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FSU BSC 2011 - UNIT I STUDY GUIDE

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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. Spears1. (a) Compare and contrast (i) DNA, (ii) mRNA, and (iii) protein.(i) DNA: A double – stranded, helical nucleic acid molecule; capable of being replicated and determining the inherited structure of a cell’s proteins. (ii) 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.(iii) Protein: A biologically functioning molecule consisting of one or more polypeptides folded and coiled into a specific three-dimensional structure. (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?(i) DNA replication is the process by which a DNA molecule is copied; also called DNA synthesis. It occurs in the nucleus of the cell. (ii) 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)(iii) Gene expression is generally controlled at gene level which is transcriptional control in the nucleus of the cell. 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 transcription. b. They turn on and off and modulate the amount of transcription by influencing binding of RNA polymerase. c. The particular TF’s in a cell determine which genes are expressed in different cell 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 mechanism)d. Permits production of large quantities of a gene product for a specific period of time. e. Permits cells to become differentiated during development (by “selective gene expression”3.


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