DNA & RNA
DNA – Chromosomes & DNA replication
– RNA & Protein Synthesis – Mutations –
Gene Regulation
Chapter 12
Pages 287 - 312
DNA
• Sometimes organisms, unicellular in this case, can pass beneficial
genes to other organisms that do not possess them.
• EXAMPLE: in Griffith’s experiment, heat-resistant bacteria passed
their heat-resistant genes to strains of bacteria that weren’t heatresistant. What was the result? __________________________
• This process is called transformation – When genes are passed from
one organism to another and the recipient organism is permanently
changed or “transformed”.
• What is the function of DNA? To ___________ and ___________
genetic information. What do these genes “inform”?
_________________
• What is the structure of DNA? _________________
• A bacteriophage is a type of virus that infects bacteria and can be
composed of DNA or RNA and a protein coat. How do you think a
protein coat serves the “phage”?
• Where does a bacteriophage attach to a cell that it is attacking?
DNA
DNA
• DNA is a long molecule made up of units called _____________.
• What are the four nucleotides that make up a molecule of DNA?
• Watson & Crick are the two scientists that are noted to have
developed the double-helix model of DNA structure. Franklin
studied the DNA molecule using a technique called X-ray diffraction.
These are the three names you will need to be familiar with and
responsible for knowing on future graded assessments.
• In a double-helix structure, there are two strands of molecular
structure that are wound around each other.
• In a double helix, a principle that is noted is base-pairing. The
“bases” involved in the structure are adenine (abbreviated “A”),
thymine (T), cytosine (C ), and guanine (G). They pair via hydrogen
bonding. A always bonds to T while G always bonds to C.
DNA
Chromosomes & DNA Replication
• Prokaryotes lack ____________ and their DNA is located in the
______________. Most of them have a single _____________ DNA
molecule containing most of all the cell’s ___________ information.
• Eukaryotic DNA generally have 1000 times the __________ of DNA as
prokaryotic organisms. Eukaryotic DNA is located where?
______________.
• Eukaryotic chromosomes contain both _____ and protein that are
tightly packed together to form a substance called ____________. This
term is not new. Histones are proteins that the cell uses to “wrap up”
genetic information. Refer to figure 12-10 on page 297 for a visual of
the role that histones play in organizing a single cells vast genetic
information.
• What does “replication” mean?
• During DNA replication, DNA molecules separate into two strands to
produce two new strands. Each strand serves as a template. What is a
template?
Chromosomes & DNA Replication
• A single strand with a base pair consisting of TACGTT will produce a
complementary strand consisting of ATGCAA. Remember A  T and
G  C in DNA (which is not exactly the same for RNA – we will get to
that shortly).
• But how does DNA replicate itself?
• One word  ENZYMES! And what type of macromolecule are
enzymes? (macromolecules: lipids, carbs, proteins and nucleic acids)
• These enzymes “unzip” the double helix structure and other enzymes
proceed to replicate according to each base pair’s compliment, again, A
 T and G  C.
• The principle enzyme involved in DNA replication is DNA polymerase.
• ETYMOLOGY TIME! Poly means ________; Polymer means ________;
and –Ase always indicates an ___________.
• DNA polymerase also ___________ each new DNA strand to maximize
the odds that each molecule is a perfect copy of the original DNA.
Chromosomes & DNA Replication
RNA and Protein Synthesis
• The first step of decoding genetic messages stored in DNA is to copy the
nucleotide sequence from ______ to ________. What does DNA stand
for? What does RNA stand for?
• What are all nucleic acids composed of?
• There are three major differences between DNA and RNA. 1) the 5carbon sugar in RNA is ribose not ___________. 2) RNA is generally
_____________. 3) RNA contains ________ instead of __________.
• RNA is involved mostly in protein synthesis.
• What are the 3 main types of RNA found in a cell?
• Note figure 12-12 on page 300. Which of the three types of RNA is
shaped like a clover…or a key?
• Which type of RNA carry copies of instructions from DNA?
