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BIO251 Biology Actual Exam With Answers (204 Solved Questions)

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    NEW BIO251 - EXAM 2 ACTUAL EXAM WITH CORRECT ANSWERS GRADE A+ 3 main process of DNA replication - - answer -- initiation - elongation - termination Central Dogma - - answer - DNA - > RNA - > Protein The process by which DNA is used to encode proteins what some of the characteristics of transcrip tion/RNA - - answer -- Only specific regions are copies - RNA strands are produced, which do not bind with the DNA (exist as single strands) - No proofreading what are the 5 steps in transcription - - answer - Step 1: RNA polymerase binds to the promoter (a re gulatory region directly upstream of the gene) and initiates DNA unraveling Step 2 : RNA polymerase facilitates the assembly of free ribonucleotides into chains of RNA, using the DNA as a template Step 3: The RNA polymerase continues along the gene addin g to the RNA chain, which does not permanently pair with the DNA, but exists as a single strand Step 4: RNA synthesis continues until the RNA polymerase encounters a specific region of DNA known as a terminator

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    Step 5: Once the terminator is reached, the RNA polymerase stalls and a rho termination protein facilitates the RNA polymerase and RNA strand to disassociate from the DNA The DNA is re - wound and the RNA is free to go on to the next step name for groups of 3 base pairs of the mRNA - - answer - codons how many codons are non - coding or stop codons? - - answer - 3 are non - coding or stop codons only 61 of the 64 encode amino acids which molecule can bind both RNA and amino acids - - answer - T - RNA group of three bas es on a tRNA molecule that are complementary to an mRNA codon - - answer - Anticodon t - RNA is considered to be "charged" - - answer - when an amino acid is bound to t - RNA how many different t - RNA there are - - answer - 64, one for each codon the study of how the heredity material (DNA and RNA) is transferred. - - answer - genetics all genetic material in a cell - - answer - genome what is the sub division of genome - - answer -- chromosome - plasmid

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    what is the sub division of chromosomes - - answe r - genes (coding region) non - coding re gion what composes the DNA back bone - - answer - sugar phosphate which are the 4 nucleotides in DNA - - answer - Adenine Thymine Cytosine Guanine Uracil (only in RNA) what is the difference between bacterial and Eukaryo ta chromosomes - - answer - Most bacteria have only one circular chromosome, whereas eukaryotes tend to have multiple linear chromosomes Why is DNA semi - conservative? - - answer - When DNA divides, each copy receives one half of the original DNA and one half ne w DNA . enzyme(s) that uncoiled the DNA - - answer - topoisomerase and gyrase, and begins at a region called the origin of replication enzyme that unwinds and begins separating the DNA strands in both directions - - answer - helicase enzyme that stabilize the single stranded DNA - - answer - single strand binding proteins

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    what is required for the addition of nucleotides in DNA replication? - - answer - a free 3' hydroxyl group enzyme that adds an RNA primer to the strand being replicated - - answer - primase enzyme that makes sure the proper nucleotide is bound, and connects it to the growing DNA strand - - answer - DNA polymerase DNA lagging strand - - answer -- DNA is synthesized in pieces - multiple RNA primers are added - assembled together by the enzymes DNA - polymerase and ligase the structures where protein synthesis (translation) occurs - - answer - Ribosomes which are the 2 microbial ribosome subunits - - answer - the 30S and 50S, which come together to form a functional 70S ribosome what does the "S" in ribosomal subunits stands for - - answer - Svedberg units, which measures the rate of sedimentation during centrifugation what are the 3 functional domains of the large microbial ribosome subunit - - answer - Aminoacyl site (A) site of entry for tRNA's Peptidyl (P) site Site of peptide bond formation

