Chapter 10.1-10.3 Flashcards
What were the four important characteristics of genetic material that biologists knew it had to contain even before nucleic acids were recognized?
- genetic material must contain complex information - must be capable of storing large amounts of info
- genetic material must replicate with precision and accuracy
- Genetic material (genotype) must encode phenotype
- Genetic material must be able to vary to allow differences in genetic makeup
The genetic material must carry large amounts of info, replicate faithfully, express coding instructions as phenotypes and have the capacity to vary.
Why was the discovery of the structure of DNA so important for understanding genetics?
It was impossible to understand how genetic information was encoded or expressed without first knowing the structure of DNA
Who discovered a material that he named nuclein when he isolated the nuclei in the white blood cells of pus. What was it later renamed?
Johann Friedrich Miescher
Later renamed nucleic acid
Miescher’s nuclein must have consisted of _____ and ____
Miescher’s nuclein must have consisted of DNA and protein
In the late 1800’s, ______ carried out work on the chemistry of DNA and determined that it contains four nitrogenous bases
In the late 1800’s, Kossel (Albrecht) carried out work on the chemistry of DNA and determined that it contains four nitrogenous bases
Who discovered that DNA consists of large number of linked, repeating units called nucleotides?
Pheobus Aaron Levene
Levine came up with what (incorrect) hypothesis regarding nucleotides?
Tetranucleotide hypothesis: DNA consists of a series of four-nucleotide units each containing all four bases in a fixed sequence
Who disproved the tetranucleotide hypothesis?
Erwin Chargaff and his colleagues
What are “Chargaff’s Rules”
Rules developed by Erwin Chargaff concerning the ratios of bases in DNA
What contribution did Levene make to our understanding of DNA structure?
He determined that DNA consists of nucleotides
______ identified the basic rules of heredity in 1866
Mendel identified the basic rules of heredity in 1866
By the early 1900s biologists had concluded that genes resided on ______ which were known to contain both _____ and _____
By the early 1900s biologists had concluded that genes resided on chromosomes which were known to contain both DNA and protein
What two things provided pivotal evidence that DNA (not protein) was the genetic material?
Two sets of experiments, one on bacteria and the other on viruses
Who first observed the phenomenon of transformation?
Griffith, Fred
What is transformation?
Transformation occurs when bacteria take up DNA from the medium in which it is growing; ie incorporates foreign DNA into its own genome
What is the transforming principle (as named by Griffith after his experiment with mice)
Substance responsible for transformation. DNA is the transforming principle
Who (microbiologist) set out to understand the nature of Griffith’s transforming factor?
Avery, oswald
After 10 years of research, _____, ______, and ______ succeeded in isolating and partially purifying the transforming substance
After 10 years of research, Avery, Macleod, and McCarty succeeded in isolating and partially purifying the transforming substance
Avery, MacLeod and MacCarty showed that the transforming substance had a chemical composition closely matching that of _____ and quite different from that of _____
Avery, MacLeod and MacCarty showed that the transforming substance had a chemical composition closely matching that of DNA and quite different from that of Protein
Avery, MacLeod and McCarty showed that the transforming substance ______ at the same rate as purified DNA and that it absorbed ______ _____ at the same wavelength as DNA - thus providing compelling evidence that the transforming principle (and therefore genetic material) lies in the DNA
Avery, MacLeod and McCarty showed that the transforming substance precipitated at the same rate as purified DNA and that it absorbed Ultraviolet Light at the same wavelength as DNA - thus providing compelling evidence that the transforming principle (and therefore genetic material) lies in the DNA
If Avery, MacLeod and McCarty had found that samples of heat-killed bacteria treated with RNase and DNase transformed bacteria but that samples treated with protease did not, what conclusion would they have drawn?
(remember, in their experiment, the tube treated with DNase had no transformed type IIIS bacteria whereas the tubes treated with RNase and protease did)
Protein is the genetic material
The second piece of evidence that suggested DNA was the genetic material came from a study done by _____ and ______
The second piece of evidence that suggested DNA was the genetic material came from a study done by Hershey and Chase
What was the Hershey-Chase study?
Hershey and Chase worked with the T2 bacteriophage (virus) and showed that when a phage attaches to the outer wall of bacterial cell, it injects its DNA not its protein into the cell where it replicates and directs the cell to synthesize phage proteins.
