Bio Exam: Final Nov 28 Telomeres : o on the lagging strand, the primer at the end of the chromosome is removed leaving a gap, the point is that every time the DNA is duplicated the chromosomes are going to get shorter by the length of one primer and as the chromosomes get shorter it starts to eat into important genes which can cause problemso Only a problem in eukaryotes because linear chromosomeso Prokaryotes have circular chromosome, they don't have endso Telomeres solve problemo TTAAGGG repeated between 100-1000 times. Its not a gene, its just there to protect the DNAo Therefore the telomeres get shorter not the important chromosomeso Can take blood cells out of arm and separate white and red, put white blood cells in medium and grow and divide and eventually have a large culture. In cultured cells you can have up to 40 cell divisions and after about the 40th division the cells wont divide anyone no matter how much medium is in the culture and after a week or two they will dieo What happens is with every round of division the telomeres get shorter and after many rounds they die because after a while all the telomeres are eaten up and it starts eating into the important geneso The question is now is if telomeres affect aging because they cells start to die after the telomeres dieo Progeria= age very quickly, live til 10-15 years, chromosome telomeres are unusually shorto Germ cells: give rise to gametes so your ovaries/testes contain cells that divide and divide to form gamete, the chromosomes in gametes are passed to offspring so when fertilization occurs it contains chromosomes from body.  What about the genes that are passed down from generation to generation, why don't their telomeres get shorter,  Germ cells contain telomerase: enzyme that regenerates telomeres in the germ line, cells in your body that form your gametes.o Cancer: a distinction of cancer cells is that they divide and divide rapidly in an uncontrolled fashion, absence oftelomere in some cells of your body may be able to protect you form some cancers Somatic cells there is not active telomerase, chromosomes get shorter In many cancer cells, you can find telomerase When a cell changes from a normal cell into a cancer cell, the term used it “Transformed” When they think happens when transformation occurs is the gene for telomerase is some how turned on which regenerates the cells and keeps them from dying Cure cancer by cancelling telomerase? People doing researchChapter 17: From Gene to Protein Albino Deer: have no pigment in fur and eyeso This phenotype is caused by an autosomal recessive alleleo We have a dominant allele, normal pigment. Recessive, no pigment- albinismo The way this works is the final pigment that is produced in a normal deer is called melanino Melanin is synthesized from an amino acid called tyrosine o In albino deer, the enzyme that changes tyrosine doesn't work so it cant make melanino Recessive allele often results in not producing an enzyme at all or producing an enzyme that doesn't worko The dominate allele produces a functioning enzyme o The DNA of genes is used to produce proteins, many of which are enzymes and these proteins determine phenotypeo The DNA inherited from parents causes me to have my distinctive traits by dictating types of proteins my cells produce Genes contain the information to make proteins (3 Steps)1. Begin with gene which is copied into RNA (Transcription: copy)2. mRNA = messenger RNA goes out into the cytoplasm and translation occurs: when information in mRNA is used to make the protein3. Protein is madeo Francis Crich in 1957 named this the “Central Dogma”o GenemRNAProtein (or RNA)o One discovery is in a lot of cases the product of the gene is an RNA molecule and they have their own function instead of always making a proteino In some cases RNA can be copied into DNA instead of the reverse, and exam is the virus that causes AID, genes made of RNA, inserts in cells, used to make DNA, inserted into chromosomes where it does all its harmo Eukaryote:o Transcription occurs in the nucleus of the cello The immediate product of transcription is pre- mRNA that has to be processed into mRNAo The bases of RNA specify an amino acid sequence of a proteino Prokaryote:o Transcription occurs in the cytoplasm of the cell (because they don't have a nucleus)o The immediate product of transcription is mRNAo Translation involves a ribosome connecting to mRNA and the ribosome can read mRNA and synthesize the proteino DNA is a sequence of nucleotides, the gene is transcribed eventually making mRNA, the mRNA is complementary to DNAo Translation because going from one language to another going from a sequence of nucleotides to amino acids The genetic codeo The code that allows us to convert nucleotides to amino acidso mRNA is organized into words called codons, each codon specifies an amino acido mRNA is composed of 4 different bases: A,U,C,Go A codon is 3 letters long, Syndey Brenner argued for a triplet codon because that was the most parsimonious (economical) hypothesis: 43=64o Marshall worked on genetic code and came up with invitro protein synthesis Invitro: in labs- way cells synthesized in lab Invivo: in life- way cells synthesized in lifeo The codons are read in the 5 prime to 3 prime directiono Important about genetic code: 64 codons (43)  3 codons mean stop: 61 codons code for amino acidso QUESTION ON FINAL: THE GENETIC CODE IS BOTH UNABIGUOUS AND REDUNDANT. WHAT DOES THIS MEAN? UNAMIGUBOUS BECAUSE A PARTICULAR CODON ALWAYS CODES FOR A SPECIFIC AMINO ACID. AAA ALWAYS CODES FOR LYSINE, THIS IS TRUE NO MATER WHAT. THE SAME CODONS ALWAYS CODE FOR THE SAME AMINO ACID REDUNDANT BECAUSE YOU CAN HAVE MORE THAN ONE CODON FOR THE SAME AMINO ACID; 4 codons that code for arginine, 2 for tyrosineo AUG has a dual function Means start- implies the mRNA always begins with AUG It codes for amino acid methionine- implies that every protein that the cells makes begins with a methionineo The genetic code is comma less, so if a piece of mRNA is AAATTTGGGCCC No spacers or commas between codons, no punctuation Its non overlapping (AAA)(UUU)(AAA) NOT( A[AA)(U]U[U)AA]A The reading frame is critical:- “The dog ate the red fox.”- In order to read this sentence right, you have to read one word at a time and in sequence, you wouldn't read it “Th edo gat eth ere