Download Genetics part 2 (cp)

Part 2:
Non-Mendelian
Genetics
We’ve learned about Mendelian
Genetics.
• Now week we will learn about Complex
Patterns of Inheritance.
• Complex inheritance does not follow the
patterns that Mendel described.
Exceptions to Simple
Dominance
1. Incomplete dominance
2. Co dominance
3. Multiple alleles
4. Sex-linked Traits
• Incomplete DominanceWhen the
heterozygous
phenotype is an
intermediate (mix)
between those of the
two homozygous
parents.
Example
• AA=red
aa=white
Aa=pink
Incomplete Dominance
(One allele for a specific trait is not completely dominant over the other
allele. This results in a combined (blended) phenotype.)
Genotype
Phenotype
Example
Homozygous
dominant
Dominant
Curly hair
Heterozygous
dominant
Intermediate
(blend)
Wavy hair
Homozygous
recessive
Recessive
Straight hair
Practice Problem: Incomplete
Dominance
• A wildcat comes in three colors, blue, red,
and purple. A homozygous (BB) individual
is blue, a homozygous (bb) individual is
red, and a heterozygous (Bb) individual is
purple. What would be the genotypes and
phenotypes of the offspring if a blue wildcat
were crossed with a red one?
Key:
BB=blue
Bb=purple
bb=red
P1 Cross
Blue X
BB X
Red
bb
F1
Genotype
:
Phenotyp
e:
Codominance - both alleles are
expressed. Neither allele is
dominate over the other.
PP = Pink
ww = white
Pw = Pink and
white
A Case of Codominance: Sickle
Cell Anemia
Codominance
(Forms of the gene are equally dominant to each other.)
Genotype
Phenotype
Example
Homozygous
dominant
Dominant
Red horse hair
Heterozygous
dominant
Intermediate
(mixed)
Roan hair
Homozygous
recessive
Recessive
(red AND white)
White horse
hair
Practice Problem: Codominance
• In cattle, reddish coat color is not
completely dominant to white coat color.
Heterozygous individuals have coats that
are roan colored (ie. reddish, but with spots
of white hairs).
• Show a cross of a homozygous dominate
red bull to a roan cow.
• (hint roan is heterozygous)
Key:
BB= Red
Bb= Roan
bb= White
(both of red and white)
P1 Cross
Red X
BB X
Roan
Bb
F1
Genotype
:
Phenotyp
e:
Co-Dominance Vs. Incomplete Dominance
Make a poster with a fictitious animal or plant illustrating
Co-Dominance and Incomplete Dominance.
1. Give your new organism a name and title your poster “ Complex
Inheritance pattern of ___________”
2. Make a “key” with the genotypes and phenotypes listed.
3. List the parents genotype and draw a small image of each then
draw one offspring larger, list the genotype. (see example)
4. List and Define the Vocab word at the bottom of poster
5. Must be COLORED and NEAT!!
You may NOT copy my example think of something on your OWN!!
•
•
•
•
What is Incomplete Dominance?
What is Codominance?
How are they different from each other?
How are they different from Complete
Dominance?
Multiple alleles- having more than
2 alleles for a specific trait
• Remember a gene is an inherited trait (hair
color) and an allele is a form of that gene
that codes for the phenotype (brown, blond,
red, etc.)
Multiple allele
(Multiple alleles can demonstrate a hierarchy of dominance)
in this example, there a 4 possible alleles: M, mb , mc , m
Genotype
Phenotype
MM, Mmb, Mmc, Mm Dominant to all
others
Example
Ace beats the
mbmb, mbmc, mbm
Version b
King beats the
(dominant to mc & m)
Queen & Jack
mcmc, mcm
mm
King, Queen,
Jack
Version c (dom. Queen beats
the Jack
to rec.)
Recessive to
all others
The hair color of chinchillas would be an example of a multiple allelic trait.
Jack
Chinchilla Genetics
http://www.chinchillachronicles.com/chinchilla_geneti
cs.html
Blood cells are an example of multiple alleles
and Co-Dominance
As you can count, there are 6 different genotypes &
4 different phenotypes for blood type.
Bottom line for Multiple alleles
• The presence of multiple alleles allows for
an increased number of genotypes and
phenotypes, thus creating more variation.
• Why might variation be a good thing????
Practice Problem: Multiple
alleles
• A woman with
Type O blood and
a man who is Type
AB have are
expecting a
child. What are
the possible blood
types of the kid?
Type O X Type AB
This Chart will Always be provided for you
• Worksheet Multiple Alleles what’s not
done is HW
Sex linked
• Sex linked traits- characteristic controlled
by genes that are on the X chromosome.
*Remember*
Male Genotype: XY Female Genotype: XX
Sex-linked
(traits carried on sex chromosome, usually X-linked)
Genotype
Phenotype
Example
XX
XY
Non-afflicted,
not a carrier
Normal female
Normal male
XcX
Carrier but
not afflicted
XcXc
XcY
Both are
afflicted
Carrier female
*males cannot be
carriers!
Colorblind
female & male
Why are more
males affected
by X-linked
traits than
females?
Why are more males affected by
X-linked traits than females?
• Males have an XY genotype, since males
have only one X chromosome, they are
affected by recessive X linked traits more
often than females.
• Females have an XX genotype and the other
X chromosome would likely mask the
recessive trait.
Sex-Linked Traits
• Can you see a number
inside this circle?
• About 8% of males a
color blind and only
.5% of females
Punnett Square
• XB = Normal
• Xb = affected trait
• Y= Normal Y
chromosome
XB
Y
XB XBXB XB Y
Xb XBXb Xb Y
Practice problem: Sex-linked
• Hemophilia is due to a sex-linked recessive
gene (Xh) and the normal condition to the
gene (XH). Show a cross between a
hemophiliac man and a woman does not
carry the trait.
hemophiliac man X normal woman
Key
Xh =
Normal
XH =
Hemophiliac
*Remember*
Male Genotype: XY Female
Genotype: XX
• Sex linked traits WS what’s not done is HW
Lets review our new terms!!
• Sex linked traits- characteristic controlled by
genes that are on the X chromosome.
• Incomplete dominance- When the heterozygous
phenotype is intermediate between those of the
two homozygous parents.
• Codominance- both alleles are expressed, neither
allele is dominate over the other
• Multiple alleles- having more than 2 alleles for a
specific trait