Structure and Function of the Genetic Material

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Structure and Function of the Genetic Material

• Genetics what genes are, how they work and how
  they are passed ____________
• ________________________________
• DNA double stranded helix with hydrogen bonds
  between ____, and _____
• One geneone protein
• Gene A segment of DNA which codes for a
  functional product

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The Central Dogma of Biology

• DNA coded in the sequence of nitrogenous bases
  is the genetic information
• The information is _________ onto mRNA, and then
  it is _______________into protein with the help
  of tRNA and ribosomes (rRNA)

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Genotype Vs. Phenotype

• The entire genetic composition of an organism-all
  its genes, whether expressed or not the
  _____________
• Those genes which are expressed, the observable
  characteristics of an organism, the proteins that
  it make the _______________

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DNA vs. Chromosomes

• Chromosome means ________ _________
• Chromosomes consist of tightly coiled DNA(double
  helix) complexed with _______ which help regulate
  the activity of the genes
• DNA is duplicated every time a cell prepares to
  divide, so that each daughter cell receives a
  replicate (exact) copy of the genetic information
• Bacterial DNA is circular
• Ex. E. coli 4 million base pairs-strung out
  would be ____________________ X longer than the
  cell!!!!!!!
• Genomics new science of characterizing genomes
  at the molecular level

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DNA Replication

• The double strands separate (__________ bonds
  are broken), a replication fork forms, enzymes
  called ____________ help new nucleotides to
  bond by complementary base pairing (A-T, C-G) to
  the old strands.
• Proofreading enzymes check for errors
• Result is _____________ new strands each
  complementary and paired to the parent strands

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DNA Replication
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DNA Replication

• Each new strand contains ½ new and ½ old
  _______ ________________
• 5 3 the polymerase can only work in one
  direction
• The two strands of DNA are ________parallel
• Each oriented in an opposite direction
• Replication is continuous in one direction,(5
  3 ), and discontinuous in the other direction

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Continuous Vs. Discontinuous Replication
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RNA and Protein Synthesis

• Transcription RNA polymerase synthesizes an
  mRNA from _____ strand of the DNA which serves as
  a __________
• Base pairing is the same with the substitution of
  ________ for Thymine
• Transcription occurs from Promoter region to
  Terminator region

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Transcription
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Translation

• Base sequence in the mRNA is translated into a
  sequence of _______ ________ in a protein
• Ribosomes and rRNA
• Three base units on the mRNA are called
  __________-each specifies an amino acids
• The genetic code is the specific ____ base code
  which specifies a specific amino acid

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The Genetic Code
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The genetic code is degenerate (?)

• There are ____ codons (3 base units)
• 61 code for amino acids-several codons for each
  amino acid degenerate
• ____ are terminator or stop codons
• _____is the start codon and codes for the amino
  acid methionine

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Translation Part I
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Translation cont.
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Translation more!
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Translation finally!
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Summary of translation

• mRNA has the ________
• tRNA has the ______ ___________ (complements)
• The _____ site is the first site on the
  ribosome
• The _____ site is the second site
• There is a different _____________ for each amino
  acid
• Peptide bonds join the amino acids to make the
  polypeptide
• Translation begins at _______ which codes for
  methionine
• Translation ends when one of the three
  ___________ codons is encountered
• Translation can begin ________________
  transcription is complete! (only in prokaryotes)

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Regulation of gene expression On and Off
switches in the genes

• Some genes are ______ transcribed when _______
  needed (efficient!)
• ________________
• End product represses the production of enzymes
• ________________
• presence of certain chemicals induces the
  synthesis of enzymes-
• Ex. ß- galactosidase by E. coli in the presence
  of lactose

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Mutation

• Any change in the base sequence
• _________ mutation substitution of one base for
  another
• Can cause disease, death or NOTHING!
• ____________ mutation addition or loss of one or
  more bases causes all codons after to be changed!
• ______________ cause changes to DNA
• Mutations however, do occur spontaneously even
  without mutagens!

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Mutation one base substitution, remainder same
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Mutations how they are inherited
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Mutagens

• Base pair mutagens
• _________________ analogs
• Ionizing radiation
• UV radiation- thymine ____________
• Can be repaired by enzymes

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Mutagens base analogs
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Mutation thymine dimers
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Frequency of mutation

• The probability that a gene will mutate
• Expressed as 10 raised to some negative power
• A low rate of mutation is natural and
  _____________to introduce new genes into species!
• New genes create the ______________in populations
  upon which natural selection acts
• Mutagens raise the frequency of mutation

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Identification of mutants

• ___________ media can detect mutants
• Different appearance can detect mutants
• Specific tests can be run to detect
  mutants-positive selection rejects non-mutants
• Replica plating is used to detect mutants by
  ______________selection

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Replica plating negative selection
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Ames test

• Identifies possible carcinogens (mutagens)
• Principle if a mutagen is present then a mutant
  cell can re-mutate to the normal state

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Ames test
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Genetic Transfer and Recombination

• Horizontal gene transfer happens in bacteria
  producing recombinants
• 3 ways
• T_______________________
• C_______________________
• T_______________________

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Transformation
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Conjugation
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Transduction
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Plasmids and Transposons

• _________________ tiny circular pieces of DNA,
  not essential for life, may contain genes for
  resistance, toxin productions or other
  factors-can be transferred from one bacterium to
• ________________ portions of the DNA which move
  from one area of the chromosome to another-can
  jump on and off plasmids
• horizontal transfer and vertical transfer

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Diversity

• Diversity lends ______________ to a population of
  organisms
• They can adapt to changing environmental
  conditions
• Mutation, transformation, conjugation,
  transduction, plasmids and transposons all
  increase the diversity of a population of
  bacteria
• Bacteria are champions in diversity and in
  their ability to mutate and share genes