Mutations to Aid in Gene Study

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Mutations to Aid in Gene Study

• By Yvette Medina
• Cell Phys. 4454

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Gene Mutation Summary

• Study of Gene Mutation can be useful in
• 1. the study of new genes required for the
  process
• 2. the order in which gene products aid in the
  process
• 3. how different protein encodings are effected
  by different gene interaction.

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Quick definitions

• Alleles variants of genes
• Mutation a new form of an allele
• Mutagen agent which causes heritable DNA
  sequence change
• Wild type standard genotype in breeding
  experiments ( higher frequency of appearance)

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Genotype versus Phenotype

• Genotype
• 1. particular set of alleles for all genes
  carried by an individual.
• 2. Alleles under examination

• Phenotype
• 1. physical attributes of traits of an individual
  due to genotype
• 2. the physical result of alleles under
  examination

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Gene Function due to Mutant Recessive/ Dominant
Alleles.

• Single set of chromosomes (Haploid)
• Two copies of each chromosome (Diploid)
• Homozygous identical alleles
• Heterozygous different alleles
• Dominant Mutation loss of function of certain
  genes
• Haplo-Insufficient both alleles are required for
  function
• Removing or inactivating a single allele
• Dominant Negative structural change in a protein
  interferes with function of another protein on
  another allele

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Contd

• Recessive Mutant allele both alleles are mutant
  and show mutant phenotype
• Results from inactivation gene
• Leading to loss of function partially or
  completely
• Remove part of the gene from chromosome
• Disrupt expression of gene
• Alter the encoded protein
• Dominant Mutant allele one allele is wild type
  and the other is mutant
• Cause gain of function
• Increase the activity of encoded protein
• Confer new activity
• Lead to inappropriate spatial of temporal
  expression patterns

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Chemical Enhanced Mutations

• EMS (ethylmethane sulfonate) common agent used
  for inducing mutations
• Ex. Chemical modification of Guanine ? G-C to
  A-T base pairs
• Point Mutations alteration of the sequence of
  genes base pairs.
• Silent Point Mutation no change of amino acid
  sequence or coded protein activity.
• Missense Mutation substitution of one amino acid
  for another.
• Nonsense Mutation introduction of premature
  stop.
• Frameshift Mutation change in reading frame of
  gene.

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Breeding reveals Dominance and Recessivity
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Isolate and Identify Mutants

• Genetic Screen a simple procedure to identify
  and isolate Mutations which is dependent on
  haploid or diploid recessive or dominant.
• Haploid Yeast Study-
• Conditional Mutations
• Temperature-Sensitive Mutations isolated in
  bacteria and lower eukaryotes.
• Nonpermissive temperature at which the mutant
  is phenotypically observed.
• Permissive Mutant phenotype is not observed but
  is present.
• 
  
  
  

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Complementation Tests for Same Gene Recessive
Mutations

• Complementation test used to determine mutations
  are on the gene.
• Done by restoration of the wild type phenotype by
  mating two different mutants.
• Two recessive mutations are on the same gene, the
  diploid phenotype will show the mutation.
• If the mutation is on separate genes, diploid
  heterozygote phenotype will show the
  wild-typecomplement.

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Protein Function From Mutations

• Mutations for two different genes affect the same
  cellular process with distinct different
  phenotypes
• Double Mutants revel function order
• Can be used for Biosynthetic Pathways and
  Signaling pathways

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Interacting and Redundant Proteins

• Suppressor Mutations the function of one protein
  to suppress the function of another.
• Synthetic Lethal Mutation mutation can be
  exacerbated by a second mutation.

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Summary

• Mutation can aid in identify different biological
  pathways function.
• Mutations are used to learn breeding patterns of
  genes
• Lastly the associated effects of mutations from
  one gene to another.
• DNA Mutation Analysis