MOLECULAR GENETICS

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CHAPTER 12

• MOLECULAR GENETICS

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• Ch. 12.1 DNA The Genetic Material
• You will be doing this section in small groups.
• Each group will read Section 12.1.
• You will divide up the section so that everyone
  is reading equal amounts.
• As you read your section you will put down some
  important information, such as
• Year for the discovery
• Person(s) who did the discovery
• What was discovered /or how they made discovery
• Next, you will put together all of your
  information into a timeline for the discoveries

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• Ch. 12.1 DNA THE GENETIC MATERIAL
• Key points from Section 1
• Nucleotides
• Nucleotides are subunits of the macromolecule
  group of nucleic acid
• Composed of 5 carbon sugar, a phosphate group,
  and a nitrogenous base
• Nucleic acid
• 2 different types
• DNA
• Nucleotide is composed of deoxyribose sugar, a
  phosphate group and a nitrogenous base
• Nitrogenous bases are
• Adenine (A), Guanine (G), Cytosine (C), or
  Thymine (T)
• RNA
• Nucleotide is composed of ribose sugar, a
  phosphate group and a nitrogenous base
• Nitrogenous bases are
• Adenine (A), Guanine (G), Cytosine (C), or Uracil
  (U)

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• Section 12.1 Key Points Continued
• Purines are double ringed bases such as
• Guanine and Adenine
• Pyrimidine are single ringed bases such as
• Thymine, cytosine, and uracil
• Chargaffs Rule
• C G
• T A
• Watson (IU graduate) Crick built the double
  helix model for DNA
• Unique feature of the DNA molecule is the
  direction the 2 strands run which is opposite of
  each other or antiparallel.

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• Section 12.1 Key Points Continued
• Chromosome Structure
• A human chromosome length ranges from 51 million
  to 245 million base pairs long.
• A DNA strand that is 140 million nucleotides long
  would measure approximately 5 cm. long (2 in.)
• To fit all of this into the nucleus of the cell
  the DNA tightly coils around a beadlike protein
  called a histone
• The histone the DNA together creates a
  nucleosome.
• The nucleosomes group together into chromatin
  fibers, which supercoil to create the DNA
  structure called a chromosome.
  biology.kenyon.edu

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• SECTION 12.2 REPLICATION OF DNA
• MAIN IDEA DNA replicates by making a strand
  that is complementary to each original strand.
• REVIEW
• What nitrogen bases pair together?
• What is contained in the nucleotide for DNA?
• What nitrogen bases would you find in DNA?
• What is contained in the nucleotide for RNA?
• What bases would you find in RNA?

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• SEMICONSERVATIVE REPLICATION
• Semiconservative replication is where parental
  strands of DNA separate and serve as the template
  to produce DNA molecules that have one strand of
  parental DNA and one strand of new DNA.
• csls-text2.c.u-tokyo.ac.jp
• Where does DNA replication take place?
• During what phase does DNA replication take
  place?
• Will DNA replication take place in mitosis,
  meiosis, or both?

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• UNWINDING AND BASE PAIRING
• DNA helicase, an enzyme, will unwinding unzip
  the double helix leaving single strands of DNA.
• DNA polymerase, an enzyme, helps in adding the
  correct nucleotides to the new DNA strand.
• Adenine (A) pairs with thymine (T)
• Guanine (G) pairs with cytosine (C)
• Base pairing
• Template A T C C A G G T G
• DNA copy
• Produces identical copies to the original double
  stranded DNA
• DNA replication will begin at many places along
  the chromosome

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• SECTION 12.3 DNA, RNA, AND PROTEIN
• MAIN IDEA DNA codes for RNA, which guides
  protein synthesis.
• QUESTION How does DNA replication relate to
  mitosis?
• How does DNA replication relate to meiosis?
• How does DNA replication relate to reproduction?

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• CENTRAL DOGMA
• Remember proteins function as structural
  building blocks for the cells and as enzymes.
• Central Dogma of biology DNA codes for RNA,
  which controls the synthesis of proteins.
• DNA ? RNA ? PROTEIN
• RNA is a nucleic acid that is similar to DNA,
  except
• RNA contains the sugar ribose, uracil replaces
  thymine, and is single stranded.

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• TRANSCRIPTION
• Transcription is the step in the central dogma
  synthesis of the mRNA from the DNA
• Transcription DNA ? RNA
• Transfers the DNA code to mRNA in the nucleus.
• mRNA takes the code into the cytoplasm for
  protein synthesis
• To create mRNA the DNA is unzipped in the nucleus
  and RNA polymerase binds to a specific section
  and creates the mRNA
• The strand of DNA that is read by the RNA
  polymerase is called the template strand.
• The strand of DNA not read by is called the
  nontemplate strand.
• Uracil is used instead of thymine in mRNA
• New mRNA strand leaves the nucleus through the
  nuclear pores into the cytoplasm

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• CENTRAL DOGMA CONTINUED
• 3 main types of RNA
• Messenger RNA (mRNA)
• Long strands of RNA nucleotides that are formed
  complementary to one strand of DNA
• Leave the nucleus and go to the ribosomes to
  direct the synthesis of a specific protein
• Ribosomal RNA (rRNA) faculty.southwest.tn.edu
• Type of RNA that combine with proteins to form
  ribosomes in the cytoplasm. legacy.hopkinsville.ed
  u
• Transfer RNA (tRNA)
• Small segments of RNA nucleotides that transport
  amino acids to the ribosome.

