Week 12
description
Transcript of Week 12
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Week 12
Genetics IChapter 11 pages 189-201
Genetics IIChapter 11 pages 202-209
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EXAM III RESULTS
Total Students = 39 Total Pass= 15 (38.5%)Total Fail= 24 (61.5%)
Class Average = 63Top Score = 94Low Score = 32
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90-100 80-89 70-79 60-69 50-59 40-49 30-390
1
2
3
4
5
6
7
8
9
EXAM III GRADE DISTRIBUTION
Number of Students
A B C D F F F
2
5
8 8
6
7
3
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TROUBLE SPOTS
Questions answered incorrectly:#2 (61.5% (24/39))
#3 (41% (16/39))
#9 (46% (18/39))#19 (67% (26/39))#26 (47% (23/39))#49 (69% (27/39))
#s 10 and 50 were well answered in general
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#49 A. MEIOSIS B. Pairing of homologous chromosomes only occurs in meiosis crossing over
Pairing of x-somes
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HOMEWORK
Chapter 12 ALL including Self-tests
EXAM III Extra Credit- DUE MAY 10th
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Aneuploidy
Euploidy= Correct number of chromosomes in a species
Aneuploidy= A change in the number of chromosomes due to nondisjuction
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CHANGES IN CHROMOSOME STRUCTURE
Changes in chromosome structures are mutationsX-somes can break due to radiation, organic
chemicals and virusesEnd of chromosomes break and can go back
together improperly which leads to chromosomal mutations:
DeletionsDuplicationsTranslocationsInversions
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Deletions Duplications
Inversions Translocations
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DNA exists as chromatin or as a chromosome
DNA- Deoxyribonucleic Acid
A POLYMER of NUCLEOTIDES
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How do we know that certain complications will arise if genes are added or deleted to portions
of chromosomes?Through the Study of Genetics!
Genetics is the study of biologically inherited traits
Ex. How will the deletion of section ‘a’ affect disease?
Genomics is the study of all of the genes in an organism
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Genetics and Genomics
‘Inherited traits are determined by the elements of heredity that are transmitted from parent to offspring in reproduction; these elements of heredity are called genes.’
DNA is the molecule of heredity
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Gregor Mendel, 1822-1884
The Father of GeneticsDarwin 1809-1882
Austrian Monk
Developed ‘ParticulateTheory of Inheretance’By studying Pea Plantsin the 1860s
Combined Math andBiology!
Used statistics and lawsof probability to studybiology
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Mendel studied garden pea plants to understand the units of heredity
WHY?
At the time, the ‘Blending Concept of Inheritance’ was widely accepted
Blending Concept of Inheritance= an offspring’s genetic makeup is intermediate to that of its parents
Ex. A cross between red and white flowers will only generate PINK flowers
Is this true?
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NO!! Because…
Red, Pink andWhite flowersresult in the 2nd
Generation!
Diverse forms couldnot evolve if the blending theory wascorrect.
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If we only had intermediate forms with little variation, how could all of the
diversity we see have evolved?• Confused both Mendel and Darwin
• Genes had not been discovered and would not be discovered until 1869 by Friedrich Miescher
• The molecular makeup of genes was discovered, but the function of genes was still not well understood.
• By 1900 it was understood that chromosome number is nearly constant in the cells of any species.
• Seemed likely that chromosomes were carriers of genes.
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How did Mendel and others come to the conclusion that chromosomes were the
carriers of genes?
Through the study of phenotypes and crossings of pea plants with various traits
GENOTYPE
The genes present in a particular organism orcell
PHENOTYPE
The set of an organism’sobservable properties resultingfrom the interaction of the organismsgenotype with its environment
‘ATCCGCATTACG’
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P = Parental GenerationF1= First GenerationF2= Second Generation
Mendel’s 7 Pea Plant Traits
1.
2.
3.
4.
5.
6.
7.
