DNA Primer

JL Lo and HC Lee

2000 June-July

Introduction

protein_2.ps

intro1.ps

What is DNA (去氧核糖核酸 )?• Huge 1D molecule - two strands of nucleotides – d

ouble helix• Information for life

• Cell > DNA > Nucleotide (核甘酸 ) > Base pair

• Nucleotide bases(鹼基 )

– Guanine (G) ， Adenine (A), Cytosine (C) Thymine (T)

Structure of DNA

Nucleotides

Bases of Nucleotides 核甘酸的鹼基

• Pyrimidine 嘧啶（鹼基）– T (Thymine) 胸腺嘧啶– C (Cytosine) 胞嘧啶

• Purine 漂呤（鹼基）– A (Adenine) 胺漂呤– G (Guanine) 鳥漂呤

How big is the Human Genome?

• Contains over 3 billion base pairs

• One meter long when fully streched

• Size of 6 billion genomes, one from each person on earth = 1 meter long human hair

• 150000 times under

• electron micrograph

Scale Comparison

What is a Gene?

One Gene One ProteinOver 100,000 genes reside in the human genome

• Each gene (DNA sequence) contains the genetic code of a protein (amino acid sequence)

• Gene to protein

transcription

translation

From DNA to Protein (I)

• Transcription 轉錄– Copies and splices a gene (single strand of DN

A sequence) into an mRNA sequence

• Translation 翻譯– Converts mRNA into a protein (string of amino

acids) • Promoter

– tells the cell when to turn on the gene and how much transcription will occur

From DNA to protein (II)

Beginner's guide to Molecular Biology.htm

Transcription 轉錄• Start signal (e.g. TATAAT) and stop signal

(e.g. AAAAA)

• Splicing: keep exons

外碼子 , throw out

intron 內碼子 • mRNA: concatena-

tion of exons

Transcription I - copying

Transcription II - splicing

Translation 翻譯

• Genetic code: – 3-nucleotides = a CODON

• 64 codons (密碼子 )– 3 stop codons – Rest (61) codes to 20 amino acid

s• Figure gene.pdf

Human Chromosome

Genomes Guide Homo sapiens.htm

Chromosome Packing

Mutation of Chromosome

Mitosis

Meiosis