INCOMPLETE DOMINANCE, CODOMINANCE, MULTIPLE ALLELES, POLYGENIC TRAITS.
Patterns of Inheritance Incomplete Dominance, Codominance, Multiple Alleles, Genetic Disorders, &...
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Transcript of Patterns of Inheritance Incomplete Dominance, Codominance, Multiple Alleles, Genetic Disorders, &...
Patterns of Inheritance
Incomplete Dominance, Codominance, Multiple Alleles, Genetic Disorders, &
Sex-Linked Genes
I) Incomplete Dominance
A) Snapdragon Flowers
I) Incomplete Dominance
B)Individual has a trait that appears to be an intermediate form of the traits displayed by each parent
• R = Red• W = White• RW=Pink
• R = W
• Pink X Pink Flower Cross
I) Incomplete Dominance
R
WW
RR
R
W
W
RW
RW
• Genotypes–RR: 1
–RW: 2
–WW: 1
• Phenotypes–Red: 1
–Pink: 2
–White: 1
II) Codominance
A) Roan Horse Color
II) Codominance
B)Both genes of the heterozygote are fully expressed; thus, you see both colors
II) Codominance
• R = Red
• W = White
• RW = Roan (Red/White)
• R = W
• Roan X Roan Horse Cross
R
WW
RR
R
W
W
RW
RW
• Genotypes–RR: 1
–RW: 2
–WW: 1
• Phenotypes–Red: 1
–Roan: 2
–White: 1
III) Multiple Alleles
A) Human ABO Blood Types
III) Multiple AllelesB)Some traits are
controlled by genes that have more than two alleles
III) Multiple Alleles• iA > i• iB > i• iA = iB
• iAiA or iAi = A-Blood• iBiB or iBi = B-Blood• ii = O-Blood• iAiB = AB-Blood• Cross a heterozygous A-
blood man with a heterozygous B-blood woman
iB
ii
iAiB
iA
i
i
iAi
iBi
• Genotypes–iAiB: 1
–iBi: 1
–iAi: 1
–ii: 1
• Phenotypes–AB Blood: 1
–B Blood: 1
–A Blood: 1
–O Blood: 1
IV) Sex-Linked Inheritance
A) Colorblindness & Hemophilia
IV) Sex-Linked InheritanceB) Colorblindness: genetic disease characterized
by the inability to see certain colors (there are different types of colorblindness)
1) Mutation is on the X-chromosome
C) Hemophilia: genetic disease characterized by the blood’s inability to clot
1) Mutation is on the X-chromosome
IV) Sex-Linked Inheritance
• X > XC
• Y plays no part
• XX = Normal ♀• XXC = Carrier ♀• XCXC = Colorblind ♀• XY = Normal ♂• XCY = Colorblind ♂• Cross a carrier ♀ with
a normal ♂
X
XCY
XX
X
Y
XC
XY
XXC
• Genotypes–XX: 1
–XXC: 1
–XY: 1
–XCY: 1
• Phenotypes–Normal ♀: 1
–Carrier ♀: 1
–Normal ♂: 1
–Colorblind ♂: 1
V) Polygenic Traits
A) Interaction of several genes
VII) Polygenic Traits
B) Traits controlled by two or more genes
C) Often show a wide range of phenotypes
V) Polygenic Traits
VI) Pedigrees
VI) Genetic Disorders
A) Sickle-Cell Anemia & Cystic Fibrosis
VI) Genetic DisordersA) Sickle-Cell Anemia:
1) Recessive disorder affecting hemoglobin, on chromosome #11
2) Gives red blood cells a deformed appearance
3) Heterozygous carriers are more immune to malaria; Recessives are immune to malaria
4) Malaria afflicts 300-500 million a year, killing nearly 3 million a year (largest killer in the world)
VI) Genetic DisordersB) Cystic Fibrosis:
1) Recessive disorder on chromosome #72) Mucous builds-up, making it difficult to
breath & digest food; this allows bacteria to damage the linings of the lungs (often fatal by early adulthood)
3) Heterozygous carriers are more immune to not dehydrating from cholera, & recessives are immune to cholera
4) Cholera afflicts hundreds of thousand yearly, killing many thousands