Garden Pea Plant
Pisum sativum
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Mendel’s Particulate Theory of Inheritance
• Mendel used the scientific method to understand inheritance in pea plants
• He created ‘pure’ or ‘true-breeding’ lines of plants for specific traits (ex. Round or smooth seeds, purple or white flowers…)
• He observed and tracked these phenotypes through multiple generations of pea plants
• Based on his studies, he determined that hereditary information is passed from parents to offspring in the form of discrete “particles” (which we now refer to as GENES)
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Why study the Garden Pea Plant?
• Easy to cultivate• Short generation time• Can self pollinate - Able to create ‘true-breeders’• Can cross pollinate by hand• Traits easy to observe• Can observe dominant or recessive characteristics
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‘True-Breeding’
- Anther contain Sperm
- Ovules in ovary contain Eggs
- Pea plants are able to ‘self- pollinate’
- Therefore, offspring are identicalto the parents
- Mendel bred plants ‘true’ to ensure the purity of each trait
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Why secure the purity of each trait?
• Had to ensure that the trait he was observing was not confounded by other discrete particles
• Ex. He had to make sure that a white colored flower was truly white before making any crosses
• His experiments would have failed because he would have observed different outcomes each generation
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Cross-Pollination
onto the stigmaof plant B
From plant AAfter self pollinatingplants for several generations to obtain‘true-breeding’ plantsMendel used the anther from one true-bred plant to pollinate the Stigmaof another true-bredplant= Cross Pollination
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Mendel’s HypothesisHypothesis
Hereditary information is passed from parents to offspring in the form of discrete “particles”
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Mendel’s Observations (3:1, D:R)
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Mendel’s Laws
Based on his observations of cross-pollination studies:
1 LAW OF SEGREGATION
2 LAW OF INDEPENDENT ASSORTMENT
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LAW OF SEGREGATION
Based on the hypothesis that if the blending theory of inheritance were true, then a cross should yield an “intermediate” phenotype in comparison to the parents
Ex. Tall plant x Short plant = Medium plant
Mendel tested this by crossing plant varieties that differed by only 1 single trait…
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LAW OF SEGREGATIONMendel performed ‘reciprocal’ crosses:Dusted pollen of Tall plants onto Short plantsDusted pollen of short plants onto Tall plants
All F1 resembled the TALL parent! NOT intermediate!
Mendel allowed the F1s to self-pollinate ¾ of the F2 plants were Tall and ¼ of the F2 plants were short!
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ALL F1s were TallNo intermediates observed!
ALL F1s would have hadthe same genetic makeupbecause the parents were bred true.
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ALL of the F1 generation plants would have had a Tt genotype
One T from parent 1 (bred true for TALL) and one t from parent 2 (bred true for SHORT)
What happens when you cross two F1 generation plants?
X
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Gametes
A true-bred TALL plant gametes will only be T
A true-bred SHORT plant gametes will only be t
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Gametes
THEREFORE, the ONLY resulting GENOTYPE for the F1 generation is T t
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F1 CROSS
X
What will the GENOTYPES of the GAMETES look like for this MONOHYBRID CROSS?
The F1s are allTt, therefore whenCross with each otherIt is a ‘mono’(one type) ‘hybrid’ (Tt) cross
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What will the GENOTYPES of the GAMETES look like for this F1 MONOHYBRID
CROSS?
T t T t
F1 F1
T
tT t
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T
t
T tF1 GAMETES
F2 GENOTYPESand PHENOTYPES
WHAT IS THE PHENOTYPIC RATIO OF TALL TO SHORT?
WHAT IS THE GENOTYPIC RATIO OF TALL TO SHORT?
