Download - Cytogenetics Lesson 4
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InheritanceandPedigrees
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Genetics Terminology:Chromosomes & Genes
Genome - Completecomplement of anorganisms DNA.
Cellular DNA isorganized inChromosmes
Genes have specificplaces on chromosomes.
Image: Chromosome & gene, Graham Colm,National Human Genome Research Institute From the Virtual Cell Biology Classroom on ScienceProfOnline.com
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Mendel's Laws
1. Law of Dominance
2. Law of Segregation
3. Law of Independent Assortment
Image: Gregor Mendel, Mendel's Principlesof Heredity: A Defense by Bateson, William. From the Virtual Cell Biology Classroom on ScienceProfOnline.com
(Johann)GregorMendel(1822-1864)Austrianmonk
whodiscoveredbasicprinciplesofhereditythrough
hisexperimentswithgardenpeasReceivedno
recognionforhisworkduringhislifeme
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Mendels Law of DominanceIn a cross of parents that are pure for contrasting traits, only one form
of the trait will appear in the next generation.Offspring that are hybrid for a trait will have only the dominant trait inthe phenotype.
Mendels Law of Segregation- During the formation of gametes (eggs or sperm), the two alleles
(hereditary units) responsible for a trait separate from each other.- Alleles for a trait are then "recombined" at fertilization, producing
the genotype for the traits of the offspring.
Mendels Law of Independent Assortment- Alleles for differenttraits are distributed to sex cells (& offspring)
independently of one another.
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AutosomalRecessive
AutosomalDominant
X-linkedrecessive
X-linkeddominantY-linked
Mitochondrial
WhatisMendelianInheritance?
MendelianInheritancereferstothetransmissionofinheritedtraitsfrom
generaontogeneraonthroughthetransmissionofgenes
Defini=onofterms:seenotes
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______
Dominant & Recessive
Genotypes& Phenotypes____________ genotype:
Both recessive alleles must be present (rr).
___________ genotype:
At least one dominant allele is present (R-).
Character: Tongue Rolling
Being able to roll your tongue is a dominantphenotype.
Harry:Being able to roll your tongue is the dominant trait(phenotype).Q: How would we represent thegenotypeof hewashomozygous dominant?
Hermione:Not being able to roll your tongue is therecessive (phenotype).Q: What would be the recessive
genotype?
______
______
Q: Would Harriet be able to roll her tongue?
Genetics Terminology
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
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Autosomaldominantinheritancewhen
oneparentcarriestheautosomal
dominantfaultygenecopy.The
autosomaldominantfaultygenecopy
isrepresentedbyD;theworkingcopy
ofthegenebyd.
Autosomaldominantinheritancewhen
bothparentscarrytheautosomal
dominantfaultygenecopy.The
autosomaldominantfaultygenecopyis
representedbyD;theworkingcopyof
thegenebyd.
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Parents
Gametes
Autosomaldominantinheritance
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Parents
Gametes
Autosomaldominantinheritance
At
conception
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Parents
Gametes
Autosomaldominantinheritance
At
conception
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Parents
Gametes
Autosomaldominantinheritance
At
conception
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Parents
Gametes
Autosomaldominantinheritance
At
conception
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Parents
Gametes
Autosomaldominantinheritance
Affected Affected Unaffected
At
conception
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Autosomalrecessiveinheritancewhen
bothparentsareunaffectedgene=c
carriersforthecondi=on.Thefaulty
copyofthegenecontainingarecessive
muta=onisrepresentedbyr;the
workingcopyofthegenebyR.
Autosomalrecessiveinheritancewhen
onlyoneoftheparentsisanunaffectedgene=ccarrierforthecondi=on.The
faultycopyofthegenecontaininga
recessivemuta=onisrepresentedbyr;
theworkingcopyofthegenebyR
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Autosomalrecessiveinheritancewhen
oneoftheparentsisanaffectedor
predisposedtodevelopthecondi6on.andtheotherparentisanunaffected
gene6ccarrierforthecondi6on.The
faultycopyofthegenecontaininga
recessivemuta6onisrepresentedbyr;
theworkingcopyofthegenebyR.
Autosomalrecessiveinheritancewhen
bothparentsareaffectedorpredisposed
todevelopthecondi6on.Thefaultycopyofthegenecontainingarecessive
muta6onisrepresentedbyr;the
workingcopyofthegenebyR.