Chapter 12 Biology Owens
Why is it good that hydrogen bonds are weak?
Because the ability of the 2 strands to separate is critical to DNA's functions.
What is the independent variable in the Hershey-Chase experiment?
The independent variable was which molecules were radioactive.
What is the process of transformation in relation to Griffith's experiments?
When one type of bacteria (the harmless form) had been changed permanently into another (the disease-causing form).
What is the process in which a cell duplicates its DNA?
replication
How does DNA replication differ in prokaryotic cells and eukaryotic cells?
1. Replication in most prokaryotic cells starts from a single point and proceeds in 2 directions until the entire chromosome is copied. 2. In eukaryotic cells, replication amt begin at dozens or even hundreds of places on the DNA molecule, proceeding in both directions until each chromosome is completely copied.
What is a bacteriophage?
A kind of virus that infects bacteria. It eats the bacteria they infect.
=Which 2 scientists performed the most important experiments relating to Avery's discovery?
Alfred hershey and Martha Chase
What clues did bacterial transformation yield about the gene?
By observing bacterial transformation, Avery and other scientists discovered that the nucleic acid DNA stores and transmits genetic information from one generation of bacteria to the next.
What are thr chemical components of DNA?
DNA is a nucleic acid made up of nucleotides joined into long strands or chains by covalent bonds.
What role does DNA polymerase play in copying DNA?
DNA polymerase is an enzyme that joins individual nucleotides to produce a new strand of DNA.
In 1928, which British scientist was trying to figure out how bacteria make people sick?
Frederick Griffith
How did Watson and Crick come up with the idea of the double helix?
From seeing Franklin's picture from X-ray diffraction.
What is a summary of Griffith's experiments?
Griffith injected mice with four different samples of bacteria. When injected separately, neither heatkilled, disease-causing bacteria nor live, harmless bacteria killed the mice. The two strains injected together, however, caused fatal pneumonia. From this experiment, Griffi th inferred that genetic information could be transferred from one bacterial strain to another.
In Griffith's first experiment, what did he do to the S strain?
He heated the cells to kill them, then injected the heat-killed bacteria into laboratory mice.
In Griffith's second experiment, what did he mix?
He mixed the heat-killed S-strain bacteria with live, harmless bacteria from the R strain.
Who studied a bacteriophage that was composed of a DNA core and a protein coat?
Hershey and Chase
Summarize the Hershey-Chase experiment.
Hershey and Chase used different radioactive markers to label the DNA and proteins of bacteriophages. The bacteriophages injected only DNA, not proteins, into bacterial cells.
What role did bacterial viruses play in identifying genetic material?
Hershey and Chase's experiment with bacteriophages confirmed Avery's results, convincing many scientists that DNA was the genetic material found in genes - not just in viruses and bacteria, but in all living cells.
What does base pairing in the double helix explain?
How DNA can be copied, or replicated, because each base on one strand pairs with one - and only one - base on the opposite strand.
Who was the Canadian biologist that led the experiment which wanted to determine which molecule in the heat-killed bacteria was most important for transformation?
Oswald Avery
Who began to study DNA in the early 1950s?
Rosalind Franklin
What are nucleic acids made up of?
Smaller subunits, linked together to form long chains.
What does replication ensure?
That each resulting cell has the same complete set of DNA molecules.
What happens during replication?
The DNA molecule seperates into 2 strands and then produces two new complementary strands following the rules of base pairing.
What is the role of DNA in heredity?
The DNA that makes up genes must be capable of storing, copying, and transmitting the genetic information in a cell.
What clues helped scientists solve the structure of DNA?
The clues in Franklin's X-ray pattern enabled Watson and Crick to build a model that explained the specific structure and properties.
What does the double-helix model tell us about DNA?
The double-helix model explains Chargaff's rule of base pairing and how the 2 strands of DNA are held together.
What is the role of enzymes in DNA replication?
The enzymes first "unzip" a molecule of DNA by breaking the hydrogen bonds between base pairs and unwinding the strands of the molecule. Each strand then serves as a template for the attachment of complementary bases.
What is the result of DNA replication?
The result is 2 DNA molecules identical to each other and to the original molecule. Each DNA molecule resulting from replication has one original strand and one new strand.
What is the dependent variable in the Hershey-Chase experiment?
Their dependent variable was whether or not the bacteria is radioactive.
What do the nitrogenous bases absorb?
UV light
What did Hershey and Chase want to determine in their experiments?
Which part of the virus-the protein coat or the DNA core -- entered the bacterial cell.
What technique did Franklin use to get information about the structure of the DNA molecule?
X-ray diffraction
What was the transforming factor in Griffith's experiments?
a gene
What do nucelotides made up of?
a phosphate group, deoxyribose (sugar), and a nitrogenous base.
What are the 4 nitrogenous bases?
adenine, guanine, thymine, cytosine.
How does telomerarse solve the problem of slow telomere replication?
by adding short, repeated DNA sequences to the telomeres.
What bonds form between certain nitrogenous bases?
hydrogen bonds
How do the two strands of the double helix run?
in opposite directions, or antiparallel
In the Hershey and Chase experiment, nearly all of the radioactivity in the bacteria was from what? (phosphorus or sulfur)
phosphorus (P32)
What is base pairing?
principle that bonfd in DNA can form only between adenine and thymine and between guanine and cytosine.
What is the enzyme cells use becasue telomeres are difficult to replicate?
telomerarse
What are DNA at the tips of chromosomes called?
telomeres
Which part of the virus did Hershey and Chase want to determine entered the cell?
the protein coat or the DNA coat
What produce new bacteriophages?
viral genes