A Note On Human Diseases

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EXAM 5
Types of dominance:
Heterozygote has intermediate phenotype
Cross red and white flowers, get an array of colors
Co-dominance: both alleles are expressed in heterozygote
ABO blood types
Multiple alleles: three or more forms of a gene trait
Human blood typing system:
Presence of sugar (antigen) determines ABO
Type A: antigen A present
Type B: antigen B present
Type O: no antigen present
Antibodies in blood react within antigen
Specific antibodies for antigens not present
No antibodies to antigens present
Definitions
Polygenic trait: expression of a trait depends on alleles at more than one locus
Skin color, height, weight
Epistasis: alleles at one locus can mask alleles at another locus
Albinism
Pleiotropy: one gene can affect many traits
Sickle-cell anemia
Genetic disorders
Recessive disorders
Cystic fibrosis: chloride accumulation in cells
Tay-sachs disease: abnormal hemoglobin molecule causes deformed RBCs
Sickle-cell anemia: abnormal hemoglobin
Dominant disorders
Huntington’s disease: mental disorientation
Dwarfism
Hypercholesterolemia: excess cholesterol in blood
Linked genes
Genes that have a tendency to be inherited together during meiosis due to close proximity on a chromosome
Don’t show independent assortment
Why are linked genes?
Close together on the same chromosome, they do not assort independently
Gene duplication
A portion of genetic material is replicated
Results in multiple copies in the same region
Inversion
A segment of genetic material is broken away
Deletion
Loss of genetic material
Caused in errors in
Autosomal vs. sex chromosomes
Sex chromosomes: responsible for gender determination (2)
Autosomes: any chromosome not considered a sex chromosome (44)
Sex determination
Humans
XX is female
XY is male (father determines sex of offspring)
Birds/moths/butterflies
ZZ is male
ZW is female
Bees
XX is female
X_ is male
Sex-linked traits
Genes that occurs on the x chromosome and not on the y chromosome
Hemophilia, color blindness, glucose-6-phosophate, dehydrogenase deficiency
Why are male calico cats rare?
Male cat must inherit two x chromosomes in addition to the y chromosome
Klinefelter Syndrome
Lionization: one of the x chromosomes inactivates by supercoiling into a Barr boy. Leaves only one active x chromosome
Is random in each cell, impossible to predict which x chromosome will become inactivated
How is color blindness inherited?
Sex-linked recessive
Trait is carried on x chromosome
Male must inherit colorblindness allele from both parents
Hemophilia is similar, but generally lethal
Why does sex-influenced trait mean?
Expression of the phenotype of an allele is related to the sex of the individual
Pattern baldness
Dominant in males
Recessive in females
Huntington’s disease
Deterioration of nervous system beginning at age 35 or older
Autosomally inherited
Dominant
Evolution
All of the changes in organisms that have occurred since the origin of life
Genetic change in a populations of organisms
Early views
Plato (440 BC)
Real World (perfect vs. illusory world)
Aristotle (350 BC)
Linnaeus
Founded taxonomy
Naming of organisms
Binomial nomenclature: Genus species

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Strata in rocks
A layer of sedimentary rock with characteristics that distinguish it from another
Younger rock is closer to the surface
Fossils within strata are evidence of succession on flora and fauna
Lyell and Hutton
Gradualism
Hutton: geological landforms arise through slow/continuous processes
Lyell: geologic processes are uniform and balance each other out
Mountains and erosions
Influence on Darwin gradualism state that the earth must be more than 6,000 years old as stated by Natural Theology
Lamarck
Correct
Recognized descent lines
Realized earth must be much older than previously thought
Organisms adapt to their environments…