UNIT 4 DNA, RNA, and Gene Expression
DNA STRUCTURE
DNA is the primary material that causes
recognizable, inheritable characteristics in
related groups of organisms.
DNA is the GENETIC MATERIAL
Contain genes which are segments of DNA which
code for specific traits.
DNA is a relatively simple molecule
Composed of only four different subunits:
adenine, guanine, thymine, and cytosine (we will
talk more about these later)
DNA STRUCTURE CONT.
James Watson and Francis Crick discovered the
structure of DNA.
A winding Staircase: A DNA molecule is shaped
like a spiral staircase and is composed of two
parallel strands of linked subunits.
Known as a double helix
Each subunit is called a nucleotide.
Each nucleotide is made up of three parts: a
phosphate group, a five-carbon sugar, and a nitrogen
base.
The phosphate group and the five-carbon sugar link
together to form the “backbone” of the DNA
A NUCLEOTIDE
Deoxyribose
Can be Adenine,
Thymine, Guanine,
Cytosine
THE STRUCTURE OF DNA
The structure of DNA is very important
The information in DNA is contained in the order
of the bases (adenine, thymine, guanine,
cytosine)
BASE-PAIRING RULES
Adenine always pairs with thymine, and guanine
always pairs with cytosine to connect each side of
the helix.
These bases are held together by weak hydrogen
bonds.
THE CELL CYCLE: DNA REPLICATION
DNA REPLICATION
When cells divide , each new cell contains an
exact copy of the original cell’s DNA.
What is the name of this process?
Remember DNA is always made of two strands of
complementary base pairs.
The process of making a copy of DNA is called
DNA Replication
DNA molecule unwinds, two sides split apart
(splitting hydrogen bonds), new nucleotides are
added to each side until two identical sequences
result.
DNA REPLICATION CONT.
The location where the DNA separates is called
the replication fork.
At the replication fork, new nucleotide bases are
added.
REPLICATION PROTEINS
During the replication of DNA, many proteins
form a machinelike complex of moving parts
LIKE A FACTORY!!!!!!
DNA Helicase Protein that unwinds the DNA
double helix during replication.
DNA Polymerase Aids in the formation of the
new DNA sequences.
At the replication fork, DNA Polymerase moves along
the strands adding nucleotides to produce the new
double helix.
What if DNA polymerase messes up???
Oops mutations Cancer
THE BACKBONE OF DNA CONSISTS OF:
A. Deoxyribose Sugar only
B. Phosphate only
C. Deoxyribose Sugar and Phosphate
D. Adenine, Thymine, Cytosine, and Guanine
WHICH OF THE FOLLOWING LISTS BOTH
PURINES:
A. Guanine and Cytosine
B. Adenine and Thymine
C. Thymine and Guanine
D. Adenine and Guanine
THE REPLICATION PROTEIN INVOLVED IN
REASSEMBLY OF TWO NEW DNA STRANDS:
A. DNA Helicase
B. DNA Polymerase
C. DNA Ribase
D. DNA Phosphase
THE REPLICATION PROTEIN INVOLVED IN
UNZIPPING AND UNWINDING PARENT DNA
A. DNA Helicase
B. DNA Polymerase
C. DNA Ribase
D. DNA Phosphase
NITROGEN BASES ARE HELD TOGETHER BY
WHICH BOND TYPE
A. Covalent
B. Ionic
C. Sulfuric
D. Hydrogen
EOC: A NUCLEOTIDE IS COMPOSED OF SUGAR,
A PHOSPHATE GROUP, AND WHICH OF THE
FOLLOWING?
A. Amino Acid
B. Fatty acids
C. Glycerol
D. Nitrogenous Base
EOC: CHARGAFF’S RULE STATES THAT IN A GIVEN STRAND OF
DNA, THE PERCENTAGE OF ADENINE WILL EQUAL THE
PERCENTAGE OF THYMINE. IF A SEGMENT OF DNA WAS
COMPOSED OF 23% A, WHAT PERCENT OF T WILL THE SEGMENT
CONTAIN? A. 77%
B. 26%
C. 23%
D. 99%
GENE EXPRESSION
DNA does not directly make proteins.
RNA is essential in taking the genetic
information from DNA and building proteins!
Genes from DNA produce proteins at the
RIBOSOME, but this cannot be completed without
RNA!
TRANSCRIPTION: DNA TO RNA
The first stage– making RNA from the
information in DNA
Called TRANSCRIPTION
You can think of transcription as copying notes from the
board (DNA) to a notebook (RNA)
DNA vs. RNA
DNA RNA
Deoxyribose sugar, phosphate group,
nucleotide
Ribose sugar, phosphate group,
nucleotide
Double stranded Single stranded
Adenine (A), Cytosine (C), Guanine (G) ,
Thymine (T)
Adenine (A), Cytosine (C), Guanine (G) ,
Uracil (U)
MESSENGER RNA (MRNA)
Messenger RNA (mRNA)
When DNA is transcribed into RNA, mRNA is the
type of RNA that is produced. The mRNA carries
instructions for making a protein from a gene and
delivers them to ribosomes.
