Chapter 16 Flashcards
(139 cards)
1
Q
What is the main concept discussed in Concept 16.1?
A
DNA is the genetic material
This concept highlights the identification of DNA as the hereditary molecule.
2
Q
Who showed that genes are located on chromosomes?
A
T. H. Morgan’s group
Their work established a critical link between genes and chromosomes.
3
Q
What are the two components of chromosomes that became candidates for the genetic material?
A
- DNA
- Protein
This distinction was crucial in understanding the molecular basis of inheritance.
4
Q
What was the initial source of evidence for DNA’s role in heredity?
A
Studies of bacteria and the viruses that infect them
This research laid the groundwork for later discoveries about DNA.
5
Q
Who conducted the research that began to uncover the genetic role of DNA?
A
Frederick Griffith
His experiments in 1928 were pivotal in demonstrating DNA’s function in heredity.
6
Q
Which two strains of bacteria did Griffith work with?
A
- Pathogenic (S strain)
- Nonpathogenic (R strain)
The differences between these strains were key to Griffith’s experiments.
7
Q
True or False: The S strain of Griffith’s bacteria is harmless.
A
False
The S strain is pathogenic, while the R strain is nonpathogenic.
8
Q
What is the term for microorganisms that can cause disease?
A
pathogenic
Pathogenic refers to organisms that can lead to illness or disease in a host.
9
Q
What is a variant of a species, often used in the context of microorganisms?
A
strain
A strain is a genetic variant or subtype of a microorganism.
10
Q
What experiment involved heat-killed S strain and live R strain to demonstrate transformation?
A
Figure 16.2 Transformation
This experiment showed that living R cells could transform into pathogenic S cells when mixed with heat-killed S cells.
11
Q
What were the results when living S cells were introduced to a mouse?
A
Mouse dies
Living S cells are pathogenic and can lead to the death of the host.
12
Q
What were the results when living R cells were introduced to a mouse?
A
Mouse healthy
Living R cells are nonpathogenic and do not harm the host.
13
Q
What substance was identified by Oswald Avery, Maclyn McCarty, and Colin MacLeod as the transforming factor?
A
DNA
Their work provided evidence that DNA is the genetic material responsible for transformation.
14
Q
What type of viruses infect bacteria?
A
bacteriophages (or phages)
Bacteriophages are specific to bacteria and have been used extensively in genetic research.
15
Q
What is the structure of a virus?
A
DNA (sometimes RNA) enclosed by a protective coat
This protective coat is often made of protein.
16
Q
What has been widely used as tools by researchers in molecular genetics?
A
Phages
Bacteriophages serve as essential tools for genetic manipulation and study.
17
Q
True or False: Many biologists were initially skeptical about DNA being the genetic material.
A
True
Skepticism was due to the limited knowledge about DNA at the time.
18
Q
Who showed that DNA is the genetic material of the phage known as T2?
A
Alfred Hershey and Martha Chase
Their experiment was pivotal in molecular biology.
19
Q
What year did Hershey and Chase conduct their experiment?
A
1952
This experiment is a landmark study in genetics.
20
Q
What was the main finding of the Hershey-Chase experiment?
A
Only one of the two components of T2 (DNA or protein) enters an E. coli cell during infection
This finding indicated that DNA carries genetic information.
21
Q
What conclusion did Hershey and Chase reach regarding the injected component of the phage?
A
The injected DNA of the phage provides the genetic information
This conclusion was critical in establishing DNA as the genetic material.
22
Q
Fill in the blank: The phage studied by Hershey and Chase is known as _______.
A
T2
T2 is a bacteriophage that infects E. coli.
23
Q
True or False: The Hershey-Chase experiment demonstrated that proteins carry genetic information.
A
False
The experiment showed that DNA, not protein, is the carrier of genetic information.
24
Q
What was the main focus of the Hershey-Chase experiment?
A
To determine whether DNA or protein is the genetic material
25
What are the components of a nucleotide?
A nitrogenous base, a sugar, and a phosphate group
26
List the nitrogenous bases found in DNA.
* Adenine (A)
* Thymine (T)
* Guanine (G)
* Cytosine (C)
27
Who reported that DNA composition varies between species?
Erwin Chargaff
28
True or False: DNA is a polymer of amino acids.
False
29
Fill in the blank: In 1950, Erwin Chargaff found that DNA composition varies from one _______ to the next.
[species]
30
What did the molecular diversity among organisms suggest about DNA?
