80 Questions
What was the major challenge to biologists in the 20th century?
To identify the molecules of inheritance
What were the two components of chromosomes that were candidates for the genetic material?
DNA and protein
What was the initial reason why protein was a stronger candidate than DNA for the genetic material?
Protein was seen as more complex and likely to contain genetic information
What characteristics did the genetic material need to have?
Be easy to copy, be variable, and contain information
Which organisms were studied to first discover the role of DNA in heredity?
Bacteria and viruses
What is the process of creating a copy of DNA called?
DNA replication
What is the name of the scientists who contributed to the discovery of the structure of DNA?
Watson and Crick
What is the name of the chapter in Campbell Biology that discusses DNA structure and function?
Chapter 16
What is the result of a condensation reaction in DNA synthesis?
A molecule of water is excluded
What is the shape of a bacterial chromosome?
Circular double-stranded
Where are eukaryotic chromosomes located?
In the nucleus
What is the function of histone H1?
To stabilize the interaction between DNA and nucleosomal histones
What is the structure of a nucleosome?
8 histone molecules and 168 base pairs of DNA
What is the term for loosely packed chromatin that enables gene expression?
Euchromatin
During which stage of the cell cycle is chromatin highly condensed?
Mitosis
What is the purpose of histone modification in chromatin structure?
To stabilize chromatin structure
What is the shape of the E. coli chromosome?
Circular
How many origins of replication do eukaryotic chromosomes have?
Several
What is the function of helicases during DNA replication?
To untwist the double helix at the replication forks
What is the function of single-strand binding protein during DNA replication?
To bind and stabilize single-stranded DNA
What is the direction of nucleotide addition by DNA polymerases?
5'-3'
What is the purpose of topoisomerase during DNA replication?
To correct 'overwinding' ahead of replication forks
What is the limitation of DNA polymerases in terms of initiation of replication?
They can only add nucleotides to a pre-existing nucleotide chain
What is the shape of the region at the end of each replication bubble where new DNA strands are elongating?
Y-shaped
What is the role of primase in DNA replication?
To synthesize a short RNA primer
What is the direction of DNA synthesis by DNA polymerase?
5’-3’
What is the purpose of the RNA primer in DNA replication?
To provide a starting point for DNA synthesis
What is the difference between dATP and ATP?
The type of sugar they contain
What is the function of DNA ligase in DNA replication?
To join Okazaki fragments
What is the direction of leading strand synthesis?
5’-3’
What is the function of the sliding clamp in DNA replication?
To hold DNA polymerase in place
What is the result of the modified 3’-OH group in AZT?
Blocked DNA replication
What is the role of primase during DNA replication?
To synthesize short RNA primers
Which enzyme is responsible for adding DNA nucleotides to each primer in the 5'→3' direction?
DNA polymerase III
What is the direction of DNA synthesis during lagging strand synthesis?
5'→3'
What is the purpose of DNA ligase during DNA replication?
To join DNA fragments to the subsequent Okazaki fragments
What happens to the RNA primer after DNA pol III reaches the next RNA primer?
It is detached by DNA polymerase III
What is the role of DNA polymerase I during DNA replication?
To replace RNA primers with DNA nucleotides
What is the overall direction of replication during lagging strand synthesis?
5'→3'
What is the purpose of Okazaki fragments during DNA replication?
To facilitate DNA synthesis in the 5'→3' direction
What is the primary function of histone H1 in chromatin structure?
To stabilize the interaction between DNA and nucleosomal histones
What is the term for the highly condensed form of chromatin that inhibits gene expression?
Heterochromatin
During which stage of the cell cycle is most chromatin in a loosely packed form?
Interphase
What is the diameter of the 30-nm chromatin fiber?
30 nm
What is the result of a condensation reaction in DNA synthesis?
A molecule of water is excluded
What is the structure of a nucleosome?
Histone octamer + ds DNA
What is the purpose of nucleosomes in chromatin structure?
To compact DNA into the nucleus
What is the structure of the chromatin fiber that is 10 nm in diameter?
Nucleosomes
What is the type of sugar found in DNA nucleotides?
Deoxyribose
What is the bond that holds the two strands of DNA together?
Hydrogen bond
What is the direction of the sugar-phosphate backbone in a DNA molecule?
Both 5’ to 3’ and 3’ to 5’
What is the purpose of the nitrogenous bases in DNA?
To encode hereditary information
What is the base pairing rule described by Watson and Crick?
Adenine pairs with thymine, and guanine pairs with cytosine
What is the term for the equal number of A and T bases, and G and C bases in any species?
Chargaff’s rule
What is the shape of the DNA molecule described by Watson and Crick?
Double helix
What is the function of the phosphate group in a DNA nucleotide?
To form a phosphodiester bond with the sugar molecule
What is the primary function of DNA polymerases during replication?
To proofread and correct mismatched nucleotides
What type of DNA damage is caused by UV light and X-rays?
Radiation damage
What is the primary function of mismatch repair (MMR)?
To correct errors during DNA replication
What is the name of the process by which DNA polymerases correct mismatched nucleotides during replication?
Proofreading
What is the term for the type of DNA lesion that is repaired by nucleotide excision repair (NER)?
Bulky helix-distorting lesions
What is the direction of the exonuclease activity of DNA polymerases during proofreading?
3'→5'
What is the primary function of base excision repair (BER)?
To remove small non-helix distorting DNA lesions
What is the result of DNA polymerases' proofreading and exonuclease activity during replication?
Removal of mismatched nucleotides
What is the main consequence of Xeroderma pigmentosum?
Increased susceptibility to skin cancers
What is the type of DNA damage caused by UV light?
Thymine dimers
Which repair mechanism is responsible for repairing thymine dimers?
Nucleotide excision repair (NER)
What is the genetic disorder caused by a mutation in the genes encoding for the NER repair enzymes?
Xeroderma pigmentosum
Which type of DNA damage is repaired by the MMR repair mechanism?
Mismatched bases
What is the type of DNA repair mechanism that is inactive in Xeroderma pigmentosum patients?
Nucleotide excision repair (NER)
What is the result of the inactivation of the NER repair mechanism in Xeroderma pigmentosum patients?
Increased susceptibility to skin cancers
Which type of DNA damage is caused by chemicals?
Chemical modification of bases
What is the result of DNA replication according to the semiconservative model?
Each daughter molecule has 1 old strand and 1 newly synthesized strand.
What is the purpose of origins of replication in DNA replication?
To initiate the synthesis of a new strand.
How many origins of replication can a eukaryotic chromosome have?
Hundreds or thousands.
What is the direction of replication from each origin?
Bidirectional.
What is the structure of the newly synthesized DNA molecule during replication?
A double helix with one old strand and one new strand.
What is the result of the separation of DNA strands during replication?
A replication bubble forms.
What is the significance of the semiconservative model of DNA replication?
It ensures that the genetic information is preserved during DNA replication.
What is the characteristic of DNA replication that makes it a fast and highly accurate process?
It involves multiple enzymes and other proteins.
Test your understanding of the molecular basis of inheritance, including the Watson and Crick model of DNA, chromosome structure and function, and DNA replication. This quiz covers the learning objectives from Campbell Biology Chapter 16, including DNA structure and function, chromatin organization, and the process of DNA replication.
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