Transcript Teacher quality grant

Biology Partnership
(A Teacher Quality Grant)
Genetics II
Modes of Complex Inheritances and Pedigrees
Nancy Dow
Jill Hansen
Tammy Stundon
February 23, 2013
Gulf Coast State College
Panhandle Area Educational Consortium
5230 West Highway 98
753 West Boulevard
Panama City, Florida 32401
Chipley, Florida 32428
850-769-1551
877-873-7232
www.gulfcoast.edu
Pre-test
Q and A board
Was Mendel wrong?
Why aren’t humans as simple
as ‘tall’ or ‘short’?
Why are most colorblind
people males?
Florida Next Generation
Sunshine State Standards
BENCHMARK
• SC.912.L.16.2* Discuss observed inheritance patterns caused by
various modes of inheritance, including dominant & recessive
which are simple inheritance & codominant, sex-linked, polygenic,
and multiple alleles (complex inheritance). (HIGH)
Florida Next Generation
Sunshine State Standards
Benchmark Clarifications
•Students will identify, analyze, and/or predict inheritance patterns
caused by various modes of inheritance.
Content Limits
•Items referring to general dominant and recessive traits may address but will
not assess the P and F1 generations.
•Items addressing dihybrid crosses or patterns that include codominance,
incomplete dominance, multiple alleles, sex- linkage, or polygenic inheritance
may assess the P and F1 generations
Florida Next Generation
Sunshine State Standards
Stimulus Attributes
•Inheritance outcomes may be expressed in percent, ratios, or
fractions.
•Scenarios may refer to codominance or incomplete
dominance but not both codominance and incomplete
dominance.
•Punnett squares may be used to predict outcomes of a cross.
Response Attribute
•Options may include codominance or incomplete dominance
but not both.
Mendel’s Results
Character
Dominant x Recessive
F1
F2 Generation
Ratio
Dominant Form: Recessive Form
Flower
Color
purple x white
all
purple
705 purple: 224 white
2.96
Seed Color
yellow x green
all
yellow
6022 yellow: 2001 green
3.01
Seed Shape
round x wrinkled
all round
5474 round: 1850 wrinkled
2.96
Pod
Color
green x yellow
all green
428 green: 152 yellow
2.82
Pod Shape
inflated x pinched
all
inflated
882 inflated: 299 pinched
2.95
Flower
Position
axial x terminal
all axial
651 axial: 207 terminal
3.14
Plant
Height
tall x short
all tall
787 tall: 277 short
2.84
Ways to inherit traits
• Simple inheritance – the present of a dominant or
two recessive alleles will express the trait
– Dominant simple
– Recessive simple
• Sex-linked (x-linked) – where the 23rd
chromosome work on different rules
• Complex inheritance – the most common
–
–
–
–
Multiple Allele –
Co-dominance –
Polygenetic inheritance
Incomplete dominance
Simple inheritance (single gene)
1. Dominant Inheritance – Rr or RR
Traits include widow’s peak, hitchhiker’s thumb, etc.
• Capital letter = Dominant trait .
• When just one dominant gene is present, the
trait will be shown
• Two dominant alleles does not enhance the trait
• For a recessive trait to be expressed both parents
MUST pass on the recessive allele for this trait to be present
• Which genotype would be the carrier for the recessive trait?
EXAMPLES OF SINGLE-GENE TRAITS
Widow’s peak is
Dominant
Straight hairline
is recessive
Regular thumb is
Dominant
Hitchhiker’s is
recessive
Six digits (D)
Tongue rolling is
Dominant
Not able to roll the
tongue is recessive
EXAMPLES OF
SINGLE-GENE TRAITS
Cleft chin = r
Non-cleft chin =D
Unattached earlobes = D
Attached earlobes = r
Simple Dominant
Inheritance Disease
Huntington’s Disease
•Chromosome #4; gene makes the brain cells to
basically commit suicide
•neurological spasms, mental problems, motor
function problems
•no treatment
•CAG is repeated too many times;
the number of repeats predicts the age
of onset; 40 reps = late middle age
Carriers
• Only the genotype Ff is considered to be a
‘carrier’
• If (F) = freckles, what is this person’s
phenotype?
• What type of simple inheritance are they
expressing?
• Effect if this was a disorder and not a trait?
• Why wouldn’t the other simple inheritance
genotype be considered as a carrier?