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3:1 TALL: SHORT Dominant:Recessive
Monohybrid crosses ALWAYS result in a 3:1 ratio
The SHORT trait is masked by the TALL trait in the F1 generation and is observed in the F2 generation
TALL is a dominant trait and SHORT is a recessive trait
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LAW OF SEGREGATION
1 Each individual has two factors for each trait2 The factors ‘segregate’ during the formation
of gametes3 Each gamete contains only one factor from
each pair of factors4 Fertilization gives each new individual two
factors for each trait (haploiddiploid)
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Dominance
‘Tallness’ in pea plants is dominant to ‘shortness’Tall = TShort= t
If parent 1 = TT (tall plant) and parent 2 = tt (short plant)
ALL F1 generation plants will be Tt
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Dominance
Genes occur at a particular ‘locus’ on a chromosome
Alternative versions of the same gene are called ‘alleles’
The dominant allele masks the expression of the recessive allele
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A gene occurs at a particular locus
Alleles= Alternative versions of the same gene
MOM
DAD
If purple is dominant to white, the purple phenotype is observed, but you are a carrier for white!
Remember: only 1 allele of each trait is in a gamete (meiosis!)
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GENOTYPES
TT = Homozygous dominant (Tall Plant)Tt = Heterozygous (Tall Plant) tt = Homozygous recessive (Short Plant)
Phenotypes
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PUNNETT SQUARES
• Used to predict breeding outcomes• Able to calculate probability of traits
Example:T tt t
T tt t
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MENDEL’S LAW OF INDEPENDENT ASSORTMENT
Mendel experimented with plants that differed in 2 traits
The plants are hybrid in 2 ways therefore the crosses between the F1 generation are ‘DIHYBRID CROSSES’
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2 traitsTallGreen pods
2 traitsshortYellow pods
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DiHybrid Cross Cont.’d
X
Sperm Eggs
?F1 GAMETES ?
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DiHybrid Cross Cont.’d
X
Sperm Eggs
F1 GAMETES
TG
Tg
tG
tg
TG
Tg
tG
tg
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Mendel’s Dihybrid Cross Hypothesis I
If the dominant factors always segregate together (=TG) and the recessive factors segregate together (=tg), then there would be two phenotypes among the F2 plants ONLY, tall plants (T) with green pods(G) and short plants (t) with yellow pods (g)
Did Mendel observe this to be true? NO!!!
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Mendel’s Dihybrid Cross Hypothesis II
If the four factors (T, G, t, g) segregate into the F1 gametes independently, then there would be four phenotypes among the F2 plants
Tall and green podsTall and yellow podsShort and green podsShort and yellow pods
Did Mendel observe this to be true? YES!!!!!
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Mendel’s Dihybrid Cross Observations 9:3:3:1
9:3:3:1Dihybrid crosses always have this phenotypic ratio!!!
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LAW OF INDEPENDENT ASSORTMENT
1 Each pair of ‘factors’ segregates (assorts) independently of the other pairs
2 All possible combinations of factors can occur in the gametes
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Mendel and Meiosis
Homologous pairs of chromosomes line up randomly at the metaphase plate
This allows for independent segregation during gamete formation
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Probability
Wouldn’t it be nice to know the outcome of a particular cross?
- Punnett squares enable us to calculate the chance or probability of genotypes and phenotypes of offspring
- How likely is it that an offspring will inherit a specific set of two alleles, one from each parent?
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The Product Rule of Probability
What is the chance of offspring having:
EE
Ee
eE
ee
1/2 1/2
1/2 1/2
1/2 1/2
1/2 1/2
x
x
x
x
=
=
=
=
1/4
1/4
1/4
1/4
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The Product Rule of Probability
In a monohybrid cross, we know that eachChild has a 25% (1/4) chance of having attached Earlobes
The SUM Rule tells us that we can add togetherall of the same phenotypic traits:Ex. ¾ or 75% of the children will have unattachedEarlobes (¼ + ¼ + ¼ = 3/4)
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Ratios
MONOHYBRID Crosses ALWAYS result in a:3:1 ratio
3 Dominant: 1 Recessive trait(Rr x Rr)
DIHYBRID Crosses ALWAYS result in a:9:3:3:1 ratio
9 Dominant: 3 Dominant and Recessive: 3 Dominant and Recessive :1 Recessive
(TtGg x TtGg)
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YOUR TURN!
