DNA Replication and Gene Expression Notes

Flashcards about DNA, replication, and gene expression that cover from Hershey and Chase experiment, Additional Evidence That DNA Is the Genetic Material Furthermore, Building a Structural Model of DNA: Scientific Inquiry, the double helix, replication, repair, and more.

What was the conclusion of the Hershey and Chase experiment regarding DNA?

Hershey and Chase concluded that the DNA injected by the phage must be the molecule carrying the genetic information that makes the cells produce new viral DNA and proteins.

What did Erwin Chargaff do in his experiment?

Analyzed the base composition of DNA from a number of different organisms. Reported that the base composition of DNA varies from one species to another.

What are Chargaff's rules?

(1) DNA base composition varies between species, and (2) for each species, the percentages of A and T bases are roughly equal, as are those of G and C bases.

Who first came up with the complete answer regarding the structure of DNA?

American James Watson and the Englishman Francis Crick.

What does each DNA nucleotide monomer consist of?

A nitrogenous base (T, A, C, or G), the sugar deoxyribose, and a phosphate group.

In the Watson model, what does antiparallel mean?

The two sugar-phosphate backbones are antiparallel-that is, their subunits run in opposite directions.

What are the nitrogenous bases of the double helix paired with?

Adenine (A) with thymine (T), and guanine (G) with cytosine (C).

What did the Watson-Crick model take into account?

Wherever one strand of a DNA molecule has an A, the partner strand has a T. Similarly, a G in one strand is always paired with a C in the complementary strand.

When a cell copies a DNA molecule, what does each strand serve as?

Each strand serves as a template for ordering nucleotides into a new, complementary strand.

What does Watson and Crick's model predict?

Each of the two daughter molecules will have one old strand, from the parental molecule, and one newly made strand.

What are the three models of DNA replication?

A conservative model, a semiconservative model, and a dispersive model.

What happens in the dispersive model?

All four strands of DNA following replication have a mixture of old and new DNA.

What happens in the semiconservative model?

The two strands of the parental molecule separate, and each functions as a template for synthesis of a new, complementary strand.

What happens in the conservative model?

The two parental strands reassociate after acting as templates for new strands, thus restoring the parental double helix.

Who devised a clever experiment that distinguished between the three models of DNA replication?

Matthew Meselson and Franklin Stahl.

What is remarkable about the copying of DNA?

The copying of DNA is remarkable in its speed and accuracy.

How replication of chromosomal DNA starts?

Proteins that initiate DNA replication recognize this sequence and attach to the DNA, separating the two strands and opening up a replication “bubble”. proceeds in both directions until the entire molecule is copied.

Which proteins participate in the unwinding?

The unwinding (Figure 16.13). Helicases are enzymes that untwist the double helix at the replication forks.

What is an important characteristic of DNA polymerases?

DNA polymerases cannot initiate the synthesis of a polynucleotide; they can only add DNA nucleotides to the end of an already existing chain that is base-paired with the template strand.

How does the DNA polymerase catalyze the addition of each monomer?

DNA polymerase catalyzes the addition of each monomer via a dehydration reaction.

What is important information to know about DNA polymerases?

DNA polymerases can add nucleotides only to the free 3' end of a primer or growing DNA strand, never to the 5' end.

What are segments of the lagging strand called?

Okazaki fragments.

What joins RNA nucleotides into a primer?

Primase joins RNA nucleotides into a primer.

After the double helix, what other inspiration that Watson and Crick have had?

There is specific pairing of nitrogenous bases in DNA.

What happens during DNA replication?

During DNA replication, many DNA polymerases proofread each nucleotide against its template as soon as it is covalently bonded to the growing strand.

What happens during mismatch repair?

In mismatch repair, other enzymes remove and replace incorrectly paired nucleotides that have resulted from replication errors.

Base pair amounts are equivalent confirmed by..?

The amounts are exactly equal using modern DNA sequencing techniques.

