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# Probability of Inheritance Lesson 3 PowerPoint PPT Presentation

Probability of Inheritance Lesson 3. Mrs. Anna Ward Seventh Grade Science James Martin MS. DO NOW!!!!.

Probability of Inheritance Lesson 3

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### Probability of InheritanceLesson 3

Mrs. Anna Ward

James Martin MS

DO NOW!!!!

In rats, gray fur is dominant over white fur. Complete a Monohybrid Cross to identify the possible fur colors of offspring between a rat that is heterozygous for gray fur (Gg) with a rat that is homozygous recessive (gg) for white fur. In addtion, give the ratios of gray fur to white fur.

### G=Gray fur Dominantg=white fur recessiveGg x gg1 Gg to 3 gg1 gray rat to 3 gray ratsor 25 % gray75 white

DO NOW!!!

Solution

G

g

g

g

• Quiz today to check for understanding

### Announcements

• Short video review on Punnett Squares

• Quiz

• Calculating Ratios from Punnett Squares

• Independent Practice

• Ink Think Article “Genes tell old Story”

### REVIEW FROM YESTERDAY:PUNNETT SQUARES

In humans, brown eyes (B) are dominant to blue eyes (b).

• What are the possible phenotypes for eye color as listed above?

• What would the be genotype of:

• a homozygous dominant human?

• A homozygous recessive human?

• A heterozygous human?

• Which genotype(s) would code for brown eyes?

• Which genotype(s) would code for blue eyes?

• Draw a Punnett Square that crosses a homozygous dominant woman with a heterozygous man.

• What are the possible genotypes?

• Draw a Punnett Square that crosses a heterozygous female with a homozygous recessive male.

• What are the possible genotypes?

### Quiz

• For Monohybrid Crosses, the ratios are always going to occur in fourths, because there are four squares.

• To Calculate the GENOTYPIC RATIOS, count the number of each GENOTYPE and put that over 4.

• Example:

The Genotypic Ratio in the figure to the right is:

1 BB to 2 Bb to 1 bb

or 1:2:1

### Calculating Ratios from Punnett Squares

• To Calculate the PHENOTYPIC RATIOS, count the number of each PHENOTYPE and put that over 4.

• There are typically only two phenotypes for monohybrid crosses, the dominant & the recessive trait.

• Example:

The Phenotypic Ratio in the figure to the right is:

3 Brown to 1 Blue

or 3:1

### Calculating Ratios from Punnett Squares

• This is something you should be very familiar with from MATH class.

• For monohybrid crosses, it is always going to be a factor of 25%, because there are 4 squares.

• You can calculate the percentages based on the phenotype or genotype.

• Example:

• The genotype is 25% BB, 50% Bb, and 25% bb.

• The phenotype is 75% brown, 25% blue.

### Now you try!

Question # 1

In Rabbits, Black Fur (F) is dominant to White Fur (f).

Imagine you have a Homozygous Dominant Black Male Rabbit that you are going to mate with a Homozygous Recessive White Female Rabbit.

Draw the Punnett Square to predict the offspring.

What is the genotype ratio?

What is the phenotype ratio?

Genotype Ratio: 100 % Heterozygous or Bb

Phenotype Ratio: 100 % Black Fur

### Now you try!

Question # 2

In Rabbits, Black Fur (F) is dominant to White Fur (f).

Imagine you have a Heterozygous Black Male Rabbit that you are going to mate with a Homozygous Recessive White Female Rabbit.

Draw the Punnett Square to predict the offspring.

What is the genotype ratio?

What is the phenotype ratio?

Genotype Ratio: 50% Heterozygous (Bb) Rabbits to 50% Homozygous Recessive Rabbits (bb)

Phenotype Ratio: 50% Black Rabbits, 50% White Rabbits

### Independent PracticeSheets

• Remember this from last week?

• Underline or highlight things you want to remember or you deem important

• Circle words you don’t know

• ? Mark thinks you don’t understand

• Attach the Passage in your Science Notebook.

### INK THINK:“Old Genes Tell the Story”

In Rabbits, Black Fur (F) is dominant to White Fur (f).

Imagine you have a Heterozygous Black Male Rabbit that you are going to mate with a Heterozygous Black Female Rabbit.

• Draw the Punnett Square to predict the offspring.

• What is the genotype ratio?

• What is the phenotype ratio?

### EXIT TICKET OUT THE DOOR

My sister’s bunny, Basil Q. Hoppenfluff