8.1. Identifying DNA as the Genetic Material

1
8.1. Identifying DNA as the Genetic Material
2
Griffith finds a transforming principle.

• Griffith experimented with the bacteria that
  cause pneumonia.
• He used two forms the S form (deadly) and the R
  form (not deadly).
• Dead S made R deadly

3
Avery identified DNA as the transforming
principle.

• Avery performed three tests on the transforming
  principle.

• Showed DNA was present.
• Matched chemical makeup to DNA
• No DNA no transformation

4
Hershey and Chase confirm that DNA is the genetic
material.

• Hershey and Chase studied viruses that infect
  bacteria, or bacteriophages.

• Used radioactive DNA and proteins
• DNA found in bacteria, proteins not

5
8.2. Structure of DNADNA is composed of four
types of nucleotides.

• DNA is made up of a long chain of nucleotides.
• Each nucleotide has three parts.
• a phosphate group
• a deoxyribose sugar
• a nitrogen-containing base

6

• The nitrogen containing bases are the only
  difference in the four nucleotides.

7
Watson and Crick determined the three-dimensional
structure of DNA by building models.

• Double helix
• Sugar-phosphate backbone
• Nitrogen base rungs

8

• Watson and Cricks discovery built on the work of
  Rosalind Franklin and Erwin Chargaff.

• Franklin even width
• Chargaffs rules stated that AT and CG.

9
Nucleotides always pair in the same way.

• The base-pairing rules show how nucleotides
  always pair up in DNA.

• A pairs with T

• C pairs with G

• Because a pyrimidine (single ring) pairs with a
  purine (double ring), the helix has a uniform
  width.

10

• The backbone is connected by covalent bonds.

• The bases are connected by hydrogen bonds.

11
8.3. DNA ReplicationReplication copies the
genetic information.

• A single strand of DNA serves as a template for a
  new strand.
• Directed by base pairing
• Each body cell gets acomplete set ofidentical
  DNA.
• What process allows this to happen?

• Review During which phase does the DNA replicate?

12
Proteins carry out the process of replication.

• DNA serves only as a template.
• Enzymes and other proteins do all work
• Enzymes unzip the double helix.
• Free-floating nucleotides form hydrogen bonds
  with the template strand.

13
3. DNA polymerase enzymes bond the nucleotides
4. Polymerase enzymes form covalent bonds between
nucleotides in the new strand.
14

• Two new molecules of DNA are formed, each with an
  original strand and a newly formed strand.

• DNA replication is semiconservative.

15
Concept Check

• On a separate sheet of paper
• List each scientist and draw a picture showing
  his/her/their contribution to DNA knowledge.
• Draw and label each part of a nucleotide
• Draw the picture at right, number and explain the
  steps for DNA replication on the picture. The
  first one is done for you as an example.
• What would be the next 4 bases on the left
  strand?

16
Replication is fast and accurate.

• DNA replication starts at many points in
  eukaryotic chromosomes.
• Why does replication need to happen at multiple
  points?

• DNA polymerases can find and correct errors.

17
KEY CONCEPT Transcription converts a gene into a
single-stranded RNA molecule.
18
Movie Review

• Put the structure used in the video next to each
  thing listed below.
• Chefs
• Castle
• Recipe Book
• Recipes
• Ingredients

19
RNA carries DNAs instructions.

• The central dogma states that information flows
  in one direction from DNA to RNA to proteins.

20

• The central dogma includes three processes.
• Replication
• Transcription
• Translation
• RNA is a link between DNA and proteins.

21

• RNA differs from DNA in three major ways.
• RNA has a ribose sugar.
• RNA has uracil instead of thymine.
• RNA is a single-stranded structure.

22

• Transcription is catalyzed by RNA polymerase.
• RNA polymerase and other proteins form a
  transcription complex.
• The transcription complex recognizes the start of
  a gene and unwinds a segment of it.

23

• Nucleotides pair with one strand of the DNA.
• RNA polymerase bonds the nucleotides together.
• The DNA helix winds again as the gene is
  transcribed.

24

• The RNA strand detaches from the DNA once the
  gene is transcribed.

25
Concept Check

• Use a Venn Diagram to compare and contrast DNA
  replication and transcription

Transcription
Replication
26
The transcription process is similar to
replication.

