BIO 130
Lecture Exam 3
CHAPTER 8
DNA Structure, Function and Replication
Be able to differentiate the following processes: DNA replication, recombination and gene
expression. (Fig. 8.2)
● DNA Replication: genetic information can be transferred vertically to the next
generation of cells (parent to offspring)
● Recombination: genetic information can be transferred horizontally between cells of the
same generation
● Expression: genetic information is used within a cell to produce the proteins needed for
the cell to function
What are genes? Chromosomes? How are these related to a DNA molecule?
● Genes: segments of DNA that encode functional products, usually proteins
● Chromosomes: supercoiled structure of DNA
What is a nucleotide? Review what its components are from Chapter 2.
● Nucleotide: phosphate and 5-carbon sugar (make up the backbone); A-T and C-G (make
up the rungs)
What does complementary base pairing mean? How does it work?
● Adenine with Thymine
● Cytosine with Guanine
What does “anti-parallel” mean?
● The end of one strand matches up with the beginning of the other (5’ end matches with
3’ end and vice versa); sequence is always ready from 5’ to 3’
On DNA replication:
•Be able to describe the process on both the leading and lagging strands of DNA
● Leading Strand is synthesized continuously, Lagging Strand is not, creating short
fragments (Okazaki fragments)
Know the function of each of its key enzymes. Think about what would happen to DNA
replication if any of these genes were missing.
● DNA Gyrase: relaxes supercoiling ahead of the replication fork
● DNA Ligase: makes covalent bonds to join DNA strands; Okazaki fragments, and
new segments in excision repair
● DNA Polymerases: synthesizes DNA; proofreads and repairs DNA
● Helicase: unwinds double-stranded DNA
, ● Primase: an RNA polymerase that makes RNA primers from a DNA template
● Topoisomerase: relaxes supercoiling ahead of the replication fork; separates
DNA circles at the end of DNA replication
Know in which “direction” the new DNA strand grows (or, how does DNA polymerase add a
new nucleotide?)
● DNA polymerase adds nucleotides to the growing DNA strand in the 5’ 🡪 3’
direction
Be able to describe the semi-conservative nature of DNA replication.
● After the replication of one DNA helix each of the two daughter helixes that
result contain one newly-synthesized and one pre-exciting strand of DNA
(template/old strand and new strand)
Describe the structure of a bacterial chromosome and how bacterial DNA replication
proceeds: from which specific region does it begin? What does bidirectional mean?
● DNA Replication in Bacteria:
● Begins at the origin of replication
● Bidirectional (two replication forks moving in opposite directions and
eventually meeting)
● Each offspring cell receives one copy of the old DNA molecule (semi-
conservative)
● Replication is very fast and highly accurate
Gene Expression
Be able to describe the central dogma of molecular Biology. What does gene expression
mean?
● Central Dogma: explains the flow of genetic information from DNA to RNA to make a
functional product (protein)
● Gene has to be “turned on” to be expressed
● DNA sequence is transcribed into an RNA sequence
● RNA sequence may be translated into protein
What happens during transcription?
● Transcription:
● Synthesis of a complementary mRNA strand from a DNA template
● Begins when RNA polymerase binds to the promoter sequence on DNA
● Proceeds in the 5’ 🡪 3’ direction; only one of the two DNA strands is transcribed
● Ends at the terminator sequence on DNA
•What type of molecules does the process produce? (DNA, RNA or protein?)
● RNA
Lecture Exam 3
CHAPTER 8
DNA Structure, Function and Replication
Be able to differentiate the following processes: DNA replication, recombination and gene
expression. (Fig. 8.2)
● DNA Replication: genetic information can be transferred vertically to the next
generation of cells (parent to offspring)
● Recombination: genetic information can be transferred horizontally between cells of the
same generation
● Expression: genetic information is used within a cell to produce the proteins needed for
the cell to function
What are genes? Chromosomes? How are these related to a DNA molecule?
● Genes: segments of DNA that encode functional products, usually proteins
● Chromosomes: supercoiled structure of DNA
What is a nucleotide? Review what its components are from Chapter 2.
● Nucleotide: phosphate and 5-carbon sugar (make up the backbone); A-T and C-G (make
up the rungs)
What does complementary base pairing mean? How does it work?
● Adenine with Thymine
● Cytosine with Guanine
What does “anti-parallel” mean?
● The end of one strand matches up with the beginning of the other (5’ end matches with
3’ end and vice versa); sequence is always ready from 5’ to 3’
On DNA replication:
•Be able to describe the process on both the leading and lagging strands of DNA
● Leading Strand is synthesized continuously, Lagging Strand is not, creating short
fragments (Okazaki fragments)
Know the function of each of its key enzymes. Think about what would happen to DNA
replication if any of these genes were missing.
● DNA Gyrase: relaxes supercoiling ahead of the replication fork
● DNA Ligase: makes covalent bonds to join DNA strands; Okazaki fragments, and
new segments in excision repair
● DNA Polymerases: synthesizes DNA; proofreads and repairs DNA
● Helicase: unwinds double-stranded DNA
, ● Primase: an RNA polymerase that makes RNA primers from a DNA template
● Topoisomerase: relaxes supercoiling ahead of the replication fork; separates
DNA circles at the end of DNA replication
Know in which “direction” the new DNA strand grows (or, how does DNA polymerase add a
new nucleotide?)
● DNA polymerase adds nucleotides to the growing DNA strand in the 5’ 🡪 3’
direction
Be able to describe the semi-conservative nature of DNA replication.
● After the replication of one DNA helix each of the two daughter helixes that
result contain one newly-synthesized and one pre-exciting strand of DNA
(template/old strand and new strand)
Describe the structure of a bacterial chromosome and how bacterial DNA replication
proceeds: from which specific region does it begin? What does bidirectional mean?
● DNA Replication in Bacteria:
● Begins at the origin of replication
● Bidirectional (two replication forks moving in opposite directions and
eventually meeting)
● Each offspring cell receives one copy of the old DNA molecule (semi-
conservative)
● Replication is very fast and highly accurate
Gene Expression
Be able to describe the central dogma of molecular Biology. What does gene expression
mean?
● Central Dogma: explains the flow of genetic information from DNA to RNA to make a
functional product (protein)
● Gene has to be “turned on” to be expressed
● DNA sequence is transcribed into an RNA sequence
● RNA sequence may be translated into protein
What happens during transcription?
● Transcription:
● Synthesis of a complementary mRNA strand from a DNA template
● Begins when RNA polymerase binds to the promoter sequence on DNA
● Proceeds in the 5’ 🡪 3’ direction; only one of the two DNA strands is transcribed
● Ends at the terminator sequence on DNA
•What type of molecules does the process produce? (DNA, RNA or protein?)
● RNA
