Draft 1 Essay2: Somatic and germ line mutations

Somatic and germ line mutations

Draft 1

In genetics, a gene mutation is known as a change in the DNA sequence.  A mutation can be of small or large proportions, and cause a gene to lose its function and therefore prevent the organism from working correctly. It can change only a single DNA base, or a big piece of DNA sequence in a chromosome.  Some mutations can be silent, having no effect on the organism’s phenotype but other s can cause great changes in the organism’s physical traits. There are two ways in which gene mutations occur: they can be inherited or can develop throughout lifetime.  While somatic mutations are not inherited, are caused by mutations in the individual cells and have no effect on the overall organism’s phenotype, germ line mutations are inherited, and have effects on the phenotype; it is evident that these two types of mutations play a key role in evolution.

Somatic mutations affect somatic cells: regular cells that make up tissues of the body. Somatic mutations occur while a cell is undergoing regular cell division, or mitosis.  They can be found by comparing DNA from different cells from the same individual. These mutations occur after fertilization and throughout life, therefore they cannot be inherited. There are two general categories of mutations: point and chromosomal mutations. Point mutations are ones that change one nucleotide either by a deletion or substitution of a nucleotide in the DNA sequence. Chromosomal mutations change the DNA sequence with insertions, inversions or translocations of more than nucleotide. The most common mutations that occur in somatic cells are point mutations. Somatic mutations can have no effect on the phenotype, but more often affects the genotype.  Some of these changes can go unnoticed or silent.  If the mutation is cancerous then the body will keep producing these cells until the person dies.  Somatic mutations can cause damages in the bladder, liver and kidney function.  Among somatic mutations the most dangerous are the ones that occur in the regulation of growth and cellular division.  Cells start reproducing without control and start forming cancerous cells.

Germ cells or sexual reproductive cells are developed either into a sperm or an egg.  The process of creating reproductive cells is known as meiosis and it is in this process that germ line mutations occur. If a germ line mutation occurs all the germ cells in the body will contain this mutation. If a parent has a mutation in their germ cells its offspring will inherit these cells and carry the mutation.  Germ line mutations have a higher incidence of occurring in male gametes since males carry more sperm that are constantly produced through meiosis, compared to the fixed amount of eggs women carry.  To be able to find a germ line mutation, germ cells from two different individuals must be compared.  Germ line mutations are associated with genetic diseases.  Different types of mutations that occur in the chromosomes can have effects on the phenotype or can cause cancer.  Some examples are: Down syndrome, Cri du chat syndrome (cry of the cat), Turner Syndrome and breast cancer. Most dangerous germ line mutations are the ones that interfere with the function of the organism.  Such mutations may change the way we interact with diseases’, or the environment. For example, red-greed blindness (Daltonism) affects your ability to distinguish colors, and type 1 diabetes is a mutation that prevents you from producing insulin and digesting sugar. However, there are germ line mutations that increase your chances of getting cancer.  If an individual carries such mutation in all its cells, fewer somatic mutations are needed to change it to the cancerous state.  For example, BRCA1 mutation is known to increase the chances of breast cancer hundreds of times.  This explains why cancers tend to run in certain families but not in others.

Not all the mutations are the same: they are different by type, effect, mechanism, and location.  Fortunately, there is repair mechanism: or cells can fix mutations, otherwise there would be too many of them.  However, not all mutations are harmful.  Some of germ line mutations are neutral, or can actually improve your body.  These mutations are rare, but they happen often enough to contribute to the variation between individuals, or serve as material for evolution of the species.