Introduction to Halotyopes

molecular biology

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Genetic identification is key evidence a series of factors need to be investigated such as

 who was?

the victim ,the assailant,present at the scene the father,the corpse

 what was?

  • The organism involved
  • The species involved


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The genes

Every organism is genetically unique

  In E. coli the mutation rate is 1 in 104 per generation (4.6 Mbase genome)           Even identical twins will have some differences

not all the cells in your body are identical such as:                                                   

  • somatic cellmutation                                                                                                            origins of cancer

 however differences within species are rare as                                                             we share the same sequences as other humans at many sites                                      we share many genes with great apes

 There are  highly conserved loci and there are hypervariable loci

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Conserved vs variable genes

The subtle differences at loci shared by all organisms can discriminate at the species level

    e.g. 16S rRNA or cytochrome C sequences

        sequence polymorphisms

hypervariable repeated sequences are only shared by some individuals combinations give individual discrimination

   VNTR & STR length polymorphisms

  Some genes encode single gene traits such as variants cause disease e.g. cystic fibrosis, huntingdon’s

other phenotypes are extremely complex genetically - though heritability is still seen   schizophrenia, heart disease

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  • Multigene disorders, multifactorial trait
  • Genetic component of behaviour is relevant to criminal behaviour 
  • Relating appearance to genotype however ethnicity cannot be determined. 
  • reliably however there's some progress with red hair
  • Relating family origin directly without comparison to other members
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Haplotypes are single nucleotide polymorphisms or length polymorphisms which are inherited together (linked).

        SNPs have been used to identify candidate genes associated with multifactorial diseases

        on Y chromosome have been associated with ethnic origin and  particular surnames (Y-STRs)

  • Inherited down the male line
  • only one set per genome so no recombination
  • Useful for mixed male/female evidence samples
  • used in genealogy


Y-STRs could be used to focus within  a long list of suspects by surname

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