Gene mutations and their effects

A-Level: Biology

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Furthermore, alterations in the number or structure of chromosomes are called chromosome mutations. Chromosome mutations can happen during mitosis and meiosis when chromosomes are being condensed and pulled apart. Homologus chromosomes may fail to separate, resulting in non-disjunction. Chromosome mutations also occur during interphase when DNA replicates, and during crossing over when sections of chromosomes are exchanged. There are many types of mutations in the gene. These are substitution, deletion, and insertion of addition, duplication and translocation.
Inversion of Genes
This is where the order of a particular order of genes is reversed as seen below.

In the process of inversion or addition mutation, a broken chromosome segment is reinserted in the wrong direction, changing the order of the genes, which will be transcribed and transferred backwards. The new sequence may not be viable to produce an organism, depending on which genes are reversed. Advantageous characteristics from this mutation are also possible. Where a particular nucleotide sequence is reversed, and is not as serious as the above mutations. This is because the nucleotides that have been reversed in order only affect a small portion of the sequence at large.
Duplication of Genes
In this mutation, the mutants’ genes are displayed twice on the same chromosome due to duplication of these genes. This can prove to be an advantageous mutation as no genetic information is lost or altered and new genes are gained.

The number one shows a normal gene before mutation and then number two shows how genes from the homologous chromosome are copied and inserted into the genetic sequence .The new chromosome possesses all its initial genes plus a duplicated one, which is usually harmless. Similar to the effects of deletion, where a nucleotide is inserted into a genetic sequence and therefore alters the chain thereafter. This alteration of a nucleotide sequence is known as frame shift.
Deletion of a Gene
As the name implies, genes of a chromosome are permanently lost as they become unattached to the centromere and are lost forever

In this type of mutation, the loss of a chromosome fragment takes place and theses chromosome fragments are lost for forever. New chromosome lacks certain genes which may prove fatal depending on how important these genes are. Here, certain nucleotides are deleted, which affects the coding of proteins that use this DNA sequence. If for example, a gene coded for alanine, with a genetic sequence of C-G-G, and the cytosine nucleotide was deleted, then the alanine amino acid would not be able to be created, and any other amino acids that are supposed to be coded from this DNA sequence will also be unable to be produced because each successive nucleotide after the deleted nucleotide will be out of place.
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