o Bio Exam Final Nov 28 Telomeres 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 problems Only a problem in eukaryotes because linear chromosomes Prokaryotes have circular chromosome they don t have ends Telomeres solve problem TTAAGGG repeated between 100 1000 times Its not a gene its just there to protect the DNA Therefore the telomeres get shorter not the important chromosomes 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 die o o o o o o o 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 genes The question is now is if telomeres affect aging because they cells start to die after the telomeres die Progeria age very quickly live til 10 15 years chromosome telomeres are unusually short 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 Cancer a distinction of cancer cells is that they divide and divide rapidly in an uncontrolled fashion absence of telomere 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 research Chapter 17 From Gene to Protein Albino Deer have no pigment in fur and eyes This phenotype is caused by an autosomal recessive allele o o We have a dominant allele normal pigment Recessive no pigment albinism o o o o o o The way this works is the final pigment that is produced in a normal deer is called melanin Melanin is synthesized from an amino acid called tyrosine In albino deer the enzyme that changes tyrosine doesn t work so it cant make melanin Recessive allele often results in not producing an enzyme at all or producing an enzyme that doesn t work The dominate allele produces a functioning enzyme The DNA of genes is used to produce proteins many of which are enzymes and these proteins determine phenotype The DNA inherited from parents causes me to have my distinctive traits by dictating types of proteins my cells produce o Genes contain the information to make proteins 3 Steps Begin with gene which is copied into RNA Transcription copy 1 2 mRNA messenger RNA goes out into the cytoplasm and translation occurs when information in mRNA is used to make the protein Protein is made Francis Crich in 1957 named this the Central Dogma Gene mRNA Protein or RNA 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 protein 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 harm Eukaryote o o o Prokaryote o o Transcription occurs in the nucleus of the cell The immediate product of transcription is pre mRNA that has to be processed into mRNA The bases of RNA specify an amino acid sequence of a protein Transcription occurs in the cytoplasm of the cell because they don t have a nucleus The immediate product of transcription is mRNA Translation involves a ribosome connecting to mRNA and the ribosome can read mRNA and synthesize the protein o o o o 3 o o o o o o o o o o o o o o DNA is a sequence of nucleotides the gene is transcribed eventually making mRNA the mRNA is complementary to DNA Translation because going from one language to another going from a sequence of nucleotides to amino acids o The genetic code o o mRNA is organized into words called codons each codon specifies an amino acid o mRNA is composed of 4 different bases A U C G o The code that allows us to convert nucleotides to amino acids A codon is 3 letters long Syndey Brenner argued for a triplet codon because that was the most parsimonious economical hypothesis 43 64 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 life The codons are read in the 5 prime to 3 prime direction Important about genetic code 64 codons 43 3 codons mean stop 61 codons code for amino acids QUESTION ON FINAL MEAN AUG has a dual function THE GENETIC CODE IS BOTH UNABIGUOUS AND REDUNDANT WHAT DOES THIS 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 tyrosine 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 methionine 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 dfo x Notice you lose the meaning Reason for the start codon AUG helps you know where to begin Shows order Similar amino acids have similar codons Example aspartic acid and glutamic acid o o o o Quite