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Biological Beginnings
Module 2
Part 1- GeneticFoundations
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The genetic process
Cell
Nucleus
Chromosomes
DNA
Genes
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Chromosomes
Threadlike structuresthat contain thegenetic substanceDNA.
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DNA (Deoxyribonucleic
acid)
A complex moleculethat contains geneticinformation.
Within cells, DNA isorganized into X-shaped structurescalled chromosomes
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Genes
Units ofhereditaryinformation composed ofDNA. Genes direct cells to
reproduce themselves andmanufacture the proteinsthat maintain life
A gene is the basic unit of
heredity in a living organism.
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Genome
The complete set ofdevelopmental instructions forcreating proteins that initiatethe making of a humanorganism.
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Mitosis
Cellular reproduction inwhich the cells nucleus
duplicates itself with twonew cells being formed,each containing the sameDNA as the parent cell,
arranged in the same 23pairs of chromosomes.
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Meiosis
A specialized form of celldivision that occurs to
form eggs and sperm.
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Zygote
A single cell formedthrough fertilization.
It is the next stage in inthe process of ofreproduction.
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Sources of variability
X chromosome and Ychromosome
Genotype- all of a personsgenetic material.
Phenotype-the way anindividual genotype isexpressed in observed and
measurable characteristics.
Heredity environmentinteraction.
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Genetic principles
Dominant recessive genesprinciple
Sex linked genes
Genetic imprinting
Polygenic inheritance
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Dominant recessive genes principle
Dominant Inheritance a pattern ofinheritance in which, when a child receivescontradictory alleles, only the dominant one isexpressed.
Recessive Inheritance a pattern of
inheritance in which a child receives identicalrecessive alleles, resulting in expression of anon dominant trait.
Alleles paired genes (alike or different) that
affect a trait. When bot
hthe alleles are t
hesame , the person is is homozygous . When
they are different the person is heterozygous.
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Homozygous possessing two identicalalleles for a trait.
Heterozygous possessing differingalleles for a trait.
Polygenic inheritance pattern ofinheritance in which multiple genes
affect a complex trait.
Multifactorial transmission acombination of genetic andenvironmental factors to produce certaincomplex traits.
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Chromosomal and gene linkedabnormalities
Down syndrome trisomy 21.
Failure of the 21st chromosome toseparate during meiosis. In some cases anextra broken piece of a 21st chromosomeis present.
Downs syndrome is characterized by-
Mental retardation.
Memory and speech problems, limitedvocabulary and slow motor development.
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Distinct physical features which include-a short stocky build, a flattened nose, a
protruding tongue, almond shaped eyes,and an unusual crease running acrossthe palm of the hand.
Others conditions include eye
cataracts, heart and intestinal defects
Short lifespan.
Difficulties in breathing and feeding.
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Other abnormalities.
Cooley anemia (R)
Cystic fibrosis (R)
Phenylketoneuria (R)
Sickle cell anemia (R)
Tay sachs disease (R)
Huntington disease (D)
Marfan syndrome (D)
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Abnormalities related to the
sex chromosomes
XYY syndrome extra ychromosome. Above avgheight, large teeth andsometimes severe acne.Intelligence male sexualdevelopment and fertilityare normal
1 in 1000 male birthsNo special treatment isnecessary.
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Triple X syndrome- extra
X chromosome . Tallnessand impaired verbalintelligence. Female sexual
development and fertilityare normal.
1in 500 to 1250 female
births
Special edu to treat verbaland ability problems.
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Klienfelter syndromeXXY extra Xchromosome. Tallness, body
fat distributing females,incomplete development ofsex characteristics atpuberty, sterility, andimpaired verbal intelligence.
1 in 900 male births .
Hormone therapy atpuberty to stimulatedevelopment of sex
characteristics.
Specialeducation to treat verbal
ability problems.
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Tuner syndrome (XO)- missingx chromosome. Short stature,
webbed neck, incompletedevelopment of sex characteristicsat puberty, sterility and impairedspatial intelligence.
1 in 2500 to 8000 female births.
Hormone therapy in childhood tostimulate physical growth and atpuberty to promote development
of sex characteristics. Special eduto treat spatial ability problems.
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References