It made DNA a more credible candidate for the genetic material
31
What type of experiment did Hershey and Chase conduct?
A blender experiment
32
What are Chargaff's rules?
1. In any species, the number of A and T bases is equal. 2. The number of G and C bases is equal.
## Footnote
Chargaff's rules highlight the specific pairing of nucleobases in DNA.
33
How does the base composition of DNA vary?
It varies between species.
## Footnote
Different species have different proportions of nucleobases in their DNA.
34
What discovery clarified the basis for Chargaff's rules?
The discovery of the double helix structure of DNA.
## Footnote
Watson and Crick's model of DNA structure provided the framework for understanding base pairing.
35
Which bases are represented by the letter A in DNA?
Adenine.
## Footnote
Adenine pairs with Thymine (T) in the DNA structure.
36
Which base pairs with Cytosine (C) in DNA?
Guanine (G).
## Footnote
G and C pair together according to Chargaff's rules.
37
Fill in the blank: The number of _______ bases is equal to the number of Thymine (T) bases in any species.
Adenine (A)
38
Fill in the blank: The number of _______ bases is equal to the number of Cytosine (C) bases in any species.
Guanine (G)
39
Who discovered the double helix structure of DNA?
Watson and Crick.
## Footnote
Their work was pivotal in molecular biology.
40
What is the significance of the phosphate groups in DNA and RNA?
They are part of the backbone structure of both DNA and RNA.
## Footnote
The phosphate groups connect the sugar molecules in the nucleic acid structure.
41
What does the notation 3' indicate in the context of DNA and RNA?
It refers to the directionality of the nucleic acid strands.
## Footnote
The 3' end of a DNA strand has a hydroxyl group attached to the 3rd carbon of the sugar.
42
What was the challenge after DNA was accepted as the genetic material?
To determine how its structure accounts for its role in inheritance
## Footnote
Understanding the relationship between structure and function in DNA was crucial for genetics.
43
Which technique did Maurice Wilkins and Rosalind Franklin use to study molecular structure?
X-ray crystallography
## Footnote
This technique allows scientists to visualize the arrangement of atoms in a molecule.
44
What significant contribution did Rosalind Franklin make to the study of DNA?
She produced a picture of the DNA molecule using X-ray crystallography
## Footnote
This image was critical for understanding the structure of DNA.
45
What did Franklin's X-ray crystallographic images allow James Watson to deduce about DNA?
That DNA was helical
## Footnote
The helical structure is key to understanding DNA's function in heredity.
46
What specific measurements could Watson deduce from the X-ray images of DNA?
The width of the helix and the spacing of the nitrogenous bases
## Footnote
These measurements were vital for constructing the accurate model of DNA.
47
What pattern did the X-ray diffraction photograph suggest about the DNA molecule?
That the DNA molecule was made up of two strands, forming a double helix
## Footnote
The double helix structure is fundamental to DNA's stability and replication.
48
How did Watson and Crick initially think the bases paired?
They thought bases paired like with like (A with A, etc.)
## Footnote
This initial thought was later proven incorrect as it did not result in a uniform width.
49
What type of pairing resulted in a uniform width consistent with X-ray data?
Pairing a purine (A or G) with a pyrimidine (C or T)
## Footnote
This pairing provided the structural consistency needed for the DNA model.
50
What did Watson and Crick reason about base pairing?
The pairing was more specific, dictated by the base structures
## Footnote
This specificity suggests that certain bases only pair with designated counterparts.
51
Which bases pair together according to Watson and Crick?
* Adenine (A) pairs with Thymine (T)
* Guanine (G) pairs with Cytosine (C)
## Footnote
This pairing is essential for the structure of DNA.
52
What do Chargaff's rules state?
In any organism, the amount of A = T, and the amount of G = C
## Footnote
Chargaff's rules reflect the base pairing specificity observed by Watson and Crick.
53
What type of bonds hold nitrogenous base pairs together?
Hydrogen bonds
## Footnote
These bonds are crucial for the stability of the DNA structure.
54
What is the basic principle of DNA replication?
Base pairing to a template
## Footnote
Each strand of DNA acts as a template for building a new strand.
55
What does each strand of DNA yield during replication?
Two exact replicas of the 'parental' molecule
## Footnote
This occurs because the strands are complementary.
56
What model of DNA replication did Watson and Crick propose?
Semiconservative model
## Footnote
This model predicts that each daughter molecule has one old strand and one newly made strand.
