Dihybrid crosses
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Student Expectation (SE) 6F - predict possible outcomes of various genetic combinations such as monohybrid crosses , dihybrid crosses and non- Mendelian inheritance. Dihybrid Crosses. Monohybrid Cross Review.

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Dihybrid Crosses

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Dihybrid crosses

Student Expectation (SE) 6F - predictpossible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses and non-Mendelian inheritance

Dihybrid Crosses


Dihybrid crosses

Monohybrid Cross Review

Two heterozygous red-flowering plants are crossed. If red is dominant over white, what is the most likely phenotype in the offspring?

Rr

Rr

R

r

R

RR

Rr

Red

r

Rr

rr


1 dihybrid crosses

1. Dihybrid Crosses

  • A dihybrid cross is a prediction of an offsprings genotype for two traits such as:

    • Yellow seeds and wrinkled seeds

    • Blond hair and blue eyes

    • Purple lipped and one legged


Dihybrid crosses

2. Show how the gametes form from a cross between Round,yellow seeds (RRYY) and Wrinkled, green seeds (rryy)

RRYY

rryy

2n

Meiosis 1

2n

rryy

rryy

RRYY

RRYY

Meiosis 2

RY

RY

RY

RY

ry

ry

ry

ry

n


Dihybrid crosses

RrYy

RY

Fertilization of the F1 Generation!

?

RrYy

RrYy

ry


Dihybrid crosses

  • 3. Show how the gametes form from a cross between two offspring from the F1 generation

RrYy

RrYy

2n

Meiosis 1

2n

RrYy

RrYy

RrYy

RrYy

Meiosis 2

RY

ry

Ry

rY

RY

ry

Ry

rY

n


4 dihybrid cross

Round/Yellow = ?

Round/green = ?

wrinkled/Yellow = ?

wrinkled/green = ?

RY

ry

Ry

rY

RY

ry

Ry

rY

4. DihybridCross


5 dihybrid cross short cut

5. DihybridCross Short Cut

Muppets can either have Ruffled feathers (R) or smooth feathers (r). They can also have Yellow eyes (Y) or green eyes (y)

Big Bird and Mrs. Bird are heterozygous for ruffled feathers and yellow eyes. What are the chances their offspring will have smooth feathers and Yellow eyes?


Dihybrid cross

Dihybrid Cross

Step 1) figure out what this means:

Big Bird and Mrs. Bird are heterozygous for ruffled feathers and yellow eyes

Heterozygous: different

That means Mr. and Mrs. Bird are both:

RrYy


Dihybrid crosses

Find the chances of having one trait…

  • What are the chances the baby will have smooth feathers?

Rr

Rr

R

r

R

RR

Rr

¼ chance of smooth feathers

r

Rr

rr


Dihybrid crosses

Find the chances of having one trait…

  • What are the chances the baby will have yellow eyes?

Yy

Yy

Y

y

Y

YY

Yy

¾ Chance of yellow eyes

y

Yy

yy


Step 3

Now, multiply

Step 3

  • There is a 3/16 chance the baby will have smooth feathers and yellow eyes.

Chances of smooth feathers

Chances of yellow eyes

Chances of smooth feathers AND yellow eyes

=

x


Now you try zork worksheet due at the end of class

Now you try!Zork worksheet due at the end of class


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