In many cases from DNA damage, what occurs?

A segment of the strand containing the damage is cut out (excised) by a DNA-cutting enzyme—a nuclease-and the resulting gap is then filled in with nucleotides, using the undamaged strand as a template.

One such DNA repair system is called..?

Nucleotide excision repair.

What is an important function of DNA repair enzymes in skin cells?

Repair genetic damage caused by the ultraviolet rays of sunlight.

Once a mismatched nucleotide pair replicated, what happens?

Once a mismatched nucleotide pair is replicated, the sequence change is permanent.

What sequences are found at eukaryotic chromosomal DNA molecules?

Telomeres at their ends (Figure 16.21). Telomeres do not contain genes; instead, the DNA typically consists of multiple repetitions of one short nucleotide sequence.

Telomeres have repetitive sequences, what is an example?

One short nucleotide sequence. In each human telomere, for example, the six-nucleotide sequence TTAGGG is repeated between 100 and 1,000 times.

What does telomerase do?

Telomerase catalyzes the lengthening of telomeres in eukaryotic germ cells, thus restoring their original length and compensating for the shortening that occurs during DNA replication.

What is a gene?

A region of DNA that can be expressed to produce a final functional product that is either a polypeptide or an RNA molecule.

Explain DNA replication or cloning.

Isolate the DNA to get a recombinant, then put it into a plasmid, then the host cell replicates and divides the copy.

What is true about the polymerase chain reaction?

PCR is speedy and very specific.

What was the conclusion of the Hershey and Chase experiment regarding DNA?

Discuss the experimental design and results obtained by Hershey and Chase. How did their findings contribute to the understanding of DNA as the carrier of genetic information?

What did Erwin Chargaff do in his experiment?

Explain Erwin Chargaff's contributions to the study of DNA composition. How did his findings challenge the tetranucleotide hypothesis, and what significance did his rules have in determining DNA structure?

What are Chargaff's rules?

Describe Chargaff's rules and explain their significance in the context of DNA structure. How do these rules relate to the base pairing observed in the double helix?

Who first came up with the complete answer regarding the structure of DNA?

Outline the key steps and reasoning that led Watson and Crick to develop their model of DNA structure. What were some of the critical experimental findings and insights they relied upon?

What does each DNA nucleotide monomer consist of?

Describe the components of a DNA nucleotide monomer, including the nitrogenous base, sugar, and phosphate group. How do these components link together to form a DNA strand?

In the Watson model, what does antiparallel mean?

Explain the concept of antiparallelism in the Watson-Crick model of DNA. Why is the antiparallel arrangement important for DNA structure and function?

What are the nitrogenous bases of the double helix paired with?

Describe the specific base pairing rules in the DNA double helix. Explain the significance of these pairings in maintaining the structural integrity of DNA and in DNA replication.

What did the Watson-Crick model take into account?

Explain how the Watson-Crick model accounts for the observed base pairing ratios in DNA. How does the model explain the complementary nature of DNA strands?

When a cell copies a DNA molecule, what does each strand serve as?

Discuss the role of each strand of DNA as a template during DNA replication. How does this process ensure the accurate transmission of genetic information?

What does Watson and Crick's model predict?

Describe the prediction made by Watson and Crick's model regarding the composition of daughter molecules after DNA replication. How does this relate to the concept of semiconservative replication?

What are the three models of DNA replication?

Compare and contrast the three models of DNA replication: conservative, semiconservative, and dispersive. What are the key differences between them?

What happens in the dispersive model?

Explain the distribution of old and new DNA strands in the dispersive model of DNA replication. How does this model differ from the semiconservative model?

What happens in the semiconservative model?

Describe the semiconservative model of DNA replication and discuss its experimental evidence. How does this model ensure genetic continuity between generations?

What happens in the conservative model?

Explain the conservative model of DNA replication and discuss why it does not accurately describe the process of DNA replication in cells.

