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

What are the advantages and disadvantages of using DNA sequence data for assessing relationships between the major groups of land plants?

Extracts from this document...

Introduction

Plants What are the advantages and disadvantages of using DNA sequence data for assessing relationships between the major groups of land plants? The relationships between land plants, particularly the lower levels of the Bryophytes and the origins of the Angiosperms, has been a highly contested debate throughout the history of plant sciences. The introduction of molecular analysis of the relationships between these major groups, in the form of DNA sequence data, has revolutionised the subject in the last twenty years. It has affected the key aspects of plant phylogeny. Robust and unequivocal interactions have been identified confirming the phylogenetic tree, although it's intricacies and temporal detail is still far from complete. Although it may seem that DNA sequence data is the answer to these problems there are still things that require morphological evidence, a practice that is as old as plant sciences itself. This essay will outline the contributions made by DNA sequencing data to plant phylogeny and its limitations. The taxonomy of the land plants and subsequent theories of their evolution has been investigated for the past two centuries, however the contributions of Linnaeus in 1753 laid a sound foundation for future study of the subject. Morphological data has been accumulating steadily for the past 250 years, but for the first 100 it mainly concerned the question of taxonomy. ...read more.

Middle

that lineage of plants and there is very little statistical probability that an exactly comparable character could of arose independently in another lineage, even in 5S rRNA the chances of an exact match are 4120 and even if an exact match is not required the numbers are still astronomical. Another advantage of the heritable traits of DNA is that specific markers exist which are common to all plants, the characters are not reliant on being expressed in the phenotype, which allows for analysis across families and of loss of function (the gene will still be present but inactivated). There are however problems regarding the collection of DNA sequence data. The main problem is that DNA at the moment can only be obtained from extant species; the implications of this will be discussed later. Obtaining ancient DNA from fossilised tissue is very difficult and prone to experimental contamination. 1990 was the first occurrence of ancient DNA sequence data (Goldberg et al) obtained from plant fossils 15-20 MYA. Although sequences had been identified the microscopic amounts of DNA were subject to PCR product contamination and the results were disputed. Smith [4] created these guidelines for the acceptance of ancient DNA data; 1. Amplification products should make sense. ...read more.

Conclusion

Fossil data based on morphological analysis provides the answer to many of these problems. Fossils provide direct evidence for the rapid divergence and mass extinction processes, allowing absolute temporal calibration of the molecular clock. They also provide information that can be used to "fill in the gaps" where DNA sequence data fails to concerning the branching of the tree if outgrouping is unsuccessful, resolving conflicts at the nodes. This allows for the correct rooting of groups, removing long branch attrition artefacts that have to be based on extant species. The ability to analyse extinct species provides key information regarding the topology of the tree constructed and larger data sets across more taxa leading to a more detailed tree. Conclusions DNA sequence data has not removed the need for morphological assessment of the relationships between land plants, but it has provided a new route of analysis which provides much higher resolution and statistically robust data from which new hypothesis can be drawn from. It is reassuring to know that molecular analysis has not upset the overall topology of the tree, in fact it has re-affirmed conclusions regarding groups and families drawn up on morphological characters. Although morphology is limited in its robustness it does provide the key framework to which all DNA sequence analysis is hung from and the data obtained serves to augment and refine the work already provided by 300 years of study. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our University Degree Genetics 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 University Degree Genetics essays

  1. Biology - PCR Lab

    Annealing takes place at temperatures ranging from 45-60�C. The temperature entirely depends on the primers used, and it is usually about 5�C lower than their melting point. The primers are the point where the DNA polymerase begins to synthesize the new DNA strands.

  2. DNA Fingerprinting: A review of the criticisms of DNA evidence. Is it really the ...

    Currently in England LCN DNA has been used in the most serious cases. Peter Shand, head of a Hampshire police operation to find DNA links between unsolved sex attacks, added: "There is a waiting list of cases for LCN. At the moment, every case that is looked at has to be of a very serious nature.

  1. The Integration of DNA Applications in Forensic Science

    A "window of uncertainty" determines the matching process where two bands must fall close enough in size to be within the limits of their respective measurements. This method is a measurement confirmation step based on the size of the band-producing fragment.

  2. Who were the Neanderthals? Discuss the importance of genetic evidence for understanding Neanderthal extinction

    It has also been found that mines at a Spanish site not far northeast of Gibraltar, called Zafarraya Cave, recently revealed new fossil evidence of the Neanderthals, their stone tools and food debris, and indicated that they had remained

  1. Compare and contrast the different techniques used in separating biomolecules.

    Molecules that are larger than gel pores are excluded. Molecules that are smaller than the gel pores diffuse throughout the pores, because smaller molecules can enter the pores, they have a larger volume of liquid accessible to them. Molecules larger than the pores only have the liquid surrounding the beads accessible to them, and thus move through the column faster.

  2. IRES (Internal Ribosomal Entry Site) Identification in Regulation and Gene Expression.

    In this study, they performed deletion and mutational analyses of IRES contained within the 720-nucleotide (nt) 5' leader of the Rbm3 mRNA and demonstrated that this IRES is highly modular, with at least 9 discrete cis-acting sequences. The different cis-acting sequences are included a 22-nt IRES module, a 10-nt enhancer, and 2 inhibitory sequences.

  1. Using DNA to Solve Crimes.

    is the substantial backlog of unanalysed DNA samples and biological evidence from crime scenes, especially in sexual assault and murder cases. Too often, crime scene samples wait unanalysed in police or crime lab storage facilities. Timely analysis of these samples and placement into DNA databases can avert tragic results.

  2. Explain How The Development of Electrophoretic Techniques has played a key role in (a) ...

    Along with these set of experiments and the method he invented combined made moving boundary electrophoresis an accurate analytical method. All experiments and studies of this nature throughout the 1940s and 1950s were carried out using "Tiselius"-type apparatus equipped with Schlieren optics to visualize nucleic acid separations4.

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