Exam 1 review Flashcards
A repeating DNA sequence at the end of chromosomes that prevents them from losing base pair sequences at their ends and from fusing together is called?
Telomere
The enzyme responsible for initiating the unwinding of double-stranded DNA (eliminating supercoiling) by nicking a single strand of the DNA molecule is?
Topoisomerase
The enzyme that accomplishes the unwinding of the original double stranded DNA molecule, once supercoiling has been eliminated, by breaking the hydrogen bonds that hold the two strands together are?
Helicase
The enzyme that stitches Okazaki fragments together (along the lagging strand) is called?
DNA ligase
The enzyme “x” removes RNA primers attached by primase and this gap is then filled in by DNA polymerase I. The enzyme “x” is?
RNase H
The enzyme that (during replication) proceeds along one of the strands of a DNA molecule adding deoxynucleotide-triphosphates to hydrogen bond with their appropriate complementary dNTP on the other single strand and to form a covalent phosphodiester bond with the previous nucleotide of the same strand is called?
DNA Polymerase III
DNA Polymerase III is actually an aggregate of several different protein subunits. So it is often called a?
Holoenzyme
A major difference between DNA replication in prokaryotes and eukaryotes is?
There is only one replication origin in prokaryotes
The enzyme that creates a short RNA oligonucleotide at initiation sites where replication is to be carried out is called?
Primase
DNA is a polymer of?
deoxinucleotides
What are pyrimidines?
Cytosine and Thymine
What are purines?
Adenine and Guanine
A nucleic acid was analyzed and found to contain 32% A, 18% G, 17% C, and 33% T. The nucleic acid must be?
double-stranded DNA
A nucleic acid was analyzed and found to contain 37% A, 16% G, 22% C, and 25% T. The nucleic acid must be?
single-stranded DNA
For double-stranded DNA, consider the following base ratios: 1. A/G 2. C/T 3. C/G 4. (A+C)/(G+T) 5. (A+G)/(C+T) 6. (A+T)/(G+C) Which of those ratios always equals 1?
Answer:
- C/G
- (A+C)/(G+T)
- (A+G)/(C+T)
The two polynucleotide chains in DNA are?
Antiparallel
In the Meselson-Stahl experiment, which model of DNA was eliminated by the analysis of DNA isolated from bacteria one replication cycle after shifting from 15N to 14N medium?
Conservative
In the semiconservative replication of DNA, progeny DNA molecules consist of?
All molecules with one parental and one new strand
In the conservative model for replication of DNA, progeny DNA molecules consist of?
One-half of the molecules with two parental strands and one-half of the molecules with two new strands
What are the complementary base-pairing rules?
The specific pairing of bases on the two polynucleotide chains of a double helix, that is, A with T and G with C
What is the base sequence of the DNA strand that would be complementary to the following single-stranded DNA molecule?
5’-GGATCTGATCCAGTCA-3’
3’-CCTAGACTAGGTCAGT-5’
The percent of cytosine in a double-stranded DNA is 21. What is the percent of thymine in that DNA?
T=29%.
If C=21 then G=21 and G+C=42. Therefore A+T=100-42=58, T=58/2=29%
The percent of adenine in a double-stranded DNA is 38. What is the percent of cytosine in the DNA?
C=12%.
If A=38 then T=38 and A+T=76. Therefore G+C=100-76=24, C=24/2=12%
The percent of guanine in a double-stranded DNA is 14. What is the percent of adenine in the DNA?
A=36%.
If G=14 then C=14 and G+C=28. Therefore A+T=100-28=72, A=72/2=36%
Explain how the bacterial chromosome replication stops.
The bacterial chromosome replication stops when DNA Pol III reaches a termination sequence in which case DNA Pol III is removed and the process of ligation is initiated.
What direction is 5’ to 3’?
Sense
What direction is 3’ to 5’?
Anti-sense
What base is found on RNA and not on DNA?
Uricil
How many bases are in a codon? In an anti-codon?
Codon = 3 and Anticodon = 3
How many amino acids are attached to a single transfer RNA?
1 amino acid
Transcription occurs in the __________ direction.
5’ to 3’
Translation occurs in the __________ direction.
3’ to 5’
The process of making RNA from DNA is called what? In which direction does it occur?
Transcription and it occurs in 3’ to 5’ direction
The process of assembling a protein from RNA is called what? In which direction does it occur?
Translation and it occurs in the 5’ to 3’ direction
The end of a strand of nucleic acid that has a OH group on the number 3 carbon of the deoxyribose or ribose and is not linked to another nucleotide is?
3’ end
The covalent bond that links ribonucleotides together to form RNA is?
phosphodiester bond
The portion of DNA that contains the actual message for protein synthesis is?
coding sequence
A molecule synthesized by complementary base pairing of ribonucleotides with deoxyribonucleotides to match a portion of one strand of DNA coding for a polypeptide or protein is?
mRNA
A series of three consecutive mRNA bases coding for one specific amino acid is?
codon
A segment of DNA that determines what region of the DNA and which strand of DNA will be transcribed into RNA is?
promoter
The enzyme that initiates transcription, joins the RNA nucleotides together, and terminates transcription is?
RNA polymerase
A “stop” signal at the end of a gene that causes the completed mRNA to drop off the gene is?
transcription terminator