READING THE GENE
Transcription begins with a molecule called RNA
polymerase that unwinds and locates a “start”
codon.
mRNA molecule comes in at that locations and
starts producing the complementary RNA
molecule.
RNA polymerase eventually reaches a “stop”
codon where the mRNA stops getting longer.
INSTEAD OF CONTAINING THE BASE
THYMINE, RNA CONTAINS THE BASE:
A. Uracil
B. Catalase
C. Pepsin
D. Helicase
E. Polymerase
WHICH OF THE FOLLOWING WOULD DESCRIBE
A SIMILARITY BETWEEN DNA AND RNA?
A. Made of a single strand of nucleotides
B. Contain the base Uracil
C. Leaves the nucleus through nuclear pores
D. Contains phosphate in its “backbone”
E. Contain the base Thymine
TRANSLATION: RNA TO PROTEINS
Uses information in RNA to make a specific
protein.
mRNA codes for specific amino acids, that, when
linked together, form proteins.
TRANSFER RNA (TRNA)
During translation, tRNA reads the mRNA
sequence.
tRNA has amino acids connected to them
Attach these amino acids to a growing protein
chain
BASED ON THE DNA SEQUENCE :
ATCTGA , WHAT IS THE CORRECT
COMPLIMENTARY MRNA SEQUENCE?
A. TAGACT
B. CGCGCT
C. UAGACU
D. UAGACT
THE PROTEIN THAT UNWINDS DNA TO
ALLOW FOR TRANSCRIPTION IS CALLED:
A. DNA Helicase
B. DNA Polymerase
C. RNA Polymerase
D. RNA Helicase
THE PROCESS OF TRANSCRIPTION
PRODUCES:
A. tRNA
B. DNA
C. mRNA
D. Amino Acids
THE PROCESS OF TRANSLATION PRODUCES:
A. Amino Acid Chain
B. tRNA
C. mRNA
D. DNA
BASED ON THE MRNA SEQUENCE UCG,
WHAT IS THE CORRECT ANTICODON?
A. AGC
B. ACG
C. TGC
D. TCG
BASED ON THE DNA SEQUENCE AAG,
WHAT IS THE CORRECT ANTICODON?
A. TTC
B. UUC
C. AAG
D. UUA
NAME THE AMINO ACID CODED FOR BY
THE FOLLOWING CODON: GUC
A. Phenylalanine
B. Valine
C. Serine
D. Leucine
NAME THE AMINO ACID CODED FOR BY
THE FOLLOWING CODON: ACA
A. Valine
B. Tyrosine
C. Serine
D. Threonine
EOC: WHICH OF THE FOLLOWING MRNA
SEQUENCES CODES FOR VAL-GLU-SER,
RESPECTIVELY
A. UGG AGG CUA
B. GUA GGG AGC
C. GUC GAA ACU
D. GUG GAG AGC
JOINING AMINO ACIDS TOGETHER AT THE
RIBOSOME PRODUCES:
A. Carbohydrates
B. Proteins
C. Lipids
D. Nucleic Acids
EOC: WHICH MUTATION IS SHOWN
DNA-> ACC GTC ATT CGG
MUTATED DNA-> ACC GTC ATT CAG G
A. Frameshift Deletion
B. Frameshift Insertion
C. Point Mutation
D. Polymerase Mutation
REGULATING GENE EXPRESSION
How do butterflies develop from caterpillars?
We know that every cell in an individual starts with the same genes.
So, during a butterfly’s lifetime, not every gene is always at work.
Some genes are ON, while others are OFF. (Genetic Switch)
GENE EXPRESSION
Cells have complex systems that regulate
whether or not specific genes are expressed.
Expression depends on the cell’s needs and
environment. This is called gene regulation.
Accounts for changes during development.
OPERONS
The major form of gene regulation in
prokaryotes depends upon operons that
respond to environmental factors.
An operon is a gene regulation system in
which DNA segments control the
expression of a gene.
Operons are common in bacteria, but
uncommon in eukaryotes.
SO HOW DOES A EUKARYOTE (YOU)
REGULATE GENES?
Like prokaryotic cells, eukaryotic cells have
proteins that regulate transcription.
Transcription factors interact with RNA
polymerase to promote transcription.
Some transcription factors act as activators, and
some act as repressors.
Activators can bind at enhancer DNA segments
and when they interact with promotor region
(where RNA polymerase attaches), transcription
begins.
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