Bio Exam Final Nov 16 Aneuploidy chromosomal aberration Having too many or too few chromosomes Rare Caused by chromosomal nondisjunction when the chromosomes don t separate properly during meiosis In meiosis I instead of one chromosome going to each pole they both going to one pole At the end have two chromosomes and the other is missing one Four gametes half have extra and half are missing a chromosome Monosomy 2N 1 Trisomy 2N 1 Or nondisjunction can happen in meiosis II Caused from spindle apparatus kinetochore microtubules don t attach properly Of the autosomes Almost always lethal Miscarriage occurs spontaneous abortion When embryo is formed that is 2N 1 or 2N 1 doesn t normally survive long enough to be born fairly common Trisomy 21 down syndrome acceptation to rule have extra chromosome on 21 Extra copy of 21 isn t lethal because so small only survival case Of sex chromosomes Dosage Compensation dosage of X chromosomes as men do even though females have two X chromosomes they have the same About the 16th day after conception one of the two X chromo condenses into a dark mass of chromatid called a barr body Take a swab of the mouth and look at cells of a female and see a bar body and look at a male s and wont see one at all Its because one of the female s X chromosome is condensed The embryo is composed of hundreds of cells it s a coin toss of which X chromosome becomes the barr body genetic mosaics in terms of X linked genes A heterozygous female carrier for color blindness it means that some of the cells in her body the X chromosome with the normal allele is present and turned on and this will result in normal color vision In other parts of her body the X chromosome with the mutant allele is turned on If you look at the retina of a carrier half of the cells will not be able to distinguish red and green and the other half roughly can Depends on which chromosome becomes the barr body Turner s Syndrome case of monsomy X missing chromosome female only type of monsomy that is survivable in humans Triomy 47 XXX survival able two barr bodies in each chromosome taller than normal Klienfelters syndrome 47 XXY male one X becomes barr body Trisomy XYY survivable because Y is so small not many genes Chapter 16 Genetics DNA is the genetic material Genes are composed of 300 diff amino acids 20 different amino acids proteins are composed of AA DNA is compost of 4 nucleotides adenine thymine cytosine guanine simple compared to proteins Connected by phosophodiester linkages Hersey Chase Experiment Supported DNA is genetic material Involves bacteria phages a virus composed of genetic material can be either DNA or RNA and a capsid a protein coat inside is the chromosome of DNA some RNA either Viruses insert chromosomes into a host cell takes over the metabolism of host cell and so instead of the cell doing what its supposed to do the virus uses the metabolism of the host cell to make new viruses daughter viruses released from host cell Viruses are compose of DNA and a protein coat they have no metabolism cant do anything without a host cell Showed that the material injected into bacterial cells took over the metabolism was DNA Found it from S 35 radioactive sulfur and P 32 radioactive phosphorous Added phages infect bacterial cells put in blender breaks capsids put solution in centrifuge spin it bacterial cells go to top supernatant water and fragments Where DNA was radioactive contain P 32 was in bacterial cells DNA was inserted not protein supported hypothesis DNA is genetic material Nucleotides are composed of a phosphate sugar and a base Francis Watson and James Crich Proposed hypothesis for structure of DNA in Nature magazine They knew the structure of nucleotides and polynucleotide Base is either pyrimidine T C or a purine A G Phosophodiester linkage holds nucleotides together Polynucleotides are structurally polarized one end is 5 prime phosphate other is 3 prime hydroxyl Had help from scientist named Shargaf he put DNA in test tube added strong acid hydrolyzed DNA measured how many of each of 4 nucleotides that he got Adenine almost always thymine guanine thymine X ray defraction purified DNA made defraction pattern of it found it has a helical shape and uniform diameter o o o o o o o o o o o o o o o o o o o o o o o o o
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