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MOLECULAR BIOLOGYby Dr.rer.nat.Tri Yudani MR, MAppSc
DNA MoLECULE of HEREDITY
• DNA/RNA structures• GENETIC code• Transcription
DNAOverview:
Background/history
DNA structure
Genetic information in eukaryotic
A Short History1869 - Miescher isolated DNA the first time1953 - Watson and Crick proposed the double
helix as the structure of DNA1957 - Kornberg discovered DNA polymerase1961 - Marmer and Doty discovered DNA
renaturation1962 - Arber, Nathans and Smith discovered
restriction endonucleases1966 - Nirenberg, Ochoa, and Khorana figured
out the genetic code
• DNA (deoxyribonucleic acid) is a double helix: two strands of genetic material spiraled around each other.
• Everyone’s chemical structure of DNA is the same, the only difference is in the ordering of base pairs.
What is DNA?
BUILDING BLOCK of DNA
• Nucleotides consist of a sugar, phosphate and nitrogenous base
Nitrogenous base of DNA
Purine nucleotides• A - Adenine• G - Guanine
Pyrimidine nucleotides
• T - Thymine• C - Cytosine
Chemical composistion of DNA
DNA strand extend from 5’ to 3’
• The DNA back-bone was connected by phosphodiester bond
Strand of DNA A-A-C-T-G-A-T-A-G-G-T-C-T-A-G T-T-G-A-C-T-A-T-C-C-A-G-A-T-C
POLYNUCLEOTIDE FORMATION
DNA structure Watson-Crick double helix
• The two helical polynucleotide chain coil around the common axis. The chains are antiparalel in polarity
• Purine and pyrimidine bases are inside the helix, whereas the phosphate and deoxyribose units are on the outside.
DNA base composition is governed by Chargaff’s Rule
• DNA has equal number of A and T residue (A-T) and equal number of G and C residue (G-C)
• DNA base composition range from 25-75% G+C content.
RNA (ribonucleic acid)
• Component = DNA except for nitrogenous base is replaced by Uracyl
RNA STRUCTURE
rRNA
From DNA to chromosome
• Humans have 23 pairs of chromosomes.
• A part of chromosome that dictates a particular trait is called a gene.
Chromosome map
• two chrom arms are referred to as p and q (short and long respectively). Bands are numbered from the centromere.
• Ex. band 9q34.1 means the 1st subband of the 4th subband of the 3rd band of the long arm of chromosome 9!
GENE
Gene : a sequence within the genome that functions by giving rise to a discrete product (protein or RNA)
Locus: a position on a chromosome at which the gene for a particular trait resides, locus may be occupied by any one of the alleles for the gene.
Allele
• alternate forms of the same gene• The allele occurring most frequently
in a population wild-type (wt) allele (the “normal” allele)
• Wt allele is usually dominant and is expressed as the wild-type phenotype
• Wt allele used as “standard” for comparison of all mutations of the gene/locus
GENE ORGANISATION
Operon:• Is a unit of gene expression and
regulation including structural genes and control elements in DNA recognised by regulator gene product/s.
Gene organization
PROKARYOTE
Dogma of molecular biology
genome < transcriptome <proteome
1 gene 10 or more proteins
DNA Replication
• Components of Replication process:
• helicase• DNA ligase• DNA polymerase
• VIDIO DNA rep
GENE EXPRESSION
Stages of gene expression
DNA transcription
RNA processing
Protein synthesis
post-transcriptionalmodification
DNA pre-RNA
Pre-RNA m-RNA
m-RNA protein
glycosylation, lipidolationlimited proteolysis
initiationelongationtermination
initiationelongationtermination
splicing, editing,encapping
Transcription process
TRANSCRIPTION IS A PROCESS OF TRANSFER GENETIC INFORMATION FROM DNA INTO RNA
• REQUIRE :Enzyme RNA polymerase• Eukariot : RNA polymerase II• Prokariot : RNA polymeraseDNA template4 Nucleotide (ATP, GTP, CTP dan UTP)
• RNA elongate in 5’ 3’ direction• begin start codon (AUG )and ending
with stop codon (UAA; UAG dan UGA)
• RNA polymerase• DNA template
strand or antisense strand
• DNA coding strand = mRNA
Transcription machine in bacteria
Transcription maschine
STAGES IN TRANSCRIPTION
Eukaryotic : mRNA processing
• A eukaryotic mRNA is modified in the nucleus during or shortly after transcription
Cont- mRNA processing
• 1. addition of a methylated cap at the 5’ end
• Addintion of poly(A) at the 3’ end• Splicing via splicesosome
mRNA is exported from nucleus to cytoplasm only after all modifications have been completed