57
In the semiconservative model, what does each daughter molecule contain?
One old strand and one newly made strand
## Footnote
The old strand is derived from the parent molecule.
58
What are the two competing models of DNA replication?
* Conservative model
* Dispersive model
## Footnote
The conservative model suggests both parent strands rejoin, while the dispersive model indicates each strand is a mix of old and new.
59
Fill in the blank: Each strand of DNA acts as a _______ for building a new strand in replication.
template
60
True or False: In the dispersive model, each strand consists entirely of either old or new DNA.
False
## Footnote
In the dispersive model, each strand is a mix of old and new DNA.
61
What type of replication model was supported by experiments conducted by Matthew Meselson and Franklin Stahl?
Semiconservative model
## Footnote
The semiconservative model indicates that each new DNA molecule consists of one old strand and one new strand.
62
What was disproven by the experiments conducted by Meselson and Stahl?
Other replication models
## Footnote
The experiments provided evidence against alternative models of DNA replication.
63
What is the significance of the semiconservative model in DNA replication?
It shows that each daughter DNA molecule contains one parental strand and one newly synthesized strand
## Footnote
This model contrasts with conservative and dispersive models.
64
Fill in the blank: The _______ model of DNA replication was proven by Meselson and Stahl's experiments.
semiconservative
65
True or False: The experiments by Meselson and Stahl supported multiple models of DNA replication.
False
## Footnote
The experiments specifically supported the semiconservative model and disproved others.
66
What are the sites called where replication begins?
Origins of replication
## Footnote
These are specific locations on the DNA where the two strands separate to initiate the replication process.
67
How many origins of replication can a eukaryotic chromosome have?
Hundreds or even thousands
## Footnote
This allows for efficient replication of large eukaryotic genomes.
68
In which directions does replication proceed from each origin?
Both directions
## Footnote
This bidirectional replication helps to ensure that the entire DNA molecule is copied quickly.
69
What is formed when the two DNA strands are separated at the origins of replication?
Replication bubble
## Footnote
This structure allows the replication machinery to access the single strands of DNA.
70
What are the two types of DNA molecules mentioned?
* Circular DNA
* Linear DNA
## Footnote
These refer to the structural forms of DNA found in prokaryotic and eukaryotic cells, respectively.
71
What are the parental strands in DNA replication?
Template strands
## Footnote
These are the original DNA strands used as templates for synthesizing new daughter strands.
72
What do you call the new strands synthesized during DNA replication?
Daughter strands
## Footnote
These are the newly formed DNA strands that complement the parental strands.
73
What is the term for the area where the DNA strands are actively being unwound and replicated?
Replication fork
## Footnote
This is the Y-shaped region where the double helix is separated into two single strands.
74
True or False: Replication occurs only in one direction from each origin.
False
## Footnote
Replication proceeds in both directions from each origin.
75
What is a replication fork?
A Y-shaped region where parental DNA strands are being unwound
## Footnote
It is found at the end of each replication bubble.
76
What is the function of helicases?
Enzymes that untwist the double helix at the replication forks
## Footnote
They are essential for unzipping the DNA strands.
77
What do single-strand binding proteins do?
Bind to and stabilize single-stranded DNA
## Footnote
This prevents the strands from re-annealing during replication.
78
What role does topoisomerase play in DNA replication?
Relieves the strain of twisting of the double helix by breaking, swiveling, and rejoining DNA strands
## Footnote
It helps prevent supercoiling during the unwinding process.
79
What enzyme catalyzes the synthesis of new DNA at a replication fork?
DNA polymerases
## Footnote
They are crucial for DNA replication.
80
What do DNA polymerases require to add nucleotides?
A primer
## Footnote
This is necessary for initiating the synthesis of new DNA.
81
What is the initial nucleotide chain in DNA replication?
A short RNA primer
## Footnote
This primer is crucial for the starting point of DNA synthesis.
82
Which enzyme synthesizes the RNA primer?
Primase
## Footnote
It lays down the RNA primer that DNA polymerases extend.
83
From which end of the RNA primer does the new DNA strand start?
3' end
## Footnote
DNA synthesis occurs in the 5' to 3' direction.
84
What is the direction in which a new DNA strand can elongate?
5' → 3'
## Footnote
This directionality is critical for DNA replication.
85
What type of structure does the double helix of DNA have?
Antiparallel
## Footnote
The antiparallel structure is significant for replication processes.
