56. Example of Pedigree Charts
Dominant or Recessive?
Is this pedigree dominant or recessive?

57. Answer
Recessive
It is recessive because a parent in every generation does not have the disorder. Remember the disorder can skipped a generation if the disorder is recessive. The parents can be heterozygous and be carriers of the disorder but not have the symptoms of the disorder.

58. Pedigree Chart