Chöông IV
ÑÒNH NGHÓA
– Nucleic acid: ñaïi phaân töû mang thoâng tin di truyeàn
– Hieän dieän trong nhaân vaø teá baøo chaát
– Coù hai loaïi :
• Deoxyribonucleic acid (DNA) trong nhaân teá baøo
• Ribonucleic acid (RNA) trong teá baøo chaát
CAÁU TRUÙC
Nucleotic = Base Nitô + Pentose + H3PO4
– Base Nitô: mang thoâng tin di truyeàn
Nucleotid + ( nucleotid)n Nucleic acid
– Pentose vaø H3PO4: vai troø caáu truùc
Base chöùa Nitô
Base laø daãn xuaát pyrimidine
Base laø daãn xuaát purine
Base pyrimidine
(ARN)
Uracine (2- 4 dioxy pyrimidine)
(ADN)
Cytosine (2 oxy - 4 amino pyrimidine)
Thimine (2- 4 dioxy 5 methyl pyrimidine)
Base purine
Adenine (6- amino purine ) Guanine (Daïng ceton) (2- amino – 6 oxy purine)
Söï bieán ñoåi daïng ENOL CETON
Guanine (ceton) Guanine (enol)
Ñöôøng Pentose
. Ribose . Deoxyribose
Acid phosphoric
O HO – P – OH OH
Nucleoside
Nucleoside = Base Nitô + Ñöôøng Pentose
Deoxythymidine
Guanosine
Caùc loaïi nucleoside
Base Ribonucleoside
Deoxyribonucleosi de
Adenine Adenosine Deoxyadenosine
Guanine Guanosine Deoxyguanosine
Uracil Uridine
Cytosine Cytidine Deoxycythidine
Thimine Deoxythymidine
Nucleotid không tham gia cấu tạo nucleic acid
Nucleotide
Phosphate ester cuûa nucleoside Caùc nucleosid monophosphat:
Ribo–nucleoside 5’P Deoxyribo–nucleoside 5’ùP Base
d AMP d GMP d CMP
AMP GMP CMP UMP
d TMP Adenine Guanine Cytosine Uracil Thimine
DNA & RNA
Phaân bieät RNA vaø DNA
RNA DNA
Deoxyribose A, G, C, T
Thaønh phaàn Ñöôøng Base Nitô Caáu taïo Ribose A, G, C, U 1 chuoãi nucleotid 2 chuoãi nucleotid
DNA
1. Soá löôïng A = T ; C = G
C / G =1
A / T = 1;
Tæ leä
thay ñoåi theo loaøi
TA CG
2. Caáu hình khoâng gian
DNA coù hình xoaén oác Hai chuoãi nucleotid
song song ngöôïc chieàu nhau vaø boå sung nhau Quy taéc boå sung: A – T
& C – G
Giöõa caùc chuoãi coù lieân
keát hydrogen
Chuổi xoắn kép của ADN
Khoaûng caùch 2 base: 0.34 nm
Chieàu daøi moät voøng xoaén: 3.4nm
Đường kính cuûa vong xoắn: 2nm
DNA
– Hieän dieän trong nhieãm
saéc theå
– Coù 2 chöùc naêng chính: Taùi baûn – töï taùi taïo
khi teá baøo phaân chia
Truyeàn thoâng tin –
thoâng qua vieäc toång hôïp protein
Cô cheá taùi baûn DNA
Enzym toång hôïp DNA: DNA polymerase I Boán loaïi tieàn chaát hoaït hoùa: d ATP, d GTP, d CTP,
d TTP Mg2+ Ñoaïn moài DNA coù nhoùm 3 ù OH töï do Khuoân DNA
Söï taùi baûn DNA
DNA ñöôïc toång hôïp töø khuoân cuûa moät sôïi DNA theo cô cheá baùn baûo thuû
=> taùi baûn baùn baûo thuû
ARN
– Caáu taïo: Ñöôøng Ribose Base: A, G, C, U
– Chæ goàm 1 chuoãi ñôn – Lieân keát hydrogen giöõa caùc
ñoaïn
– Boå sung: giöõa 2 RNA khaùc hoaëc
treân cuøng 1 phaân töû • A – U • C – G
– Phaân loaïi: rRNA, tRNA, mRNA
r RNA: RNA ribosom: laø nôi toång hôïp protein
t RNA: chuyeån Amino Acid trong teá baøo chaát ñeán ribosome.