86
What do DNA polymerases add nucleotides to?
Free 3' end
## Footnote
DNA polymerases can only synthesize DNA by adding nucleotides to the 3' end.
87
What is synthesized continuously along one template strand during DNA replication?
Leading strand
## Footnote
The leading strand is synthesized in the same direction as the replication fork.
88
True or False: DNA polymerases can add nucleotides to the 5' end of a growing strand.
False
## Footnote
DNA polymerases can only add nucleotides to the free 3' end.
89
What is the role of the replication fork in DNA replication?
It is the area where DNA strands are unwound for replication
## Footnote
The replication fork is crucial for the synthesis of new DNA strands.
90
Fill in the blank: DNA polymerases synthesize a leading strand continuously, moving toward the _______.
Replication fork
## Footnote
This movement allows for efficient DNA replication.
91
What is the direction of synthesis for the lagging strand during DNA replication?
Away from the replication fork
## Footnote
This is due to the antiparallel nature of DNA strands.
92
What are the segments called that make up the lagging strand?
Okazaki fragments
## Footnote
These fragments are later joined together by DNA ligase.
93
What enzyme is responsible for joining Okazaki fragments?
DNA ligase
## Footnote
DNA ligase connects the short DNA segments on the lagging strand.
94
What is the primary role of DNA polymerase in DNA replication?
To synthesize new DNA strands
## Footnote
DNA polymerase adds nucleotides to the growing DNA chain.
95
Fill in the blank: The new strand synthesized in the direction toward the replication fork is called the _______.
leading strand
96
True or False: The lagging strand is synthesized continuously.
False
## Footnote
The lagging strand is synthesized in short segments.
97
What is the function of Helicase in bacterial DNA replication?
Unwinds parental double helix at replication forks
## Footnote
Helicase is essential for initiating DNA replication by separating the two strands of DNA.
98
What role does the Single-strand binding protein play during DNA replication?
Binds to and stabilizes single-stranded DNA until it is used as a template
## Footnote
This protein prevents the single strands from re-annealing or forming secondary structures.
99
What is the function of Topoisomerase in DNA replication?
Relieves overwinding strain ahead of replication forks by breaking, swiveling, and rejoining DNA strands
## Footnote
Topoisomerase is crucial for preventing supercoiling of DNA.
100
What does Primase do in the DNA replication process?
Synthesizes an RNA primer at the 5' end of the leading strand and at the 5' end of each Okazaki fragment of the lagging strand
## Footnote
Primase is necessary for providing a starting point for DNA synthesis.
101
How does DNA polymerase I function in DNA replication?
Uses parental DNA as a template to synthesize a new DNA strand by adding nucleotides to an RNA primer or a pre-existing DNA strand
## Footnote
DNA polymerase I also plays a role in removing RNA primers.
102
What is the function of DNA ligase during DNA replication?
Joins Okazaki fragments of the lagging strand on leading strand, connects 3' end of DNA that replaces primer to the rest of leading strand DNA
## Footnote
DNA ligase is essential for completing the DNA strand after replication.
103
What is a DNA replication machine?
A large complex formed by the proteins that participate in DNA replication
## Footnote
This complex coordinates the various steps of DNA replication efficiently.
104
True or False: The DNA replication machine is stationary during the replication process.
True
## Footnote
Recent studies suggest that the DNA replication machine may remain in place while DNA is being synthesized.
105
What do DNA polymerase molecules do during DNA replication?
Reel in parental DNA and extrude newly made daughter DNA molecules
## Footnote
This mechanism helps in efficiently synthesizing the new DNA strands.
106
Fill in the blank: The exact __________ of the DNA replication mechanism is not yet resolved.
mechanism
## Footnote
Ongoing research is focused on understanding the precise processes involved in DNA replication.
107
What is the function of helicase in bacterial DNA replication?
Unwinds parental double helix at replication forks
## Footnote
Helicase is essential for separating the two strands of DNA to allow replication to occur.
108
What role does the single-strand binding protein play during DNA replication?
Binds to and stabilizes single-stranded DNA until it is used as a template
## Footnote
This protein prevents the single strands from re-annealing or forming secondary structures.
109
What is the function of topoisomerase in DNA replication?
Relieves overwinding strain ahead of replication forks by breaking, swiveling, and rejoining DNA strands
## Footnote
Topoisomerase is crucial for managing the supercoiling of DNA that occurs during replication.
110
What does primase do in the context of DNA replication?
