文档介绍：Chap 4 ic Engineering: Procaryotes
DNA (deoxyribonucleic acids)
DNA:
The basic ic material to establish and maintain the cellular and biochemical functions.
Central Dogma (Gene expression): by Franscis Crick
Structure of DNA (discovered by Watson and Crick)
DNA basic unit: deoxynucleotides, composed of anic base, a pentose and a phosphate group.
base: 4 in DNA: Adenine (A), Thymine (T), Guanine (G), Cytosine(C)
Note: RNA (ribonucleic acid) is similar to DNA except that in RNA
T is replaced by Uracil (U) (A, U, G, C).
The pentose is a ribose, not deoxyribose.
RNA is single stranded (.) while DNA is double stranded (ds).
Precursor of nucleic acid synthesis: (deoxyribonucleoside triphosphate, dNTP)
The nucleotides of DNA are joined by the addition of dNTP to the polynucleotide chain (the P at the a position is added to the 3’-OH at the growing nucleotide chain).
=> 5’-ATGC-….3’
**DNA synthesis proceeds from 5’ to 3’
Double stranded DNA forms a double helix
Note:
A only pairs with T, G only pairs with C. These reactions are called base pairing, the paired bases are referred to plementary.
The length of DNA is expressed by base pair (bp). The two strands run in opposite direction => one is 5’→3’, the other is 3’→5’
Because 2 strands plementary ∴ if one strand is 5’-TAGGCAT-3’
the other strand must be 3’-GTA-5’
Usually the sequence is read from left to right
The ic information is stored in the sequence of these 4 bases, analogous to the storage of information puter by the sequence of 0 and 1. The sequence determines what the polypeptide sequence it encodes, what the protein function is and the cellular activities.
Every 3 bases form a codon, which codes for a specific amino acid or nonsense.
coding strand
-TAC C C T
transcription
-AUGGGA-
translation
template strand
-Met-Gly-
-ATGGGA
Bacterial chromosomes
Bacterial chromosomes posed of DNA and histones, the principal repositories of the cell’s ic information.
Gene: a segment o