1. CHAPTER “HEREDITY”
P. 126

3. Heredity - is the passing of traits from parent to offspring.
Genetics
- the study of how traits are inherited through the action of alleles.
- are different forms of the same trait

4. If the trait is hair color,
blonde
brunette
- are possible alleles.
red

5. If the trait is eye color,
blue
brown
- are possible alleles.
hazel

6. Genetics was ‘started’ by Gregor Mendel.
he experimented with pea plant traits in the 1800’s.
is considered the ‘father’ of genetics. (p )

8. Purebred
- an organism that always produces the same traits in its offspring.
Ex. St. Bernards produce St. Bernards
Ex. Siamese cats produce Siamese kittens

9. Mendel “crossed” traits and discovered that some traits appear more often.
- called dominant
Ex. Brown eyes over blue eyes.
Ex. Tall pea plants over short plants.

10. The dominant trait “masks” the hidden trait:
- called recessive.
Ex. Blue eyes
Ex. Red hair
Ex. Attached ear lobes

12. Mendel then allowed the “crossed” tall and short plants to reproduce.
surprising results.
out of 4 plants =
3 tall / 1 short
(because the tall were dominant)
- always got a 3:1 ratio.

13. What is the ratio of girls to boys in your row?
What is the ratio of plants to people in this room?

14. Because of ratios, Mendel could create probabilities of what the offspring would be.
he could predict which traits would appear.
Ex. The offspring of the tall and short plant cross
75% chance of tall
25% chance of short
Coin Flip
Probability = 50% heads / 50% tails
Ratio = 1:1

15. t t Tt Tt Tt Tt T PUNNETT SQUARES
Purebred tall and purebred short cross
= All Tall offspring
The crossed offspring produce
3 talls and 1 short

16. t t Tt Tt Tt Tt T Tt is a hybrid - or mix. Notice the 3:1 ratio
Ratio? Probability?
4:0
100% tall 0% short
Tt is a hybrid - or mix.
Notice the 3:1 ratio

17. 1:3 75% 25% Ratio of short to tall?
Probability of having tall offspring?
75%
Probability of having short offspring?
25%

19. A punnett square shows the genotype of an organism.
actual genetic traits (can’t see)
Ex. Bb, TT.
-the alleles.
B b BB Bb B b bb Bb

20. phenotype - the visible traits. (can see or touch)
Hazel eyes
Attached ear lobes

22. If the alleles are the same (BB or tt) - they are called homozygous.
If the alleles are different (Bb or Tt)
- they are called heterozygous.
(or purebred)
(or hybrid)
(for animals only!)

23. ASSIGNMENT: WORKSHEET “WHAT IS GENETICS. P
ASSIGNMENT: WORKSHEET “WHAT IS GENETICS? P. 132 SELF CHECK (ON BACK)

24. Incomplete dominance - when one trait is not dominant over another.
R R Rr Rr r Rr Rr
Ex. four o’clock flowers
RR = red
rr = white
4 Pink! (Rr)
Results:
Ratio: Red:white:pink
0:0:4

25. R r RR Rr R r Rr rr 25% 50% 1:2:1 25% Results: 1 red, (RR)
2 pink, (Rr)
1 white (rr)
R r RR Rr R r Rr rr
Probability of a pink flower?
50%
Probability of a white flower?
25%
Ratio: red/pink/white
1:2:1
Probability of a red flower?
25%

26. R R RR RR R r Rr Rr 0% 50% 2:2:0 50% Results: 2 red, (RR) 2 pink, (Rr)
0 white (rr)
R R RR RR R r Rr Rr
Probability of a pink flower?
50%
Probability of a white flower? 0%
Ratio: red/pink/white
2:2:0
Probability of a red flower?
50%

27. Polygenic inheritance
when a group of genes -
not just two -
combine to form a trait.
Ex. blood type, eye color, skin color, height, etc.

28. Codominance - a phenotype that is blended or “mixed”

30. Sex Determination the male determines the sex of the offspring.
XX = female (two X chromosomes)
XY = male (one X, one Y chromosome)

31. X X X Y XX XX XY XY Probability of having a girl? 50%
Probabilty of having a boy?
Ratio of boys to girls?
2:2 or 1:1
X X X Y XX XX XY XY

32. WORKSHEET “PUNNETT SQUARES”

33. Sex-linked Disorders
inherited “conditions” linked to the X chromosome.
Ex. color blindness, hemophilia.
these disorders are carried on the females’ X chromosome.
(the female is a carrier)

35. X Xc X Y XX XXc XY XcY Results: XX - 1 normal girl XY - 1 normal boy
XXc - 1 carrier girl
XcY - 1 colorblind
boy
X Xc X Y XX
XXc XY
XcY
For a girl to be colorblind, the trait must appear on both alleles. (XcXc)

36. Colorblind Tests

37. How a colorblind person would see a strawberry plant:

38. Hemophilia - a disease where the blood will not clot
Hemophilia - a disease where the blood will not clot. It was common in the royal families of Europe.

39. X X Xh Y XXh XXh XY XY Hemophilia Results: XXh = two carrier females
two normal males
X X Xh Y
XXh
XXh XY XY
Probability of having a hemophilic child? 0%
Probability of having a female carrier?
100%

40. X X Xh Y XXh XXh XY XY Hemophilia
Ratio of carrier females to normal males?
2:2
or 1:1
X X Xh Y
XXh
XXh XY XY
Probability of having a hemophilic female? 0%
Probability of having a normal male?
100%

41. X Xh Xh Y XXh XhXh XY XhY Hemophilia Results: XXh = carrier female XY
= unaffected male
XhXh
= hemophilic female
XhY
= hemophilic male
X Xh Xh Y
XXh
XhXh XY
XhY
Probability of having a hemophilic child?
50%

42. Pedigree
a record of an organism’s ancestors.
it traces the occurrences of a trait.
(p. 139 in text)

43. X Y XX XXh XY XhY Pedigree Is the pedigree correct? Do the punnett!
Results:
1 normal male
1 normal female
1 carrier female
1 affected male
X Xh X Y XX
XXh XY
XhY

44. The Symbols of a Pedigree:
Female (normal)
Male (normal)
Female with trait
Male with trait
Female carrier
Male carrier
?!!
Read pp
“Human Genes and Mutations”.

45. ASSIGNMENT: WORKSHEET “GENETICS”