Transfer RNA (tRNA)
Vuøng gaén Amino Acid
Acceptor Arm amino acid gaén vaøo ñaàu 3’
TyC Arm
5’
59
Py
A C C 73 72 71 70 69 68 67 66
1 2 3 4 5 6 7
A*
U*
Pu
65 6463
62
C
16
17
A 13
9 12 Py 10
5051
52
G
Pu C
T
y
49 Py
47:16
17:1 G* G
47:15
22 23 Pu A
25 26
20
20:2
20:1
44
45
46
D Arm
47
47:1
Extra Arm – Ñoaïn coù kích thöôùc thay ñoåi
127 28 29 30 31
43 42 41 40 39
Py* U 34
38 Pu* 36
35
Ñoái code vôùi mRNA
m RNA m RNA toàn taïi vaøi phuùt vaøi ngaøy Chöùc naêng: m RNA mang thoâng tin di truyeàn
Information transmission
Information stored in DNA transferred
• Transcription - information transcribed from DNA
to RNA and then expressed in the structure of proteins – Two steps in process:
into mRNA
• Translation - information in mRNA translated into
primary sequence of a protein
Transcription
Information transcribed from DNA
into RNA – mRNA carries information for
protein structure, but other RNA molecules formed in same way
• RNA polymerase binds to
promoter nucleotide sequence at point near gene to be expressed
• DNA helix unwinds • RNA nucleotides assemble along one DNA strand (sense strand) in complementary sequence to order of bases on DNA beginning at start codon (AUG - methionine)
• Transcription of DNA sense strand
ends at terminator nucleotide sequence
From: Tortora, GJ & Grabowski SR (2000) Principles of Anatomy and
• mRNA moves to ribosome • DNA helix rewinds
Physiology (9th Ed). New York: John Wiley & Sons. P88.
Translation (protein synthesis)
Thoâng tin di truyeàn töø mRNA ñöôïc dòch thaønh trình töï töông öùng cuûa caùc amino acid treân protein theo 4 böôùc: – HOAÏT HOÙA – KHÔÛI ÑOÄNG – KEÙO DAØI – KEÁT THUÙC
Translation (protein synthesis)
HOAÏT HOÙA – Amino acid
ñöôïc hoaït hoùa baèng caùch taùc ñoäng vôùi ATP. – Amino acid gaén
Adapted from: Bettelheim FA and March J (1990) Introduction to Organic and Biochemistry (International Edition). Philadelphia: Saunders College Publishing p398
vaøo tRNA synthetase chuyeân bieät.
Translation (protein synthesis)
KHÔÛI ÑOÄNG.
– mRNA gaén vaøo tieåu
theå nhoû cuûa ribosome
– tRNA gaén vaøo start
codon
– 2 tieåu theå lôùn cuûa
From: Tortora, GJ & Grabowski SR (2000) Principles of Anatomy and Physiology (9th Ed). New York: John Wiley & Sons. P88.
ribosome keát gaén vôùi nhau.
Translation (protein synthesis)
KEÙO DAØI
– Anticodon cuûa tRNA gaén vaøovò
trí codon treân mRNA nôi ribosome ñang keát gaén.
• Moãi tRNA ñaëc thuø cho moät
amino acid only. Coù amino acids ñöôïc maõ bôûi 6 loaïi codon.
– Order of bases in mRNA
codons determine which tRNA anticodons will align and therefore determines order of amino acids in protein
– Amino acid môùi ñöôïc mang tôùi
lieân keát vôùi amino acid tröôùc ñoù laøm keùo daøi maïch peptide.
– Ribosome tieán theâm 01 codon vaø chuaån bò cho moät tRNA tieáp theo gaén vaøo.
Translation (protein synthesis)
KEÁT THUÙC
– Codon treân mRNA
mang daáu hieäu chaám döùt.
– Taùc nhaân phoùng thích
ngaét ñoaïn polypeptide vöøa hình thaønh ra khoûi tRNA. – mRNA phoùng thích
From: Tortora, GJ & Grabowski SR (2000) Principles of Anatomy and Physiology (9th Ed). New York: John Wiley & Sons. P88.
khoûi ribosome
