DNA what is itProteinsDNA ReplicationMutationSlide 5Slide 6Slide 7MutagenTranscriptionSlide 10TranslationSlide 12ChromosomesSlide 14KaryotypeChromosome AberrationsSlide 17Slide 18NondisjunctionAutosomal AneuploidySlide 21Down SyndromeSex Chromosome AneuploidySlide 24Turner SyndromeSlide 26Klinefelter SyndromeAlterations in Chromosome StructureSlide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37GeneticsSlide 39Slide 40Slide 41Slide 42Slide 43PedigreesSlide 45Single-Gene DisordersSlide 47Slide 48Slide 49PenetranceExpressivitySlide 52Slide 53Slide 54Autosomal Recessive DisorderConsanguinitySex-Linked DisordersSlide 58Slide 59Gene MappingMosby items and derived items © 2006 by Mosby, Inc.1DNA what is itPentose sugar (deoxyribose)Phosphate molecule Four nitrogenous basesPyrimidines: cytosine and thyminePurines: adenine and guanineMosby items and derived items © 2006 by Mosby, Inc.2ProteinsOne or more polypeptidesComposed of amino acids20 amino acids of 64 total known are found in the structure of all plants and animals 6 we can not manufacture from scratch and are essential in dietDirected by sequence of bases along DNA strans 3 consecutive bases = a codonMosby items and derived items © 2006 by Mosby, Inc.3DNA ReplicationUntwisting and unzipping of the DNA strandSingle strand acts as a template for replication and transcription to RNAComplementary base pairing done by action of DNA polymeraseAdenine-thymine; cytosine-guanine Chargraf’s rulesMosby items and derived items © 2006 by Mosby, Inc.4MutationAny inherited alteration of genetic materialChromosome aberrations major changes in the entire DNA strand and entire piece missing or an extra chromosome or even an extra complete set examples include Cri – du – chat mising piece of #5 or trisomy 21 Downs syndrome extra 21 chromosomeBase pair substitutionOne base pair is substituted for another Silent substitutionSubstitution that does not result in an amino acid change because genetic code is redundantRNA codons GUU, GUC, GUA, GUG all code for the amino acid valineMosby items and derived items © 2006 by Mosby, Inc.5MutationFrameshift mutationInsertion or deletion of one or more base pairsCauses a change in the entire “reading frame”Examples include sickle cell anemiaMosby items and derived items © 2006 by Mosby, Inc.6MutationMosby items and derived items © 2006 by Mosby, Inc.7MutationSpontaneous mutationMutation that occurs in absence of exposure to known mutagensMutational hotspotsAreas of the chromosomes that have high mutation ratesA cytosine base followed by a guanine are known to account for a disproportionately large percentage of disease-causing mutationsMosby items and derived items © 2006 by Mosby, Inc.8MutagenAgent known to increase the frequency of mutationsRadiationChemicalsMosby items and derived items © 2006 by Mosby, Inc.9TranscriptionRNA is synthesized from the DNA templateResults in the formation of messenger RNA (mRNA)mRNA moves out of the nucleus and into the cytoplasmMosby items and derived items © 2006 by Mosby, Inc.10TranscriptionMosby items and derived items © 2006 by Mosby, Inc.11TranslationProcess by which RNA directs the synthesis of a polypeptideSite of protein synthesis is the ribosometRNA contains a sequence of nucleotides (anticodon) complementary to the triad of nucleotides on the mRNA strand (codon)The ribosome moves along the mRNA sequence to translate the amino acid sequenceMosby items and derived items © 2006 by Mosby, Inc.12TranslationMosby items and derived items © 2006 by Mosby, Inc.13ChromosomesSomatic cellsContain 46 chromosomes (23 pairs)Diploid cellsGametesContain 23 chromosomesHaploid cells One member of each chromosome pairMeiosisFormation of haploid cells from diploid cellsMosby items and derived items © 2006 by Mosby, Inc.14ChromosomesAutosomesThe first 22 of the 23 pairs of chromosomes in males and femalesThe two members are virtually identical and thus said to be homologousSex chromosomesRemaining pair of chromosomesIn females, it is a homologous pair (XX)In males, it is a nonhomologous pair (XY)Mosby items and derived items © 2006 by Mosby, Inc.15KaryotypeOrdered display of chromosomesMosby items and derived items © 2006 by Mosby, Inc.16Chromosome AberrationsEuploid cellsCells that have a multiple of the normal number of chromosomes Haploid and diploid cells are euploid forms When a euploid cell has more than the diploid number, it is called a polyploid cell Triploidy: a zygote having three copies of each chromosome (69)Tetraploidy: four copies of each (92 total)Both triploid and tetraploid fetuses don’t surviveMosby items and derived items © 2006 by Mosby, Inc.17Chromosome AberrationsAneuploidyA somatic cell that does not contain a multiple of 23 chromosomesA cell containing three copies of one chromosome is trisomic (trisomy)Monosomy is the presence of only one copy of any chromosomeMonosomy is often lethal, but infants can survive with trisomy of certain chromosomes “It is better to have extra than less”Mosby items and derived items © 2006 by Mosby, Inc.18Chromosome AberrationsDisjunction Normal separation of chromosomes during cell division NondisjunctionUsually the cause of aneuploidyFailure of homologous chromosomes or sister chromatids to separate normally during meiosis or mitosisMosby items and derived items © 2006 by Mosby, Inc.19NondisjunctionMosby items and derived items © 2006 by Mosby, Inc.20Autosomal AneuploidyPartial trisomyOnly an extra portion of a chromosome is present in each cellChromosome mosaicsTrisomies occurring only in some cells of the bodyMosby items and derived items © 2006 by Mosby, Inc.21Autosomal AneuploidyDown syndromeBest-known example of aneuploidyTrisomy 211:800 live birthsMentally retarded, low nasal bridge, epicanthal folds, protruding tongue, poor muscle toneRisk increases with maternal ageMosby items and derived items © 2006 by Mosby, Inc.22Down SyndromeMosby items and derived items © 2006 by Mosby, Inc.23Sex Chromosome AneuploidyOne of the most common is trisomy X. This is a female that has three X chromosomes. Termed “metafemales”Symptoms are variable: sterility, menstrual irregularity, and/or mental retardationSymptoms