Biology Core Principles 1.5 - Nucleic Acids

Developed from the resources provided by Peter Symonds College

There are lots of flashcards, just to ensure that everything is covered for any eventuality in the exams

What does DNA stand for and what is its function?
Deoxyribonucleic Acid; Carries the genetic code which codes for the sequence of Amino Acids in the Polypeptide Chain
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What are the two Purines and the two Pyrimidines?
Purines: Adenine, Guanine; Pyrimidines: Cytosine, Thymine
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What are the Base Pairs?
Adenine and Thymine (2 Hydrogen Bonds); Cytosine and Guanine (3 Hydrogen Bonds)
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What is the structure of a DNA Nucleotide?
Phosphate bonded to the Pentose (5C) Sugar (Deoxyribose), bonded to the Organic Nitrogenous Base (A, T, G, C)
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What joins the Nucleotides together?
Phosphodiester Bonds, protected by the Sugar Phosphate Backbone
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How is a Polynucleotide formed?
Condensation Reaction; two strands of DNA run anti-parallel to each other, the hydrogen bond between the complementary base pairs form the double helix
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What is RNA?
Ribonucleic Acid
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What are the three types of RNA?
mRNA (Messenger Ribonucleic Acid), tRNA (Transfer Ribonucleic acid), rRNA (Ribosomal Ribonucleic Acid)
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What is the structure and function of mRNA?
Structure: single stranded molecule formed into a helix; Function: Manufactured in the nucleus, carries genetic code from the DNA in the nucleus to the Ribosomes
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What is the structure and function of tRNA?
Structure: single stranded molecule formed into a clover leaf (one end contains the bases CCA (Amino Acid attaches here), 3 bases called the anti-codon at the other end); Function: brings Amino Acids to Ribosome, polypeptide chain can be synthesised
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What is the structure and function of rRNA?
Structure: Long, large complex single stranded molecule; Function: Ribosomes are made up of rRNA and proteins synthesised in the nucleolus
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What is the structure of a RNA Nucleotide?
Phosphate bonded to the Pentose (5C) Sugar (Ribose), bonded to the Organic Nitrogenous Base (A, U, G, C)
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What is the complementary base pair rule for RNA?
Cytosine and Guanine (3 hydrogen bonds), Uracil and Adenine (two hydrogen bonds); if Thymine is on DNA, then it can bond with Adenine on the RNA, but if Adenine is on the DNA, it will bond with Uracil in the RNA
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What are the differences between DNA (D) and RNA (R)?
(D) One less Oxygen in Ribose/(R) One more Oxygen in Ribose; (D) Nitrogenous Base contains A, T, G, C/(R) Nitrogenous Base contains A, U, G, C; (D) Double stranded helix/(R) Single stranded; (D) Bigger/(R) Smaller
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What is ATP and ADP?
Adenosine Triphosphate (Condensation (Endergonic Reaction) of ADP + Pi (30.6KJ) and Adenosine Diphosphate (Hydrolysis (Exergonic Reaction) of the 2nd/3rd Phosphate group + Inorganic Group)
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Why is ATP referred to as the "Universal Energy Currency of the Cell"?
It is used by all living organisms in every cell; carriers energy from energy-releasing reactions to energy-consuming reactions; used to provide the energy for nearly all biochemical reactions
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What are the roles of ATP?
Active Transport (move against concentration gradient); Metabolic Processes (large complex molecules); Movement (muscle contraction); Nerve Transmission (sodium-potassium pumps across membrane); Secretion (packaging/transport of products to vesicles)
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What is ADP?
Adenine is a Nitrogen containing Organic Base
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What are the comparisons between ATP (A) and Glucose (G)?
(A) Hydrolysis of ATP requires 1 enzyme/(G) Many enzymes required; (A) ATP-ADP is a single step reaction/(G) Many intermediates for breakdown; (A) Small energy amounts/(G) Large energy release; (A) Small soluble molecules; (G) Large polar molecules
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Name the enzyme required to convert ADP to ATP
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Name the enzyme required to convert ATP to ADP
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Where is energy stored in ATP?
Energy is stored in the bond between the phosphate groups, released through the Hydrolysis of ATP to ADP + Pi
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What is the enzyme used to unwind the base-pairs and separate the DNA strands?
DNA Helicose (breaks Hydrogen bonds, the two polypeptide chains produce a replication fork)
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What is DNA Polymerose?
Joins to both template strands; free DNA Nucleotides are added according to the base-pair rule; new Hydrogen bonds are formed
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What happens after Hydrogen bonds form between the base pairs?
The new complementary nucleotides are joined by condensation reactions down the sugar phosphate backbone by phosphodiester bonds
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What is semi-conservative DNA replication?
Where half of a DNA strand is conserved, used as a template, and half is newly synthasised DNA
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How was Semi-Conservative Replication proven to be true?
Generation 0 was grown in E.Coli and was just N15; Generation 1 is then grown in N14 and spun in a centrifuge to produce two bands one band of N14N15 in a tube; Generation 2 is then grown in N14, two bands are produced in the tube (N14N15 N14N14)
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How was Conservative Replication disproven?
Conservative replication is disproved because the actual results showed a bonding in the middle area of the test tube, and not two bands, one at the top and one at the bottom
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How was Dispersive Replication disproven?
In Dispersive Reaction, generation 2 shows one single N14N15 band in the middle of the Boiling Tube, and not a N14N15 band and a N14N14 band at the top.
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Name the part of the DNA molecule which contained the N14
Nitrogenous Base
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Explain why complementary base-pairing is important in DNA replication