Simple inheritance (single gene)
2. Recessive Inheritance – rr
• Disorders – Tay-sachs – Jewish, C#15
Cystic Fibrosis – Caucasians, C#7
PKU – C#12, metabolic disorder
• Why certain disorders have appeared?.......
• Lack of genetic variation ? Adaptation?
A SINGLE BAD GENE WHICH WILL NOT PRODUCE
THE ENZYME TO CONVERT PHENYLALANINE TO TYROSINE (BOTH AMINO
ACIDS). THIS CAUSES A CONDITION CALLED “PKU”. THIS CAN CAUSE A BUILDUP OF PHENYLALANINE IN THE BRAIN WHICH CAN CAUSE MENTAL
RETARDATION---CAN BE TREATED WITH DIET AVOIDING THIS AMINO ACID.
Why cover disorders?
•Higher order thinking questions!
•They have to know what type of
inheritance the disorder is in order to
answer the question (by either doing
a Punnett square or pedigree.)
•Many test bank questions will
indicate the inheritance of a trait;
Freckles are dominant.
Human Autosomal Trait Lab
Refer to the slides with the simple inheritance traits!
Non-Mendelian Genetics
• Mendelian genetics describes inheritance
patterns based on complete dominance or
recessiveness.
• There are other types of inheritance that
Mendel never considered:
–
–
–
–
–
Incomplete Inheritance
Codominance
Multiple Alleles
Polygenic Traits
Sex-linked
Non-Mendelian Genetics
The relationship between genotype and phenotype is rarely simple
Non-Mendelian Genetics
• Many researchers have
encountered exceptions to
Mendelian Principles – so was
he wrong?
• Majority of heritable
characters not as simple as
peas
– Phenotypes affected by: many
alleles or many genes,
environmental factors, sex
chromosomes, etc.
Phenotype can depend on interactions of alleles.
• In incomplete dominance, neither allele is
completely dominant nor completely
recessive.
– Heterozygous phenotype is intermediate between
the two homozygous phenotypes
– Homozygous parental phenotypes not seen in F1
offspring
Incomplete Dominance
If you cross a RED flower
with a WHITE flower, you
will get a PINK flower.
NOTICE:
the RED genotype is RR
the WHITE genotype is WW
the PINK genotype is RW
INcomplete is INbetween
If this was blended inheritance –
pink • pink would only make what?
Let’s Practice!
Cross a BLACK chicken (BB) with a WHITE
chicken (WW). These alleles show
INCOMPLETE DOMINANCE
What
percent is
black?
White?
Gray?
B
B
W
BW
BW
W
BW
BW
Black: 0%
White: 0%
Gray: 100%
Let’s Practice!
Cross a BLACK chicken (BB) with a WHITE
chicken (WW). These alleles show
INCOMPLETE DOMINANCE
What is the
genotype and W
phenotype of
the F1
generation?
W
B
B
BW
BW
BW
BW
Genotype:
BW
Phenotype:
Gray
Let’s Practice!
What would the cross look like if you crossed two
GREY chickens (BW). These alleles show
INCOMPLETE DOMINANCE.
What is the
genotype and
phenotype of
the F2
generation?
PTC Testers
B
W
B
W
BB
BW
BW
WW
Genotype:
1 BB
1 WW
2 BW
Phenotype:
1 Black
1 White
2 Gray
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)
CoDominance
• Both alleles are expressed in the
heterozygous condition
• Both alleles contribute to the
phenotype.
• For Example: In chickens, the
allele for black feathers is codominant with the allele for
white feathers. These chickens
will have BOTH black and
white feathers.
COdominant alleles COllaborate together
Let’s Practice!
Cross a Black chicken (BB) with a White chicken
(WW). These alleles show CO-DOMINANCE.
How many
chickens in the W
F1 generation
are completely
black? White?
Black and
W
white?
B
B
BW
BW
BW
BW
Black: 0%
White: 0%
Both: 100%
Let’s Practice!
Cross a Black chicken (BB) with a White chicken
(WW). These alleles show CO-DOMINANCE.
B
What is the
genotype
W
and
phenotype of
the F1
generation?
W
BW
BW
B
BW
Genotype:
BW
BW
Phenotype:
Black and
white or
checkered.
Let’s Practice!
