1. Mendel & His Plants!
 Gregor Mendel bred
pea plants and
recorded inheritance
patterns in the
offspring.

2. Mendel’s Experiment
 Mendel bred true-breeding plants
 When self-fertilized, a true-breeding plant
produces offspring identical in appearance
to itself generation after generation.

3. Mendel’s Experiment
 Mendel crossed 2
plants- 1 true-breeding
for purple and 1 true-
breeding for white (P
generation)
 Hegot the following
results: (F1
generation)

4. How did he cross the plants?

5. Step 2: Crossing the F1 generation
 Onetrait is
dominant
 Onetrait is
recessive
 Ratio of Dominant :
recessive
 12 purple: 4 white =
3 purple: 1 white

6. Interest Grabber continued
Section 11-1 Mendel’s Results
Parents (P) First Generation (F1) Second Generation (F2)
Long stems × short stems All long 787 long: 277 short
Red flowers × white flowers All red 705 red: 224 white
Green pods × yellow pods All green 428 green: 152 yellow
Round seeds × wrinkled seeds All round 5474 round: 1850 wrinkled
Yellow seeds × green seeds All yellow 6022 yellow: 2001 green
Go to
Section:

7.  1. In the first generation of each
experiment, how do the characteristics of
the offspring compare to the parents’
characteristics?
 2. How do the characteristics of the
second generation compare to the
characteristics of the first generation?

8. Using Diagrams to show
inheritance: Punnett Squares
 Alleles=
P P p p
alternativ
e forms of
genes
P = Pp P p
purple
 p= white
P p P p

10. A B C D F
1
2
3
4
5

11. Rules for Punnett Squares
 1. Draw a square
 Place the traits for each parent across the top
and side (alleles)
 Bring down the alleles from the top and across
from the side
 Write the final ratio for the genotype &
phenotype
 Add proper vocab terms
(homozygous/heterozygous AND Dom &
Recessive)

12. Perform the following cross from the F1
generation using a Punnett Square

13. Try Another!

14. Inheritance & Probability
 We have been examining inheritance using
probablilty
 Probabilities predict AVERAGES! Not
individuals.
 The offspring may not exactly match the
predicted outcome (the larger the sample, the
closer the expected values)

15.  25% WW (homozygous dominant)
 25% ww (homozygous recessive)
 50% Ww (heterozygous)
 75% White
 25% Black
 Will it always turn out this way???

16. Two Factor/ Two Trait Crosses
 Law of Segregation
 Alleles
separate from one another during
meiosis
 Law of Independent Assortment
 Alleles
segregate independently of one
another (one does not depend on the other)

17. Two Trait Crosses
 Separatethe alleles using the FOIL
method (kind of like a )
R rYy
RY Ry rY ry
RrYy x RrYy

18. RY Ry rY ry
RY Ry rY ry
 RrYy x
RrYy

19. Two Trait Crosses
Genotypic Ratio:
1/16 RRYY 1/8 Rryy
1/8 RRYy 1/8 rrYy
1/16 RRyy 1/16 rrYY
1/8 RrYY 1/16 rryy
¼ RrYy

20. Phenotypic Ratio
9 Yellow Round
 3 Yellow wrinkled
 3 green round
 1 green wrinkled
 ALLHeterozygote two-trait crosses will
result in a 9:3:3:1 ratio

21. Phenotypic Ratio for 2 trait crosses
9 dominant dominant
 3 dominant recessive
 3 recessive dominant
 1 recessive recessive

22. A Few Different Types of
Inheritance
 http://www2.edc.org/weblabs/incompletedom/incomp

23. A New Kind of Inheritance
 Heterozygous
phenotype is a
blending of the
recessive and
dominant traits.
 What kind of
inheritance?
 Incomplete Dom.

24. Codominance
 The dominant AND
the recessive are both
expressed
 RR x rr

25. Multiple Alleles
 Genes with more than two alleles.
 Ex: Rabbits
C = full color; dominant to all other alleles
 Cch = chinchilla, partial defect in
pigmentation, dominant to ch and c alleles
 ch Himilayan, color on certain parts of the
body
 c= albino, no color

26. cchch?
Cc?
cc?
chc?

27. Codominant Cross
 Predictthe genotypic and phenotypic ratio
of a cross between a Full Color Rabbit
(Cch) and a himilayan (chc).
 Genotype:25% Cch, 25%Cc, 25% chch, chc
 Phenotype: 50% Full color, 50% himilayan

28. Sex-Linked Genes
 Even the X and Y chromosomes code for traits
 Since males only have one X chromosome, all traits are
expressed… even the recessive!
 This explains why males are much more likely to develop
 Colorblindness
 Hemophilia
 Duchenne Muscular Dystrophy
 These are all genes on the X
chromosome!

29. Sex Linked Cross
XH Y
XH X X
H H XH Y
Xh XH Xh XhY

30. X-Inactivation
 How many X chromosomes do females
have?
 How many X chromosomes do males
have?
 Why do females need 2?