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

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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
ATPsynthase
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Name the enzyme required to convert ATP to ADP
ATPase
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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?
Uracil
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What does Thymine bond to in RNA?
Adenine
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What does Uracil bond to in RNA?
Adenine
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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

Front

What are the two Purines and the two Pyrimidines?

Back

Purines: Adenine, Guanine; Pyrimidines: Cytosine, Thymine

Card 3

Front

What are the Base Pairs?

Back

Preview of the front of card 3

Card 4

Front

What is the structure of a DNA Nucleotide?

Back

Preview of the front of card 4

Card 5

Front

What joins the Nucleotides together?

Back

Preview of the front of card 5
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