grade 9 lesson about genetics

1. Non-Mendelian Genetics
Inheritance Concepts Mendel
Never Imagined!

2. Non-Mendelian Genetics
 But, not all inheritance is based on the
rules of Complete Dominance!!

3. Incomplete Inheritance
 The hybrid (heterozygous) offspring
displays a THIRD Phenotype!! Neither trait
is completely dominant, as a result, there
appears to be a blending phenotype.
Red Flower X White Flower = Pink
(RR) (WW) (RW)

4. Incomplete Inheritance Problem
 What is the probability of pink flowers if
pink flowers are bred with red flowers?
50%
chance
of Pink
Flowers

5. Incomplete Inheritance Problem
 What is the probability of white flowers if
pink flowers are bred with pink flowers?

6. CoDominance
 Both traits are dominant, and show up in
the phenotype together. Co means
“together”
 Black Cow X White Cow = Spotted Cow
(BB) (WW) (BW)

7. 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

8. Blood Type Inheritance Rules:
1. A person with the IA allele
will have A carbohydrates.
2. A person with the IB allele
will have B carbohydrates.
3. A person with the recessive
i allele will have no
carbohydrates.
4. Or a person with both IA and
IB alleles will have both A
and B carbohydrates on
their cells.
Cells Genotypes Blood types
IAi, IAIA Type A
blood
IBi, IBIB Type B
blood
IAIB Type AB
blood
ii Type O
blood

9. Blood Type Problems
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?
IA IB
i
i
IA i
IA i
IB i
IB i

10. Blood Type Problems
Blood Type Problem 2: A
woman with type B blood
has a child with type O
blood. How is this possible
if her husband has type A
blood?

11. Multiple Alleles
 When more than 2 varieties exist in a trait.
Many animals have a variety of coat
colors.

12. Polygenic Traits
Require more than one gene (allele) to
determine trait.
Skin tone is determined by 4-6 genes—that
means that there may be six different
chromosomes involved!

13. Sex-linked Inheritance
 Genes for some traits are found on the sex
chromosomes (X or y)
 Most of these traits are recessive the normal
gene is dominant
 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

14. Color blindness is a sex-linked
recessive trait. The gene for this trait is
inherited through the X chromosome.
If a 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?
Xc Y
X
X
XXc
XXc
XY
XY

15. Non-Mendelian Genetics
What are the similarities and differences
between each of these forms of inheritance?
How will you remember? What are
examples of each type?
 Incomplete inheritance
 CoDominance
 Multiple Alleles
 Polygenic Traits
 Sex-linked inheritance