Chapter 13: The Molecular Basis of Inheritance Flashcards
What does the term “transformation” refer to?
A change in genotype and phenotype due to the assimilation of external DNA by a cell.
What is the term that refers to viruses that infect bacteria?
Bacteriophages
How is a “virus” defined?
Little more than DNA (or sometimes RNA) enclosed by a protective coat, which is often simply protein.
DNA is composed of three components. What are they?
A nitrogenous (nitrogen-containing) base, a pentose sugar called deoxyribose, and a phosphate group.
The nitrogenous bases can be made of four different nucleotides. What are these 4?
Adenine, Thymine, Cytosine, and Guanine.
Chargaff analyzed the base composition of DNA from different organisms. What did he discover?
The base composition of DNA varies from one species to another.
What are Chargaff’s two rules?
1) the base composition varies between species
2) within a species, the number of A and T bases are roughly equal and the number of G and C bases are roughly equal.
What term can define how the two sugar-phosphate backbones run in opposite directions?
Antiparallel
Which two nitrogenous bases are purines?
Adenine and Thymine
Which two nitrogenous bases are pyrimidine?
Cytosine and Guanine
The pairs of nitrogenous bases in a DNA double helix are held together by…
hydrogen bonds.
When the two DNA strands are separated, each parental strand acts as a…
template for a new complementary strand
Define a Conservative Model of DNA.
The two parental strands reassociate after acting as templates for new strands, thus restoring the parental double helix.
Define a Semiconservative Model of DNA.
The two strands of the parental molecule separate, and each functions as a template for synthesis of a new, complementary strand.
Define a Dispersive Model of DNA.
Each strand of BOTH daughter molecules contains a mixture of old and newly synthesized DNA.
Each of our calls have ____ DNA molecules in its nucleus.
46.
The replication of a DNA molecule begins at particular sites called…
Origins of Replication
Proteins that initiate DNA replication recognize this sequence and attach to the DNA, separating the two strands and opening up a replication…
“bubble.”
At the end of each DNA bubble, there is a…
replication fork
What is a “Replication Fork?”
A Y-shaped region where the parental strands of DNA are being unwound.
What is the name of the enzyme that untwists the double helix at the replication forks?
Helicase
After the parental strands separate from helicase, what binds to the unpaired DNA strands, keeping them from re-pairing?
Single-Strand Binding Proteins
The untwisting of the double helix causes tighter twisting and strain ahead of the replication fork. What is the name of the enzyme that helps relieve this strain from breaking, swiveling, and rejoining DNA strands?
Topoisomerase
What is the name of the enzyme that helps relieve the strands of parental DNA from breaking, swiveling, and rejoining?
Toposiomerase
What is a Primer?
The initial nucleotide chain that is produced during DNA synthesis (which is actually a stretch of RNA)
Primer is synthesized by what enzyme?
Primase
What does the enzyme Primase do after Helicase causes the replication forks to seperate?
Starts adding complementary RNA chain from a single RNA nucleotide, adding RNA nucleotides one at a time, using the parental DNA strand as a template.
What dose the enzyme DNA Polymerase do?
It catalyzes the synthesis of new DNA by adding nucleotides to a preexisting chain.
What are Okazaki fragments?
The segments of the lagging strand.
What does DNA ligase accomplish?
Joins the sugar phosphate backbones of all the Okazaki fragments into a continuos DNA strand.
