Transcript CHAPTER 11: Complex Inheritance and Human Heredity

CHAPTER 11: Complex
Inheritance and Human Heredity
BIOLOGY
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11.1 Basic Patterns of Human
Inheritance
• RECESSIVE GENETIC DISORDERS: a recessive
trait is expressed when the individual is
HOMOZYGOUS RECESSIVE for that trait… bb
• Carrier: is an individual who is HETEROZYGOUS
recessive (Bb) for a recessive disorder.
• CYSTIC FIBROSIS, ALBINISM, TAY-SACHS DISEASE,
AND GALACTOSEMIA
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DISORDER, CAUSE, EFFECT, AND TREATMENT…
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Dominant Genetic Disorders
• Huntington’s Disease: affects nervous
system, symptoms first appear
between ages of 30-50 yrs old., gradual
loss of brain function, uncontrollable
movements, and emotional
disturbances, NO PREVENTATIVE
TREATMENT OR CURE EXISTS
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• Achodroplasia: person has small
body with similarly short limbs, most
common form of dwarfism, avg
height of 4 ft, normal life expectancy,
75% born to normal sized parents
due to new mutation or genetic
change.
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Pedigrees
• A pedigree is a diagram that traces the
inheritance of a particular trait through
several generations.
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11.2 Complex Patterns of Inheritance
• Incomplete dominance: heterozygous phenotype
is an intermediate phenotype between the two
homozygous phenotypes
• Codominance: both alleles are expressed in the
heterozygous condition
– Sickle-cell disease: genetic changes in the proteins in
hemoglobin cause cells to change to sickle shape…do
not transport oxygen well
– Sickle-cell and Malaria: people who are heterozygous
for sickle-cell disease are more resistant to Malaria
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Multiple Alleles
• Blood groups in Humans: ABO groups have 3
alleles: IA = type A, IB = type B, i = type O (no
AB markers)..i is recessive to IA and IB, IA and
IB are codominant
• Blood Types: A+, A-, AB, B+, B-, O+, O-
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• Epistasis: varying coat colors…. Yellow – black
in labs…these traits have two alleles for each
trait: 1 for pigment/not, the other for how
dark/light the pigment is
• Sex Chromosomes: determine an individual’s
gender…. XX – female….. XY – male
• Autosomes: non-sex chromosomes….the
other 22 chromosome sets that determine
skin tone, eye color, hair type, etc.
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Dosage Compensation
• Chromosome inactivation: parts of the X
chromosome don’t activate correctly causing
blotches….calico cats
• Barr Bodies: only females of any species have
these
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Sex-Linked Traits
• Sex-Linked Traits: traits controlled by genes on
the X and Y chromosomes
• Males have only 1 X so they are more likely to
show X-linked recessive traits (male pattern
baldness)
• Red-green Colorblindness: recessive X-linked
trait…8% of males in the US have this
• Hemophilia: delayed clotting of blood…easy
bleeders…more men than women….men die at
early age
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Polygenic Traits
• Polygenic traits: arise from the interaction of
many alleles for the same trait…skin color,
height, eye color
• Environmental Influences: certain traits can
be inherited (heart disease) but your
environment can also have a large affect (diet)
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