• Ribosomes are made of which type of RNA?
• The RNA type that transfers amino acids to the ribosome is called?
• What is the function of a ribosome in a cell?
RNA and Protein Synthesis
• The process of copying part of a DNA nucleotide sequence to a
complementary RNA sequence is called_____________.
• What enzyme carries the process transcription?
• What enzyme is responsible for separating the double helix structure of
DNA required for the process of transcription?
• Promoters are signals in DNA that indicate to the enzyme
___________________ where to bind to make RNA.
• What is the difference between exons and introns?
• A codon consists of ______________________ nucleotides that specify a
single amino acid that will be added to a polypeptide.
• What is a polypeptide?
• UCGCACGGU  UCG-CAC-GGU  (codes for) Serine-Histidine-Glycine
• Ser, His, Gly are all amino acids. There are about 20 amino acids used by
the human body. What do amino acids do?
RNA and Protein Synthesis
• During the process of _____________, a cell uses information from
messenger RNA to produce proteins.
• If a messenger RNA (mRNA) strand codes for AUGUUC, what will the
transfer RNA complimentary sequence read? Remember, in RNA, T is
always replaced by uracil, U.
• Study figure 12-19 on page 306 to solidify your understanding of how
RNA and DNA operate.
• So, during transcription, the DNA is “transcribed” by mRNA and the
mRNA is complimentary to the template DNA.
• Then, during translation, the mRNA is “translated” into peptides,
polypeptides and proteins by the transfer RNA (tRNA) according which
codons are present in the mRNA strand.
Mutations
• When cells make mistakes during the copying and translation processes,
this results in ____________.
• ____________________ are changes in one or only a few nucleotides.
These can be defined as substitutions, deletions or insertions.
• Most mutations are ___________.
• In some cases, however, mutations can be ____________ or
______________.
• Mutations in most cells of the body affect only the individual such as
_____________.
• However, when mutations in ___________ occur, these mutations can
be passed on to offspring.
• What do you think the significance of mutation may be to living
organisms?
Mutations
Gene Regulation
• What is a group of genes that operate together?
• What are promoter genes?
• What are repressor genes?
• How are genes “turned off” or “turned on”?
• Generally, are operons found in eukaryotic cells?
• Most eukaryotic genes are controlled individually and have
_____________________ that are much more complex than those found
in prokaryotic cells.
• Cells don’t just grow and divide during embryonic development, they
also undergo ________________. This means that they become
specialized in _____________ and ______________.
• For example, does a neural cell have the same structure as a skin cell?
Do they have the same function? This is differentiation.
Gene Regulation
Chapter 12 Quiz
• 1. When a unicellular organism passes a beneficial gene to an organism
that does not have this beneficial gene, this is called what?
• 2. What is a bacteriophage?
• 3. What is the purpose of a protein coat on a bacteriophage?
• 4. Name three scientists credited for discovering the structure of a DNA
molecule.
• 5. In a DNA strand, what are the four base pairs or nucleotides?
• 6. In a DNA strand, how do these nucleotides hydrogen bond with each
other?
• 7. If a DNA strand has the nucleotide sequence TACGTT, what will its
complimentary DNA strand sequence look like?
• 8. What are histones?
• 9. What are the three main differences between DNA and RNA?
• 10. True/False. Most mutations are beneficial because they help species
to adapt.
ANSWERS
• 1. Transformation
• 2. A virus that attacks bacterial cells
• 3. To protect the virus’ genetic material
• 4. Watson, Crick, Franklin
• 5. A, T, C, G – adenine, thymine, cytosine, guanine
• 6. A  T & C  G
• 7. ATGCAA
• 8. Proteins that allow a cell to ‘wrap up’ its DNA into chromatin
• 9. RNA has ribose for a 5-Carbon sugar whereas DNA has deoxyribose;
RNA is single stranded; RNA uses uracil in place of thymine as a
nucleotide base pair
• 10. False – most mutations are neutral and have no affect on the
organism.