In Pea Plants, yellow seed color (Y) is dominant over green seed color (y).
When two heterozygous plants are crossed, what percentage of plants would have yellow seeds?
What percentage would have green seeds?¾ or 75%
¼ or 25%
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YOUR TURN!
In humans, pointed eyebrows (B) are dominant over smooth eyebrows (b). Mary’s father has pointed eyebrows, but she and her mother have smooth eyebrows. What is the genotype of the father?
Mary’s father can’t have a BB genotype otherwise all of the offspring would have pointed eyebrows. He can’t be bb otherwise he would havesmooth eyebrows. He MUST have a Bb genotype in order for Maryto have smooth eyebrows.
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Testcrosses
Testcrosses are performed in order to figure out the genotype underlying a particular phenotype
Mendel performed test crosses of F1 individuals with “true-bred” individuals to figure out the laws of segregation (that alleles segregate independently during gamete formation)
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Testcrosses
One-trait test cross:
Individual w/ Dominant phenotype is heterozygous
Individual w/ Dominant phenotype is homozygous
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Testcrosses
Two trait test-crosses:Individual w/ dominant phenotype is crossed
with one having the recessive phenotype
Is the fly on the left heterozygous or homozygous for wing and body color?
WE HAVE NO IDEA SO WE MUST TESTCROSS TO DETERMINE THE GENOTYPE!!
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For fruit flies (Drosophila melanogaster) we know:
L = long wings G=gray bodiesl = short (vestigial) wings g =black bodies
What are the genotypes for these flies?
The black fly with short wings MUST be llgg
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If these are the offspring between the homozygous recessive (black/short wings) and the gray body with long wings, what was the gray/long fly’s
genotype? llgg x ? =
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For fruit flies (Drosophila melanogaster) we know:
L = long wings G=gray bodiesl = short (vestigial) wings g =black bodies
What is the genotype for the gray/long fly?
llggIf Dominant for both traits=
If Heterozygous for both traits =
LLGG
LlGg
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If Dominant Homozygous:
llggLLGG xGametes
LGLGLGLG
Gametes
lglglglg
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Punnett Square
lg lg lg lg
LG
LG
LG
LG
LlGg
LlGg
LlGg
LlGg LlGg
LlGg
LlGg
LlGg LlGg
LlGg
LlGg
LlGg LlGg
LlGg
LlGg
LlGg
X
ALL of the flies would have the same phenotype if the gray/long fly had a LG genotype!!
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We know these are the offspring and they are not all gray with long
wings!!! So…..
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If Dominant Homozygous:
llggLlGg xGametes
LGLglGlg
Gametes
lglglglg
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Punnett Square
lg lg lg lgX
LG
Lg
lG
lg
LlGg LlGg LlGg LlGg
Llgg Llgg Llgg Llgg
llGg llGg llGg llGg
llgg llgg llgg llgg
25%=Long/Gray
25%=Long/Black
25%=Short/Gray
25%=Short/Black
25%= LlGg, 25%= Llgg, 25%= llGg, 25%= llgg
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MUST be heterozygous for both traits!!
This is the only way a homozygous recessivefly could have been produced!
When crossing a heterozygous for two trait Individual w/ an individual recessive for both Traits the ratio is always:
1:1:1:1
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Mendel’s Laws and Human Genetic Disorders
Two types of human genetic disorders:
1 Autosomal (x-somes other than X or Y)– Recessive– Dominant
2 X-linked (x-somes that are X or Y)
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Autosomal Patterns of Inheritance
Autosomal DominantIndividual with AA or Aa HAS the disordera = recessive
Autosomal RecessiveInvididual with aa HAS the disorderA= dominant
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Pedigrees
Pedigrees are used to track patterns of inheritance of a particular condition and to determine dominance or recessiveness
For Example:
= MALE
= FEMALE
= A UNION
= A CHILD
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Pedigrees
-The shaded/colored shapes do not indicate whether the person is dominant or recessive
-Only indicates that the person is affected
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PedigreesIn these pedigrees, which is autosomal
dominant and which is autosomal recessive?
