Nucleic Acids Flashcards
(27 cards)
What is the structure of a nucleotide?
- pentose sugar (deoxyribose or ribose)
- nitrogenous base (guanine,cytosine,adenine, thymine or uracil)
- phosphate
What is the anti parallel structure?
DNA has two strands that have the same sequence running in the opposite direction.
Which nitrogenous bases are complementary?
A <—> T or U (two hydrogen bonds between them)
C <—> G (three hydrogen bonds between them)
What are purines?
Nitrogen bases with a large double ring structure.
Adenine and Guanine are purines
What are pyrimidines?
A nitrogen base with a small single ring structure
Thymine,Uracil and Cytosine are pyrimidines
What are the differences between DNA and RNA?
- Different ribose sugars
- RNA has uracil ,DNA has thymine
- DNA is double stranded whereas RNA is single stranded. Therefore DNA contains hydrogen bonds.
What is the phosphodiester bond?
Bond between pentose sugar and phosphate group.
Catalysed by RNA/DNA polymerase
What is adenine triphosphate (ATP)?
A phosphorylated nucleotide
What is the structure of ATP?
- ribose sugar
- adenine
- three phosphate group
What happens when ATP is a hydrolysed?
- Forms ADP + P
- Reaction is catalysed by ATP hydrolase
- releases energy
- the phosphate csn beer attached to other molecules making it more reactive
What catalyses the condensation reaction of ADP?
ATP synthase
What are the steps of semi conservative DNA replication?
1) DNA helicase unwinds the double helix, by breaking the hydrogen bonds.
2) Complementary nucleotides bind to the single stand of DNA
3) DNA polymerase catalyses the formation of phosphodiester bonds between nucleotides
4) Two identical daughter strands are formed
How does a mutation in DNA affect an organism?
Change in base sequence —> change in sequence of amino acids —> change in folding of protein —> change/lose the function of protein
What are the three types of RNA needed to know?
- mRNA (messenger RNA)
- tRNA (transfer RNA)
- rRNA (ribosomal RNA)
What are the characteristics of mRNA?
- produced during transcription
- carries the genetic code from the nucleus to the cytoplasm
- made of up triplets of bases called codons
What are the characteristics of tRNA?
- carries amino acids to the ribosomes during translation
- contains amino acid binding sites and anticodons on opposite ends
What is the function of anticodons?
They bind the complementary codons on mRNA to convert the mRNA sequence into the proteins primary structure.
What does rRNA do?
Associates with proteins to form the two sub-units of a ribosome.
What are the two stages of protein synthesis?
- transcription
- translation
What is the prompter region?
A region in a gene which doesn’t code for an amino acid but facilitates transcription but giving RNA polymerase a place to bind with the strand.
What are the steps of transcription?
1) RNA polymerase will bind to the gene at the prompter region, to separate the strands
2) As RNA polymerase move along the template strand it adds complementary nucleotides and connects them with phosphodiester bonds
3) This process will then stop at the stop codon and a molecule of mRNA would have been made
What are the steps of translation?
1) The mRNA finds it’s way to the ribosome
2) Ribosomes attach itself to the RNA molecule
3) The ribosome reads the RNA molecule in a series of codons
4) tRNA molecules with complementary anticodons carry amino acids to the ribosomes
5) the ribosomes catalyse the peptide bond formation between amino acids
What are the four ways to describe the genetic code?
- triplet coded
- non-overlapping
- degenerative
- universal
What does it mean that the genetic code is triplet coded?
Three nucleotides make up a codon which codes for a particular amino acid
