Bio Exam: Final Nov 16 Aneuploidy- chromosomal aberrationo Having too many or too few chromosomes (Rare)o Caused by chromosomal nondisjunction, when the chromosomes don't separate properly during meiosis o In meiosis I, instead of one chromosome going to each pole, they both going to one poleo At the end have two chromosomes and the other is missing oneo Four gametes, half have extra and half are missing a chromosomeo Monosomy- 2N-1, Trisomy- 2N+1o Or nondisjunction can happen in meiosis IIo Caused from spindle apparatus, kinetochore microtubules don't attach properlyo 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 caseo Of sex chromosomes: Dosage Compensation : even though females have two X chromosomes, they have the same dosage of X chromosomes as men do - 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 ata 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 thiswill 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 genesChapter 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 proteinso Connected by phosophodiester linkages Hersey Chase Experimento Supported DNA is genetic materialo Involves bacteria phages- a virus- composed of genetic material can be either DNA or RNA and a capsid (aprotein coat)- inside is the chromosome of DNA some RNA (either)o 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)o Viruses are compose of DNA and a protein coat, they have no metabolism- cant do anything without a host cello Showed that the material injected into bacterial cells took over the metabolism was DNAo 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 o Nucleotides are composed of a phosphate, sugar, and a base Francis Watson and James Crich o Proposed hypothesis for structure of DNA in Nature magazineo They knew the structure of nucleotides, and polynucleotideo Base is either pyrimidine (T & C) or a purine (A & G)o Phosophodiester linkage holds nucleotides togethero Polynucleotides are structurally polarized (one end is 5 prime phosphate, other is 3 prime hydroxyl)o 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 goto Adenine almost always= thymine, guanine = thymine X-ray defraction: purified DNA, made defraction pattern of it, found it has a helical shape, and uniform
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