Download Non-Mendelian Traits

Non-Mendelian Genetics
Inheritance patterns that are
neither dominant nor recessive
Do Now: Take out homework.
Then…clear desks.

Homework: finish practice sheets
Genetics:
Dihybrid Crosses
BbHh X bbhh (parents)
1.
2.
3.
What gametes will each parent
produce?
What will be the genotypes of their
offspring?
What would be the phenotypes?
Easter Egg Genetics
PP=purple
 pp=pink
 Pp=orange
 BB=blue
 bb=yellow
 Bb=green

Bp=red
 BP=white
 Pb=yellow spotted
 bp=white spotted
 Black=genetic
mutation!!!

An egg may be all purple, so it was PP crossed with
PP. Or it may be orange and pink, meaning it was
Ppxpp.
In Mendelian genetics (Complete
dominance), there are only two possible
phenotypes: dominant or recessive

Tall plant X Short plant = Tall plant
(TT)
(tt)
(Tt)
But, not all inheritance is based on the
rules of Complete Dominance!!
Other inheritance patterns include:
1.
2.
3.
4.
5.
Incomplete Inheritance
Codominance
Multiple Alleles
Polygenic Traits
Sex-linked
1. Incomplete Inheritance:
Blending traits
Neither trait is dominant
 Hybrids BLEND to make a
medium phenotype
Red Flower X White Flower = Pink
(RR)
(WW)
(RW)

Incomplete Inheritance Problem

What is the probability of pink flowers if
pink flowers are bred with red flowers?
50%
chance
of Pink
Flowers
2. CoDominance:
Traits show up together as
spots or stripes

Co = together

Black Cow X White Cow = Spotted Cow
(BB)
(WW)
(BW)
CoDominance Problem

What are all the possible phenotypes
when two spotted cows are bred?
Possible
phenotypes
are a black
cow, 2
spotted
cows, and a
white cow
Below are imaginary organisms. Note horn shape, leg
length, fur color and tail shape. Now determine the type of
inheritance of the four traits by examining the genotypes of
the parents and offspring.
3. Multiple Alleles: More than 2
types of alleles exist for a trait
Rabbits have more than 144 alleles for coat
color!
The same allele can be dominant or
recessive depending on context:
agouti
>
black
>
albino
What will offspring look like if a
heterozygous agouti/black rabbit was
crossed with an albino rabbit?
Blood type is determined by
Multiple alleles and Co-dominance

People have different blood types because of
different carbohydrates on their surface.
Blood Type Inheritance Rules:
1.
2.
3.
4.
A person with the IA allele will have A
carbohydrates.
A person with the IB allele will have B
carbohydrates.
A person with the recessive i allele will have no
carbohydrates.
Or a person with both IA and IB alleles will have
both A and B carbohydrates on their cells.
Blood Type Problems
Cells
Genotypes
Blood types
Type A
A
A
A
I i, I I
blood
Type B
B
B
B
I i, I I
blood
IAIB
ii
If a woman with AB blood
has children with a man
who has type O, what will
be the possible genotypes
of their children? What will
be their blood types?
A
I
Type AB
blood
Type O
blood
i
i
B
I
IA i IB i
IA i IB i
Ever wonder why there are
ranges of skin colors, or eye
colors, or hair colors, or height?
4. Polygenic Traits: Require the
interpretation of many genes
Parents:
Ll Mm Nn X Ll Mm Nn
This child
received
mostly
dominant
genes
This child
received
mostly
recessive
genes
This also explains why a couple with
heterozygous genes can have children
who look so different.
Why are some traits like colorblindness, ALD and hemophilia
found mostly in boys?
5. Sex-linked: genes are found
on the sex chromosomes (X or
 Most of these traitsY)
are recessive, the
normal gene is dominant
Sex-linked inheritance rules
Heterozygous Females (XXc) are carriers.
They do not show the trait, but carry a
gene for the trait.
 Homozygous Females (XcXc) have the trait
 Males with the gene (XcY) have the trait.—
They do not have another X to
counterbalance the affected gene

If a heterozgous woman with normal vision has
children with a man who is colorblind, what are
the chances that their children will be
colorblind? Will any children be carriers of the
trait?
X
Xc
Xc
Y
Y
c
XX
XY
XY
XcY
XcY
XcXc