• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Inherited sources of genetic variation.

Extracts from this document...

Introduction

Inherited sources of genetic variation One of the key features of all living things from single celled organisms such as amoeba, to plants and animals such as humans, is the ability to reproduce. In smaller single celled organisms such as the amoeba this reproduction is asexual and takes place by a process known as mitosis. Mitosis produces two daughter cells that are genetically identical to, or clones of their parent cell. This process however produces no genetic variation within a community; meaning that the process of evolution is limited and can only take place through an advantageous mutation over a long period of time. Mitosis also produces somatic, or body cells for growth and repair in multi-cellular organisms. To increase genetic variation other larger and more complex organisms such as plants and animals reproduce sexually by Meiosis. ...read more.

Middle

It is this random shuffling process that creates a huge variety of gametes from a single parent. Recombination occurs when pieces of chromosomes are exchanged within their homologous pair. This increases the swapping of genetic information leading to more genetic variation. Crossing over only occurs in the first division of meiosis, this is when whole groups of genes are mutually exchanged between the homologous chromosomes. The other factor allowing genetic variation to take place is mate selection. Variation is furthered by the ability of an individual to choose a mate with which to produce offspring. Different combinations of genes will come together in the offspring during fertilisation, depending on which two individuals mate. Mutations also cause variation, as they are the source of all new genetic information. Whilst most mutations are harmful, there are others that are described as 'silent' this means that these mutations have no known effect on the individual, and some can provide an improvement on the original version of the gene. ...read more.

Conclusion

This is caused by a point mutation which is located on the HBB gene on chromosome 11 and involves the substitution of one base for another this alters a single amino acid. This new amino acid makes the haemoglobin behave in a different manner as it has different properties. One other inherited disorder is Down syndrome, which is caused by Trisomy. This is when three chromosomes represent one chromosome pair. The mutation for Down syndrome occurs on chromosome 21, the most common form of this condition arises when meiosis fails to separate the pair of chromosome 21 in female ova. One in 800 babies born to mothers aged 30 to31 have Down syndrome, however this increases rapidly with the mothers age. Some of the symptoms include poor muscle tone, congenital heart disease and mental retardation. Jessica Jennings 13 Kee ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Genetics, Evolution & Biodiversity section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Genetics, Evolution & Biodiversity essays

  1. Marked by a teacher

    An Investigation into the Mitotic Nuclear Division of Allium Sativum Root Tip Cells, and ...

    5 star(s)

    The heating set used in the experimental process (the Bunsen burner, tripod, gauze and watchglass, in particular) may remain at a high temperature for a prolonged time period; even after the investigation has been completed and it is time to return equipment.

  2. The Biology of Autistic Spectrum Disorder and the Social Implications

    outlined in their statement that schools are required to, by law, to make reasonable adjustments to their lessons to enable children with autism to learn. The NAS report have also outlined that the 'biggest gap in provision for children with autism' is the lack of social skills programmes.

  1. Recombinant DNA, genetically engineered DNA prepared in vitro by cutting up DNA molecules and ...

    in species that reproduce asexually the chromosome number is the same in all the cells of the organism; among sexually reproducing organisms, each cell except the sex cell contains a pair of each chromosome For many years, scientists believed that Neanderthals were the direct ancestors of modern humans.

  2. Defense in the blood

    to the bloodstream of some unfortunate organism. (Miller writes that if his scenario is correct, then "the clotting enzymes would have to be near-duplicates of a pancreatic enzyme . . . ." (Miller 1999, 157) Pancreatic enzymes, which have to digest a wide variety of protein foodstuffs, are among the most nonspecific of enzymes).

  1. What different methods exist for studying genetic variation at a molecular level? How could ...

    of the site, as the presence of C-G pair destroys the palindromic restriction site for EcoR1. Thus, only one, larger fragment will be yielded (Figure 1). If the same procedure is applied to DNA molecules containing variable numbers of simple tandem repeat polymorphs, the number of copies of the tandem

  2. Mitosis and Meiosis

    Any mistakes can be deadly. For example, it is necessary to the cell's survival that the DNA gets replicated and the chromosomes are separated equally so that all daughter cells get the correct number of chromosomes. It is also necessary to control the frequency at which cells divide; if cells divide more often than they should, then cancerous tumours are often the result.

  1. Investigating the colour variation of Littorina littoralis and their abundance across the upper, middle ...

    For most organisms, life is a struggle to survive. Organisms are forced to compete for resources, both with members of its own species (interspecific competition) and those from outside its own species (intraspecific competition). Intraspecific competition also affects the population distribution of a species.

  2. Colour variation in Littorina littoralis on the upper, middle and lower zones of a ...

    Therefore, no sunlight would lead little or no plant life, further leading to little or no Littorina littoralis. If it were the case that the upper zone has 100% exposure to sunlight, and the lower zone has 0% exposure to sunlight, it is very likely that most periwinkles would be found in between these two extremes.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work