Could Hershey and Chase have used a radioactive isotope of carbon instead of 32P? Why or why not?
No because carbon is found in both protein and nucleic acid
DNA contains phosphorus not sulfur;
Protein contains sulfur but not phosphorus
By injecting them with sulfur and phosphorus, they could identify which part of the phage (DNA or protein) was being transferred
The experiments on the nature of genetic material set the stage for one of the most important advances in the history of biology: the discovery of the _________ by James Watson and Francis Crick
The experiments on the nature of genetic material set the stage for one of the most important advances in the history of biology: the discovery of the Three-dimensional Structure of DNA by James Watson and Francis Crick
Prior to Watson and Cricks discovery, most of the basic chemistry of DNA had already been determined by _____, _____, ______, _____ and others, who established that DNA consists of _____ and that each one contains a _____ a _____ and a ______
Prior to Watson and Cricks discovery, most of the basic chemistry of DNA had already been determined by Miescher, Kossel, Levene, Chargaff and others, who established that DNA consists of nucleotides and that each one contains a sugar a nitrogenous base and a phosphate group
In 1947 William Atsbury used a technique called ______ to study the three dimensional structure of DNA
In 1947 William Atsbury used a technique called X-Ray diffraction to study the three dimensional structure of DNA
Atsbury’s images did not provide enough resolution to reveal the structure of DNA, but ______, using the same technique, provided images critical in the eventual elucidation of the structure of DNA by watson and crick
Atsbury’s images did not provide enough resolution to reveal the structure of DNA, but Rosalind Franklin, using the same technique, provided images critical in the eventual elucidation of the structure of DNA by watson and crick
What was the key to solving the structure of DNA?
Watson recognized that adenine bases bonded with Thymine bases and that Cytosine bases bonded with guanine bases - accounting for the ratios that Chargaff had discovered earlier
The model developed by Watson and Crick showed that DNA consists of two strands of _____ that run _____ and wind around each other to form a _____ with the ____ and ____ on the outside and the _____ in the interior
The model developed by Watson and Crick showed that DNA consists of two strands of nucleotides that run antiparallel and wind around each other to form a right-handed helix with the sugars and phosphates on the outside and the bases in the interior
What did Watson and Crick use to help solve the structure of DNA?
a) X-ray diffraction images
b) laws of structural chemistry
c) models of DNA
d) All of the Above
d)
in most organisms, ___\_is the carrier of genetic information; a few viruses, however, use ___\_ not DNA, as their genetic material
in most organisms, DNA is the carrier of genetic information; a few viruses, however, use RNA not DNA, as their genetic material
Who demonstrated that some viruses use RNA as genetic information carriers?
Heinz Fraenkel-Conrat and Bea Singer
It is useful to consider the structure of DNA at three levels of increasing complexity:
- Primary
- Secondary
- Tertiary
Structures of DNA
The primary structure of DNA refers to:
It’s nucleotide structure and how the nucleotides are joined together
What does the secondary structure of DNA refer to?
It’s stable three-dimensional configuration, the helical structure (discovered by Watson and Crick)
What does the tertiary structure of DNA refer to?
The complex packing arrangements of Doube-Stranded DNA in chromosomes
The primary structure of DNA consists of a string of ______ joined together by ________ bonds
The primary structure of DNA consists of a string of nucleotides joined together by phosphodiester bonds
DNA is a polymer (chain made up repeating units). What are the repeating units?
Nucleotides
What are the three parts that comprise a nucleotide?
- Nitrogenous base (i.e. nitrogen-containing base)
- phosphate group
- a sugar
The sugars of nucleic acids (called _____ sugars) contain how many carbon atoms?
The sugars of nucleic acids (called Pentose sugars) contain 5 carbon atoms.
How are the sugars in DNA and RNA different?
RNA: Called ribose has a hydroxyl group (OH) attached to the 2’ carbon
DNA: called deoxyribose has a hydrogen (H) at the 2’ carbon (thus has one less Oxygen than ribose)
The additional oxygen in RNA has what effect?
Makes it more reactive (less chemically stable)
There are two types of nitrogenous base:
- Purine
- Pyrimadine
Each purine consists of a ______ attached to a _____
Each purine consists of a 6-member ring attached to a 5-member ring
Each pyrimidine consists of a _______ only
Each pyrimidine consists of a 6-member ring only
What are the three pyrimidines common in nucleic acids?
