Experiments Proving DNA as Genetic Material and Replication

What did Griffith's experiment demonstrate about DNA?

Griffith's experiment showed that non-viral bacteria could be transformed into virulent bacteria when mixed with heat-inactivated s cells(viral bacteria), indicating that DNA carries genetic information.

How did Avery, McCarty, and MacLeod contribute to the understanding of DNA as genetic material?

They demonstrated that DNA could transform nonvirulent bacteria into virulent ones by treating heat-killed S cells with substances that destroy proteins, RNA, or DNA, concluding that DNA was responsible for carrying genetic information.

What was the main finding of the Hershey & Chase experiment?

Hershey & Chase found that DNA, labeled with phosphorus, entered bacterial cells during infection, while protein, labeled with sulfur, did not, confirming that DNA is the genetic material.

What are the three basic chemical components of DNA?

The three basic components of DNA are phosphate, sugar, and nitrogenous base.

What are the purines and pyrimidines in DNA?

Purines (two rings): Adenine (A) and Guanine (G); Pyrimidines (one ring): Thymine (T) and Cytosine (C).

What are Chargaff's rules regarding the chemical content of DNA?

Chargaff's rules state that adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C), maintaining a 1:1 ratio between each pair.

What did Rosalind Franklin's X-ray crystallography studies reveal about DNA?

DNA is a double helix with 10 base pairs per turn.

How does Watson and Crick's model of DNA structure integrate Chargaff's and Franklin's data?

Watson and Crick's model proposed that A pairs with T and G pairs with C in a double helix structure, aligning with Chargaff's ratios and Franklin's helical structure.

What does it mean for the sugar-phosphate backbones of DNA to be antiparallel?

they both go 5 to 3 in opposite directions

What mechanism for DNA replication did Watson and Crick propose?

They suggested that the two strands of DNA unwind and separate, with each strand serving as a template for new DNA synthesis.

What was Arthur Kornberg's contribution to DNA replication?

Kornberg characterized DNA polymerase, the enzyme that catalyzes DNA synthesis, and found it requires a primer and synthesizes DNA in the 5' to 3' direction.

How does DNA replication appear to spread through a chromosome?

DNA replication starts at an origin point and proceeds bidirectionally around the circular chromosome.

What is the role of DNA polymerase III in DNA replication?

DNA polymerase III synthesizes the leading and lagging strands during DNA replication.

What function does helicase serve in DNA replication?

Helicase unwinds and separates the DNA strands at the replication fork.

What does RNAse do during DNA replication?

RNAse removes RNA primers that are laid down during the synthesis of the lagging strand.

What is the function of DNA polymerase I?

DNA polymerase I removes RNA primers and fills in the gaps left by Okazaki fragments.

What does DNA ligase do during DNA replication?

DNA ligase connects the fragments of DNA together after the gaps have been filled.

Why can't both DNA strands be synthesized continuously?

One strand is synthesized continuously (leading strand) while the other (lagging strand) is synthesized in short segments (Okazaki fragments) due to their antiparallel nature.

Describe the process of DNA replication on the leading strand.

the leading strand has an initial RNA primer and a continuous DNA polymerase follow the helicase in the 5 to 3 direction

Describe the process of DNA replication on the lagging strand.

The lagging strand is replicated in short Okazaki fragments, initiated by multiple primers, and each fragment is synthesized in the 5' to 3' direction.

What happens in a growing replication bubble?

In a growing replication bubble, the leading strand is synthesized continuously in the 5' to 3' direction, while the lagging strand is synthesized discontinuously with Okazaki fragments.

What problem arises at the ends of chromosomes during DNA replication?

When the primer is removed at the end of the lagging strand, a gap is left that cannot be filled, leading to chromosome shortening.

What is the role of telomerase in DNA replication?

Telomerase extends the single-stranded region at the ends of chromosomes, allowing for complete replication and preventing chromosome shortening.