DNA Structure
DNA Replication
Transcription
Translation
Enzymes & Proteins
100
State the names of the four bases in DNA and list which ones are purines and which ones are pyrimidines
-adenine & guanine-purines -thymine & cytosine-pyrimidines
100
What is the function of DNA polymerase?
Synthesizes new strands from the two parental template strands
100
List the three main types of RNA.
Messanger RNA (mRNA) Transfer RNA (tRNA) Ribosomal RNA (rRNA)
100
In what direction does translation take place?
Translation of the mRNA takes place from the 5' free end to the free 3' end
100
Define denaturation.
Denaturation is a structural change in a protein that results in the loss (usually permanent) of its biological properties
200
Explain how a DNA double helix is formed using complementary base pairing and hydrogen bonds. (Hint: list at least three points)
-Two polynucleotide chains of DNA are held together by hydrogen bonds between complementary base pairs -Adenine pairs with thymine (A=T) via two hydrogen bonds, guanine pairs with cytosine (G=C) via three hydrogen bonds -In order for bases to be facing each other and thus able to pair, the two strands must run in opposite directions (they are anti-parallel)
200
Why is DNA replication a semi-conservative process?
When a new double-stranded DNA molecule is formed, one strand will be from the original molecule and one strand will be newly synthesized.
200
List two differences in the structure of DNA & RNA.
DNA: has a sugar deoxyribose, has the base thymine, is double-stranded, forms a double helix RNA: has the sugar ribose, has the base uracil, is usually single-stranded, does not form a double helix
200
What do the small subunit and large subunit of ribosomes consist of? What is the function of the ribosome?
-Small subunit: Contains an mRNA binding site -Large subunit: Contains three tRNA binding sites - an aminacyl (A) site, a peptidyl (P) site and an exit (E) site -Ribosomes are enzymes, they catalyze the translation of mRNA into a polypeptide, their substrate is mRNA, each ribosome can catalyze the transcription of different mRNA
200
Explain how the lock and key model applies to enzyme-substrate interaction.
The substrate binds to a special region on the surface of the enzyme called the active site. The shape and chemical properties of the active site and the substrate match each other. This allows the substrate to bind, but not other substances. Similarly, the lock and key model explains how a lock only opens in response to a specific key.
300
Explain what introns and exons are.
-Intron: A non-coding sequence of DNA within a gene that is cut out by enzymes when RNA is made into mature mRNA -Exon: the part of the gene which codes for a protein
300
What is the function of helicase? What happens to the polynucleotide strands?
-Unwinds the DNA and separates the two polynucleotide strands by breaking the hydrogen bonds between complementary base pairs -The two separated polynucleotide strands act as templates for the synthesis of new polynucleotide strands
300
Distinguish between the sense and antisense strands of DNA.
-Sense strand: sequence will be the "DNA version" of the RNA sequence (identical except for T instead of U), not transcribed into RNA -Antisense strand: sequence will be complementary to the RNA sequence and will be the "DNA version" of the tRNA anticodon sequence, transcribed into RNA
300
List the two exceptions to the one gene, one polypeptide rule.
-Genes encoding for tRNA and rRNA do not code for polypeptide sequences (only mRNA sequences code for polypeptides) -A single gene may code for multiple polypeptides if alternative splicing occurs (the removal of exons as well as introns)
300
List three differences between fibrous and globular proteins.
-Shape: fibrous protein-long & narrow; globular protein-rounded/spherical -Role: fibrous protein-structural; globular protein-functional -Solubility: fibrous protein-generally insoluble in water; globular protein-generally soluble in water -Sequence: fibrous protein-repetitive amino acid sequence; globular protein-irregular amino acid sequence -Stability: fibrous protein-less sensitive to changes in heat, pH; globular protein-more sensitive to changes in heat, pH
400
State the two main purposes of nucleosomes.
-Protect DNA from damage -Allow long lengths of DNA to be packaged (supercoiled) for mobility during mitosis / meiosis
400
Explain the significance of complementary base pairing in the conservation of the base sequence of DNA.
-Each of the nitrogenous bases can only pair with its complementary partner (A=T ; G=C) -Consequently, when DNA is replicated by the combined action of helicase and DNA polymerase: -The new strands formed will be identical to the original strands separated from the template -The two DNA molecules formed will be identical to the original molecule
400
State the purpose of the promoter, coding sequence, and terminator in transcription.
-Promotor: Responsible for the initiation of transcription (in prokaryotes, a number of genes may be regulated by a single promoter - this is an operon) -Coding Sequence:  The sequence of DNA that is actually transcribed (may contain introns in eukaryotes) -Terminator:  Sequence that serves to terminate transcription (mechanism of termination differs between prokaryotes and eukaryotes
400
What are the functions of free and membrane bound ribosomes?
-Free ribosomes in the cytoplasm are associated with the synthesis of proteins for internal use in the cell -Ribosomes which are attached to the wall of the endoplasmic reticulum are associated with proteins which will be placed into vesicles and secreted form the cell
400
List and briefly explain the four levels of protein structure
1) primary structure-the order/sequence of the amino acids of which the protein is composed 2) secondary structure-the way the chains of amino acids fold or turn upon themselves 3) tertiary structure-the way a polypeptide folds and coils to form a complex molecular shape 4) quaternary structure-the interaction between multiple polypeptides or prosthetic groups that results in a single, larger, biologically active protein
500
List three differences between unique or single copy genes and highly repetitive sequences in nuclear DNA.
-Unique/single copy sequences: small proportion of genome, occurs once in the genome, long base sequences, usually genes, may be translated, low rate of mutation, very similar between individuals, not used for DNA profiling, exons are examples of unique sequences -Repetitive sequences: high proportion of genome, occurs many times, short base sequences, not genes, never translated, higher rate of mutation, varies greatly between individuals, used for DNA profiling, introns are examples of repetitive sequences
500
Briefly explain the purpose of RNA primase, DNA polymerase III, DNA polymerase I, and DNA ligase in DNA replication.
-RNA primase: synthesizes a short RNA primer on each template strand to provide an attachment and initiation point for DNA polymerase III -DNA polymerase III adds deoxynucleoside triphosphates (dNTPs) to the 3' end of the polynucleotide chain, synthesizing in a 5' - 3' direction -DNA polymerase I removes the RNA primers and replaces them with DNA -DNA ligase joins the Okazaki fragments together to create a continuous strand
500
List the four basic steps of transcription.
-DNA unwinds/"unzips" as hydrogen bonds break. -The free nucleotides of the RNA pair with complementary DNA bases. -RNA sugar-phosphate backbone forms (by RNA polymerase.) -Hydrogen bonds of the untwisted RNA+DNA "ladder" break, freeing the new RNA
500
List and describe the four main steps of translation.
Initiation:  Involves the assembly of an active ribosomal complex Elongation:  New amino acids are brought to the ribosome according to the codon sequence Translocation:  Amino acids are translocated to a growing polypeptide chain Termination:  At certain "stop" codons, translation is ended and the polypeptide is released
500
Explain the effects of temperature, pH, and substrate concentration on enzyme activity
-As the temperature increases enzyme stability decreases-the kinetic energy of the enzyme atoms increases causing vibrations in the enzyme molecule that lead to the hydrogen bonds to breaking, shape changes in the active site -At the optimal pH, the maximum rate of reaction is achieved; Above or below the optimal pH the rate decreases -As the substate concentration is increased the rate of reaction increases
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