Nucleic Acids and Their Functions Flashcards
What is a polynucleotide?
A molecule containing nucleotides, can comtain thousands
What are the two groups of organic bases?
Purine- double ring structure.
Pyramidine- single ring structure
What are the 2 purine cases?
Adenine
Guanine
What are the 3 pyramidine bases?
Cytosine
Thymine
Uracil
What replaces thymine in RNA?
Uracil
How is DNA structured?
Two polynucleotide strands wound into a double helix
Pentose sugar = deoxyribose
Sugar + phosphate groups on outside, form sugar-phosphate backbone.
Bases of the 2 strand face inwards and form complimentary base pairs.
How is the double helix maintained?
Hydrogen bonds form between the complementary base pairs
A-T = 2
C-G = 3
What are the carbon atom units at each end of a strand?
C3 at one
C5 at the other
The two strands are antiparallel, what does this mean?
The nucleotides are arranged in the opposite direction to those in the other strand
What are the 4 ways in which DNA’s structure helps its function?
- very stable so genetic info passes unchanged to each gen
- very large molecule so can carry large genetic info amount
- 2 strands can separate as only held by hydrogen bonds
- genetic info protected by sugar-phosphate backbone
What is RNA’s structure?
1 polynucleotide stran
Pentose sugar is ribose
What does mRNA do and where is it made?
Carries genetic code from DNA to ribosomes
Synthesised in nucleus
What is the function rRNA and where is it found?
Combines with protein to make ribosomes
Found in cytoplasm
How is tRNA (transfer) structured?
Each molecule has 3 base sequence called anticodon- Complementary to codons on mRNA.
Has amino acid attachment site. Each molecule is specific to an amino acid.
What are the 2 major functions of DNA?
Replication for cell division
Carryjng genetic code for protein synthesis in all cells.
How does replication occur?
Chromosomes make copies of themselves so that when cells divide, each daughter cell receives exact copy of genetic info.
When/where does replication take place?
Cell’s nucleus during interphase (s phase) of cell cycle.
What is transcription?
The mechanism by which the base sequence of a gene on a DNA strand is converted into the complimentary base sequence of mRNA.
Hoe does transcription occur?
DNA helicase breaks bases’ hydrogen bonds, separating 2 strands and exposing bases.
RNA polymerase binds to template strand. Free RNA nucleotides align oposite complementary bases. Polymerase moves along DNA, forming bonds that add nucleotides to RNA strand 1 at a tine.
mRNA molecule synthesised. Helix rewound behind polymerase.
Polymerase separates when it reaches a stop codon.
What is a nucleotide and what is it made up of?
A monomer of nucleoc acid comprising of a pentose sugar, a nitrogenous base and a phosphate group attached to the fifth carbon of the sugar
What is translation?
The process of translating the codons in mRNA into a specific sequence of amino acids, forming a polypeptide chain at the ribosome.
What are the 3 stages of translation?
Initiation
Elongation
Termination
How does initiation occur?
Ribosome attaches to start codon at 1 end of mRNA molecule.
First tRNA, with an anticodon complimentary to first codon on mRNA,
attaches to ribosome.
The 3 bases of mRNA’s codon and tRNA’s anticodon bond with hydrogen bonds.
A 2nd tRNA with anticodon comp to 2nd codon on mRNA attaches to other attachment site and codon-ac bind
How does elongation occur?
Ribosomal enzhme catalyses peptide bond formation between the 2 amino acids. First tRNA leaves ribosome, leaving attachment site vacant.
Ribosome moves along 1 codon on the mRNA strand.
The next tRNA binds.
