Transcript Sponge Bob Genetics

How are genetic traits
determined?
Think about how your features compare with
your parents……
What color eyes do you have? What color
eyes do your parents have?
If we know the genotypes of the parents we
can predict the traits of their offspring.
 Sponge
Bob Square Pants!!!! :)
Bikini Bottom Genetics
(see worksheet)
1. Scientists at Bikini Bottoms
have been investigating the
genetic makeup of the
organisms in this community.
Use the information provided
and your knowledge of
genetics to answer the
following questions: For
each Genotype below
indicate whether it is
heterozygous (He) or
Homozygous (Ho).
Determine Sponge Bob’s
Phenotype:
For Each Phenotype, give
the genotypes that are
possible for Patrick
Create a Punnett square to
show the possibilities that
would result if Sponge Bob and
Sponge Susie had children.
A Punnett Square
A Punnett Square is a graph used to
determine all possible combinations of
genotypes of offspring and their
probability of occurrence.
Step 1
Determine the genotype of each
parent.
Example Problem:
Cross a Sponge Bob (heterozygous square)
with Susie Roundpants (homozygous round)
Answer:
The Cross is Ss x ss
Step 2
Draw A Punnett Square
Step 3
Seperate the alleles of each parent &
put outside the squares.
Ss
FOR OUR
CROSS
S
Ss x ss
s
ss
s
s
Step 4
Fill in the Punnett Square to determine
offspring genotypes.
Ss
S
s
s
Ss
ss
s
Ss
ss
ss
Step #5
1. Report the resulting genotypes of
your cross.
Bb
2. Then determine phenotype based on
dominant traits.
Ss
ss
Ss
ss
GENOTYPES:
PHENOTYPES:
50% Ss
Ss = Square
50% ss
ss = round
RESULTS: Probability of square children
is 50% and Probability of round children
is 50%
Create a Punnett square to
show the possibilities that
would result if Sponge Bob and
Sponge Susie had children.
Try #5…
Mendel’s Laws

The Law of Segregation – Because
each organism has two different
alleles, it passes one allele for each
trait at random to each offspring.
Mendel’s Laws


The law of independent
assortment – Genes for different
traits are inherited independently of
each other.
For example: Eye color & Hair Color is
inherited independently.
Review
Basic Steps To Complete a Punnett Square
1. Determine the genotype of each parents
and determine your cross.
2. Draw Punnett Square.
3. Separate the alleles of each parent &
place them outside the square.
4. Fill in the Punnett Square to determine
combinations of alleles (genotypes).
5. Report your results and determine
phenotypes.
Dihybrid Crosses


A Dihybrid Cross is a cross in which two
traits are considered.
Mendel performed a dihybrid cross with
pea plants. He crosses both seed shape
and seed color.

We can cross parents with two traits. The
parents genotypes are TTRR and ttrr.
T= Tall
R= round

t = short
r = wrinkled
What are the phenotypes of the parents?


In a dihybrid cross traits are inherited
independently from each other. (Law of
Independent Assortment)
In order to set up your punnett square for a
dihybrid cross you must find all the possible
combinations that can be passed on for each
parent. (All the possible gamete genotypes)

Dihybrid

What are the 4 combinations of parent TtRr?
Possible Combinations
are…
TtRr