To ensure a double helix is produced; to ensure that the DNA codes for the correct protein; to ensure that the right protein is synthesised; formation of Hydrogen bonds; genetically identical copy of DNA molecule
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Suggest three precautions that Messelson and Stahl would have taken in order to ensure that the centrifugation part of their investigation produced valid results
Constant spin speed; constant speed time; same volume of concentrated sugar is used
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What is a gene?
A gene is a sequence of nucleotide bases found in DNA that codes for one (or more) polypeptide
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What roles do genes have?
Structural (Keratin, Collagen, Proteins) and Metabolic (Proteins, enzymes, antibodies, haemglobin)
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How many different triplet codes are there?
64 (each genetic code is a triplet, therefore 4x4x4 is 64)
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What is a degenerate code?
There are only 20 amino acids used in protein synthesis, therefore is deemed "degenerate" as most Amino Acids have more than one code (some codons are "Stop" codes)
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Are triplet codes universal or local?
Universal: the triplet code is widespread and is thought of as being universal, although there are some exceptions (such as RNA virus)
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Can there be any overlapping?
No, triplet codes are non-overlapping (each triplet code is read separately)
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Are Eukaryotic genes usually continuous or not?
Discontinuous: they have coding exons and non-coding introns; Prokaryotic genes are continuous genes, lacking non-coding sequences)
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What is the Central Dogma?
DNA (1 gene/triplet code) is converted to mRNA (codon) by transcription, which is converted to tRNA (anticodon) by translation, producing a polypeptide (1 polypeptide chain)
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What is transcription?
Production of mRNA - RNA polymerase links to template DNA inserting mRNA nucleotides one at a time (A-U, G-C), forming phosphodiester bonds between them.
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What is pre-messenger RNA?
A complimentary copy of the base sequence of the template strand, containing exons and introns; post-transcriptional modification of pre-mRNA removes introns from the molecule: functional mRNA (can leave through Nuclear Pore) goes to a Ribosome
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What is translation?
In translation, messenger RNA (mRNA) is decoded in a ribosome, outside the nucleus, to produce a specific amino acid chain, or polypeptide. The polypeptide later folds into an active protein and performs its functions in the cell.
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How does translation work?
Initiation (mRNA binds with ribosome on the smaller sub-unit and tRNA on the larger). two codons are exposed, first codon always AUG, tRNA comes with specific anticodon and the Amino Acid is activated whilst a second tRNA binds with the next codon
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What is Enlongation?
A peptide bond is formed between the two Amino Acids; the first tRNA molecule releases its Amino Acid and leaves the ribosome. Ribosome moves along mRNA, a third tRNA brings the next Amino Acid into position.
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What is Termination?
The process is repeated until the ribosome reaches a "stop codon", the ribosome-mRNA-polypeptide complex separates, polypeptides can be modified by the addition of carbohydrates/lipids/phosphate, can be combined in structures (i.e. haemoglobin)
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What are Mutations?
Random changes in the genetic material
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What are the two types of DNA Mutation?
Point Mutation (one base replaces another (substitution)) and Insertion/Deletion (one or more nucleotides are inserted/deleted from the length of DNA and causes a frame-shift (i.e. Cystic Fibrosis is a result of a deletion of a triple of 3 bases))
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What are potential causes of DNA Mutations?
DNA replication (mutagens may cause cancer), tar, UV light, X-Rays, Gamma Rays
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What are the Silent Mutations?
Some mutations change the base sequence but if the mutation is in the intron, it is a silent mutation as the same Amino Acid is coded for by the exon; some mutations may have no advantage/disadvantage (called Silent Mutations)
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What does Adenine bond to in RNA?
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What does Thymine bond to in RNA?
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What does Uracil bond to in RNA?
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What might explain the difference in DNA percentage rations compared to standard DNA ratios?
Single stranded DNA
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Name the process that removes base sequences from pre-mRNA to form mRNA
Splicing or Post-Transcriptional Modification
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Why is the genetic code described as being universal?
Codes for the same Amino Acids in all species
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Define Bulk Transport
The movement of very large molecules into/out of the cell, requiring ATP
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What is Endocytosis?
Movement into the cell of large molecules
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What are the two types of Exocytosis?
Phagocytosis (movement of solids) and Pinocytosis (movement of liquids)
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What is Exocytosis?
Movement out of the cell (e.g. secretion of hormones or enzymes from a cell)
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What do Exocytosis and Endocytosis both require?
Breaking/fusing the membrane; ATP from aerobic respiration (affected by cyanide/respiratory inhibitors/requires ATP to work); Vesicles
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Other cards in this set

Card 2


What are the two Purines and the two Pyrimidines?


Purines: Adenine, Guanine; Pyrimidines: Cytosine, Thymine

Card 3


What are the Base Pairs?


Preview of the front of card 3

Card 4


What is the structure of a DNA Nucleotide?


Preview of the front of card 4

Card 5


What joins the Nucleotides together?


Preview of the front of card 5
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