Synthesizes an RNA primer at the 5' end of the leading strand and at the 5' end of each Okazaki fragment of the lagging strand
## Footnote
Primase provides the starting point for DNA synthesis.
111
What is the function of DNA polymerase III in DNA replication?
Using parental DNA as a template, synthesizes new DNA strand by adding nucleotides to an RNA primer or a pre-existing DNA strand
## Footnote
DNA polymerase III is the primary enzyme involved in prokaryotic DNA replication.
112
What is the role of DNA ligase during DNA replication?
Joins Okazaki fragments of the lagging strand; on the leading strand, joins 3' end of DNA that replaces primer to rest of leading strand DNA
## Footnote
DNA ligase is essential for sealing nicks in the sugar-phosphate backbone of DNA.
113
Fill in the blank: _______ synthesizes an RNA primer at the 5' end of the leading strand.
Primase
114
True or False: Topoisomerase is responsible for synthesizing new DNA strands.
False
## Footnote
Topoisomerase's role is to relieve strain, not to synthesize DNA.
115
What are the two main roles of DNA polymerase I?
Removes RNA nucleotides or primer from 5' end and replaces them with DNA nucleotides added to 3' end of adjacent fragment
## Footnote
DNA polymerase I also has proofreading capabilities.
116
What is the role of DNA polymerases?
Proofread newly made DNA and replace any incorrect nucleotides
## Footnote
DNA polymerases are essential for maintaining the integrity of the genetic code during DNA replication.
117
What is mismatch repair of DNA?
Repair enzymes replace incorrectly paired nucleotides that have evaded the proofreading process
## Footnote
This mechanism helps prevent mutations from becoming permanent in the DNA sequence.
118
What can damage DNA?
Harmful chemical or physical agents such as cigarette smoke and X-rays; spontaneous changes
## Footnote
Understanding the sources of DNA damage is crucial for cancer prevention and treatment.
119
What is nucleotide excision repair?
A process where a nuclease cuts out and replaces damaged stretches of DNA
## Footnote
This repair mechanism is vital for fixing bulky DNA lesions that can interfere with replication.
120
What condition is associated with an inability to repair thymine dimers?
Xeroderma pigmentosum
## Footnote
Individuals with this condition are at a much higher risk of developing skin cancer upon sun exposure.
121
True or False: DNA mutations can arise from spontaneous changes.
True
## Footnote
Mutations can occur naturally during DNA replication or due to environmental factors.
122
Fill in the blank: In mismatch repair, _____ enzymes replace incorrectly paired nucleotides.
repair
## Footnote
This process is crucial for correcting errors that escape the initial proofreading.
123
What is the error rate after proofreading and repair in DNA?
Low but not zero
## Footnote
This indicates that while the DNA replication process is generally accurate, mistakes can still occur.
124
What are sequence changes in DNA that can become permanent called?
Mutations
## Footnote
Mutations are essential for genetic variation and evolution.
125
What is the significance of mutations in evolution?
They are the source of genetic variation upon which natural selection operates and are responsible for the appearance of new species
## Footnote
Mutations can lead to inherited genetic traits and may contribute to conditions like cancer.
126
What happens if chromosomes of germ cells become shorter in every cell cycle?
Essential genes would eventually be missing from the gametes produced
## Footnote
This could have detrimental effects on reproductive success and species survival.
127
What enzyme catalyzes the lengthening of telomeres in germ cells?
Telomerase
## Footnote
Telomerase is often referred to as the immortality enzyme due to its role in maintaining chromosome integrity.
128
Fill in the blank: The enzyme called _______ catalyzes the lengthening of telomeres.
Telomerase
129
What is the state of most chromatin during interphase?
Loosely packed
130
What is the term for loosely packed chromatin?
Euchromatin
131
What regions of chromatin are highly condensed during interphase?
Centromeres and telomeres
132
What is the term for highly condensed chromatin?
Heterochromatin
133
What type of fiber is associated with heterochromatin?
10 nm fiber
134
What is a consequence of the dense packing of heterochromatin?
Difficult for the cell to express genetic information
135
What is a chromosome composed of?
A DNA molecule packed together with proteins
136
What role do histones play in chromatin?
They can undergo chemical modifications
137
What can changes in histone modifications affect?
Gene expression
138
Fill in the blank: During mitosis, chromatin is _______.
condensed
139
True or False: Euchromatin is more accessible for gene expression than heterochromatin.
True
