Ch. 13 and 14 Flashcards
What are the four nitrogenous bases found in DNA?
- thymine
- guanine
- cytosine
- adenine
What are the four nitrogenous bases found in RNA?
- uracil
- gunaine
- cytosine
- adenine
What are the complementary bases in DNA?
- adenine + thymine (A+T)
- guanine + cytosine (G+C)
What are the complementary bases in RNA?
- adenine + uracil (A+U)
- guanine + cytosine (G+C)
What kind of bond holds nitrogenous base pairs together?
hydrogen bonds
What discovery was Chargaff best known for?
concluding that in natural DNA, the number of G=C and the number of A=T
What are purines?
one of two nitrogenous bases characterized by a 6-membered ring fused to a 5-membered ring
Which nitrogenous bases are purines?
adenine and guanine
What are pyrimidines?
one of two types of nitrogenous bases characterized by a 6-membered ring
Which nitrogenous bases are pyrimidines?
cytosine, thymine, and uracil
What is a semiconservative model?
a type of DNA replication in which the replicated double helix consists of one old strand and one newly made strand
What is helicase?
- an enzyme that untwists the double helix of DNA at replication forks
- separates the two strands and makes them available as template strands
- “scissors” that cut DNA in half
What is DNA polymerase?
- an enzyme that catalyzes the elongation of new DNA by the addition of nucleotides to the the 3’ end of an existing chain
- “builders” that assemble nucleotides on DNA molecules
What is DNA ligase?
- a linking enzyme that fills in the gaps made from Okazaki fragments to make on continuous strand
- “glue” that patches DNA together
What is a replication bubble?
a loop that is generated by the unwinding of the double helix
What is a replication fork?
a Y-shaped region on a replicating DNA molecule where the parental strands are being unwound and new strands are being synthesized
In what direction is DNA always synthesized?
5’-3’ direction
What is a leading strand?
the new complementary DNA strand synthesized continuously along the template strand toward the replication fork
5’-3’ direction
What is a lagging strand?
a discontinuously synthesized DNA strand that elongates by means of Okazaki fragments synthesized away from the replication fork
5’-3’ direction
What is a lagging strand?
a discontinuously synthesized DNA strand that elongates by means of Okazaki fragments synthesized away from the replication fork
5’-3’ direction
What are Okazaki fragments?
- short segments of DNA synthesized away from the replication fork on a template strand
- segments are joined together to make up the lagging strand of newly synthesized DNA
What is the flow of genetic information?
- the “flow” of genetic info from DNA to RNA to proteins
- through transcription and translation, info from genes is used to make proteins
“central dogma”