Genetic Disease and Genes Study Guide PDF

Genetic Disease and Genes ​ 23 pairs/46 chromosomes (euploidy amount) ​ 22 pairs are autosomal, 1 pair is sex chromosomes ​ Histone: any of a group of basic proteins found in chromatin ​ Chromatin: complex of DNA and protein found in eukaryotic cells ○​ Function: packing DNA structu...

Genetic Disease and Genes ​ 23 pairs/46 chromosomes (euploidy amount) ​ 22 pairs are autosomal, 1 pair is sex chromosomes ​ Histone: any of a group of basic proteins found in chromatin ​ Chromatin: complex of DNA and protein found in eukaryotic cells ○​ Function: packing DNA structures into dense models ​ Chromosome: thread like structure made of protein and a single molecule of DNA ○​ Function: carry genetic info cell to cell ​ Gene: sequence of nucleotides (DNA or RNA), basic units of inheritance ​ Locus: fixed position on chromosome where specific gene/genetic marker is ​ Alleles: different versions of DNA sequence at given genomic location ​ Genotype: genetic make-up of cell or organism ​ Phenotype: observable characteristics resulting from genotype and environment ​ Homozygous: 2 same alleles HH,hh ​ Heterozygous: 2 different alleles Hh ​ Dominant gene: requires one allele to be expressed ​ Recessive gene: requires two alleles to be expressed ​ Centromere: where spindle attaches on chromosome during cell division ​ Short arm: top half of chromosome ​ Long arm: bottom half of chromosome ​ Aneuploidy: presence of/absence of one or more chromosomes ○​ 1 copy=monosomy=fatal(except in sex chromosomes) ○​ 3 copies=trisomy=can survive ​ Nondisjunction: causes aneuploidy, failure of chromosomes/sister chromatids separating ○​ Autosomal example=Trisomy 21/Down's syndrome ○​ Sex chromosome example=Turner syndrome, Klinefelter syndrome ​ Down’s Syndrome: Trisomy 21, example of aneuploidy resulting from nondisjunction ○​ 1/800 survive ○​ Risk factor: mother over 35 years old ○​ Manifestations: intellectual disability, low nasal bridge, epicanthal fold(eyes), protruding tongue, low set ears, poor muscle tone, intestinal malformation, flat occiput(back of head) ​ Turner Syndrome: females with only one x-chromosome, usually inherited from the mother ○​ Manifestations: underdeveloped ovaries (usually sterile), short stature (around 4’7”) webbing of neck, edema, underdeveloped breasts, wide set nipples, increased number of aborted fetuses (usually how they get diagnosed) ​ Klinefelter's Syndrome: individuals with at least 2 x-chromosomes and 1 y-chromosome ○​ Ex: XXY or XXXY, the more X’s the more abnormalities  ○​ Manifestations: male appearance, female-like breasts(gynecomastia), small testes(usually sterile), sparse body/facial hair, tall, long limbs ​ Single Gene Diseases ○​ Autosomal Dominant: one defective gene needed ○​ Autosomal Recessive: two alleles needed/ both parents carriers or have the disease ○​ X-linked recessive/dominant: more prevalent in men because they only have one x-chromosome ​ Pedigree: used to track genetic disorders within families ​ Recurrence Risk: probability that individual will develop a genetic disease ○​ Of an autosomal dominant trait: when 1 parent is affected and 1 is normal, occurrence/recurrence risk is ½ for each child ​ Penetrance: the probability of a gene/trait being expressed ○​ Incomplete penetrance: individual who has the gene for a disease but does not express it ○​ Genotypes ​ Expressivity: variation in the extent that the phenotype is expressed ○​ Example: Hemophilia A leads to a mutation that alters 1 amino acid which is a mild case, mutation on a “stop” codon is a more severe condition ​ Autosomal Dominant Inheritance: only 1 allele needed for expression, only 1 parent has to carry the gene, Hh or HH ○​ No carriers, unaffected people do not transmit the disorder ○​ Conditions can become evident later in life, but does not skip generations ○​ Examples ​ Huntington’s disease-chromosome 4(hunt is 4 letters) neurodegenerative, ​ Marfan’s Syndrome=connective tissue abnormalities ​ Neurofibromatosis= chromosome 17, neurofibromas, cafe au lait spots ​ Vonwillebrand’s=slowed clotting process ​ Autosomal Recessive Inheritance: both parents need to carry/pass the gene, hh ○​ Recurrence risk for offspring is 25% ○​ male/female affected equally ○​ Often caused by consanguinity/incest ○​ Examples ​ Cystic Fibrosis: defective gene CFTR, lungs(mucus, chronic inflammation, chronic infection), digestive(pancreatic enzymes blocked), maldigestion ​ Sickle Cell: deoxygenation/dehydration of RBC solidify and elongate/sickle, replace glutamic acid with valine, cause CVA, paralysis, death, hemorrhage, avascular necrosis(shoulders and hips), hepatomegaly(enlarged liver)  ​ Phenylketonuria(PKU): blocks PAH(enzyme) ​ Tay-Sachs: lack hexosaminidase A ​ X-linked inheritance ○​ sex-linked , males affected/ females are carriers, located on x-chromosomes, recessive most common ○​ consanguinity/incest ○​ Males cannot give to sons but will to daughter, female’s sons will have 50% recurrence ○​ Example: ​ Hemophilia: serious bleeding disorder, gene deletion/point mutation ​ A=factor viii ​ B=factor ix ​ C=factor xi ​ Muscular dystrophy ​ Red-Green color blind ​ Alport Syndrome ​ Multifactoral Inheritance: genetic and environmental ○​ Example: ​ Cleft palate ​ Congenital hip dislocation ​ Congenital heart disease ​ Type 2 diabetes ​ Diagnostic Tools/Tests ○​ Family history, previous child with abnormalities, ethnic group with high risk, pregnancy over 35 years old ○​ Prior to conception, during pregnancy, newborns ○​ Low alpha-fetoprotein levels=trisomy 21