Transcript Mendel Genetics Part 2x

Intermediate Inheritance/alleles
SOMETIMES it is possible for genes
to work together to create new
phenotypes that are neither
Dominant nor Recessive
Intermediate Inheritance/alleles
These traits are
considered Intermediate
Inheritance, and are the
result of gene-blending
by Co-dominance.
Intermediate Inheritance/alleles
Co-dominance means that
sometimes there are more
than 1 Dominant Trait.
If you receive 2 codominant alleles, they will
blend together to create a
new phenotype.
Intermediate Inheritance/alleles
Example: Mice hair color genes
have a co-dominance with Black
and White—meaning that BOTH
black and white are dominant
alleles.
Brown is the recessive allele in
mice.
Intermediate Inheritance/alleles
If a mouse’s genotype is
heterozygous Black and White,
these co-dominant genes will
blend together and create a
mouse with a grey phenotype.
Intermediate Inheritance/alleles
In Mice, the grey phenotype is
considered an Intermediate
Trait because its phenotype is
neither truly dominant or
recessive, but rather a blend.
Intermediate Inheritance/alleles
Some flowers are Co-dominant Red and White, and
if cross-pollinated will produce heterozygous,
codominant Pink offspring. If the pink flowers are
crossed, then the offspring will be either Red or
White again.
Intermediate Inheritance/alleles
Other Intermediate
examples: (in humans)
Red Hair
(blending of pheomelanin
into other hair pigment)
Green /Hazel Eyes
(blending of melanin into
other pigments)
Intermediate Inheritance examples 2
Skin color
(blending of various
dark/light pigments)
Blood type
( A and B types are both
Dominant type O is
recessive) AB blood type)
Intermediate Inheritance—How it works
Ex: Andalusian Chickens come in
Black, White, or ‘Blue’.
White and Black Colors are codominant with each other.
Intermediate Inheritance—How it works
Blue is the intermediate trait, created when a Black
Color allele and a White color allele are combined
and blended.
Intermediate Inheritance Genotype
When writing these
Intermediate alleles,
the “C” for Color is
used.
With the “C”, a
superscript “W” or “B”
is used to show which
Intermediate alleles it
has.
Intermediate Inheritance—How it works
CwCw = White
CBCw = Blue chicken
CBCB = Black
Tasty Chicken…
Intermediate Inheritance Punnett Squares
A Punnett Square testcross is the same as a Monohybrid cross, but would place each intermediate
allele in each section of
the diagram.
Intermediate Test-cross (punnett square)
Mr. Vogel has Blood Type B. There is no
type O in his family, So he is
homozygous Type B
Mrs. Vogel is Type A, with some type O (recessive allele)
so her genotype is heterozygous A and O
Both A and B are co-dominant alleles, but O type is
recessive.
What are the possible outcomes of their children's’ blood
type?
Intermediate Test-cross (punnett square)
Step 1: make the square
Intermediate Test-cross (punnett square)
Step 2: create the genotypes:
T will be used for blood Type
Mr. V is homozygous B—so the genotype is TBTB
Intermediate Test-cross (punnett square)
Step 2: create the
genotypes:
Mrs. V. is Heterozygous
A and recessive O, so
the genotype is TAt. (t
= the recessive blood
type allele)
Intermediate Test-cross (punnett square)
Step 3: add the genes to the
square, and do the testcross, like normal
Intermediate Test-cross (punnett square)
Note: if you see genotypes
with both dominant traits,
then they will be blended.
Intermediate Test-cross (punnett square)
So, the outcomes of blood
types are…
_____% A
_____% AB
_____% B
______% O
Intermediate Test-cross 2 (punnett square)
Snapdragons are co-dominant red
and white. If these genes are
combined, then the produce pink
flowers.
What % of the
offspring would
white if 2 pink
parents are
mated?
Intermediate Test-cross 2 (punnett square)
Step 1 –square
Step 2: create genotypes:
--C for Color is used.
--Pink is a blend of red and
white so a pink’s genotype
must be CRCW.
Intermediate Test-cross 2 (punnett square)
Step 3: add the genes to
the square and do the
test-cross.
According to the data ____
of the offspring will be
white, and _____ will be
red.
Polygenic Inheritance

Many traits are NOT determined
by 1 set of 2 alleles alone.

Some phenotypes, like tallness, and eye
appearance are considered Polygenic, or created
from more than 1 set of genes.
Polygenic Inheritance

Ex: Height

A person’s height may
be determined by
multiple characteristics:

Length of leg-bones

Length of torso/vertebrate

Length of neck.
Polygenic Inheritance

Since these characteristics
all have their own
Genotype, and are all
combined to make a
person’s total height, Height
would be a Polygenic trait.
Polygenic Inheritance and the environment

Many traits may be affected
by their environments as well.
Polygenic Inheritance and the environment

Ex 1: a person’s polygenic
genotype may say that this
person should be very tall,
but a lack of proper nutrition
may keep the person shorter
than they
could be.
Polygenic Inheritance and the environment

Ex 2: A person may have a genotype for dark hair
color, but if they spend a lot of time outside in the
sun, then the hair color may become lighter than
the Genotype said it should be. (and makes skin
darker)
Polygenic Inheritance and the environment
Different Hormones produced
by different genders will also
have an effect on the
POTENTIAL of certain traits,
like facial/body hair, muscle
mass and body shape.