Cross two Black and White (checkered) chickens
(BW). These alleles show CO-DOMINANCE
B
List all
possible
genotypes
and
phenotypes
of the F2
generation.
B
W
BB
BW
W
BW
WW
Genotype:
1 BB
1 WW
2 BW
Phenotype:
1 Black
1 White
2 Checkered
Blood type displays both co-dominance
and complete dominance
• Blood types are different based on the
presence or absence of certain antigens on
the red blood cells (RBCs)
– The presence of a antigen (I) is dominant to
the absence of an antigen (i).
• There are two types of antigens that
may exist on the surface of RBCs
called A (IA) and B (IB).
– Cell surface antigens A and B are
codominant, which means they could also
show up at the same time on an RBC.
Blood type displays both co-dominance
and complete dominance
• Matching
compatible
blood groups
is critical for
blood
transfusions
because a
person
produces
antibodies
against foreign
blood factors.
Blood type also demonstrates inheritance
through multiple alleles
• Multiple alleles: When more than 2 varieties
exist in a trait. In this case, blood can be A/B/O
Multiple Alleles—ABO Blood Groups
Possible alleles from male
At any one time, a parent can only have TWO alleles for blood
Possible alleles from female
IA
IB
i
IA
IAIA
IAIA
IAi
IB
IAIB
IBIB
I Bi
i
IAi
IBi
ii
Blood Types
A
AB
B
O
The Genetics of Blood Lab
Polygenic Inheritance
• The inheritance
pattern is
controlled by two
or more genes
(each with two
alleles)
At the present, three gene pairs controlling human eye color are known (two on
chromosome 15 and one on pair 19).
Order of dominance: brown/amber > green/hazel > gray/blue.
Polygenic Inheritance
Creates a ‘bell curve’ distribution
• Two or more genes work
together to create a single
phenotype
– Example: Height is
controlled by anywhere from
7 – 20 different genes (and
the environment!)
Wilt Chamberlin stood 7’1” tall,
neither of his parents was over 5’9”
Polygenic Inheritance
Skin color is
determined by (at least)
3 genes. Imagine that
each gene has two
alleles, one light and
one dark, that
demonstrate
incomplete dominance.
An AABBCC
individual is dark and
aabbcc is light.
Polygenic Inheritance Activity
Sex Linked Traits
• When a trait is carried on the X
or Y chromosomes, it is called a
sex-linked trait
• These not only carry the genes
that determine male and female
traits but also those for some
other characteristics as well
• Don’t confuse this with linked
genes = when 2 genes are on
the same chromosome
Sex Linked Traits
Red – Green Color Blindness
• Gene that controls this is
on the X chromosome
• Who is more likely to be
color blind– men or
women?
– Men: only 1 X chromosome
– If they have the recessive allele
they don’t have another X to
make up for it.
Sex Linked Traits
If there is not a normal gene present to offset the
defective, recessive gene, the disorder will be present.
Gene linkage was explained through fruit flies
• Attention to detail, accurate lab records were critical
• Different than sex influenced genes
Females can carry sex-linked disorders.
• Males (XY) express all of their sex linked genes.
• Expression of the disorder depends on which
parent carries the allele and the sex of the child.
Y
X
Question:
If a normal male (do those
even exist?) has a child with a
woman who carries the
blindness allele, what are
the chances that their
children will be colorblind?
Will any children be
carriers of the trait?
X
Y
X
XX
XY
Xc
XXc XcY
Pedigrees
• A diagram that traces the inheritance of a
particular trait through several generations.
Pedigrees
• Chart showing the
genetic connections
among individuals in a
family
– Especially useful in
following recessive
alleles that are not
visible in the
heterozygote
Royal Pedigrees
I’m my own grandpa
The environment interacts with genotype.
• Phenotype is a combination of genotype and environment.
• Height is a example of a
phenotype strongly affected
by the environment.
• diet/exercise
• sunlight/water (if you’re a plant)
Nature vs. Nurture
Virtually all human diseases have
some genetic component
Eye Color and Polygenic
Inheritance/Pedigree Lab
Follow up
•Q & A
•Post Test
Everything Mendel Didn’t Know – a review of the more
complex inheritance patterns
The Ghost in Your Genes – a video with a focus on
epigenetics, it should prompt some discussion.
Eye Color and Genes –a simple visual for the variety of
melanin present in eye colors