Chromosome Mutations

By nature, the genetic information from both parents is expected to be seen in the offspring following fertilization. However, it is possible for this genetic information to mutate, which in most cases, can result in fatal or negative consequences in the outcome of the new organism. This tutorial looks at the genetic mutations and their consequences in the outcome of the new organism. This tutorial is about the different types of mutations involving a chromosome.

Non-Disjunction and Down’s Syndrome

One well-known example of a mutation is non-disjunction. Non-disjunction is when the spindle fibers fail to separate during meiosis, resulting in gametes with one extra chromosome and other gametes lacking a chromosome.

If this non-disjunction occurs in chromosome 21 of a human egg cell, a condition called Down’s syndrome occurs. This is because their cells possess 47 chromosomes as opposed to the normal chromosome complement in humans of 46.

The fundamental structure of a chromosome is subject to mutation, which will most likely occur during crossing over at meiosis. There are a number of ways in which the chromosome structure can change, as indicated below, which will detrimentally change the genotype and phenotype of the organism. However, if the chromosome mutation affects an essential part of DNA, it is possible that the mutation will abort the offspring before it has the chance of being born.

The following indicates types of chromosome mutation where whole genes are moved:

Deletion

As the name implies, genes of a chromosome are permanently lost as they become unattached to the centromere and are lost forever

Duplication

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

Inversion of Genes

This is where the order of a particular order of genes are reversed as seen below

Translocation of Genes

This is where information from one of two homologous chromosomes breaks and binds to the other. Usually, this sort of mutation is lethal

Alteration of a DNA Sequence

The previous examples of mutation have investigated changes at the chromosome level. The sequence of nucleotides on a DNA sequence are also susceptible to mutation.

All of the genetic mutations looked at through the last 2 pages more or less have a negative impact and are undesired, however, in some cases they can prove advantageous.

Genetic mutations increase genetic diversity and therefore have an important part to play. They are also the reason many people inherit diseases.