dna exist in 2 places in the cell the nucleus & the mitochondria
TRANSCRIPT
Nucleic Acids
DNARNA
DNA exist in 2 places in the cellThe nucleus & the Mitochondria
The Watson-Crick Model of the Structure of DNA
DNA consists of two chains of nucleotides in a ladder-like structure which is twisted called (Double Helix)
One Strand of DNA One strand of DNA
is a polymer of nucleotides.
One strand of DNA has many millions of nucleotides.
6
nucleotide
The Watson-Crick Model of the Structure of DNA
A. The sides of the ladder are made up of alternating molecules of phosphate and deoxyribose (Backbone)
B. The bases make up the rungs of the ladder
C. The bases that make up the rungs of the ladder are attracted by a weak chemical bonds called hydrogen bonds
• Nucleic acids are polymers of nucleotides
• The Nucleotide consists of :
• Nitrogenous bases• Adenine A• Thymine T• Cytocine C • Guanine G • Uracile U
• Sugar • Ribose• Deoxyribose
• Phosphates
The Sugars
The Basis
RNA only DNA only
DNA & RNABASE In RNA In DNA
Adenine Adenosine deoxyadenosine
Guanine Guanosine deoxyguanosine
Cytosine Cytodine deoxycytodine
Uracil Uridine Not found
Thymine Not found deoxythymidine
Genes A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a polypeptide or for an RNA chain that has a function in the organism.
Transcription of a gene produce mRN, which translated via ribosomes into functional protein
Each gene composed of (Introns & Exons ) • Introns : do not contain a functional code
(noncoding for proteins).• Exons : contain functional code (Coding for
proteins)
From gene to protein
)
From gene to protein
)
From gene to protein
Transcription performed by RNA polymerase enzyme and produce Premature mRNA
Splicing produce mature mRNA by removal of intronic sequences
Translation performed by Ribosome's and produce proteins
From gene to protein
From gene to protein
Genetic code : • The ribosome read mRNA as a code of 3 nucleotides,• Each 3 nucleotides called (Codon) that add one
amino acid to the polypeptide chain (protein)• tRNA Transfer one amino acid to the polypeptide
chain for each codon
From gene to protein
From gene to protein
read the gene sequence
from 5’ 3’
From gene to protein
The upper strand sequence : 5’-3’ : CGTACT The lower strand sequence : 5’-3’ : AGTACG
From gene to protein
• The sense strand has the same base sequence as the transcribed mRNA except that the base thymine is replaced by the base uracil. So the sense strand contain the gene code
• The anti-sense strand acts as the template for the transcription of mRNA so it is also called the Template strand
• The RNA nucleotides are added along the sugar phosphate backbone by RNA polymerase
• Promoter : determine the start of the gene and so the start of transcription
• Terminator : determine the end of the gene and so the end of the transcription
Transcription
The mRNA builds up with the RNA polymerase moving along the anti-sense strand joining the nucleotides. And so it make a copy of the sense
strand
Transcription
The RNA polymerase reaches the terminator and the RNA polymerase stops.
Transcription
Pre-mRNA has been produced through transcription of the anti-sense strand as described for prokaryotic transcription.(a) The non coding introns are spliced out of the mRNA.(b) The introns are broken down in the nucleus.
(c) The remaining mRNA is called mature mRNA and is exported from the nucleus to the cytoplasm for translation into the polypeptide in the ribosomes
Splicing
From gene to protein