8th Grade Do Now 11/17/2011• Essential Question – How can determine the phenotypes

for multiple alleles?• Objective –

– Identify what controls the inheritance of traits in an organism

– Explain the relationship between chromosomes and genes.

– Complete dihybrid and Punnett Squares to determine the traits of a genetic cross.

• Homework – Complete Solving Dihybrid and Complex Monohybrid Punnett Square Problems 1 – 6 and 8-11

• If you need help, please look at my website under Punnett Square tutorials for assistance.

• Do Now – Take out your vocabulary words and your Punnett Square Activity Packet and study it for five minutes.

YOU ARE HAVING A QUIZ TODAY!!

Finished with your quiz?

• Turn it into your class period bin.• Pick up Complete Solving Dihybrid

and Complex Monohybrid Punnett Square Problems pages from the front table and staple them in order.

• Begin reading pages 330 – 333• DO NOT TALK UNTIL EVERYONE IS DO NOT TALK UNTIL EVERYONE IS

FINISHED WITH THE QUIZ!FINISHED WITH THE QUIZ!

8th Grade Do Now 11/18/2011• Essential Question – How can determine the phenotypes

for multiple alleles?• Objective –

– Identify what controls the inheritance of traits in an organism

– Explain the relationship between chromosomes and genes.

– Complete dihybrid and Punnett Squares to determine the traits of a genetic cross.

• Homework – Complete Solving Dihybrid and Complex Monohybrid Punnett Square Problems 1 – 6 and 8-11

• If you need help, please look at my website under Punnett Square tutorials for assistance.

• Do Now – Do you think it is possible to use a Punnett Square to

determine more than one allele combination?

Gene InteractionsSolving Dihybrid and Complex Monohybrid Punnett Square Problems

Monohybrid Crosses• Up to now we have been doing

monohybrid crosses

RR Rr

Rr rr

R r

R

r

Dihybrid crosses• A dihybrid cross in involves studying

the inheritance of two traits simultaneously

• Mendel invented the dihybrid cross to determine if different traits, such as seed color and seed texture, were inherited independently or if they were somehow “linked” to each other

Law of Independent Assortment

• When gametes are formed, the segregation of one gene pair (the Y’s) does not affect the segregation of the other gene pair (the R’s)

YyRr

(yellow, round)Y = yellow

y = green

R = round

r = wrinkled

YR

yRYr

yr

These are the 4 gametes that can be made from this parent

You can also use the FOIL method!

Solving the Squares• Cross a green, heterozygous

round parent with a heterozygous yellow, heterozygous round parent

• yyRr X YyRr

yyRr X YyRr

1

9

5

13

2

10

6

14

3

11

7

15

4

12

8

16

yyRr X YyRr

yR

yr

yr

yR

yryRYR Yr

YyRR

YyRR

YyRr

YyRr

YyRr

YyRr

Yyrr

Yyrr

yyRR

yyRR

yyRr

yyRr

yyRr

yyRr

yyrr

yyrr

Phenotypes1 9

2 10

3 11

4 12

5 13

6 14

7 15

8 16

Phenotypes1 Yellow round 9 Yellow round

2 Yellow round 10 Yellow round

3 Green round 11 Green round

4 Green round 12 Green round

5 Yellow round 13 Yellow round

6 Yellow wrinkled 14 Yellow wrinkled

7 Green round 15 Green round

8 Green wrinkled 16 Green wrinkled

To find the Genotypic Ratio

• Write down all possible allele combinations.

• Count how many of each combination.• If you wanted to find the fraction put that

number over 16. (Reduce if necessary)

The Genotypic Ratio =2 YyRR : 4 YyRr : 2 Yyrr : 2 yyRR : 4 yyRr : 2 yyrr

yyRr X YyRr

yR

yr

yr

yR

yryRYR Yr

YyRR

YyRR

YyRr

YyRr

YyRr

YyRr

Yyrr

Yyrr

yyRR

yyRR

yyRr

yyRr

yyRr

yyRr

yyrr

yyrr

To Find the Phenotypic Ratio

• Write down all of the possible phenotypic allele combinations– For example:

– Yellow and Round

• Count how many of each combination there is.

The Phenotypic Ratio = 6 Yellow round : 6 green round : 2 yellow wrinkled :

2 green wrinkled