= MALE
= FEMALE
I Only the Child is affected II Only the Parents are affected
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Autosomal RECESSIVE Most affected children have unaffected parents Heterozygotes (Aa)have an unaffected phenotype Two affected parents will always have affected children Close relatives who reproduce are more likely to have affected
children Both males and females are affected with equal frequency
Aa Aa
aa Autosomal recessiveHAS disorder
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Autosomal DOMINANT Affected children will usually have an unaffected parent Heterozygotes (Aa) ARE affected Two affected parents can produce an unaffected child Two unaffected parents will not have affected children Both males and females are affected with equal frequency
Aa Aa
aa
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Carriers
In Pattern I, the parents are Carriers for the condition, but they do not exhibit the condition themselves
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Is this pattern Autosomal Dominant or Recessive?
RECESSIVE!
*The double line indicates inbreeding/breedingBetween closely related individuals(Inbreeding increased frequency of obtaining the disorder
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Is this pattern Autosomal Dominant or Recessive?
DOMINANT!
Note that BOTH heterozygotes HAVE thecondition
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Autosomal Recessive Disorders
1 Methemoglobinemia
2 Cystic Fibrosis
3 Nieman-Pick Disease
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Methemoglobinemia
An accumulation of methemoglobin in the blood causing the blood to appear blue instead of red skin appears blue in color
Hemoglobin Methemoglobin
Those affected lack enzyme diaphorase that converts Methemoglobin back to hemoglobin (enzyme is coded for in gene on x-some 22)Autosomal RECESSIVE trait
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Cystic Fibrosis (CF)
• Most common lethal genetic disease among Caucasians in the US (1/20=carrier, 1/2000 newborns has the disease)
• Caused by a defective chloride ion channel (protein channel) located in the cell membrane
• Cl- ions fail to pass through the channel which in turn does not allow Na+ or water to pass
• Lack of water leads to thick mucus in the bronchial tubes and pancreatic ducts
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Cystic Fibrosis (CF)Life expectancy is usually into the teens and twenties,
but some people can live as many as 35 years with the disease
Gene therapy is currently being researched to correct the defective gene that produces the faulty protein
CFTR= Cystic FibrosisTransmembrane ConductanceRegulator
The CFTR geneis located on Chromosome 7
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Studied Cystic Fibrosis by researching the effect of various toxins on the regulation of Chloride secretion in dogfish shark rectal glands in Mount Desert Island Biological Laboratories in Mount Desert Island, Maine
Performed dogfish shark rectal gland perfusions
Summers of 1998 and 1999
Squalus acanthias
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Nieman-Pick Disease
Caused by defective versions of the same gene located on chromosome 11
Normally, Gene codes for enzyme, sphingomyelinase which breaks down sphingomyelin (a lipid)
Without proper functioning enzyme, lipid droplets accumulate in the cells of the liver, lymph nodes and spleen
Type A= lipid droplet buildup in brain neurological disorders Type B= milder form, protein has some function Children present with persistant jaundice, feeding difficulties,
enlarged abdomen, pronounced mental retardation
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Autosomal Dominant Disorders
1 Osteogenesis Imperfecta
2 Hereditary Spherocytosis
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Osteogenesis Imperfecta
• Autosomal dominant disorder• Caused by mutations in 2 genes needed to
synthesize type I collagen• Defective collagen I is produced• Results in weak, brittle bones• Defective collagen can combine with
