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Bio Exam II

Human Genetics

intro - study of inherited variance in humans - difficulties in studying human genetics (few offspring, long gen. times, cant experiment)
How to study human genetics - pop. studies of large extended families - analyze matings that already occurred - medical attention to human genetic diseases
Use DNA Sequencing DNA sequencing- many generations, extended relatives= genetic basis
Pedigree Analysis - pedigree: family tree/ shows inheritance patterns over several gen. - determine inheritance patterns over several gen. - determine inheritance patterns "based in prevalence & distribution of trait"; used by genetic counselors
Recessively Inherited Disorders - autosomal recessive - Dom. Allele makes enough proteins
Everybody Carries Something - most human genetic disorders are single- locus autosomal recessive traits
2 Outcomes - cell destroyed immediately/ cells clump together
Sickle Cell Heterozygotes - normal & above normal hemoglobin - no phenotypic diff. usually in human homozygotes & heterozygotes
Sickle Cell & Malaria Resistance - malaria: intracellular parasite of RBC's - heterozygotes resistant - sickle- cell allele favored in regions w/ malaria
Dominant Inherited Disorders - Autosomal Dominant: rare; only one defective allele required ex. Achondroplasia: dwarfism; dom. allele
Human Traits w/ non- mendelian inheritance - changes to chromosome # - difference in # of chromosome can cause disease - typical state: disomy (2 copies of eacg chromosome)
Aneuploidy - abnormal # of a partial chromosome (extra or missing copy)
Trisomy - having 3 of a chromosome - 2n+1
Monosomy - lacking 1 member of a pair of chromosomes - 2n-1
Nondisjunction - all abnormalities in chromosome # due to nondisjunction; chromosomes aren't pulled apart properly
Aneuploidy Viability - in humans, monosomes for all autosomes inviable - most trisomies also inviable - estimated that over 50% of pregnancies end by 8 weeks
Trisomy 21 - down syndrome; named after Langdon Down - extra 21st chromosome, complete or partial - frequency increases w/ maternal age
Symptoms of Trisomy 21 - abnormalities of face, hands, tongue, eyelids -slow physical &mental development -short structure - prone to heart malformations, respiratory disease, leukemia
Aneuploidy of sex chromosome - diff. # of sex chromosomes relatively common - many sex chromosome aneuploidies are viable but infertile
Turner Syndrome- XO - 44 autosome 1X chromosomes - "XO" or "45, XO" - Common symptoms: short stature, webbed neck, sterile, no barr bodies
Klinefelter Syndrome- XXY (XXY or 47,XXY) - 44 autosomes 1 X chromosomes, 24 - no specific phenotype - usually fertile (don't transmit extra Y)
Changes to Chromosome Structure - errors in meiosis, radiation, other mutagens
4 Types deletion, duplication, inversion (backwards), translocation ex. Philadelphia chromosomes: translocation: splits a gene, high change of leukemia
Genomic Imprinting - variation in phenotype dependent on parent- specific expression of each allele - occurs during gamete formation
Genomic Imprinting pt.2 - sperm & egg imprinted differently - maternal & paternal copies expressed at diff. levels - often involves DNA methylation= 1 allele silenced= 1 allele expressed
Genetic Testing and Counseling - cancer diagnosis= better change of prevention or alleviation
Fetal testing & Genetic tests done before birth methods - amniocentesis - Chronic villus sampling (CVS) - non-invasive parental screening/testing
Amniocentesis - takes weeks to grow before taking sample
CVS - several hours; takes rapidly growing cells
Newborn Screening - some genetic disorders detected @ birth
Phenylketonuria (PKU) - every newborn tested @ birth in us - normally: phenylalanine= tyrosine - PKU: phenylalanine = phenylketones (toxic) - phenylketones accumulate= damage to nervous system= mental impairment
Managing PKU done eat PKU (anything with amino acids in it)
Created by: tennadeleta.
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