Mrs. Anna Ward
Seventh Grade Science
Ridge Road MS
DO NOW!!!!
DO NOW!!!
Solution
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 Quiz tomorrow to Check for
Understanding
 Progress Reports tomorrow at the
end of class
 Writing Tasks
 Missing Assignments—Last day for
Late Science Fair Projects is Friday
 Short video review on Punnett
Squares
 Review Questions for Stickers
 Calculating Ratios from Punnett
Squares
 Independent Practice
 Ink Think Article “Genes tell old
Story”
 http://www.youtube.com/watch?v
=d4izVAkhMPQ
Review Questions for Stickers
In humans, brown eyes (B) are dominant to blue eyes (b).
1. What are the possible phenotypes for eye color as listed
above?
2. What would the be genotype of:
a) a homozygous dominant human?
b) A homozygous recessive human?
c) A heterozygous human?
3. Which genotype(s) would code for brown eyes?
4. Which genotype(s) would code for blue eyes?
5. Draw a Punnett Square that crosses a homozygous dominant
woman (BB) with a heterozygous man (Bb). What are the
possible genotypes and phenotypes?
6. Draw a Punnett Square that crosses a heterozygous female
(Bb) with a homozygous recessive male (bb). What are the
possible genotypes and phenotypes?
 Why do we use Punnett Squares?
 What does the term PUREBRED
mean?
 Where have you heard this term before?
 Would PUREBRED BE HETEROZYGOUS or
HOMOZYGOUS?
 What does the term HYBRID
mean?
 Would HYBRID be HETEROZYGOUS or
HOMOZYGOUS?
 Any other questions from the
video?
 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:
BB
Bb
1 BB to 2 Bb to 1 bb
or 1:2:1
Bb
bb
 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
BB
Bb
Bb
bb
 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.
BB
Bb
Bb
bb
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 (FF) Recessive White
Female Rabbit (ff).
Draw the Punnett Square to predict the
offspring.
Ff
Ff
Ff
Ff
What is the genotype ratio?
What is the phenotype ratio?
Genotype Ratio: 100 % Heterozygous or Ff
Phenotype Ratio: 100 % Black Fur
Question # 2
In Rabbits, Black Fur (F) is dominant to White
Fur (f).
Imagine you have a Heterozygous Black Male
Rabbit (Ff) that you are going to mate with a
Homozygous Recessive White Female Rabbit
(ff).
Draw the Punnett Square to predict the
offspring.
Ff
ff
Ff
ff
What is the genotype ratio?
What is the phenotype ratio?
Genotype Ratio: 50% Heterozygous (Ff) Rabbits to 50% Homozygous Recessive Rabbits (ff)
Phenotype Ratio: 50% Black Rabbits, 50% White Rabbits
 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.
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.
1. Draw the Punnett Square to
predict the offspring.
2. What is the genotype ratio?
3. What is the phenotype ratio?
My sister’s bunny, Basil Q. Hoppenfluff