Genetics II Modes of Complex Inheritances and Pedigrees Nancy Dow Jill Hansen Tammy Stundon February...
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Genetics II Modes of Complex Inheritances and Pedigrees Nancy Dow Jill Hansen Tammy Stundon February 23, 2013 Gulf Coast State CollegePanhandle Area Educational
Genetics II Modes of Complex Inheritances and Pedigrees Nancy
Dow Jill Hansen Tammy Stundon February 23, 2013 Gulf Coast State
CollegePanhandle Area Educational Consortium 5230 West Highway
98753 West Boulevard Panama City, Florida 32401Chipley, Florida
32428 850-769-1551877-873-7232 www.gulfcoast.edu Biology
Partnership (A Teacher Quality Grant)
Slide 2
Pre-test Q and A board Was Mendel wrong? Why arent humans as
simple as tall or short? Why are most colorblind people males?
Slide 3
B ENCHMARK 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
Slide 4
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
Slide 5
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.
Slide 6
Mendels Results CharacterDominant x RecessiveF1F1 F 2
Generation Dominant Form: Recessive Form Ratio Flower Color purple
x whiteall purple 705 purple: 224 white2.96 Seed Coloryellow x
greenall yellow 6022 yellow: 2001 green3.01 Seed Shaperound x
wrinkledall round5474 round: 1850 wrinkled2.96 Pod Color green x
yellowall green428 green: 152 yellow2.82 Pod Shapeinflated x
pinchedall inflated 882 inflated: 299 pinched2.95 Flower Position
axial x terminalall axial651 axial: 207 terminal3.14 Plant Height
tall x shortall tall787 tall: 277 short2.84
Slide 7
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 23 rd
chromosome work on different rules Complex inheritance the most
common Multiple Allele Co-dominance Polygenetic inheritance
Incomplete dominance
Slide 8
Simple inheritance (single gene) 1. Dominant Inheritance Rr or
RR Traits include widows peak, hitchhikers 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?
Slide 9
EXAMPLES OF SINGLE-GENE TRAITS Widows peak is Dominant Straight
hairline is recessive Tongue rolling is Dominant Not able to roll
the tongue is recessive Regular thumb is Dominant Hitchhikers is
recessive Six digits (D)
Slide 10
EXAMPLES OF SINGLE-GENE TRAITS Cleft chin = rNon-cleft chin =D
Unattached earlobes = D Attached earlobes = r Autosomal Simple
Inheritance lab
Slide 11
Simple Dominant Inheritance Disease Huntingtons 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
Slide 12
Carriers Only the genotype Ff is considered to be a carrier If
(F) = freckles, what is this persons phenotype? What type of simple
inheritance are they expressing? Effect if this was a disorder and
not a trait? Why wouldnt the other simple inheritance genotype be
considered as a carrier?
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 BUILD- UP OF PHENYLALANINE
IN THE BRAIN WHICH CAN CAUSE MENTAL RETARDATION---CAN BE TREATED
WITH DIET AVOIDING THIS AMINO ACID.
Slide 15
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. Why cover disorders?
Slide 16
Human Autosomal Trait Lab Refer to the slides with the simple
inheritance traits!
Slide 17
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
Slide 18
The relationship between genotype and phenotype is rarely
simple
Slide 19
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. Non-Mendelian
Genetics
Slide 20
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 F
1 offspring
Slide 21
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?
Slide 22
Lets Practice! Cross a BLACK chicken (BB) with a WHITE chicken
(WW). These alleles show INCOMPLETE DOMINANCE BB W W BW What
percent is black? White? Gray? Black: 0% White: 0% Gray: 100%
Slide 23
Cross a BLACK chicken (BB) with a WHITE chicken (WW). These
alleles show INCOMPLETE DOMINANCE BB W W BW Genotype: BW Phenotype:
Gray What is the genotype and phenotype of the F1 generation? Lets
Practice!
