LESSON 6 : CYTOG

• Genetic mutation is a change in the genetic sequence that happens during cell division due to intrinsic or extrinsic factors such as an error in replication, exposure to UV light, exposure to mutagens or viral infection.
• Mutation can affect the nucleic acids which can be heritable, only affects carrier of mutated genes, or affect all of the carrier’s offspring.
• For mutation to happen, it must occur in cells that produce the next generation and affect the hereditary material.
• Aneuploidy refers to extra or missing chromosomes.
• Muton is the smallest unit of gene capable of undergoing mutation and it is represented by a nucleotide.
• Mutator Gene is a gene which causes another gene or genes to undergo spontaneous mutation.
• Mutable Genes are genes which show very high rates of mutation as compared to other genes.
• Mutant is an organism or cell showing a mutant phenotype due to mutant allele of a gene.
• Mutagen is a physical or chemical agent which induces mutation.
• Gene Mutations or Point Mutations are the changes which alter the chemical structure of a gene at a molecular level.
• Mutations are generally recessive and very rarely dominant.
• Mutations are generally harmful to the organism, with a small proportion of them being beneficial.
• If gene mutations are not lethal, the mutant individuals may survive.
• Mutations occur at random that is they may occur in any gene or chromosome.
• Mutations are recurrent that is same gene may undergo mutations repeatedly.
• Induced mutations often show pleiotropy due to close linkage of mutated gene with other genes.
• Many of the mutants show sterility.
• Genetic mutations occur during cell division due to error during cell division.
• Genetic mutations can be classified based on tissue of origin as Somatic Mutation and Germline Mutation.
• Genetic mutations can also be classified based on source or cause of mutations as Spontaneous Mutation and Induced Mutation.
• If the point mutation changes the single nucleotide in to a stop codon and if it happens early in the sequence of transcription then the protein will not be made and it could cause serious consequences.
• A point mutation creates a premature stop codon, truncating the protein and often leading to a nonfunctional or unstable protein.
• If it happens near the beginning of RNA transcription and the entire protein is changed, this could become a lethal mutation.
• Most bacteria develop antibiotic resistance when exposed to antibiotics.
• A deletion occurs when a nitrogen base is taken out of the sequence causing the entire reading frame to change.
• Lactase Persistence -Most beneficial mutations in recent human evolution.
• An insertion occurs when a single nitrogen base is accidentally added in the middle of a sequence, throwing off the reading frame of the DNA and the wrong amino acid is translated.
• Induced mutations don’t develop spontaneously and are induced by physical, biological, or chemical mutagens.
• Homozygous carriers of the Delta 32 mutation resulting in the genetic deletion of a portion of the CCR5 or CD195 genes are resistant to HIV-1 infection.
• Single missing or added nucleotide causes a frame shift mutation which throws off the entire reading frame of the amino acid sequence and mixes up the codons.
• Are the ultimate source of natural genetic variations in population and develop spontaneously even in the absence of a mutagen.
• A single nucleotide change results in a different amino acid being incorporated into the protein sequence.
• An individual with a harmful mutation, sickle-cell diseases are more resistant to malaria since the infestation of the malaria Plasmodium is halted by the sickling of the cells that it infest.
• A mutation allowed human to express the enzyme lactase after they are naturally weaned from breast milk, allowing adults to digest lactose.
• A nucleotide is substituted but the same amino acid is produced anyway.
• Mistakes happen spontaneously during DNA replication, DNA repair, or DNA recombination.
• Mutation happens due to replication error or spontaneous lesion.
• Genetic mutations can also be classified based on effect on survival as Lethal mutation, Sub-lethal mutation, Sub-vital mutation, and Vital mutation.
• Sickle Cell Disease, characterized by sickle-shaped cells that don’t pass easily through blood vessels, causing frequent pain episodes, swelling and inflammation of joints, and anemia.
• Germline mutations can be inherited from either parent.