normal collagen and can cause structural defects• Incidence=1/5,000 live births• Treated with drugs
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Hereditary Spherocytosis• Autosomal dominant genetic blood disorder• Caused by defective copy of ankyrin-1 gene found on
x-some 8• Leads to defective protein normally responsible for
the structure and shape maintenance of red blood cells (RBCs)
• RBCs become spherical and burst easily due to osmotic stress
• Incidence = 1/5,000• Some cases (25%) are spontaneous mutations and
are not inherited by either parent
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Mendel’s Laws and Human Genetic Disorders
Two types of human genetic disorders:
1 Autosomal (x-somes other than X or Y)– Recessive– Dominant
2 X-linked (x-somes that are X or Y)
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X-Linked Inheritance • Refers to genes that are carried on the X chromosome• Chromosome theory of inheritance (Thomas Hunt Morgan,
1900s)- specific alleles correspond specifically with the X chromosome
• The Y chromosome lacks these alleles• Males always receive an X-linked recessive mutant allele from
the female parent, therefore sex linked recessive traits appear more frequently in males
• Males can not be carriers for X-linked traits• Males express whatever allele is present on the x-
chromosome and are therefore ‘hemizygous’ for X-linked traits
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Morgan’s Observations
Used fruit flies (Drosophila melanogaster) b/c they have the same chromosome pattern as humans.
White eyes onlyObserved in Males!
Males can onlyInherit the recessiveAllele from the Female parent
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Note: the allele is nowassociated with theX chromosome
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The F1s will all have red eyes because the female is XR homozygous dominant!
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What will the F1 gametes look like?
XR XRY Xr
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The F1 Cross
Result of F1 crossis that only 1male has white eyes
Females will only havewhite eyes when theyreceive a recessiveallele from both parents
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Human X-linked Recessive Disorders
1 Color Blindness
2 Hemophilia
3 Muscular Dystrophy
4 Adrenoleukodystrophy
5 Menkes Syndrome
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Color Blindness• 3 classes of cone cells in the retina of the
human eye and each contains either:1. Blue-sensitive pigment proteins2. Red-sensitive pigment proteins3. Green-sensitive pigment proteins
Red and green sensitive pigment proteins are on the X-chromosome
Blue-sensitive pigment proteins are autosomalUsuallly passes from grandfather to grandson
through a carrier daughter
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X-linked Recessive Pedigree
8% of Caucasian males havered-green colorblindnessBright Green= tanOlive green= brownReds= reddish brownSome only see yellow, blue, blackwhite and gray
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Hemophilia
1/10,000 males is a hemophiliac
Two types:Hemophilia A- due to absence/minimal
presence of clotting factor VIIIHemophilia B- due to absence of clotting factor
IXHemophiliacs lack the ability to clot blood or
they clot blood very slowly
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Hemophilia: a Royal Pain
Queen VictoriaQueen of England (and Ireland)b.1819- d.19019 children
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Hemophilia “A Royal Disease”
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Other Types of Inheritance
1 Multiple Allelic Traits
2 Incomplete Dominance and Incomplete Penetrance
3 Pleiotropic Effects
4 Polygenic Inheritance
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Multiple Allelic Traits
When traits are controlled by multiple alleles, the gene exists in several allelic forms
Ex. Human blood types are A B OThere are 3 possible alleles that determine the
blood type BUT….
