BIOL213 Lecture Notes - Lecture 8: Circular Rna, Central Dogma Of Molecular Biology, Dna Replication
Lecture 8 – Organisation of DNA in Chromosomes
Central Dogma of Molecular Biology
• Deals with information pathways in which genetic information stored as
the nucleotide sequence is maintained and expressed.
• Crick proposed in 1956 that “once information has got into a protein it can’t get
out again” —> led to the Central Dogma.
• Three main pathways of information flow:
1. Information from parental DNA is copied to daughter DNA with high fidelity via
DNA replication
2. RNA is synthesised using DNA as a template during transcription
3. Proteins are synthesised during translation based on the information stored in
ribonucleotides in RNA
Information flow according to central dogma:
• Information never flows back from protein to RNA
• In viral replication, information can flow back from RNA to DNA
Genome:
• genome is the total genetic material of an organism or virus
• Each cell of an organism has at least one copy of the genome
• Copying of the entire genome (DNA replication) is necessary at cell division
• Genome is arranged in chromosomes.
• Usually genetic material is coded into double-stranded DNA
Gene:
• Gene is a segment of a double-stranded DNA that encodes the
information required to produce a functional biological product. Structural genes
encode for proteins.
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Lecture 8 – Organisation of DNA in Chromosomes
• Some genes within the protein are not coding for proteins, but code for rRNA
genes and tRNA genes which are necessary for translation of proteins.
• Some DNA is also transcribed to make other genes, which are translated into RNA
molecules that have other special functions.
Organisation of the genome:
• Eukaryotic cells contain linear, double-stranded DNA and many chromosomes.
• Prokaryotes contain circular double-stranded DNA and usually one chromosome
and one plasmid.
• Viruses contain linear or circular RNA or DNA.
• Circular DNA molecules are also found in mitochondria and chloroplasts.
Structure of DNA molecules:
• Linear dimensions of DNA are much bigger than the visions of cells that contain
the. DNA in the vision or cells is organised into compact forms, typically via
coiling and association with proteins.
• In every single human cell, if the DNA was stretched out it would be ~2m long!!
Chromosomes:
• consists of one covalently connected DNA molecule and associated proteins.
• Viral genomic DNA may be associated with the capsid proteins
• Prokaryotic DNA is associated with proteins in the nuceoid
• Eukaryotic DNA is organised with proteins into a complex called chromatin
DNA supercoiling:
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Document Summary
Dna replication: rna is synthesised using dna as a template during transcription, proteins are synthesised during translation based on the information stored in ribonucleotides in rna. Information never flows back from protein to rna. In viral replication, information can flow back from rna to dna. Gene: gene is a segment of a double-stranded dna that encodes the information required to produce a functional biological product. Structure of dna molecules: linear dimensions of dna are much bigger than the visions of cells that contain the. Dna in the vision or cells is organised into compact forms, typically via coiling and association with proteins. In every single human cell, if the dna was stretched out it would be ~2m long! Lecture 8 organisation of dna in chromosomes: dna in the cell must be organised to allow: Packing of large dna molecules within the cell.
