Genes, DNA, RNA
Nucleic acids carry the genetic code that determines the order of amino acids in proteins.
Genetic material stores information, can be replicated, and undergoes mutations
Differs from proteins as it has phosphorus and NO sulphur.
DNA Deoxyribonucleic Acid.
Nucleotides are smaller units of long chains of nucleic acids. Each nucleotide hasA pentose sugar (deoxyribose in DNA, ribose in RNA).
A phosphate group.
An organic base which fall into 2 groups,Purines (double rings of C and N - bigger)
Adenine or Guanine.
Pyrimidines (single ring of C and N - smaller).
Thymine or Cytosine.
Base pairing by weak hydrogen bondsAdenine-Thymine 2 H- bonds.
Cytosine-Guanine 3 H- bonds.
Chains are directional according to the attachment between sugars and. phosphate group.
They are antiparallel which is essential for gene coding and replication.
DNA molecule has 2 separate chains of nucleotides hold together by base pairing / DNA normally twist into a helix (coil) / forms a double helix.
Ribonucleic Acid (RNA).
Ribose instead of deoxyribose.
Single chain (shorter than DNA - lower molecular mass).
Base difference: Uracil instead of Thymine. Adenine, Guanine and Cytosine are the sameRibosomal RNA (rRNA)Located in the cytoplasm - ER.
Reads mRNA code and assembles amino acids in their correct sequence to make a functional protein (translation).
Messenger RNA (mRNA)Commutes between nucleus and cytoplasm.
Copies the code for a single protein from DNA (transcription).
Carries the code to ribosomes in the cytoplasm.
Transfer RNA (tRNA)In the cytoplasm.
Transfer amino acids from the cytoplasm to the ribosomes
The Genetic Code
DNA codes for assembly of amino acids / forms a polypeptide chain (proteins - enzymes)
The code is read in a sequence of three bases calledTriplets on DNA e.g. CAC TCA
Codons on mRNA e.g. GUG AGU
Anticodons on tRNA e.g. CAC UCA
(must be complementary to the codon of mRNA)
Each triplet codes for one amino acid / single amino acid may have up to 6 different triplets for it due to the redundancy of the code / code is degenerate. Some amino acids are coded by more than one codon
Same triplet code will give the same amino acid in virtually all organisms, universal code
We have 64 possible combinations of the 4 bases in triplets, 43
No base of one triplet contributes to part of the code next to it, non-overlapping
Few triplets code for START and STOP sequences for polypeptide chain formation
eg START AUG and STOP UAA UAG UGA
DNA Replication (Semi-Conservative Replication)
Happens during Interphase…
Genes, DNA, RNA