Chapter 16 Questions Flashcards
Is DNA replication similar or different between prokaryotes and eukaryotes?
DNA replication is similar in both prokaryotes and eukaryotes
What location does replication begin?
special locations called origins of replication
How many origins of replication do prokaryotes have? How many do eukaryotes have?
Prokaryotes only have one origin of replication, while eukaryotes have hundreds to thousands
Know the role of each major protein and enzyme involved in replication
Proteins: DNA helicase, single-strand binding proteins, topoisomerase
Enzymes: DNA polymerase, primase, DNA ligase
What is a replication “bubble” and how is it formed?
DNA helicase binds to the initiator proteins and begins separating double stranded DNA into single strands in a small area which forms a “replication bubble”
What is a replication fork?
DNA helicase binds to the initiator proteins and begins separating double stranded DNA into single strands in a small area which forms two replication forks at each side of replication bubble
Why is a primer needed for DNA replication?
It forms a 3’ end for DNA polymerase to attach to and initiate replication from
What form does a nucleotide have prior to being added to a growing DNA strand?
nucleoside triphosphate
What is the difference between a dNTP and a NTP?
DNA polymerase adds dNTPs to both strands of separated double stranded DNA in 5’ to 3’ direction
-RNA polymerase adds NTPs only to template DNA strand of separated double stranded DNA in 5’ to 3’ direction
(-The difference is in their sugars: dATP has deoxyribose while ATP has ribose)??
What is released after a nucleotide is added to a growing DNA strand?
two phosphate groups as a molecule of pyrophosphate
Describe the difference between the leading and lagging strands during DNA replication.
Leading - allows for DNA polymerase to continuously add DNA nucleotides since it runs in the same direction as the replication fork
Lagging - only allows DNA polymerase to add nucleotides in the direction going away from the replication fork
How are Okazaki fragments formed?
Short segments from the discontinuous addition of DNA nucleotides
How are Okazaki fragments connected?
connected together by DNA ligase to form a continuous strand
Which direction are DNA nucleotides added to the template strand? (5’to3’ or 3’to5’?
5’ to 3’
What does DNA proofreading refer to?
DNA polymerases “proofread” newly made DNA, replacing any incorrect nucleotides
Which enzyme is responsible for proofreading?
DNA polymerase
What are two common ways that DNA becomes damaged?
by exposure to harmful chemical or physical agents such as cigarette smoke and X-rays; it can also undergo spontaneous changes
What is the basic mechanism involved in DNA repair and which enzymes have roles in this process?
In nucleotide excision repair, a nuclease cuts out and replaces damaged stretches of DNA
What does a chromosome mainly consist of?
DNA and Proteins
What are the basic differences between bacterial and eukaryotic chromosomes?
- Eukaryotic chromosomes have linear DNA molecules associated with a large amount of protein - DNA is precisely combined with proteins in a complex called chromatin
- The bacterial chromosome is a double-stranded, circular DNA molecule associated with a small amount of protein - DNA is “supercoiled” and found in a region of the cell called the nucleoid
What are the different levels of chromosome packaging?
- -DNA double helix (2nm diameter)
- -Nucleosomes (10nm fibers)- consists of a core of eight histones (DNA packaging proteins) with DNA wound twice around which forms a 10nm fiber
- -30nm fibers- 10nm fibers coil into 30nm diameter fibers
- -Looped domains (300nm fibers)- 30nm fibers form loops using scaffolding protein which forms fibers with 300nm diameter
- -Metaphase chromosome- 300nm fibers coil into 700nm chromatids
What type of proteins play a major role in chromosome packaging?
Histones
What are the two major forms of chromatin present during the cell cycle?
Heterochromatin and Euchromatin
Which form of chromatin is the active form and which is the inactive form?
Heterochromatin - inactive
Euchromatin - active