• Transcription and replication both involve
  complex enzymes and complementary base pairing.
• The two processes have different end results.
• Replication copiesall the DNAtranscription
  copiesa gene.
• Replication makesone copytranscription
  canmake many copies.

27

• Transcription makes three types of RNA.
• Messenger RNA (mRNA) carries the message that
  will be translated to form a protein.
• Ribosomal RNA (rRNA) forms part of ribosomes
  where proteins are made.
• Transfer RNA (tRNA) brings amino acids from the
  cytoplasm to a ribosome.

28
KEY CONCEPT

• Translation converts an mRNA message into a
  polypeptide, or protein.

29
Amino acids are coded by mRNA base sequences.

• Translation converts mRNA messages into
  polypeptides.
• A codon is a sequence of three nucleotides that
  codes for an amino acid.

30

• The genetic code matches each codon to its amino
  acid or function.
• three stop codons
• one start codon, codes for methionine

31
A change in the order in which codons are read
changes the resulting protein.

• Regardless of the organism, codons code for the
  same amino acid.

32
Amino acids are linked to become a protein.

• An anticodon is a set of three nucleotides that
  is complementary to an mRNA codon.
• An anticodon is carried by a tRNA.

33
Ribosomes consist of two subunits

• The large subunit has three binding sites for
  tRNA.
• The small subunit binds to mRNA.

34

• For translation to begin, tRNA binds to a start
  codon and signals the ribosome to assemble.
• A complementary tRNA molecule binds to the
  exposed codon, bringing its amino acid close to
  the first amino acid.

35

• The ribosome helps form a polypeptide bond
  between the amino acids.
• The ribosome pulls the mRNA strand the length of
  one codon.

36

• The now empty tRNA molecule exits the ribosome.
• A complementary tRNA molecule binds to the next
  exposed codon.
• Once the stop codon is reached, the ribosome
  releases the protein and disassembles.

37
Recombinant DNA DNA that contains genes from
more than one organism

• Warm-Up
• Transcribe and Translate the following DNA
  sequence
• TACAATGCGAGTGAGCGCTACACT
• mRNA AUGUUACGCUCACUCGCGAUGUGA
• Amino acids MET-LEU-ARG-SER-LEU-ALA-MET-STOP

38
TRANSCRIPTION/TRANSLATIONACTIVITY EXAMPLE

• DNA Strand 10
• Using base pairing rules, write the mRNA that
  would be complementary to this strand.
• What would the tRNA anticodons be for the newly
  synthesized mRNA strand?

CTA TTA CGA ACT TAG AGC ATT AAT TAT AAA
CTT ATC
GAU AAU GCU UGA AUC UCG UAA UUA AUA UUU GAA UAG
CUA UUA CGA ACU UAG AGC AUU AAU UAU AAA CUU AUC
D N A - I S -
L I F E -
39
Transgenic organisms contains one or more genes
from another organism

• Warm-Up
• Write the steps required to go from DNA to
  proteins (do not just write transcription and
  translation!)

40
Thursday, November 10

• Gene sequencing determining the order of
  nucleotides in genes or genome
• Warm-Up
• What are the 2 types of mutations?
• Explain the difference between them.
• How might mutations be a good thing?

41
Mutations

• Amino Acid Sequence (Mutation)
• MET-PHE-LEU-ILE-ARG-GLU-HIS-HIS-CYS-GLU-PRO-CAL-GL
  U-STOP (A new protein has been made that
  increases the thickness of your fur so you can
  dig longer for nuts into the winter and only have
  to stay at your home for 15 seconds instead of 1
  minute)
• MET-LEU-STOP (No protein is made so no teeth)
• MET-PHE-SER-THR-ARG-GLU-HIS-HIS-CYS-LEU-SER-CAL-GL
  U-STOP (Protein not complete so skin in the
  fingers does not disappear and your fingers are
  all connected (webbed))
• MET-PHE-THR-ARG-GLU-HIS-HIS-CYS-GLU-PRO-CAL-GLU-ST
  OP (Missing vital components for leg protein and
  ankle bones fuse together)
• MET-LEU-LEU-ASN-SER-ARG-ALA-SER-LEU-STOP (No
  hands could form with this protein)
• MET-PHE-ASN-SER-ARG-ALA-SER-LEU-STOP (Protein
  incomplete and vision did not develop so you are
  blind)