Slide 24
What would the cross look like if you crossed two GREY chickens
(BW). These alleles show INCOMPLETE DOMINANCE. BW B W BBBW WWBW
Genotype: 1 BB 1 WW 2 BW Phenotype: 1 Black 1 White 2 Gray What is
the genotype and phenotype of the F2 generation? Lets Practice! PTC
Testers
Slide 25
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)
Slide 26
Both alleles are expressed in the heterozygous condition Both
alleles contribute to the phenotype. For Example: In chickens, the
allele for black feathers is co- dominant with the allele for white
feathers. These chickens will have BOTH black and white feathers.
COdominant alleles COllaborate together CoDominance
Slide 27
Cross a Black chicken (BB) with a White chicken (WW). These
alleles show CO-DOMINANCE. BB W W BW How many chickens in the F1
generation are completely black? White? Black and white? Black: 0%
White: 0% Both: 100% Lets Practice!
Slide 28
Cross a Black chicken (BB) with a White chicken (WW). These
alleles show CO-DOMINANCE. BB W W BW What is the genotype and
phenotype of the F1 generation? Genotype: BW Phenotype: Black and
white or checkered. Lets Practice!
Slide 29
Cross two Black and White (checkered) chickens (BW). These
alleles show CO-DOMINANCE BW W B WW BW BB List all possible
genotypes and phenotypes of the F2 generation. Genotype: 1 BB 1 WW
2 BW Phenotype: 1 Black 1 White 2 Checkered Lets Practice!
Slide 30
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 (I A ) and B (I B ). Cell surface antigens A and B are
codominant, which means they could also show up at the same time on
an RBC.
Slide 31
Matching compatible blood groups is critical for blood
transfusions because a person produces antibodies against foreign
blood factors. Blood type displays both co-dominance and complete
dominance
Slide 32
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
Slide 33
Multiple AllelesABO Blood Groups Possible alleles from female
Possible alleles from male IAIA IBIB i IAIA IAIAIAIA IAIAIAIA
IAiIAi IBIB IAIBIAIB IBIBIBIB IBiIBi iIAiIAiIBiIBiii Blood Types
AABBO At any one time, a parent can only have TWO alleles for
blood
Slide 34
The Genetics of Blood Lab
Slide 35
The inheritance pattern is controlled by two or more genes
(each with two alleles) Order of dominance: brown/amber >
green/hazel > gray/blue. Polygenic Inheritance At the present,
three gene pairs controlling human eye color are known (two on
chromosome 15 and one on pair 19).
Slide 36
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!) Polygenic Inheritance Wilt Chamberlin stood
71 tall, neither of his parents was over 59 Creates a bell curve
distribution
Slide 37
Polygenic Inheritance Activity 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
Slide 38
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 Dont confuse this with linked
genes = when 2 genes are on the same chromosome
Slide 39
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 dont have another X to make up
for it. Sex Linked Traits Red Green Color Blindness
Slide 40
Sex Linked Traits If there is not a normal gene present to
offset the defective, recessive gene, the disorder will be
present.
Slide 41
Gene linkage was explained through fruit flies Attention to
detail, accurate lab records were critical Different than sex
influenced genes
Slide 42
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. X Y
Slide 43
Slide 44
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? XY XcXc X XX c XX X c Y XY
Slide 45
Pedigrees A diagram that traces the inheritance of a particular
trait through several generations.
Slide 46
Chart showing the genetic connections among individuals in a
family Especially useful in following recessive alleles that are
not visible in the heterozygote Pedigrees
Slide 47
Royal Pedigrees Im my own grandpa Royal Pedigrees
Slide 48
The environment interacts with genotype. Height is a example of
a phenotype strongly affected by the environment. diet/exercise
sunlight/water (if youre a plant) Phenotype is a combination of
genotype and environment. Nature vs. Nurture Virtually all human
diseases have some genetic component
Slide 49
15 minutes!!
Slide 50
Eye Color and Polygenic Inheritance/Pedigree Lab
Slide 51
Follow up Q & A Post Test
Slide 52
Everything Mendel Didnt KnowEverything Mendel Didnt Know a
review of the more complex inheritance patterns The Ghost in Your
GenesThe Ghost in Your Genes a video with a focus on epigenetics,
it should prompt some discussion. Eye Color and GenesEye Color and
Genes a simple visual for the variety of melanin present in eye
colors