BSCI330 Exam 1 Study Guide The Cell Theory All living organisms are composed of nucleated cells All cells store their hereditary information in the same linear chemical code DNA All DNA is composed of the same four monomers A T C G regardless of whether the DNA is in a human cell or a bacterium All cells replicate their hereditary information by Templated Polymerization Each nucleotide consists of two parts A sugar deoxyribose with a phosphate group attached and a base A G C T The backbones of DNA are created by alternating sugars and phosphates New DNA is created on a template formed by a strand of preexisting DNA Base Pairs are held together by hydrogen bonds All cells transcribe portions of their hereditary information into the same intermediary form RNA Templated polymerization is called transcription in which segments of the DNA sequence are used as templates for the synthesis of RNA Translation is the process in which RNA directs the synthesis of protein polymers mRNA guides the synthesis of proteins from instructions on the DNA All cells use proteins as catalysts There are 20 types of amino acids the monomers of a protein polypeptide These amino acids bind with high specificity to other molecules and act as enzymes to catalyze reactions that make or break covalent bonds All cells translate RNA into proteins the same way Info from mRNA is segmented into codons 3 nucleotides that are read out by the anticodons on tRNA Molecules are linked together to form proteins The fragment of genetic information corresponding to one protein is One Gene Individual segments of the entire DNA sequence are transcribed into separate RNA molecules each such DNA segment represents one gene A gene is the segment of a DNA sequence corresponding to a single protein In All Cells the expression of individual genes is regulated The genome of a cell dictates the nature of the cell proteins and when and where they are to be made Life requires free energy G and many other reactions ATP is a carrier of free energy and phosphate groups to drive DNA and RNA synthesis All cells function as biochemical factories dealing with the same basic molecular building blocks All cells made DNA RNA and proteins All cells require ATP as a building block for DNA and RNA All cells are enclosed in a plasma membrane across which nutrients and waste materials must pass A selective barrier that enables the cell to concentrate nutrients gathered from its It is amphiphilic meaning it has one part hydrophobic and one part hydrophilic Both environment sides form a lipid bilayer A living cell can exist with fewer than 500 genes The bacterium Mycoplasma genitalium has to make DNA RNA and proteins yet functions with only 480 genes There are about 60 core genes that are shared by all species with no known exception Cells can be powered by a variety of free energy sources Light phototropic organisms mostly bacteria algae and plants that produce oxygen as a Organic chemicals organotropic energy comes from other living things or organic side product molecules they produce Inorganic chemicals Lithotropic They get energy from aerobic reactions which requires the use of oxygen and some get energy from anaerobic reactions Some cells fix nitrogen and carbon dioxide for others DNA RNA and proteins are composed of just 6 elements H C N O S P Plants fix CO2 and create oxygen as a by product while bacteria fix nitrogen Also some plants of the pea family harbor symbiotic nitrogen fixing bacteria in their roots The greatest biochemical diversity exists among prokaryotic cells Eukaryotes keep their DNA in nuclei where as prokaryotes have no nuclear compartment The tree of life has three primary branches Bacteria Archea and Eukaryotes Eukaryotes Protists fungi plants animals Archea Inhabit areas that humans do not Bacteria Some genes evolve rapidly others are highly conserved Mutations occur and can cause good bad or no change in a nucleotide sequence Through mutation and natural selection organisms evolve Segments of DNA that code for no real genetic information can change a lot very often whereas genes that code for an important regulatory protein do not alter very often and are Highly Conserved Most bacteria and archea have 1000 6000 genes Most prokaryotic cells carry very little superfluous baggage and have very small genomes New genes are generated from preexisting genes by way of 1 Intragenic Mutation an existing gene can be modified by changes in its DNA sequence through various types of error that occur mainly in the process of DNA replication occur within a particular gene 2 Gene Duplication An existing gene can be duplicated to create a pair of initially identical genes in a cell 3 DNA Segment Shuffling Two of more existing genes can be broken and rejoined to make a hybrid gene consisting of DNA segments that originally belonged to separate genes 4 Horizontal Intercellular Transfer A piece of DNA can be transferred from the genome of one cell to that of another sometimes to that of another species Gene duplications give rise to families of related genes within a single cell Orthologs Genes in two separate species that derive from the same ancestral gene in the last common ancestor of those two species Paralogs Related genes that have resulted from a gene duplication event within a single genome and are likely to have diverged from their original function Homologs A general term to cover both types of relationship above Genes can be transferred between organisms both in the laboratory and in nature Viruses act as vectors for gene transfer they are not living organisms but they are small packets of genetic material that have evolved as parasites on the reproductive and biosynthetic machinery of host cells They replicate in one cell and infect another cell in the same or different species Sex results in horizontal exchanges of genetic information within a species Sex causes a vertical exchange parent to offspring but also a large horizontal exchange between two initially separate cell lineages Normally limited to individuals of the same species Nearly all eukaryotes and even some bacteria The function of a gene can often be deduced from its sequence Many gene functions have been mapped More than 200 gene families are common to all three primary branches of the tree of life There are homologies among eukaryotes bacteria and archea Horizontal transfer of genes is largely responsible Mutations reveal the functions of genes By identifying which
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