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.(a) DNA, mRNA, and protein are all part of the central Dogma, which is the flow of genetic information. (a) DNA: Genetic information is stored in the order or sequence of nucleotides. Nucleotides code for a polypeptide (a protein) or a RNA molecule (tRNA, rRNA). A genome is all of an organism’s genetic material in a cell. RNA: The “intermediary” molecule in the flow of genetic information. 3 major types of RNA, mRNA (messenger), tRNA (transfer), rRNA (ribosomal). Proteins: Made of strands of amino acids. Types and functions: enzymes (catalyze reactions), structural (support), transport (other molecules), hormones (coordinate cell activities), receptors (respond to and bind chemical stimuli), defense, motor protein, storage (of amino acids)In short:DNA is genetic information stored in the order or sequence of nucleotidesmRNA is the template for protein synthesisA protein is any of a large group of nitrogenous organic compounds that are essential constituents of living cells(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. Replication occurs in DNA in the nucleus and makes copies of DNA. ii. Transcription occurs in the nucleus and is the organic process whereby the DNA sequence in a gene is copied into mRNA iii. Translation is the process whereby genetic information coded in messenger RNA directs the formation of a specific protein at a ribosome in the cytoplasm(c) What is the role of (i) ribosomes and (ii) tRNA? Ribosomes are composed of RNA. They are also the sites of protein synthesis, where RNA is translated into protein. Two subunits of RNA are used to make the proteins. tRNA is used to carry amino acids in the cytoplasm to help build the polypeptide (d) (i) What is meant by the “genetic code”? (ii) Distinguish between codons and anticodons.i. The genetic code is the ordering of nucleotides in DNA molecules that carries the genetic information in living cells. A codon (triplet of 3 mRNA bases) codes for one amino acid. Multiple codons can code for the same amino acid.ii. Codons are the triplets of mRNA bases and an anticodon is a group of three bases on a tRNA molecule that are complementary to an mRNA codon. (e) (i) What is a mutation? (ii) What are the different types of genetic mutations? (iii) why are mutations important to cells/organisms?i. A mutation is a change in the genetic material of a cellii. Different types of genetic mutationsa. point mutations- a change in just one nucleotideb. substitutions- exchange one base for another; may or may not change the amino acid c. insertions or deletions (indels)- extra base pair inserted or a section may be losti. causes “missense” mutationd. frameshift- alters codon reading framei. may cause a “nonsense” mutation with an early or no stop signal and NO PROTEIN.iii. Genetic mutations are essential to evolution and help species develop new, useful characteristics and traits (f) What is a gene?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 or RNA molecule. (g) What is a chromosome?Structural units composed of chromatin. 1 chromosome= 1 long double stranded helical DNA molecule and its bound proteins (h) What is chromatin? Distinguish between euchromatin and heterochromatin with respect to structure and function. Chromatin is DNA and the various proteins that bind to DNA. Euchromatin a. loosely packed DNA and proteinsb. DNA wraps around nucleosomes (8 of the 5 types of histone proteins)c. actively transcribed Heterochromatin a. tightly packed DNA and proteinsb. genetically inactive (not being transcribed) c. only found in eukaryotes (involved in gene regulation and chromosome structure).2. (a) What is meant by “gene expression”? The synthesis of mRNA using DNA as a template (the flow of genetic info)What is meant by “gene regulation”? At what level is gene expression generally controlled? Why is gene regulation important/necessary to cells/organisms?Gene regulation is the control of gene expression (regulating transcription and translation). Genes are generally controlled at the transcriptional control level. It is important because different types of cells need to turn on different genes so that they are expressed. This will alter what proteins are made by different cells. Some genes have constitutive expression, meaning they’re always on, and some are expressed or repressed as needed in facultative expression. Since all cells have the same genes, it takes regulation of the genes to turn on the right ones needed for the cell. (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 elementsi. Transcription factors are regulatory proteins that respond to a signal & bind to specific DNA sequences near a gene; regulation of gene expression on a gene level, and is the most prevalent form of gene expression. They are regulatory proteins that respond to a signal and bind to specific DNA sequences near a gene in transcription.a. TFs facilitate binding of RNA polymerase to the promoter of a gene, forming a “transcription initiation complex.”ii. Control elements are DNA sequences upstream of a gene; where you can find transcription factors. Transcription factors bind to the control elements to regulate genes at the initiation of transcription.a. TFs bind to control elements & regulate genes at the initiation of transcriptionb. they turn on, turn off, & modulate the amount of transcription by influencing binding of RNA polymerasec. the particular TFs in a cell determine which genes are expressed in different cell types3. List the different types of proteins, describe their function in a cell/organism, and provide an example of each.i. -
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