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    Exit (E) site Site of exit for uncharged tRNA's ribosome binding site Also called the Shine - Dalgarno site - - answer - 16S RNA sequence is complementary to the conserved sequence in the mRNA located just in front the of the gene being translated aligns the ribosome on the mRNA so that translation starts at the correct location 3 steps of translation - - answer - Initiation: The ribosome subunits come together around the mRNA Elongation: Amino acids are added to the growing polypeptide chain Termination: Th e ribosome - mRNA complex is disassembled and the protein is released initiation steps (translation) - - answer -- binding of the 30S (small) ribosomal subunit to the mRNA (Shine - Dalgarno alignment) - the first charged tRNA binds to the mRNA (N - formyl methio nine) - the 50S (large) ribosomal subunit binds to the 30S subunit (N - formyl methionine/p - site) elongation steps (translation) - - answer -- the next charged tRNA binds in the A site of the ribosome

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    - the polypeptide chain is moved from the tRNA in the P site to the amino acid on the tRNA in the A site - the ribosome moves forward along the mRNA by one codon what catalyzes the formation of a peptide bond between the amino acids for elongation in translation - - answer - Peptidyl transferase termination steps (translation) - - answer -- the ribosome encounters a stop codon (There is no tRNA corresponding to the stop codon) - the release factor (protein) binds to the A - site causing the polypeptide chain to be released from the tRNA in the P site - the ribosome destabilizes (subunits dissociate from each other) genetic makeup of an organism Anything an organism can make or do must be encoded for in it - - answer - Genotype observable or measurable traits an organism has For example, the ability to ferment lactose - - answer - Phenotype change in the genetic makeup (even single bases) of an organism - - answer - Mutation

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    There are three basic classifications of mutation - - answer -- Missense mutation (caused by base substitution) - Nonsense mutation (caused by base substitution) - Frameshift mutation (caused by base addition or deletion) type of mutation that occurs when a change in one nucleotide results in a change of 1 amino acid in a protein function of protein is variable, depends on locatio n. - - answer - missense mutation A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter. normally a non - functional protein. - - answer - nonsense mutation mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide lac operon - - answer - the operon that controls the metabolism of lactose is lac operon on or off when glucose is present? - - answer - lac operon is off allolactose - - answer -- formed from lactose. - an inducer for lac operon - binds and causes a structural change to the repressor protein, causing the protein to no longer bind DNA, and transcription can occur.

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    what happens when glucose stores have be en depleted - - answer - the cell then switches to lactose as its energy source what happens when glucose levels in the cell are low - - answer - - cAMP builds up which binds to another protein called catabolic activator protein (CAP), activating the protein - The activated CAP protein binds to the promoter and increases RNA polymerase binding When we refer to microbial growth, we usually refer to increases in _______________, not their ________________ - - answer - the number of organisms, not their size when d oes bacteria obtain their full size? - - answer - shortly after division which are the 2 groups of requirement for bacterial growth? - - answer - Physical requirements Chemical requirements what are the 3 subdivision of physical requirements for bacterial growth - - answer - Temperature - can range from near freezing to past boiling pH - range from 2 - 12 depending on bacteria Osmotic pressure - range from 1% to 30% NaCl what are the 3 parts of the curve on the temperature growth graph? - - answer - Minimum growth temperature Optimum growth temperature Maximum growth temperature

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    which are the 5 classifications of bacteria with respect of their temperature tolerance - - answer - Hyperthermophiles The rmophiles Mesophiles Psychrotrophs Psychrophiles what is taken in consideration for the classification of bacteria with respect of their temperature tolerance - - answer - the optimum growth temperature pH - - answer - refers to the acidity or alkalinity of a solution which bacteria tolerates low pH - - answer - acidophiles how much percentage of water bacteria are composed of? - - answer - 70 to 80 % what happens to bacterial cells when adding large quantities of sugar or salt (hypertonic environment) - - answer - c ell lysis or cell plasmolysis can occur, killing or damaging the cell name of the type of bacteria that have adjusted to survive and thrive in high salt concentrations - - answer - halophiles Obligate halophiles - - answer - require high salt concentrations, and can survive 30% solutions Facultative halophiles - - answer - do not require high salt concentrations, but can survive up to 2% salt

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