Who devised a clever experiment that distinguished between the three models of DNA replication?

Describe the experimental design used by Meselson and Stahl to distinguish between the three models of DNA replication. What were the key steps and observations that led them to support the semiconservative model?

What is remarkable about the copying of DNA?

Discuss the significance of speed and accuracy in DNA replication. What mechanisms ensure that DNA is copied efficiently and with minimal errors?

How replication of chromosomal DNA starts?

Explain the process of initiation of DNA replication in chromosomal DNA. How do proteins recognize and bind to the origin of replication, and what events follow?

Which proteins participate in the unwinding?

Describe the function of helicases in DNA replication. How do these enzymes contribute to the unwinding of the double helix at the replication forks?

What is an important characteristic of DNA polymerases?

Discuss the limitations of DNA polymerases in initiating DNA synthesis. How do they rely on pre-existing chains, and what implications does this have for DNA replication?

How does the DNA polymerase catalyze the addition of each monomer?

Explain how DNA polymerase catalyzes the addition of each monomer during DNA replication. What type of chemical reaction is involved?

What is important information to know about DNA polymerases?

Describe the directionality of DNA synthesis by DNA polymerases. Why can nucleotides only be added to the free 3' end of a primer or growing DNA strand?

What are segments of the lagging strand called?

Define Okazaki fragments and explain why they are formed during DNA replication. What is their role in the synthesis of the lagging strand?

What joins RNA nucleotides into a primer?

Describe the role of primase in DNA replication. How does it contribute to the initiation of DNA synthesis, and what type of molecule does it synthesize?

After the double helix, what other inspiration that Watson and Crick have had?

Explain the significance of specific base pairing of nitrogenous bases in DNA, as inspired by the Watson-Crick model. How does this pairing contribute to DNA stability and replication accuracy?

What happens during DNA replication?

Outline the process of proofreading during DNA replication. How do DNA polymerases ensure the accuracy of newly synthesized DNA strands?

What happens during mismatch repair?

Describe the mechanism of mismatch repair in DNA. How do enzymes identify and correct incorrectly paired nucleotides that arise from replication errors?

Base pair amounts are equivalent confirmed by..?

Explain how modern DNA sequencing techniques have confirmed the equivalence of base pair amounts in DNA. What implications does this have for our understanding of DNA structure?

In many cases from DNA damage, what occurs?

Describe the process of DNA excision repair. How do nucleases and other enzymes remove and replace damaged segments of DNA strands?

One such DNA repair system is called..?

Explain the process of nucleotide excision repair and its importance in maintaining genomic stability. What types of DNA damage does this repair system target?

What is an important function of DNA repair enzymes in skin cells?

Discuss the role of DNA repair enzymes in protecting skin cells from damage caused by ultraviolet rays of sunlight. What types of DNA lesions are commonly repaired in these cells?

Once a mismatched nucleotide pair replicated, what happens?

Explain the consequences of replicating a mismatched nucleotide pair without repair. How can such errors lead to permanent sequence changes and mutations?

What sequences are found at eukaryotic chromosomal DNA molecules?

Describe the sequences found at the ends of eukaryotic chromosomal DNA molecules, known as telomeres. What is their composition and function?

Telomeres have repetitive sequences, what is an example?

Explain the nature of repetitive sequences in telomeres and provide an example. What role do these sequences play in maintaining chromosome stability?

What does telomerase do?

Describe the function of telomerase in eukaryotic germ cells. How does telomerase prevent telomere shortening during DNA replication, and why is this important for cell survival?

What is a gene?

Define a gene in molecular terms. How can a region of DNA be expressed to produce a functional product, such as a polypeptide or RNA molecule?

Explain DNA replication or cloning.

Outline the steps involved in DNA replication or cloning. How is DNA isolated, combined into a recombinant molecule, and replicated in a host cell?

Discuss the advantages and applications of the polymerase chain reaction (PCR).