Transcript (B) is dominant to brown coats (b)

Vocabulary Review
Trait:
A characteristic (what you look like)
Gene:
A piece of DNA that controls a trait
Allele:
Version (type) of a gene
Vocabulary Review
Genotype:
your genes for a trait
Phenotype:
your trait
Dominant:
ALWAYS shown (capital letter)
Recessive:
only shown with another recessive (lowercase lett
Vocabulary Review
Heterozygous:
two different alleles (Bb)
Homozygous:
two of the same allele (BB, bb)
Black coats (B) are dominant to brown coats (b) in
guinea pigs. If a heterozygous guinea pig is crossed
with a homozygous brown guinea pig, what percent
of the offspring would have the genotype Bb?
A. 0%
B. 25%
C. 50%
D. 100%
Step 1: write which
allele is dominant
Black (B) is dominant
Black coats (B) are dominant to brown coats (b) in
guinea pigs. If a heterozygous
is
genotype
phenotypeguinea pig
term
crossed with a homozygous brown guinea pig,
what percent of the offspring would have the
homozygous
genotype
Bb?
BB
black
A. 0%
B. 25%
Bb
C. 50%
D. 100%
bb
dominant
Step 2: draw a
genotype/phenotype
black
heterozygous
table
brown
homozygous
recessive
Black coats (B) are dominant to brown coats (b) in
guinea pigs. If a heterozygous guinea pig is crossed
with a homozygous brown guinea pig, what percent of
the offspring would have the genotype Bb?
Step 3: find the
A. 0%
genotype
of the
genotype
phenotype
term
B. 25%
parents!
C. 50%
BB
D. 100%
Bb
bb
black
homozygous
dominant
black
heterozygous
brown
homozygous
recessive
Bb X bb
Black coats (B) are dominant to brown coats (b) in
guinea pigs. If a heterozygous guinea pig is crossed
with a homozygous brown guinea pig, what percent
of the offspring would have the genotype Bb?
A. 0%
B. 25%
C. 50%
D. 100%
Step 4: set up and
solve the Punnett
Square
Bb X bb
Black coats (B) is dominant to brown coats (b):
B
b
b Bb bb
b Bb bb
BB
Bb
bb
0/4 or 0%
2/4 or 50%
2/4 or 50%
Black:
50%
Brown: 50%
Black coats (B) are dominant to
brown coats (b) in guinea pigs.
If a heterozygous guinea pig is
crossed with a homozygous
brown guinea pig, what
percent of the offspring would
have the genotype Bb?
A. 0%
Step 5: find what
B. 25% the question is
asking
C. 50%
BB
Bb
bb
0/4 or 0%
2/4 or 50%
2/4 or 50%
Black:
50%
D. 100%
Brown: 50%
Black coats (B) are dominant to
brown coats (b) in guinea pigs.
If a heterozygous guinea pig is
crossed with a homozygous
brown guinea pig, what
percent of the offspring
would have the genotype
Bb?
Step 5: find what
the question is
B. 25% asking
A. 0%
C. 50%
D. 100%
BB
Bb
bb
0/4 or 0%
2/4 or 50%
2/4 or 50%
Black:
50%
Brown: 50%
Additional EOCT
Review Problems
In a certain species of dog, round
ears (R) are dominant to pointed
ears (r). In a cross between a dog
with the genotype RR and a dog
with the genotype Rr, what are the
probable genotypes of the
offspring?
In a certain species of flower,
purple flowers (P) are dominant
to pink flowers (p). In a cross
between a homozygous purple
flower and a pink flower, what
will the offspring look like?
Pedigrees
Pedigrees
• Pedigrees: show relationships in
families
• Men are drawn as: squares
• Women are drawn as: circles
Pedigrees
• Circles or squares that are completely
filled in have the disease or trait.
• Circles or squares that are half filled
are heterozygous (carrier)
• Circles or squares that are not filled
are homozygous and do NOT have
the trait.
Phenotype Filled in? Genotype
Huntington’
s Disease
Carrier
NO HD
Yes
Half
No
Term
pp
homozygou
s recessive
Pp
heterozygou
s
PP
homozygou
s dominant
Parents
Kids
I
1
2
II
1
2
3
4
5
4
5
6
III
1
2
3
Think Questions
(Bottom of Guided Notes sheet)
EXIT TICKET
Additional Pedigree
Review Problems
1.
How many children
did
individuals
1 and
2
2.
3.
girls
boys
did
did
individuals
individuals
1
1
and
and
2
2
4. How many men
5.
people
arehave
in the
thepedigree?
disease?How
What
have?
are their
many
women?
numbers?
Additional Pedigree
Review Problems
RECAP: What does a pedigree tell us?