Chapter 12 Study Guide

Describe the appearance of DNA in a typical prokaryotic cell.

It has a single, circular DNA molecules that contains nearly all of the cell's genetic information.

What was the key factor that allowed Hershey and Chase to show that DNA alone carried the genetic information of a bacteriophage?

Nearly all of the radioactivity found in the bacteria Hershey and Chase tested was from phosphorus, the marker found in DNA. They concluded that the genetic material of the bacteriophage was DNA, not a protein.

In eukaryotes, nearly all DNA is found in the

nucleus

The diagram below shows the process of DNA

replication

According to Chargaff's rule of base pairing, which of the following is true about DNA?

A=T and C=G

Which of the following researchers used radioactive markers in experiments to show that DNA was the genetic material in cells?

Alfred Hershey and Martha Chase

What is meant by the term 'base pairing'? How is base pairing involved in DNA replication?

Base pairing is the principle that hydrogen bonds form only between certain pairs. In DNA replication, base pairing ensures that the complementary strands produced are identical to the original strands.

Describe the components and structure of a DNA nucleotide

DNA is a long nucleic acid made up of nucleotides. Each nucleotide consists of a 5-carbon sugar called deoxyribose, a phosphate group, and a nitrogenous base. The 4 nitrogenous base are A, G, (purines) C, and T (pyrimidines).

The main enzyme involved in linking individual nucleotides into DNA molecules is

DNA polymerase

Explain the process of replication. When a DNA molecule is replicated, how do the new molecules compare to the original molecule?

During replication, each strand of the double helix serves as a template for the new strand. It is unzipped and DNA polymerase joins individual nucleotides to a produce a new strand. Both new molecules are identical to the original one.

What important clue from Rosalind Franklin's work helped Watson and Crick deelop their model of DNA?

Franklin's X-rays produced the image of the x-shaped pattern, which shows that the strands of DNA are twisted around each other in a helix. The angle of the X suggests that there are 2 strands in the structure and that the nitrogenous bases are near the center of the DNA molecule

Briefly describe the conclusion that could be drawn from the experiments of Frederick Griffith

Frederick Griffith inferred that genetic material could be transferred from one bacterial strain to another and that one type of bacteria can be changed permanently to another, transformation. This transforming factor had to be a gene.

Why is it significant that the two strands of DNA are antiparallel?

The antiparallel strand enable the nitrogenous bases on both strands to come in contact at the center of the molecule.

A nucleotide does NOT contain

amino acid

Before DNA could definitively be know shown to be the genetic material in cells, scientists had to show it could

carry and make copies of information

In prokaryotes, DNA molecules are located in the

cytoplasm

The process by which one strain of bacterium is apparently changed into another strain

transformation

Bacteriophages are

viruses

The bonds that hold the two strands of DNA together come from

weak hydrogen bonds between bases

Explain how Chargaff's rule of base pairing helped Watson and Crick model DNA.

Chargaff's rules suggested that adenine bonds only to thymine and cytosine bonds only to guanine.