Nucleic Acids Flashcards
What is RNA?
Ribonucleic acid is a polynucleotide
Usually single stranded
Made up of the nucleotides containing the bases adenine, uracil, cytosine and guanine
How do intermolecular bonds lead to the formation of a DNA molecule?
Adenine and thymine make two hydrogen bonds (complementary base pairing between a pyrimidine and a purine)
Cytosine and guanine make three hydrogen bonds on opposite strands.
The two bonding strands are anti parallel because their DNA polynucleotides run in opposite directions and the sugars are pointing in opposite directions.
The two chains twist to form its double helix shape.
How does DNA replicate?
Interphase, each cell needs a full copy of DNA, so DNA replicates.
Double helix untwists, hydrogen bonds between bases broken, exposes bases
Covalent bonds form between phosphate and sugar of two nucleotides
DNA polymerase (enzyme) assembles new nucleotides by reading the existing DNA (the template strand).
This is called semi-conservative replication as each new DNA molecule has one conserved strand, and one newly built strand.
These are proof-read by DNA polymerase.
What is a gene?
A sequence of DNA nucleotides that codes for a polypeptide
What are the roles of DNA and RNA in living organisms
DNA base sequence codes for proteins
The required gene can be exposed by splitting the hydrogen bonds that hold the double helix together in that region
RNA nucleotides form a complementary strand (mRNA). This is a copy of the DNA coding strand
The mRNA peels away from the DNA and leaves the nucleus from the nuclear pore
The mRNA attaches to a ribosome
Then tRNA molecules bring amino acids to the ribosome in the correct order, according to the base sequence on the mRNA
The amino acids are joined together by peptide bonds to give a protein with a specific tertiary structure
Which bases are pyrimidine, which are purine?
Pyrimidine (smaller) C, T
Purine (larger) A, G
What is DNA?
Deoxyribonuleic acid
A polynucleotide
Usually double stranded
Made up of nucleotides containing the bases adenine, thymine, cytosine and guanine
Define semi-conservative replication
One strand from original DNA, one strand newly formed
Original strand acts as a template
