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Chromosomes, Genes and DNA - Coggle Diagram
Chromosomes, Genes and DNA
What is Chromosomes?
A chromosome is a long DNA molecule with part or all of the genetic material of an organism. Most eukaryotic chromosomes include packaging proteins called histones which, aided by chaperone proteins, bind to and condense the DNA molecule to maintain its integrity.
What is Genes?
A gene is a basic unit of heredity and a sequence of nucleotides in DNA or RNA that encodes the synthesis of a gene product, either RNA or protein.
What is DNA?
Deoxyribonucleic acid is a molecule composed of two polynucleotide chains that coil around each other to form a double helix carrying genetic instructions for the development, functioning, growth and reproduction of all known organisms and many viruses. DNA and ribonucleic acid are nucleic acids.
DNA Replication
When a cell is about to divide it must first make an exact copy of each DNA molecule in the nucleus. This process is called replication. As a result, each cell formed receives exactly the same amount and type of DNA.
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Transcription
Transcription happens in the nucleus. In the chromosome, part of the DNA double helix unwinds and 'unzips', so that the two strands separate, exposing that bases along the template stand.
Translation
Converting the code in the mRNA into a protein is called translation. It takes place at the ribosomes. By this stage the code consists of set of three bases in the mRNA (e.g. AUG, CCG, ACA). These triplets of bases are called codons. Each codon codes for a particular amino acid, e.g. CCU codes for the amino acid proline, and AUG codes for methionine.
Gene Mutations
A mutation is a change in the DNA of a cell. It can happen in individual genes or in whole chromosomes. Sometimes, when DNA is replicating, mistakes are made and the wrong nucleotide is used.
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How many genes?
The entire DNA of an organism (the amount present in a diploid cell) is known as its genome. The human genome is made up of about 3.2 billion base pairs. One of the surprise discoveries of modern molecular biology is that only a small fraction of the genome consists of protein-coding genes.
Genes and Alleles
Genes are sections of DNA that control the production of proteins in a cell. Each protein contributes towards a particular body feature. Sometimes the feature is visible, such as eye colour or skin pigmentation. Sometimes the feature is not visible, such as the type of haemogoblin in red blood cells or the type of blood group antigen on the red blood cells.