1. Genetics & heredity
Chapters 9.1 & 9.2

2. Remember… If it is in RED it goes in your notes
If it is in BLACK it is important, so pay attention

3. Keep an eye out for HOOTIE!!
If you see him RAISE YOUR HAND!!
You will receive 5 ROCKS cards
IF you are correct
HINT: He won’t be this big :)

4. Mendel
What did Mendel study?
Pea plant genetics

6. He found that the plants had offspring. What does Purebred mean?
Mendel
He found that the plants had offspring.
What does Purebred mean?
Many generations have same traits without a change.
EX. TT or tt

7. What does hybrid mean? There have been changes over the generations
Mendel
What does hybrid mean?
There have been changes over the generations
Ex. Tt or Pp or Bb

8. Alleles Alleles are the different forms of genes TYPES
Dominant-ALWAYS SHOWS THROUGH. Labeled with a capital letter
Recessive-HIDDEN traits. Labeled with a lower case letter.

9. Pp
Dominant Allele
Recessive Allele

10. What trait will show through in this
T-Pink
t-Blue
What trait will show through in this
example? TT
Pink

11. What trait will show through in this
T-Pink
t-Blue
What trait will show through in this
example? Tt
Pink

12. What trait will show through in this
T-Pink
t-Blue
What trait will show through in this
example? tt
Blue

13. Is the purebred or Hybrid?
T-Pink
t-Blue
Is the purebred or Hybrid? TT
Pure

14. Is the purebred or Hybrid?
T-Pink
t-Blue
Is the purebred or Hybrid?
Hybrid Tt

15. Is the purebred or Hybrid?
T-Pink
t-Blue
Is the purebred or Hybrid? tt
Pure

16. Definitions Genotype- the genes of an organism for one specific trait
Phenotype- the physical appearance of a trait in an organism

17. Heterozygous= two different alleles for a trait (Hybrid)
HUGE TO KNOW!!!!
Homozygous= two alleles that are the same for a trait (Pure) EX. TT, tt, BB or bb
Heterozygous= two different alleles for a trait (Hybrid)
EX. Tt, Bb

18. HINT::::: HETEROZYGOUS ALWAYS MEAN DOMINANT!!!!!!!!!!!!!

19. Practice We use two letters to represent the genotype.
A capital letter represents the dominant form of a gene (allele)
lowercase letter represents a recessive form of the gene (allele).
Example below: P=dominant purple and p= recessive white
The phenotype for this flower is violet while its genotype (if homozygous) is PP.
The phenotype for this flower is white while its genotype is pp (to be white the flower must have two of the recessive copies of the allele).

20. Punnett Squares
The Punnett square is the standard way of working out what the possible offspring of two parents will be.
It is a helpful tool to show allelic combinations and predict offspring ratios.

21. Before we go further lets review how to set up a Punnett Square…
We begin by constructing a grid of two perpendicular lines.

22. B B b For this example lets consider a genotype of BB crossed with bb.
Next, put the genotype of one parent across
the top and the other along the left side.
For this example lets consider a genotype of BB crossed with bb.
B B b
Notice only one letter goes above each box
It does not matter which parent’s genotype goes on either side.

23. Next, fill in the boxes by copying the column and row head-letters down and across into the empty spaces.
B B b B b B b b B b B b

24. Punnett Squares
Now that we have learned the basics of genetics lets walk through some examples using Punnett Squares.

25. W w W w W W W w W w w w Cross 2 parents are heterozygous (Ww).
Usually write the capital letter first W w W W W w
Lets say:
W- dominant white
w- recessive violet W w w w
Cross 2 parents are heterozygous (Ww).
What percentage of the offspring will have violet flowers?
ANSWER: 25% (homozygous recessive)

26. Red hair (R) is dominant over blond hair (r)
Red hair (R) is dominant over blond hair (r). Make a cross between a heterozygous red head and a blond. r
R r r R
r r
r r
What percentage of the offspring will have red hair?
50%

27. T t t t t t T t t What are the percentage of phenotypes? 50% tall
Let’s try some more… In pea plants, tall pea plants (T) are dominant over short pea plants (t). Construct a Punnett Cross a heterozygous tall pea plant and a short pea plant.
T t
What are the percentage of phenotypes? T
t t t t
50% tall
50% short
t t

28. Black eyes (R) is dominant over red eyes (r) in rats
Black eyes (R) is dominant over red eyes (r) in rats. Make a cross between a homozygous rat with black eyes and a rat with red eyes.
R R
What is the possibility of a red eye off springs? Rr r
Discuss with students other possible answers
0% 

29. Classwork: Let’s try this together