1. PowerPoint Lecture Outlines to accompany
Hole’s Human
Anatomy and Physiology
Tenth Edition
Shier w Butler w Lewis
Chapter 24
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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2. Chapter 24 Genetics and Genomics
Genetics – study of inheritance of characteristics
Genome – complete set of genetic instructions
Genomics – looking at the body in terms of multiple, interacting genes
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3. From Gene to Protein
when the gene coding for CFTR protein is mutant, cystic fibrosis results
CFTR protein folds into a channel that regulates the flow of Cl- into and out of cells lining the respiratory tract, pancreas, and elsewhere
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4. From Protein to Person when CFTR is abnormal, it traps Cl- in cells
water in cells forms very thick mucus
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5. Normal Karyotype 23 pairs of chromosomes pairs 1-22 are autosomes
pair 23 are sex chromosomes
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6. Genotype and Phenotype
particular combination of genes
alleles are variant forms of the same gene
homozygous – identical alleles
heterozygous – different alleles
wild type allele – produces most common or normal phenotype
Phenotype
way that genes are expressed
blue eyes, presence of a protein, etc
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7. Modes of Inheritance
Dominant allele masks the phenotype of the recessive allele
Recessive allele is expressed only if in a double dose (homozygous)
Autosomal conditions are carried on a nonsex chromosome
Sex-linked conditions are carried on a sex chromosome
X-linked conditions are carried on the X chromosome
Y-linked conditions are carried on the Y chromosome
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8. Autosomal Recessive Disorder
cystic fibrosis is an example
sexes are affected with equal frequencies
offspring probabilities
25% homozygous dominant
50% heterozygous
25% homozygous recessive
punnet square and a pedigree are useful ways to express genetic information
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9. Autosomal Dominant Disorder
Huntington disease is an example
a person with one HD allele develops the disease
both sexes are equally affected
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10. Incomplete Dominance
heterozygote has a phenotype intermediate between homozygous dominant and homozygous recessive
familial hypercholesterolemia is an example
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11. Codominance different alleles are both expressed
ABO blood type is an example
three alleles of ABO blood typing are IA, IB, I
a person with type A may have the genotype IA i or IA IA
a person with type B may have the genotype IB i or IB IB
a person with type AB must have the genotype IA IB
a person with type O blood must have the genotype ii
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12. Penetrance and Expressivity
Complete penetrance
everyone who inherits the disease causing alleles has some symptoms
Imcomplete penetrance
some individuals do not express the phenotype even though they inherit the alleles (example polydactyly)
Variable expression
symptoms vary in intensity in different people
two extra digits versus three extra digits in polydactyly
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13. Gene Expression Pleiotropy
single genetic disorder producing several symptoms
Marfan syndrome is an example
people affected produce several symptoms that vary
Genetic Heterogeneity
same phenotype resulting from the actions of different genes
hereditary deafness is an example
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14. Complex Traits Monogenic determined by a single gene
expression not usually influenced by the environment
Polygenic
determined by more than one gene
height, skin color, eye color
Complex traits
traits molded by one or more genes plus environmental factors
height and skin color
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15. Variations in Height
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16. Variations in Skin Color
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17. Variations in Eye Color
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18. Sex Determination
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19. Sex Chromosomes X chromosome has over 1,000 genes
most genes on the X chromosome do not have corresponding alleles on the Y chromosome
Y chromosome
has only a few dozen genes
some genes are unique only to the Y chromosome
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20. Sex-linked Genes
Y-linked genes are transmitted only from father to son
X-linked genes are transmitted from father to daughter or from mother to daughter or son
Hemophilia A is a sex-linked disorder
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21. Hemophilia A passed from mother (heterozygote) to son
each son has a 50% chance of receiving the recessive allele from the mother
each son with one recessive allele will have the disease
each son has no allele on the Y chromosome to mask the recessive allele
each daughter has a 50% chance of receiving the recessive allele from the mother
each daughter with one recessive allele will be a carrier
each daughter with one recessive allele does not develop the disease because she has another X chromosome with a dominant allele
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22. Gender Effects on Phenotype
Sex-limited trait
affects a structure or function of the body that is present in only males or females
examples are beards or growth of breasts
Sex-influenced inheritance
an allele is dominant in one sex and recessive in the other
baldness is an example
heterozygous males are bald but heterozygous females are not
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23. Chromosomal Disorders
Polyploidy
extra set of chromosomes
most embryos die
Aneuploidy
missing a chromosome or having an extra chromosome
results from nondisjunction
trisomy is the condition of having an extra chomosome
monosomy is the condition of missing a chromosome
Euploid is a normal chromosome number
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24. Causes of Aneuploidy
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25. Prenatal Tests
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26. Gene Therapy alters, replaces, silences, or augments a gene’s function
heritable gene therapy
introduces the genetic change into a sperm, egg, or zygote
changes passed to future generations
common in plants
nonheritable gene therapy
targets only affected cells
changes not passed to future generations
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27. Sites of Gene Therapy
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28. Clinical Application Down Syndrome most common autosomal aneuploid
trisomy 21
signs include and symptoms include
short stature
mental retardation
protruding tongue
heart defects
kidney defects
suppressed immune systems
digestive disorders
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