non mendelian genetics

❑When scientists discovered

Gregor Mendel’s work on the
basics of genetics, it was
hailed as a major
breakthrough.

❑For the first time, scientists

could reliably predict and
describe what was happening
when two organisms with
known traits were bred to
produce offspring.

❑Scientists began noticing that

not all the traits that they
predicted in test crosses
followed Mendel’s laws of
inheritance.

❑ex. eye color

❑Scientists determined that,

although Mendel was correct
in his ideas, the big picture of
genetics is a lot more
complicated.

❑The dominant allele is not

completely expressed when
the recessive allele is
around.

❑The phenotype will be

somewhere in between (like
paint mixed together).

❑Ex. In snapdragons, red

flowers (RR) are crossed with
white flowers (rr) to form
pink flowers (Rr).

While mylinated (darker) skin is dominant, it is incomplete domiance to non-mylinated (light) skin. This is why some familes can have kids of varrying skin tones, all from the same 2 parents. ​

​

Human skin tone is a great example of incomplete dominance​!

Multiple Choice

Which puppies in this litter are showing incomplete dominance in their fur color?

• White (yellow)

• Black

• Chocolate

Multiple Choice

Which horse coat color shows incomplete dominance?

• Dark Brown

• White

• Light brown

Incomplete Dominance

❑Practice Problem #1:

If tail length in cats is an
incompletely dominant trait,
what would be the resulting
offspring in a cross of a long-
tailed cat (HH) with a short-
tailed cat (hh)?

HH= long tail
hh= short tail
Hh= medium tail

H

H

h

h

Hh

Hh

Hh

Hh

Incomplete Dominance

❑Practice Problem #1:

If tail length in cats is an
incompletely dominant trait,
what would be the resulting
offspring in a cross of a long-
tailed cat (HH) with a short-
tailed cat (hh)?

HH= long tail
hh= short tail
Hh= medium tail

H

H

h

h

Hh

Hh

Hh

Hh

Answer: 100% of the offspring
will have medium tail length

Incomplete Dominance

❑Practice Problem #2:

Flower color in orchids is an
incompletely dominant trait,
where homozygous individuals
are blue (HH) or yellow (hh) in
color.

In a cross between two
green orchids, what percent of
the offspring would be expected
to have green flowers? Blue
flowers? Yellow flowers?

HH= blue flowers
hh= yellow flowers
Hh= green flowers

H

h

H

h

HH

Hh

Hh

hh

Incomplete Dominance

❑Practice Problem #2:

Flower color in orchids is an
incompletely dominant trait,
where homozygous individuals
are blue (HH) or yellow (hh) in
color.

In a cross between two
green orchids, what percent of
the offspring would be expected
to have green flowers? Blue
flowers? Yellow flowers?

HH= blue flowers
hh= yellow flowers
Hh= green flowers

H

h

H

h

HH

Hh

Hh

hh

Answer:
50% will have green flowers
25% will have blue flowers
25% will have yellow flowers

Multiple Choice

A woman with curly hair and a man with straight hair produced a child with wavy hair:

• Incomplete dominance

• Codominance

• Complete dominance

❑The alleles work together.

❑Both traits are fully and

separately expressed.

❑When an organisms has two

different alleles (i.e., is a
heterozygote), it’ll express
both at the same time.

❑Ex. roan cows - Red cattle are

homozygous (RR) and white
are homozygous (WW). When
crossed, they produce red and
white cows (RW).

Multiple Choice

A calico cat shows both the traits for orange fur and black fur. What kind of allele expression is this?

• Incomplete Dominance
• Co dominance

Codominance

❑Practice Problem #1: In a

certain fish, blue scales (BB)
and red scales (bb) are
codominant. When a fish has
the hybrid genotype, it has a
patchwork of blue and red
scales. Cross a patchwork fish
and a red fish and determine
the genotypic and phenotypic
ratio.

BB= blue scales
bb= red scales
Bb= patchwork (blue and red scales)

B

b

b

b

Bb

bb

Bb

bb

Genotypic ratio: 1:1
Phenotypic ratio: 1:1 (patchwork : red)

Multiple Choice

A pink flower and a white flower produced this offspring:

• Incomplete dominance

• Codominance

• Complete dominance

Codominance

❑Practice Problem #2:

In some chickens, the gene for
feather color is controlled by
codominance. The allele for black
feathers is B, and the allele for white
feathers is W. The heterozygous
phenotype (speckled) is called
erminette. If two erminette chickens
are crossed, what is the chance that
the offspring will be white? Black?
Speckled?

BB or HBHB= black
WW or HWHW= white
BW or HBHW= erminette (speckled)

B

W

B

W

BB

BW

BW

WW

Answer:
25% will have white feathers
25% will have black feathers
50% will be speckled

Multiple Choice

A pink flower and a white flower produced this offspring:

• Incomplete dominance

• Codominance

• Complete dominance

❑a trait produced by

two or more genes

❑shows a range in

phenotype

❑ex. skin color, height,

IQ, eye color

Genes from multiple chromosomes can be

used to code for a specific trait. In this

diagram, part of chromosomes 3, 5, and 8
are going to come together to produce the

proteins needed to code for the trait.

Multiple Alleles

❑having more than two

alleles for one gene.

❑ex. rabbit fur

Key

C = full color, dominant to
all other alleles

cch = chinchilla, partial defect
in pigmentation, dominant to
c and ch alleles

ch = Himalayan, color in
certain parts of the body,
dominant to the c allele

c = albino, no color,
recessive to all other alleles

full color: CC, Ccch,Cch, Cc

chinchilla: cchch, cchcch, or cchc

Himalayan: chc or chch

albino: cc

Multiple Alleles

❑Practice problem #1: Cross a full-colored rabbit that

carries the chinchilla allele with a chinchilla rabbit that
carries the Himalayan allele.

❑What is the phenotypic ratio of
the offspring?

Key

C = full color, dominant to
all other alleles

cch = chinchilla, partial defect
in pigmentation, dominant to
c and ch alleles

ch = Himalayan, color in
certain parts of the body,
dominant to the c allele

c = albino, no color,
recessive to all other alleles

C

cch

Ccch

Cch

cchch

cch

ch

cchcch

Genotypic ratio: 1:1:1:1
Phenotypic ratio: 1: 1 (full color: chinchilla)

Multiple Alleles

❑Practice problem #2: Cross a Himalayan rabbit who

caries the albino trait with a chinchilla rabbit who carries
the albino trait.

❑What is the phenotypic ratio of
the offspring?

Key

C = full color, dominant to
all other alleles

cch = chinchilla, partial defect
in pigmentation, dominant to
c and ch alleles

ch = Himalayan, color in
certain parts of the body,
dominant to the c allele

c = albino, no color,
recessive to all other alleles

ch

c

chcch

cch

cc

cch

c

ccch

Genotypic ratio: 1:1:1:1
Phenotypic ratio: 2:1:1 (chinchilla, Himalayan, albino)

❑What determines

blood type?

Blood type is determined by proteins (antigens) on your red
blood cells. For example, type A blood contains the A antigen

on its red blood cells.