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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 –
double 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 Protein
Over 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
DNA 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: concatenation 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
acids
• Figure gene.pdf
Human Chromosome
Genomes Guide Homo sapiens.htm
Chromosome Packing
Mutation of
Chromosome
Mitosis
Meiosis