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Oncogenes are genes that induce cancer in animals. Their normal cellular counterparts are called ‘proto-oncogenes’. Mutations in two broad classes of genes namely proto-oncogenes and tumour-suppressor genes play a significant role in the development of cancer. The oncogenes produced by the mutations of proto-oncogenes encode oncoproteins that mediate the pathogenesis. In certain cases, the oncogenes […]
The integrity of the DNA is very much important for the sustainability of the cell. For this reason, a vast number of repair systems work efficiently debugging the errors. The repair process begins during replication and continues in various forms even during the post-replication. About 130 repair genes exist in human genome that codes for […]
Mutagens can even affect the chromosomes. The chromosomal changes can be either involving their structure or their number. The numerical changes are referred to as ‘ploidy’. It can be detected as ‘aneupoidy’ and ‘polyploidy’. The structural abnormalities include ‘deletions’, ‘duplications’, ‘inversions’, and ‘translocations’. These changes in the structure and the number of the chromosome are […]
Chemical Mutagens Mutations can be caused by chemicals such as: Base analogues Compounds that resemble the four bases of nucleic acids are called base analogues for example, 5-bromouracil and 2-amino purine. These base analogues can be incorporated into DNA. They lead to transition mutations (purine to purine) as a consequence of altered base pairing in […]
‘Mutation’ refers to heritable changes in the base sequence of the DNA. The most common types of change are a substitution, an addition or a deletion of one or more bases. A physical or chemical agent that causes or increases the frequency of mutation is called a ‘mutagen’. The process of producing a mutation is […]
Endogenous DNA Damages There are five main types of damage to DNA due to endogenous cellular processes (Figure 8.2). These include: Spontaneous damages can include the loss of a base, deamination, sugar ring puckering and tautomeric shifts. Figure 8.2 Types of DNA damages When compared to the nuclear DNA, the mitochondrial DNA is more […]
Inside a cell, there is a complex interplay of molecular events of which DNA repair occupies a significant importance. If proteins or RNA molecules are damaged, they can be immediately replaced using the information encoded in the DNA. However, if a DNA is damaged, it is irreplaceable and repairing the damages of the DNA, therefore, […]