Download Types of Inheritance

RP
Construct a Punnett and cross two
heterozygous brown labs.
What do we know?
If the brown phenotype is heterozygous, then
we know that brown is dominant.
We should use a B since brown is the
dominant color.
Complete the punnett and tell % of brown.
• Bb x Bb Where are the offspring?
•
B
b
25% 25%
•
B
BB
Bb
b
Bb
bb
25% 25%
%% ~ Genotypes 25% BB 50% Bb 25%bb
Phenotypes 75% Brown 25% Yellow
Probability is that 75% of the pups will be brown.
Types of Inheritance NB# 16
This power point make not make much
sense, but read through it and then go to the
online text book and read pages 120-125 in
the Holt text book.
Read over the worksheet “Types of
Inheritance” and do as directed on the work
sheet and the power point.
I. Dominant- Recessive
Mendelian
• Dominant allele masks or hides the
physical expression of the recessive allele.
•
bb
BB, Bb
What to notice here: That the recessive phenotype or trait is
hidden by the dominant train. That is what Mendel called it.
Types of Inheritance
NOW . . . Do the punnett on NB# 16
Homozygous no freckles X heterozygous freckles
Offspring
50% no freckles ff
50% with freckles Ff
II. Incomplete dominance-blending
• Alleles are neither dominant or recessive.
Heterozygote is “blended” - between the two
traits. Ex. Red allele combined with white allele
will produce a pink flower in a case of
incomplete dominance.
Pg 124
R1 = red allele R2 = white allele
•
•
R1
R2
•
•
•
R1
R1 R2 R1 R2
R2
R1 R2 R1 R2
• R1 R2 x R1 R2
Pg 124
•
•
•
R1
R1
•
•
•
R2
R2
III. Codominance-no blending
• Shared expression of a trait. Each allele is
expressed fully.
• An example would be a variegated red
and white flower, or blood type
IV. Multiples Alleles
• More than two alleles. Suspect this when
there are more than 2 phenotypes for a
trait.
• Add the following to NB#16
There are 3 different alleles for blood type.
A, B and O. A and B are co-dominant but O
is recessive to both A and B.
Blood type What do you already know?
Blood Types
(Phenotypes)
1
2
3
4
A
B
AB
O
Genotypes
AA, AO
BB, BO
AB
OO
III. Multiples Alleles
• Blood Type is
controlled by more
than two alleles.
• A, B, and O- O is
recessive
• See 612-614 if you
want to learn more
about blood type
Phenotypes
Genotypes
B
BB, BO
II
A
AA, AO
II
O
OO
ii
AB
AB
II
No Response Page Today 3/12
Quiz over punnetts and using the words
homozygous, heterozygous, genotype and
phenotype is tomorrow.
Unit Test over Genetics is next Tuesday.
Open agendas and write that down.
Then silently read over #16
Sex Linked
• Genes on the x or y chromosome
• There are some recessive traits (hidden if
dominant allele is present) that are
found/located on the sex chromosomes.
Males are determined by only one X
chromosome and a Y chromosome
• Females are determined by two x
chromosomes
• If a trait is passed down to offspring and is
caused by a gene on the X chromosome,
male offspring will express the trait
whether it is dominant or recessive
Ac
stopped
here
PEDIGREE