Transcript Polygenics & Sex-Linked traits

Different Patterns of
Inheritance
Intermediate, Codominant,
And
Polygenic
Variations of Inheritance
• Intermediate Inheritance
• Codominance (multiple alleles)
• Polygenic Inheritance
Intermediate Inheritance
• No “dominant” allele
– Heterozygous organism has completely different
phenotype
Andalusian Chickens
Black male + White female = Blue baby chick
How is this different from what we already know?...
Neither black or white is dominant over the
other
Intermediate Inheritance
Intermediate Inheritance
• Not the “blending
hypothesis” !!
– Parent phenotypes can
reappear in later generations
– cross between organisms
with two different
phenotypes produces
offspring with a third
phenotype that is a
blending of the parental
traits.
Intermediate Crossing Tips!
• Notice!!
The trick is to recognize when you are
dealing with a question involving incomplete
dominance. There are two steps to this:
Different Letters
but still a
MONOHYBRID cross!
• 1) Notice that the offspring is showing a 3rd
phenotype
• 2) Notice that the trait in the offspring is a blend
(mixing) of the parental traits.
Codominance
• Multiple Alleles = codominance
– The heterozygous expresses BOTH traits together
– Different from intermediate (blends)
Cattle can be red (RR = all red hairs), white (WW = all white
hairs),
or roan (RW = red & white hairs together)
Aww.. he
has your
eyes
Genetics
rules
Whatever
…
Blood Types
O+ Most frequent
AB- Least
Blood Types
• The A antigen, you have type A blood.
– The liquid portion of your blood (plasma) has antibodies that fight against type
B blood. In the United States, about 40% of the white population, 27% of
African Americans, 28% of Asians, and 16% of Native Americans are type A.
• The B antigen, you have type B blood.
– Your plasma has antibodies that fight against type A blood. In the U.S., about
11% of the white population, 20% of African Americans, 27% of Asians, and 4%
of Native Americans are type B.
• Neither the A nor B antigen, you have type O blood.
– Your plasma has antibodies that fight against both type A and type B blood. In
the U.S., about 45% of the white population, 49% of African Americans, 40%
of Asians, and 79% of Native Americans are type O.
• Both the A and B antigens, you have type AB blood.
– Your plasma does not have antibodies against type A or type B blood. In the
U.S., about 4% of the white population, 4% of African Americans, 5% of
Asians, and less than 1% of Native Americans are type AB.
Blood Types
A person who
has:
Can receive:
A- blood
A-, O- blood
A+ blood
A-, A+, O-, O+ blood
B- blood
B-, O- blood
B+ blood
B-, B+, O-, O+ blood
AB- blood
AB-, O- blood
AB+ blood
AB-, AB+, A-, A+, B-, B+, O-, O+
blood
O- blood
O- blood
O+ blood
O-, O+ blood
• Type O-negative blood
does not have any
antigens.
– It is called the "universal
donor" type because it is
compatible with any blood
type.
• Type AB-positive blood is
called the "universal
recipient" type because a
person who has it can
receive blood of any type.
.
Blood Typing!
Danny is type AB
Bianna is type A
What are their genotypes?
What are their possible offspring’s
blood types?
Blood Typing!
Kristina is type B but her mother
was type O
Kyle is type A but his father was type O
What are Kristina and Kyle’s genotypes?
Is it possible for their child to be type O?
Difference b/w Intermediate and
Codominance
• With intermediate, get a blending of the dominant
& recessive traits so that the third phenotype is
something in the middle (red + white = pink).
• In Codominance, the "recessive" & "dominant"
traits appear together in the phenotype of hybrid
organisms.
Or the easy way…
• Intermediate
– (red + white = pink).
• Codominant
– Red + White = Red and white spotted
Practice, Practice, PRACTICE!
A red-flowered sweet pea plant is crossed with a
white-flowered sweet pea plant. All of the
offspring are pink. What is the inheritance
pattern being expressed?
If roan cows and roan bulls are mated,
according to the principle of codominance,
______% of the offspring are expected to be
roan.
Polygenics
• Multiple GENES affect the traits being expressed
– Skin color
– Hair color
– Eye color
How it works…
Eye
Eye Color
Color == Brown
Hazel
Skin
SkinColor
Color==Light
Tan
Eye Color
QUICK FIRE
• 1. Explain the difference (and use an
example) between intermediate and
codominance.
• 2. What is polygenics?
• 3.Blood type is an example of what type of
variation in inheritance
• 4. How many phenotypes are visible in
intermediate inheritance? Codominance?
Experiment
Sex Linked Traits
• Sex Chromosomes (X, Y)
– In humans male determined sex of offspring
• Give X = female
• Give y= male
• Genes can be located on sex
chromosomes = Sex Linked Traits
– Mostly on X for humans
Discovered by Thomas Morgan when
experimenting with fruit fly eye color
Fruit Fly Eyes…Oh my
• Normally fruit flies have red eyes
– Notice some had white
– But none of them female!!
– Figured out that the trait for eye color (red) is
located only on the X chromosome
• Explains why males are white eyed
Red is dominant to White
Fly Experiment
• Eye color carried on X
• R = red r = white
• More males are white
than female be cause
Male XY Female
XX
Sex Linked Disease
Females can be carriers, males will show it
• Red- green color blindness
• Night Blindness
• Fragile X syndrome
• Sickle Cell Anemia
• Huntington's disease
• Hemophilia
MOST sex linked recessive
Sex-Linked Genetic Cross
Triple P Time!!
Practice Problem Packet!!
You are now ready to complete the BOLD
questions…