The A B O blood type is controlled by a single gene pair
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Alleles determine the presence or absence of antigens on red blood cells
IA = A antigen on red blood cellsIB = B antigen on red blood cellsi = Neither A nor B antigen on red blood cells
Possible phenotypes or genotypes:Phenotype GenotypeA IAIA, IAiB IBIB, IBiAB IAIB
O ii
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CODOMINANCEInheritance of blood types in humans is an
example of Codominance
Both IA and IB are fully expressed in the presence of the other
A person who is IAIB will have blood type ABIA is not dominant over IB
IB is not dominant over IA
IA and IB are dominant over ii
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AOAAAOAA
BOBB
AB
OO
Universal Recipient
Universal Donor
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Incomplete Dominance and Incomplete Penetrance
Incomplete Dominance:When the heterozygote (Aa) exhibits an
intermediate phenotype
Incomplete Penetrance:When the dominant allele in a heterozygote
does not lead to the dominant phenotypeThe dominant allele may not always determine
the phenotype
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Incomplete Dominance
R1 = allele for red pigmentR2 = allele for no pigment
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Incomplete Penetrance
Ex. Polydactyly (extra digits onhands, feet or both)
Is inherited as autosomal dominantBUT, not all individuals exhibit the trait who Inherit the dominant allele
Other genes may influence the appearance of the trait
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Pleiotropic EffectsOccurs when a single mutant gene affects two or more
distinct, unrelated traitsEx. Sickle-cell diseaseResults from a mutation in gene coding for hemoglobin
polypeptideMutation causes change in 1 amino acid in the
hemoglobin polypeptideCauses RBCs to be sickle-shaped
-Slows blood flow -Decreased O2 carrying
-Clogs blood vessels
-Cells have shorter life span
capacity-Resistant to Malaria!
-Severe Anemia
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Polygenic InheritanceThe expression of a trait is controlled by two or more sets of
alleles at different loci on different chromosomes =polygenes (each allele contributes to the phenotype)
Dominant alleles have a quantitative effect on the phenotype= they are additive
This leads to ‘multifactorial traits’continuous variation in phenotypes and genotypes
Ex. To what degree does a gene contribute to a trait? How much is due to Environment?
The study of this kind of inheritance= Quantitative Genetics(estimates of heritability- I did this by breeding fish!!)
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Doiminant pairs of genes
Multiple outcomes due to several pairs ofgenes controlling a trait
Orange shading represents environmentalinfluence
WHAT KIND OF HUMAN TRAITS EXHIBITPOLYGENIC/MULTIFACTORIAL INHERITANCE?
Individual genes of a polygenic trait follow Mendel's laws, but together do not produce Mendelian ratios =bell shaped curve
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WHAT KIND OF HUMAN TRAITS EXHIBITPOLYGENIC/MULTIFACTORIAL
INHERITANCE?QUANTITATIVE TRAITS:• Skin color (allele frequencies are the best indicator of shared
heritage in a population, therefore, skin color alone does not effectively indicate a person's ethnic and genetic background, sun exposure is an environmental factor)
• Height (varies continuously in a bell shape distribution, Diet and health are environmental factors)
• Hair color (little environmental influence)• Body Mass (Diet and health are environmental factors)• Finger print patterns (environmental influence possible
during gestation)• Eye color (little environmental influence, five human eye
colors, interact additively)
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HAIR COLOR– Hair color is controlled by alleles on chromosomes
3, 6, 10, and 18. – The more dominant alleles that appear in the
genotype, the darker the hair.
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Pepper Color
Gene 1: R= red r= yellow
Gene 2: Y= absence of chlorophyll (no green) y= presence of chlorophyll (green)
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Pepper Color
Genotypes: Phenotypes:
R-/Y- : (red/no chlorophyll)R-/yy : (red/chlorophyll)rr/Y- : (yellow/no chlorophyll)rr/yy : (yellow/chlorophyll)
“-” Indicates that genotype could be hetero or homozygous
RedBrown/orangeYellowGreen
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Pepper Color
• Try crossing a brown pepper (RRyy) with a yellow pepper (rrYY).
• Which trait will your offspring (F1 generation) produce?
• What traits are produced when you cross two of the peppers found in the F1 generation?
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THIS WEEK IN YOUR LAB
DNA Fingerprinting:
Restriction Fragment LengthPolymorphisms (RFLPs)
Individual 1 2 3 4 5 6 7 8 9 10
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