Molecular Genetics 2010
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Molecular Genetics 2010 Welcome to the course!. Molecular Genetics 2008 Welcome to the course!. Describes the use of Molecular Genetics to study a range of different topics

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Molecular Genetics 2010 Welcome to the course!

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Molecular genetics 2010 welcome to the course

Molecular Genetics 2010Welcome to the course!


Molecular genetics 2010 welcome to the course

Molecular Genetics 2008Welcome to the course!

  • Describes the use of Molecular Genetics to study a range of different topics

    • We don’t have time to tell you EVERYTHING about how Molecular Genetics has been/is being used, as the study of many different areas now involves molecular genetic techniques

    • So:

      • On this course we have 3 lecturers, and we will each tell you about how to use molecular genetics to study different areas of biology/biochemistry/genetics/biotechnology

      • This means that the topics covered by the 3 lecturers will probably not be linked in terms, other than that they all involve Molecular Genetics


Molecular genetics 2010 welcome to the course

Lecturers and their favourite topics!

  • Felicity Watts (8 lectures)

    • Yeast as a model system

      • Homologous recombination, mating type switching, cell cycle control, DNA integrity checkpoints

  • Majid Hafezparast (8 lectures)

    • Human and mouse

      • Gene cloning in mouse, complex traits and the HapMap project, Functional genomics

  • Neil Crickmore (4 lectures)

    • Application of Molecular Genetics to the Biotechnology Industry


Molecular genetics 2010 welcome to the course

What is the difference between classical and molecular genetics?

  • Classical genetics

    • Isolation of mutants

    • analysis of the nature of the mutants

      • e.g. dominant/recessive -look in diploid m/M

    • pathways

      • A B C D E or

    • extragenic suppressors

A B

E

C D


Molecular genetics 2010 welcome to the course

  • Molecular genetics

    • identify genes by complementation

    • genome sequencing projects

      • clone by Email!

    • clone gene by homology

      • used to use hybridisation

      • PCR

    • Create new mutants

      • e.g. delete a whole gene

      • make point mutations

    • knockout expression with antisense RNA

    • add a tag to a protein

    • microarray analysis


Molecular genetics 2010 welcome to the course

Why do we use model systems

and why don’t we all study humans?

  • Classical genetics

    • Isolation of mutants

    • analysis of the nature of the mutants

      • e.g. dominant/recessive -look in diploid m/M

    • pathways

    • extragenic suppressors

  • Molecular genetics

    • identify genes by complementation

    • genome sequencing projects

      • clone by Email!

    • clone gene by homology

      • used to use hybridisation

      • PCR

    • Create new mutants

      • e.g. delete a whole gene

      • make point mutations

    • knockout expression with antisense RNA

    • add a tag to a protein

    • microarray analysis


Molecular genetics 2010 welcome to the course

Yeasts as model organisms

EukaryotesProkaryotes

S. pombe 4,900E. coli4,286

S. cerevisiae 5,570Streptomyces >8,000

Drosophila13,919

Nematode19,622

Arabidopsis25,498

Human37,000

S. pombe: 3281 have homology with genes in S. cerevisiae/nematode

145 have homology with genes in nematode

769 have homolgy with genes in S. cerevisiae

681 are unique to S. pombe


Why analyse 2 yeasts s pombe and s cerevisiae

Why analyse 2 yeasts: S. pombe and S. cerevisiae

  • Both have small genomes

  • Both easy to grow

    • Doubling time 2-3 hours

  • Both easy to use for classical and molecular genetics

    • Many mutants

      • Both have haploid and diploid forms

    • Many cloning vectors and reagents available

    • Both genomes totally sequenced

  • So why use both?


S cerevisiae and s pombe are as related to each other as each is to humans

S. cerevisiae and S. pombe are as related to each other as each is to humans!

Humans

(mice)

S. pombe S. cerevisiae

So:

if we find processes that are common to both yeasts, they may also occur in humans


S pombe and s cerevisiae

S. pombe and S. cerevisiae

Fission yeast Budding yeast


Molecular genetics 2010 welcome to the course

Genetic recombination

  • Homologous recombination

  • site-specific recombination

  • transposition

  • illegitimate recombination/non-homologous end joining


Molecular genetics 2010 welcome to the course

Homologous recombination

  • involved in meiosis

  • repair of DNA double strand breaks (DSBs) during the mitotic cycle

homologous recombination

between sister chromatids

to repair the break

S. pombe cell

in G2

with DSB


Molecular genetics 2010 welcome to the course

Homologous recombination (HR)

  • 3 stages

    • pairing

    • formation of an intermediate

    • resolution

  • a number of models proposed as to how recombination occurs

    • these must take into account the experimental evidence

  • Many HR proteins now identified and their functions are being characterised


Molecular genetics 2010 welcome to the course

The sort of evidence that needs to be considered

Neurospora

Comes from analysing

the products of meiosis

From:

Fincham, Genetis

(1983)

Pub John Wright


The sort of evidence that needs to be considered

The sort of evidence that needs to be considered

Non-Mendelian inheritance

not common

due to gene conversion or

post-meiotic segregation

How does this occur?

Its due to heteroduplex DNA

From:

Fincham, Genetis

(1983)

Pub John Wright


Molecular genetics 2010 welcome to the course

Aberrant segregation

Recombination events can result in mismatches

Mismatches might be repaired to give 2:4 or 1:3 segregation

or might not be repaired, in which case they will give 3:5

Will explain in more detail later

X T Y

G


Molecular genetics 2010 welcome to the course

Pairing (meiosis)

  • In eukaryotes this results in a synaptonemal complex

DNA seems too far apart for recombination

to occur

but can in some cases see ‘recombination

nodules’

Unknown how homologous sequences

identify one another

possibly there is single stranded DNA

search for homology

From: M Westergaard


Molecular genetics 2010 welcome to the course

How does

Pairing occur?

Possibly by

‘horsetail’

Movement

From Chikashige et al.,

Science (1994) 264,

270


Molecular genetics 2010 welcome to the course

Timing of events


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