Biology Unit 1 Study Guide

Biology Unit 1 Study Guide - Biology Unit 1 Study Guide...

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1.(a) Compare and contrast the structure and function of (i) DNA It is the genetic material that encodes hereditary information and must pass this on. The structure was deduced by knowing its function by Watson and Crick. It is a double-stranded molecule each with a linear sequence of nucleotides . The nucleotides are composed of a phosphate group , 5-carbon sugar (deoxyribose ), and a nitrogenous base . It is connected by hydrogen bonds between the bases, 3 per pyrimidines (C,T) and 2 per purines (A,G). (ii) mRNA It is messenger RNA composed of a single stranded molecule. Contains the purines A,G and the pyrimidines C and Uracil in place of T. It also contains the sugar of ribose and not deoxyribose. It is created during transcription and its function is to encode proteins that allows for gene expression. It is an intermediary molecule in the flow of genetic information. (iii) protein They are a complex chain of amino acids that can have many multiple funtions. (b) For eukaryotes, what is the function of (i) replication, and where does it occur, DNA must be copied exactly so when a cell divides each new cell has a complete and identical set of genetic information to make protein and RNA. DNA polymerase is required to add nucleotides to the 3’ end of a growing DNA strand. The process is semi- conservative meaning that each strand of DNA remains intact as it serves as the template for the assembly of a complementary strand. Occurs within the nucleus . (ii) transcription, and where does it occur, It is the synthesis of mRNA using DNA as a template, and the template strand is the segment of DNA that is transcribed. RNA polymerase the enzyme binds to the promoter region of the DNA template. The promoter is a short sequence of DNA that RNA polymerase recognizes and binds to initiating transcription and contains a TATA sequence crucial for binding. Occurs in 3 steps initiation , elongation , and termination . During termination, a polyadenylation (AAUAA) sequence is transcribed after the stop signal and ~10-35 nucleotides before the endpoint. This ends with the pre-mRNA transcript, a 5’ cap is added to one end, and a poly AAAA tail is added to the 3’ end. Next the RNA gets spiced and the introns are taken out while the exons are spliced together, final product is mRNA. Occurs in the nucleolus . (iii) translation, and where does it occur? It is the process by which mRNA is decoded into a specific protein at a ribosome in the cytoplasm . The spiced mRNA binds to the ribosome in the cytoplasm. The correct tRNA molecule binds to the codon, a 2 nd tRNA molecule then binds to the next mRNA codon and its amino acid binds to the first amino acid starting the formation of a polypeptide chain (protein) . This continues until the stop codon is reached. (c) What is the role of
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This note was uploaded on 02/28/2012 for the course BSC BSC2011 taught by Professor Spears during the Spring '10 term at FSU.

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Biology Unit 1 Study Guide - Biology Unit 1 Study Guide...

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