BSC 2011 UNIT I STUDY GUIDE The purpose of this study guide is to encourage you to review your notes and text material and to integrate numerous facts and terms into broad but meaningful concepts Please try and work on your own at first but don t hesitate to ask for assistance from either me or your TA We will randomly select a question or part thereof to use on your Unit I exam Dr Spears 1 a Compare and contrast i DNA ii mRNA and iii protein i ii iii DNA A double stranded helical nucleic acid molecule capable of being replicated and determining the inherited structure of a cell s proteins mRNA A type of RNA synthesized using a DNA template that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein Protein A biologically functioning molecule consisting of one or more polypeptides folded and coiled into a specific three dimensional structure i ii b For eukaryotes what is the function of i replication and where does it occur ii transcription and where does it occur and iii translation and where does it occur DNA replication is the process by which a DNA molecule is copied also called DNA synthesis It occurs in the nucleus of the cell Transcription is the synthesis of mRNA using information in the DNA a gene as a template a initiation RNA polymerase binds to the promoter sequence on template DNA strand elongation The RNA polymerase then moves along the DNA template and joins RNA nucleotides that are complementary to DNA forming a single strand of mRNA termination the pre mRNA transcript disengages from the RNA polymerase Transcription occurs in the nucleus iii Translation is the process by which transcribed mRNA in the nucleus is decoded into a specific protein at a ribosome in the cytoplasm a Spliced mRNA binds to a ribosome in the cytoplasm the correct tRNA anticodon molecule binds to mRNA codon A second tRNA binds to next mRNA codon and its amino acid binds to the first amino acid The ribosome continues to move along the mRNA transcript tRNAs bind and amino acids join to form a polypeptide chain protein until the stop codon is reached c What is the role of i Ribosomes and ii tRNA i Ribosomes a structure made of proteins and RNAs adds each amino acid brought to it by tRNA to the growing end of a polypeptide chain ii tRNA the function of tRNA is to transfer amino acids from the cytoplasmic pool of amino acids to a growing polypeptide in a ribosome d i What is meant by the genetic code ii distinguish between codons and anticodons i A codon triplet of 3 mRNA bases codes for 1 amino acid This code is redundant multiple codons may code for the same amino acid ii Codons mRNA nucleotide triplets Anticodons the end of a tRNA is a nucleotide triplet which base pairs with a complementary codon on mRNA e i What is a mutation ii what are the different types of genetic mutations iii why are mutations important to cells organisms i Mutation a change in the genetic material of a cell ii Point mutation a change in just one nucleotide in a gene Silent mutation mutation of the codon that still results in the same amino acid Missense mutation substitutions that change one amino acid to another one Nonsense mutation changes the codon for an amino acid into a stop codon f i What is a gene i A gene is a discrete unit of hereditary information on part of a chromosome consisting of a specific sequence of 100 s or 1000 s of nucleotides coding for a polypeptide a protein or RNA molecule tRNA rRNA g i What is a chromosome ii What is chromatin iii Distinguish between euchromatin and heterochromatin with respect to structure and function i 1 chromosome 1 long double stranded helical DNA molecule and its bound proteins They are structural units composed of chromatin ii Chromatin DNA the various proteins that bind to DNA iii Euchromatin the less condensed form of eukaryotic chromatin that is available for transcription Has the appearance of beads on a string DNA wraps around nucleosomes Heterochromatin Eukaryotic chromatin that remains highly compacted and is generally not transcribed involved in gene regulation and chromosome structure 2 a i What is meant by gene expression ii What is meant by gene regulation iii At what level is gene expression generally controlled iv Why is gene regulation important necessary to cells organisms i Gene expression is the flow of genetic information transcription and translation ii Gene regulation is the control of gene expression regulation transcription and translation the nucleus of the cell iii Gene expression is generally controlled at gene level which is transcriptional control in a Signal molecules hormones for example will target protein receptors on in cells and control gene expression i e turn a gene on or off iv Gene regulation is important because it allows the genes in a cell to be either expressed or repressed based on the function of the cell ex the genes expressed for muscle cells will be different than those for brain cells b What is the role of each of the following with respect to gene regulation i e in what way does each affect gene regulation i transcription factors ii control elements i Transcription factors are regulatory proteins that respond to a signal and bond to specific DNA sequences near a gene They facilitate the binding of RNA polymerase to the promoter of a gene a TF s bind to control elements and regulate genes at the initiation of b They turn on and off and modulate the amount of transcription by influencing c The particular TF s in a cell determine which genes are expressed in different cell transcription binding of RNA polymerase types ii Control elements segments of non coding DNA that serve as a binding sites for the proteins called transcription factors a Efficiency saves energy material b Allows a gene to have different patterns of activity in time space c Promotes flexibility in gene expression same gene may be controlled by 1 d Permits production of large quantities of a gene product for a specific period of e Permits cells to become differentiated during development by selective gene mechanism time expression 3 List the different types of proteins describe their function in a cell organism and provide an example of each i Enzymes catalyze reactions DNA polymerase ii Structural support keratin collagen iii Transport other molecules hemoglobin iv Hormones coordinate cell organism activities insulin v Receptors respond to and bind to chemical stimuli G proteins olfactory receptors vi Defense antibodies
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