Transcription and Translation

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Transcription and Translation

• S. HS. 3.2.1

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DNA

• DNA (DeoxyriboNucleic Acid) is the information
  for life it is made of repeating nucleotides and
  appears as a twisted ladder shape (double helix).
  Watson and Crick are responsible for developing
  a model of this structure.
• Nuleotides of DNA consist of
• 1.)deoxyribose-5 carbon sugar
• 2.)phosphate
• 3.)1 nitrogen base-adenine, guanine, cytosine, or
  thymine

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DNA

• The nitrogen bases form the steps on the ladder
  or rungs of the ladder they do this by pairing
  with their compliment
• A pairs with T
• C pairs with G
• ?A nucleotide is named according to the base it
  contains
• ?phosphate and sugar form the backbone(sides) of
  ladder
• ?nitrogen bases stick out like teeth on a zipper
• (picture)

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DNA

• Before a cell can divide, DNA must make a copy of
  itself (DNA Replication)
• Without this process, new cells only have half
  the DNA of their parents
• With this, the genetic makeup of an organism can
  be passed to new cells during mitosis or to new
  generations through meiosis followed by sexual
  reproduction.

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DNA to Protein

• The sequence of nucleotides in an organism is the
  genetic code of an organism and can be converted
  to a sequence of amino acids in proteins.
• RNA like DNA is a nucleic acid, like DNA. It too
  is made up of nucleotides
• ?3 major differences
• 1.)RNA is single stranded-DNA is double
• 2.)RNA has ribose-DNA has deoxyribose
• 3.)RNA has uracil-DNA has thymine
• (picture)

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Transcription

• DNA ? mRNA
• (in nucleus) (leaves nucleus, goes to
  ribosome)
• ?Transcription (rewriting the code) takes place
  in the cells nucleus where enzymes make an RNA
  copy of a DNA strand mRNA is made.
• ?This process is similar to DNA replication
  except that the result is one single stranded RNA
  molecule.

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Transcription

• ? DNA unzips first, then free floating RNA
  nucleotides pair with their complimentary DNA
  nucleotides on one DNA strand
• ? When pairing is complete, mRNA breaks away and
  leaves the nucleus

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Translation

• mRNA ? protein
• (nucleotides) (amino acids)
• Translation is the process of converting the
  info in mRNA into an amino acid sequence
• Translation takes place at the ribosomes in the
  cytoplasm.
• All organisms use the same amino acids, making
  the genetic code universal.

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Transcription and Translation

• If one DNA strand has the base sequence G C T A A
  T G C A, the other strand is
• _ _ _ _ _ _ _ _ _ (its compliment)
• Once you have found the compliment, the mRNA
  strand must be completed.
• After the mRNA is complete, the codons can be
  underlined.
• The codons can then code for an amino acid.
• For instance, using the above strand, the process
  would appear as this
• DNA G C T A A T G C A
• CS C G A T T A C G T
• mRNA C G A U U A C G U
• A.A. Arg Leu Arg

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Mutations

• Mutations are changes in DNA these are natural
  processes that produce genetic diversity in
  organisms
• There are different types of mutations
• Point or Substitution Mutation a single
  nucleotide is replaced by another of the three
  nucleotides
• DNA T A G G C A
• (m)DNA T A C G C A Notice two amino acids
  will still be coded
• Frameshift Mutation a single nucleotide is
  inserted or deleted into the DNA strand when
  this occurs, the reading of the amino acids will
  shift to the right or left respectively by one
  base
• DNA T A G G C A - Italicized G is
  deleted
• (m)DNA T A G C A Notice only one amino
  acid will be coded
• DNA T A G G C A An adenine
  nucleotide is added
• (mDNA) T A G G A C A Notice that still
  only two amino acids can be formed because a
  codon must include three nucleotides in order to
  form an amino acid

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Transcription and Translation Questions

• 1.) A base sequence is shown below.
• ACAGTGC
• How would the base sequence be coded on mRNA?
• A TGTCACG
• B GUGACAU
• C UGUCACG
• D CACUGUA

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Transcription and Translation Questions

• 2.) A scientist puts nucleotide chains of UUUUUU
  in a test tube under conditions allowing protein
  synthesis. Soon the test tube is full of
  polypeptide chains composed of only the amino
  acid phenylalanine. What does this experiment
  indicate?
• A The amino acid phenylalanine is composed of
  uracil.
• B UUU codes for the amino acid phenylalanine.
• C Protein synthesis malfunctions in test tubes.
• D Most proteins contain only one type of amino
  acid.

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Transcription and Translation Questions

• 3.) 5 ATCAGCGCTGGC 3
• The above sequence of DNA is part of a gene.
  How many amino acids are coded for by this
  segment?
• A 4
• B 8
• C 12
• D 20

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Transcription and Translation Questions

• 4.) A strand of mRNA containing the repeating
  sequence AAGAAGAAGAAG could code for which of the
  following amino acid sequences?
• A lys-arg-glu-lys
• B ser-ser-glu-glu
• C lys-arg-lys-arg
• D lys-lys-lys-lys

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Transcription and Translation Questions

• 5.) Although there are a limited number of amino
  acids, many different types of proteins exist
  because the
• A size of a given amino acid can vary.
• B chemical composition of a given amino acid
  can vary.
• C sequence and number of amino acids is
  different.
• D same amino acid can have many different
  properties.

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Transcription and Translation Questions

• 6.) 5 G T A _ _ _ A A 3
• 3 C A T G C A T T 5
• This segment of DNA has undergone a
• mutation in which three nucleotides
• have been deleted. A repair enzyme
• would replace them with
• A CGT.
• B GCA.
• C CTG.
• D GTA.

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Mutations

• 7.) Which of these would most likely cause a
  mutation?
• A the replacement of ribosomes on the
  endoplasmic reticulum
• B the insertion of a nucleotide into DNA
• C the movement of transfer RNA out of the
  nucleus
• D the release of messenger RNA from DNA

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Mutations

• 8.) Mutations within a DNA sequence are
• A unnatural processes that are harmful to
  genetic diversity
• B unnatural processes that always affect the
  phenotype
• C natural processes that always affect the
  phenotype
• D natural processes that produce genetic
  diversity

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Genetic Engineering Questions

• 9.) The bacterium Agrobacterium tumefaciens
  infects plants, and a portion of its DNA is
  inserted into the plants chromosomes. This
  causes the plant to produce gall cells, which
  manufacture amino acids that the bacterium uses
  as food. This process is a natural example of
• A hybridization.
• B grafting.
• C genetic manipulation.
• D polyploidy

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Genetic Engineering Questions

• 10.) Genetic engineering has produced goats
  whose milk contains proteins that can be used as
  medicines. This effect was produced by
• A injecting foreign genes into the goats
  udders.
• B mixing foreign genes into the milk.
• C inserting foreign genes into fertilized goat
  eggs.
• D genetically modifying the nutritional needs
  of the goats offspring.

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Slide Answers

• 1) C 6) A
• 2) B 7) B
• 3) A 8) D
• 4) D 9) C
• 5) C 10) C