Genetics
Heredity
• Heredity is the passing of
traits from parent to
offspring.
How do the traits get
passed?
• Chromosomes contain genes.
• Different forms of the same
gene are called alleles
Alleles
• Example
–Gene– hair color
–Alleles—black, brown, blonde, red
The Importance of Meiosis
• During Meiosis, when the pairs of
chromosomes separate, they separate the
alleles.
alleles
XX
This provides genetic variation
• When alleles separate during
meiosis and then form different
combinations during fertilization,
it is like shuffling a deck of cards
to create different combinations
of 2. The possibilities are
endless!
Genetics
• Genetics is the study of
how traits are inherited.
Gregor Mendel
•
•
•
•
The “Father of Genetics”
Studied pea plants
First to use math in plant science
First to trace 1 trait through several
generations
Mendelian Genetics
• Key terms:
– Purebred
– Hybrid
– Dominant
– Recessive
– Homozygous
– Heterozygous
– Genotype
– Phenotype
Purebred vs. Hybrid
• Hybrid- when the
• Purebred- when
the same traits are
traits seen are
seen generation
different than the
after generation in
parent generation
a species
Dominant & Recessive
Every person has 2 alleles for every trait!
• Dominant-when
one allele covers
up another
• Recessive- the
allele that gets
covered up or
disappears.
B
b
Genotype & Phenotype
• Genotype- the
letters used to
represent the
alleles
Bb
• Phenotype- the
way the organism
looks
Black
Heterozygous & Homozygous
• Heterozygous2 different alleles
(1 dominant & 1
recessive)
Bb
• Homozygous2 of the same
alleles (either 2
dominant or 2
recessive)
BB or bb
Probability
• Probability is the branch of math that
deals with predicting the chances
that something will happen.
• Ex: flip a coin
• 50 % heads
• ½ heads
Punnett Squares
• Punnett Squares are used to show every
possible combination of alleles from the
parents
• Used to predict what the offspring will
look like
How to set up a Punnett Square
Aa X AA
• The alleles of one parent go across the top,
one allele in each place
How to set up a Punnett Square
Aa X AA
• The alleles of one parent go across the top,
one allele in each place
A
a
How to set up a Punnett Square
Aa X AA
• The alleles of one parent go across the top,
one allele in each place
A
a
How to set up a Punnett Square
Aa X AA
• The alleles of the other parent go down the
side, one allele in each place
A
A
A
a
How to set up a Punnett Square
Aa X AA
• The alleles of the other parent go down the
side, one allele in each place
A
A
A
a
How to set up a Punnett Square
Aa X AA
• Then, you bring one allele down and one
across to fill in the boxes
A
A
A
a
How to set up a Punnett Square
Aa X AA
• Then, you bring one allele down and one
across to fill in the boxes
A
A
A
AA
a
How to set up a Punnett Square
Aa X AA
• Then, you bring one allele down and one
across to fill in the boxes
A
A
A
a
AA
Aa
How to set up a Punnett Square
Aa X AA
• Then, you bring one allele down and one
across to fill in the boxes
A
a
A
AA
Aa
A
AA
How to set up a Punnett Square
Aa X AA
• Then, you bring one allele down and one
across to fill in the boxes
A
a
A
AA
Aa
A
AA
Aa
Using a Punnett Square
Aa X AA
• Now you can use this information to make
predictions about the offspring.
A
a
A
AA
Aa
A
AA
Aa
Using a Punnett Square
Aa X AA
• What are the chances that the offspring will
be heterozygous?
A
a
A
AA
Aa
A
AA
Aa
Using a Punnett Square
Aa X AA
• What are the chances that the offspring will
be heterozygous?
A
a
A
AA
Aa
A
AA
Aa
½ or 50%
Let’s try another Punnett Square
Problem
• A dog has black fur (Bb) and it mates with a
blonde dog (bb). What are the chances that
one of their puppies will have black fur?
X
Let’s try another Punnett Square
Problem
• A dog has black fur (Bb) and it mates with a
blonde dog (bb). What are the chances that
one of their puppies will have black fur?
B
b
b
Bb
bb
b
Bb
bb
50%
Let’s try another Punnett Square
Problem
• A dog has black fur (Bb) and it mates with a
blonde dog (bb). What are the chances that
one of their puppies will have blonde fur?
B
b
b
Bb
bb
b
Bb
bb
Let’s try another Punnett Square
Problem
• A dog has black fur (Bb) and it mates with a
blonde dog (bb). What are the chances that
one of their puppies will have blonde fur?
B
b
b
Bb
bb
b
Bb
bb
50%
1. Who is known as the
“Father of Genetics”?
A.Rosalind Franklin
B.James Watson
C.Francis Crick
D.Gregor Mendel
1. Who is known as the
“Father of Genetics”?
A.Rosalind Franklin
B.James Watson
C.Francis Crick
D.Gregor Mendel
2. Is a dog that has blonde fur
(bb) homozygous or
heterozygous?
A.Homozygous
B.Heterozygous
2. Is a dog that has blonde fur
(bb) homozygous or
heterozygous?
A.Homozygous
B.Heterozygous
3. Is Bb homozygous or
heterozygous?
A.Homozygous
B.Heterozygous
3. Is Bb homozygous or
heterozygous?
A.Homozygous
B.Heterozygous
4. Is “red hair” considered a
genotype or phenotype?
A.Genotype
B.Phenotype
4. Is “red hair” considered a
genotype or phenotype?
A.Genotype
B.Phenotype
5. What is the genotype of a
fruit fly who has the recessive
trait of white eyes?
A.EE
B.Ee
C.ee
5. What is the genotype of a
fruit fly who has the recessive
trait of white eyes?
A.EE
B.Ee
C.ee
6. What is the genotype of a
fruit fly heterozygous for wing
length?
A.WW
B.Ww
C.ww
6. What is the genotype of a
fruit fly heterozygous for wing
length?
A.WW
B.Ww
C.ww
7. Why is Meiosis important?
A. It separates alleles
B. It allows for genetic variation
when fertilization occurs
C. All of the above
D. None of the above
7. Why is Meiosis important?
A. It separates alleles
B. It allows for genetic variation
when fertilization occurs
C. All of the above
D. None of the above
8. What phenotype will the
offspring represented in the
Punnett square have?
T
t
T TT Tt
A. All recessive
T TT Tt
B. All dominant
C. Half recessive, half dominant
D. All will have different phenotypes
8. What phenotype will the
offspring represented in the
Punnett square have?
T
t
T TT Tt
A. All recessive
T TT Tt
B. All dominant
C. Half recessive, half dominant
D. All will have different phenotypes