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Unit 7 . Gene Expression and Mistakes. 1 Genetic Expression. Involves putting genetic information into action to make proteins for living cells Simply put: genes code for proteins

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unit 7

Unit 7

Gene Expression and Mistakes

1 genetic expression
1 Genetic Expression
  • Involves putting genetic information into action to make proteins for living cells
  • Simply put: genes code for proteins
  • Proteins are tools specifically designed to build (structural) or operate (functional) components of living things
  • The central dogma is that

information is passed from

DNA to RNA to protein to

trait, and all organisms do

this (exception?)

2 mutations
2 Mutations
  • Heritable changes in genetic information
  • Will be passed on to every cell that develops from the original one
  • Most important in sex cells
  • Often caused by mistakes made during DNA replication

- Occur roughly once in every 10 million bases

  • Can also be caused by mutagens
3 mutagens
3 mutagens
  • chemical (pesticides, smoke) or physical (x-rays, UV radiation) agents in the environment
  • Can change DNA base sequence permanently
  • Can interfere with base-pairing during DNA replication
  • Can weaken the DNA strands, causing breaks and inversions
4 point mutations
4 Point Mutations
  • Gene mutations that involve changes in one or a few nucleotides
  • Occur at a single point
  • Generally occur during DNA replication
  • There are three types: substitutions, insertions, and deletions (genetic information is lost)
5 substitutions
5 Substitutions
  • One base is changed to a different base
  • Sometimes this has no effect (ex. CCC and CCA still code for proline)
  • Sometimes results in changing an amino acid (ex. CCA to ACC changes from proline to threonine)
6 insertions and deletions
6 Insertions and Deletions
  • Where one base is inserted or removed from the DNA sequence
  • Remember that DNA is read three bases at a time, so inserting or deleting will causing those groupings to shift in every codon after that mutation
  • Called frame shift mutations because they shift the reading frame of the genetic message
  • Usually change every amino acid after the mutation, altering a protein so much that it is not able to perform its normal functions
7 chromosomal mutations
7 Chromosomal mutations
  • Sometimes the mutation is a whole region on the chromosome
  • Can have deletion, duplication, inversion (oriented in reverse direction), and translocation (involves 2 chromosomes)
8 effects
8 Effects
  • MOST havelittle to no effect on the expression of genes
  • Some produce genetic variations, which could be good or bad
  • Some negatively disrupt gene function
  • The amount of change is what determines whether the effect will be good or bad
  • Mutations can also be a source of genetic variation, the base upon which organisms evolve
9 harmful
9 harmful
  • When the structure of the protein has changed dramatically
  • Can also make an organism less adapted to its environment
  • Some cancers
  • Sickle cell anemia – point mutation in one of the polypeptides, changes it shape so that it cannot carry oxygen
10 beneficial
10 Beneficial
  • Often produce proteins with new or altered functions that can be useful to organisms in different or changing habitats
  • For example: mutations in insects that help them resist pesticides; mutations in bacteria to resist antibiotics
  • In humans, mutations that have increased bone density and strength and that increase resistance to HIV
11 evolution
11 Evolution
  • Genetic variety is essential to evolution
  • Mutations sometimes create better proteins that in some way allow the organism to be better adapted to its environment
  • This is how new traits are introduced into a population
  • Has to be a mutation in the sex cells in order for it to be passed on
12 polyploidy
12 Polyploidy
  • When chromosomes fail to separate in meiosis, resulting in gametes that are 3N or 4N (extra sets of chromosomes)
  • Common in plants (about 1/3 of flowering plants)
  • In plants, creates larger and often stronger plants
  • Ex. Bananas, limes
13 polyploidy in animals
13 Polyploidy in Animals
  • 1-2% of human fetuses are polyploidy but never make it to birth.
  • Essentially never seen in animals
  • Does in occur in some insects
  • Trisomy disorders are more common for animals, where you get an extra copy of only one chromosome, not a whole set, but most of these do not make it to birth except for 13, 18 and 21.
slide15

What might be the effect of a mutation in the promoter sequence of a gene? Polymerase would not be able to bind.

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