DNA Structure and Replication Study Guide

These flashcards cover key concepts from the lecture notes on DNA structure and replication, including processes, enzymes, and properties of genetic material.

What properties are required for genetic material?

Genetic material must be able to store information, be stable, replicate accurately, and undergo mutation.

What experiment led to the discovery of transformation?

Frederick Griffith's experiment used Streptococcus pneumoniae to demonstrate that non-virulent bacteria could be transformed into virulent bacteria.

What are the two types of Streptococcus pneumoniae used in Griffith's experiment?

Smooth (S) type, which is virulent, and rough (R) type, which is non-virulent.

What is competence in bacteria?

Competence is the ability of bacteria to take up foreign DNA from their environment.

What effect did live S type bacteria have on mice?

Live S type bacteria caused the death of the mice.

What effect did heat-killed S type bacteria have on mice?

Heat-killed S type bacteria had no effect on the mice and did not cause death.

What effect did live R type bacteria have on mice?

Live R type bacteria had no effect on the mice and did not cause death.

What effect did a combination of live R type and heat-killed S type bacteria have on mice? Why did this effect occur?

The combination caused the mice to die due to transformation; live R types took up DNA from heat-killed S types.

Did Griffith's results support that DNA is the genetic material? Why or why not?

Yes, as they showed that DNA from dead S type could transform R type into virulent S type.

What are nucleic acids made of?

Nucleic acids are made up of subunits called nucleotides.

How are nucleotides connected to form a nucleic acid strand?

Nucleotides are connected by covalent bonds, specifically phosphodiester bonds.

What is the structure of a DNA molecule?

A DNA molecule has a double helix structure made of two strands of nucleotides.

What is the basic structure of a chromosome?

A chromosome consists of a long DNA molecule wrapped around proteins (histones) to form a compact structure.

What is a genome?

A genome is the complete set of genetic material in an organism.

What are the three components of a nucleotide?

A nucleotide consists of a nitrogenous base, a sugar, and a phosphate group.

What sugar is found in deoxyribonucleotides? In ribonucleotides?

Deoxyribonucleotides contain deoxyribose and ribonucleotides contain ribose.

Where are the phosphates attached to the sugar in nucleotides?

Phosphates are attached to the 5’ carbon of the sugar.

What nitrogenous bases are found in DNA?

In DNA, the bases are adenine (A), thymine (T), cytosine (C), and guanine (G).

Which nitrogenous bases are purines? Which are pyrimidines?

Adenine and guanine are purines; cytosine and thymine are pyrimidines.

What type of covalent bond links nucleotides in a strand of DNA?

Phosphodiester bonds link nucleotides together.

What is the difference between the 5’ and 3’ ends of a DNA strand?

The 5’ end has a phosphate group and the 3’ end has a hydroxyl group.

What are complementary base pairs?

Complementary base pairs are pairs of nitrogenous bases that form hydrogen bonds; A pairs with T, and G pairs with C.

What type of bonds hold the complementary strands of DNA together?

Hydrogen bonds hold the complementary strands of DNA together.

How many bonds form between A/T base pairs? Between G/C base pairs?

Two hydrogen bonds form between A and T; three hydrogen bonds form between G and C.

What is semiconservative replication?

Semiconservative replication is the process where each new DNA molecule consists of one old and one new strand.

What is bidirectional replication?

Bidirectional replication means DNA is synthesized in both directions from the origin of replication.

In what direction is DNA synthesized and read during replication?

DNA is synthesized 5’ to 3’ and the template strand is read 3’ to 5’.

What enzyme synthesizes DNA during replication?

DNA polymerase synthesizes DNA during replication.

What is the function of primase?

Primase synthesizes short RNA primers needed for DNA polymerase to initiate synthesis.

What is the function of ligase in DNA replication?

Ligase connects Okazaki fragments on the lagging strand by sealing nicks in the DNA.

What contributes to the fidelity of DNA replication?

The fidelity of DNA replication is contributed by proofreading ability of DNA polymerases and other repair mechanisms.

What is the structure of a prokaryotic chromosome?

A prokaryotic chromosome is typically a single circular DNA molecule that is not associated with histones.

What proteins are used to organize and package the prokaryotic chromosome?

Proteins like HU and IHF help organize and package the prokaryotic chromosome.