- Thymine (restricted to DNA)
- Cytosine
- Uracil (replaces thymine in RNA)
What are the two purines?
- Adenine
- Guanine
In a nucleotide, the nitrogenous base always forms a covalent bond with the ______ carbon atom of the sugar
In a nucleotide, the nitrogenous base always forms a covalent bond with the 1’- carbon atom of the sugar
What is a nucleoside?
Ribose or deoxyribose bonded to a nitrogenous base
How do the sugars of RNA and DNA differ?
a) RNA has a six-carbon sugar; DNA has a 5-carbon sugar
b) The sugar of RNA has a hydroxyl group that is not found in the sugar of DNA
c) RNA contains uracil, DNA contains thymine
d) DNA’s sugar has a phosphorus atom; RNA’s sugar does not
How do the sugars of RNA and DNA differ?
a) RNA has a six-carbon sugar; DNA has a 5-carbon sugar
b) The sugar of RNA has a hydroxyl group that is not found in the sugar of DNA
c) RNA contains uracil, DNA contains thymine
d) DNA’s sugar has a phosphorus atom; RNA’s sugar does not
DNA is made of many nucleotides connected by _____ bonds which join the _____ group of one nucleotide to the _____ group of the next nucleotide
DNA is made of many nucleotides connected by covalent bonds which join the 5’-phosphate group of one nucleotide to the 3’ hydroxyl group of the next nucleotide
The covalent bonds that connect nucleotides are called:
Phosphodiester linkages
What is a polynucleotide strand?
Series of nucleotides linked together by phosphodiester bonds
What is the 5’ end?
End of a polynucleotide chain at which a phosphate group is attached to the 5’carbon atom of the sugar in the nucleotide
What is the 3’ end?
End of a polynucleotide chain at which an OH group is attached to the 3’carbon atom of the sugar in the nucleotide
The polynucleotide strands of a DNA helix are antiparallel. What does this mean?
The orientation of the two polynucleotide strands of the DNA double helix in opposite directions
(5’ end of one is the 3’ end of the other)
The two strands of DNA are held together by various molecular forces. _____ bonds link the bases on opposite strands
The two strands of DNA are held together by various molecular forces. hydrogen bonds link the bases on opposite strands
Adenine normally pairs with thymine through ____ ____ bonds
Adenine normally pairs with thymine through two hydrogen bonds
Cytosine normally pairs with guanine through _____ _____ bonds
Cytosine normally pairs with guanine through three hydrogen bonds
The two polynucleotide strands of a DNA molecule are not identical, but are _____, which is important for efficient and accurate ______
The two polynucleotide strands of a DNA molecule are not identical, but are complementary, which is important for efficient and accurate DNA replication
The second force holding the two DNA strands together (recall the first is hydrogen bonds) is the interaction between the _____ ____ ____ in the interior of the molecule
The second force holding the two DNA strands together (recall the first is hydrogen bonds) is the interaction between the stacked base pairs in the interior of the molecule
Stacking interactions of base pairs helps to ____ the DNA molecule
Stabalize
Concept Check:
The antiparallel nature of DNA refers to:
a) its charged phosphate groups
b) the pairing of bases on strand with bases on the other strand
c) the formation of hydrogen bonds between bases from opposite strands
d) the opposite direction of the two strands of nucleotides
Concept Check:
The antiparallel nature of DNA refers to:
a) its charged phosphate groups
b) the pairing of bases on strand with bases on the other strand
c) the formation of hydrogen bonds between bases from opposite strands
d) the opposite direction of the two strands of nucleotides
The three-dimensional structure of DNA described by Watson and Crick is termed the
B-DNA - right-handed helical structure of DNA that exists when water is abundant
DNA can also assume the A-DNA structure. what is this?
Right-handed helical structure of DNA that exists when little water is present
A third secondary structure of DNA is called the Z-DNA. Describe it
Secondary structure of DNA characterized by 12 bases per turn, a left-handed helix, and a sugar-phosphate backbone that zigzags back and forth
CONCEPT CHECK 8
How does B-DNA differ from Z-DNA
Z-DNA has a left-handed helix; B-DNA has a right-handed
The sugar-phosphate backbone of Z-DNA zigzags back and forth whereas the backbone of B-DNA forms a smooth continuous ribbon
