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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.



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