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• RNA PROCESSING
• Scientists noticed that mRNA was shorter than the
  coding region of DNA
• Found that the DNA is interrupted by sequences,
  called INTRONS, that are not in the final mRNA
• Coding sequences that remain to make up the mRNA
  are called EXONS.
• Before mRNA leaves the nucleus the INTRONS are
  removed

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• TRANSCRIPION CONTINUED
• Remember Base pairs in RNA
• Cytosine? Guanine Guanine?Cytosine
• Adenine ? Uracil Uracil ? Adenine
• Thymine (from DNA)? Adenine
• DNA Strand A T G C T A A
  G C
• RNA Strand ________

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• THE CODE
• There are 20 amino acids that are used to make
  proteins.
• DNA code is read as a 3 base code.
• In DNA or mRNA the 3 base code is called a CODON
• The codon that will start the reading of the mRNA
  is the codon AUG, which codes for the amino acid
  methionine

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• GENETIC CODEemc.maricopa.edu

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• CIRCLE GENETIC CODE krishnascience.info

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• The Genetic Code
• Proteins are made by joining amino acids into
  long chains called polypeptides
• amino acids are like puzzle pieces
• Proteins would be like the whole puzzle

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• TRANSLATION
• Translation RNA ? protein
• Once the mRNA is made and the introns are removed
  and exons are left mRNA leaves the nucleus and
  goes and attaches to a ribosome in the cytoplasm
• This is where the mRNA is read and translated to
  make a protein through a process called
  translation.
• Translation involves
• tRNA that acts as the interpreters of the mRNA
  codon sequence.
• tRNA has a cloverleaf shape that has a 3 base
  coding sequence called the anticodon.
• Anticodons are complementary to a codon on the
  mRNA.

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• ROLE OF THE RIBOSOME
• Ribosomes consists of 2 subunits.
• When mRNA leaves the nucleus the 2 subunits of
  the ribosome come together and attach to the
  mRNA.
• Now the tRNA will bring in the correct amino acid
  and attach to the mRNA.
• This continues until a stop codon is reached and
  it is the end of the protein synthesis.
• Protein is now released.

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• TRANSLATION ajinomoto-eurolysine.com

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• SECTION 12.4 GENE REGULATION AND MUTATION
• MAIN IDEA Gene mutation is regulated by the
  cell, and mutations can affect this expression.
• QUESTION What words and images come to mind
  when you hear the words mutation or mutant?

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• HOX GENES
• Gene regulation is crucial during development.
• Eukaryotes develop from a single cell called a
  zygote.
• Zygote produces all the different kinds of cells
  needs by the organism by mitosis.
• Hox genes helps control how the body of an
  organism develops.
• Mutations in the Hox genes can cause a fruit fly
  to develop a leg where its antennae should be.

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• HOX GENE MUTATION palaeos.com

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• MUTATIONS
• Mutation is a permanent change in a cells DNA.
• Types of gene mutations
• Point mutation is a chemical change in one base
  pair and could cause a genetic disorder.
• Types of point mutations
• Substitution (missense) one base is exchanged
  for another
• EX C is replaced with G (now codes for the
  wrong amino acid)
• Substitution (nonsense) changes the codon for
  an amino acid to a stop codon causing translation
  to end early resulting in a protein that cannot
  function normally.

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• MUTATIONS CONTINUED
• Types of gene mutations continued
• Frameshift Insertion adds a nucleotide to the
  DNA sequence shifting the reading frame
• EX original strand A C C G G C C A A
• amino acids __________________________
  _______
• mutated strandA C C C G G C C A A
• amino acids __________________________
  _______
• Frameshift Deletion deletes a nucleotide from
  the DNA sequence shifting the reading frame
• EX original strnad A C C G G C C A A
• mutated strand A C G G C C A A

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• CHROMOSOMAL MUTATIONS
• Deletions
• Part of chromosome is deleted/gone completely
• Original A B C D Deleted A C D
• Duplications
• Part of chromosome is duplicated/repeated
• Original A B C D Duplicated A A B C D
• Inversions
• Part of code is read in a different direction
  (reverses the directions of the parts of the
  chromosome)
• Original A B C D, Inverted A C D B
• Translocations
• Entire sections of chromosome are shifted (when
  part of one chromosome breaks off and attaches
  itself to another chromosome) http//staff.tuhsd.k
  12.az.us/gfoster/standard/bmut.htm

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• CAUSES OF MUTATIONS
• Some mutations, like point mutations, occur
  spontaneously.
• Cells proofread so it happens rarely
• Mutagens are some types of chemicals and/or
  radiation

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• BODY CELL VS. SEX CELL MUTATION
• Body cell
• Mutation in a body cell (somatic cell) is in that
  one cell and the future daughter cells that this
  cell makes.
• If these mutations do not cause problems for the
  cell it is called a neutral mutation.
• If these mutation cause problems in the cell the
  cell could become cancerous or the cell may die.
• These mutations are not passed down to offspring
• Sex cell
• If the mutations occurs in the sex cells it will
  be passed down to the offspring and will be
  present in every cell of the offspring.
• The mutation may or may not affect the offspring.