Chapter 21 DNA Biology Technology What does DNA do o It replicates to be passed on to the next generation o DNA stores genetic hereditary information o It undergoes mutations to provide genetic diversity Some mutations are good DNA structure A review o It is a double stranded helix One DNA strands flipped inverted in respect to another o DNA is composed of repeating nucleotides made of a pentose sugar phosphate and a nitrogenous base THEY ARE COMPLIMENTARY ANTIPARALLEL o Sugar and phosphate make up the backbone while the bases make up the rungs of the ladder o Bases have complementary pairing cytosine C pairs with guanine G and adenine A pairs with thymine T DNA replication o The 2 strands unwind as the H bonds are broken by helicase enzyme o Complementary nucleotides are added to each strand 5 3 of new strand by DNA polymerase enzyme o Each new double stranded helix is made of 1 new strand and one old strand semiconservative replication o The sequence of bases makes each individual unique o Second phase in interphase RNA structure and function o It is single stranded o It is composed of repeating ribonucleotides o Ribose sugar phosphate is the backbone o Bases are A C G and uracil U RNA structure and function o 3 types of RNA o Messenger RNA mRNA carries genetic information from DNA to the ribosomes o Ribosomal RNA rRNA joins with proteins to form ribosomes o Transfer RNA tRNA transfers amino acids to a ribosome where they are added to a forming protein Comparing DNA and RNA o Similarities o Differences They are nucleic acids They are made of nucleotides The have sugar phosphate backbones DNA is double stranded while RNA is single stranded DNA has T while RNA has U DNA has deoxyribonucleotides RNA has They are found in the nucleus ribonucleotides Proteins A review RNA is also found in the cytoplasm as well as the nucleus while DNA is not o Proteins are composed of subunits called amino acids o The sequence of amino acids determines the shape of the protein o They are synthesized at the ribosomes o Peptide bonds connect amino acids in a protein together o Proteins are important for diverse functions in the body including hormones enzymes and transport o They can denature causing a loss of function When exposed to extreme conditions high or owe pressures etc That s why we need to maintain homeostasis 2 steps of gene expression 1 Transcription DNA is read to make a mRNA in the nucleus 2 Translation mRNA is read to make a protein in the cytoplasm Combinations of condons make genetic code Condon sequence of nucleotide The genetic code It is made of 4 kinds of bases Bases act as a code for amino acids used in translation Every 3 bases of the mRNA is called a codon a typical codon specifies a particular amino acid in translation Transcription helicase enzyme unwinds the double helix mRNA is made from a DNA template mRNA is processed before leaving the nucleus mRNA moves to the ribosomes to be read Processing of mRNA after transcriptions Modifications of mRNA o 5 Capping One end 5 of the RNA is capped o Splicing Introns non coding sequences are removed o Poly A tailing A poly A tail is added to 3 end Regulation of gene expression 5 levels 1 Pretranscriptional control nucleus e g chromatin density and DNA accessibility 2 Transcriptional control nucleus e g transcription factors 3 Post transcriptional control nucleus e g mRNA processing 4 Translational control cytoplasm e g differential ability of mRNA to bind ribosomes 5 Posttranslational control cytoplasm e g changes to the protein to make it functional Processing of mRNA after transcriptions DNA technology Gene cloning through recombinant DNA altering DNA in bacteria viruses plants and animal cells through recombinant DNA technology Recombinant DNA contains DNA from 2 or more different sources o Automated DNA sequencer and an electropherogram The order of nucleotides in a DNA sequence is determined Now performed using dyes attached to nucleotides with a laser and computerized machine to determine sequence o Recombinant DNA contains DNA from 2 or more different sources that allows genes to be cloned o Bacteria used to clone the human insulin gene human DNA with the insulin gene Restriction enzyme is used to cut the vector plasmid and the DNA ligase seals together the insulin gene and the plasmid Bacterial cells take up plasmid the gene is copied and the product can be made Polymerase chain reaction PCR contains DNA from 2 or more different sources o Polymerase chain reaction is used to clone small pieces of DNA o It is important for amplifying DNA for analysis such as in DNA fingerprinting DNA fingerprinting organisms that have a foreign gene inserted into them o Fragments are separated by their charge size ratios o Results in a distinctive pattern for each individual o Often used for paternity testing or to identify an individual at a crime scene or unknown body remains Biotechnology products from bacteria plants and animals using natural biological systems to create a product or to achieve an end desired by humans o Biotechnology products Transgenic organisms organisms that have a foreign gene inserted into them Important uses Production of Insulin Human growth hormone HGH Clotting factor VIII Tissue plasminogen activator t PA Hepatitis B vaccine o Bio technology products Transgenic plants engineering Important uses antibodies Plants resistant to herbicides Plants resistant to insects Plants resistant to frost Naturally occurring oil degrading bacteria can be made more effective through genetic Produce human proteins in their seeds such as hormones clotting factors and Corn soybean and cotton plants are commonly genetically altered In 2011 94 of the soybeans and 80 of the corn planted in the United States had been genetically engineered o Bio technology products Transgenic animals Gene is inserted into the egg that when fertilized will develop into a transgenic animal Current uses Gene pharming production of pharmaceuticals in the milk of farm animals Mouse models the use of mice for various gene studies Xenotransplantation pigs can express human proteins on their organs making it What did we learn from the Human Genome Project HGP easier to transplant them into humans The human genome consists of about 3 billion bases and 25 000 genes The human genome was sequenced in 2003 There are many polymorphisms or small regions of DNA that vary among individuals identified Genome size is not correlated with the number of genes or complexity
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