Anonymous
06-03-2004, 10:00 PM
The replication fork
In this diagram of the process of DNA replication at a replication fork, the strand labeled B is the:
http://www.biology.arizona.edu/molecular_bio/problem_sets/nucleic_acids/graphics/dnarep.gif
DNA Replication
The two antiparallel strands are replicated simultaneously in both directions.
RNA primers are used to initiate a new strand.
The parent strand at the 3' end of the template determines the daughter or leading strand in continuous replication.
The parent strand at the 5' end of the template produces the lagging strand as short pieces of DNA (100-200 nucleotides in eukaryotes and longer in prokaryotes).
The lagging strand fragments are called Okazaki fragments after their discoverer, Reiji Okazaki.
The RNA primers are removed by DNA polymerase and the fragments are joined by DNA ligase.
Direction of replication
http://www.biology.arizona.edu/molecular_bio/problem_sets/nucleic_acids/graphics/dna5.gif
New strands are always synthesized in the 5' to 3' direction. The 5' triphosphate can only be added to a free 3'OH of deoxyribose
The replication fork
http://www.biology.arizona.edu/molecular_bio/problem_sets/nucleic_acids/graphics/repfork1.gif
http://www.biology.arizona.edu/molecular_bio/problem_sets/nucleic_acids/graphics/repfork2.gif
ans:
1. C leading strand
The leading strand is the newly synthesized DNA with addition of nucleotides moving in the same direction as the replication fork. Since DNA replication is 5' to 3', this means that the leading strand will always have its 3' end towards the replication fork.
Other problems:
http://www.biology.arizona.edu/molecular_bio/problem_sets/nucleic_acids/graphics/dnarep.gif
2. In this diagram of the process of DNA replication at a replication fork, the newly synthesized DNA strand labeled C is the:
In this diagram of the process of DNA replication at a replication fork, the newly synthesized DNA strand labeled C is the:
A coding strand
B parental DNA
C leading strand
D lagging strand
ans: D lagging strand
The lagging strand is the newly synthesized DNA where addition of nucleotides is on the end opposite or away from the replication fork. This fragment has its 5' end near the replication fork, and must be synthesized as short Okazaki fragments to fill in the spaces created by unwinding the DNA.
3. In this diagram of the process of DNA replication at a replication fork, the black boxes labeled D and E are:
A RNA primers
B DNA template strands
C Okazaki fragments
D DNA polymerase
E Newly synthesized DNA strand
ans:
A RNA primers
The initiation of replication always starts with a short RNA piece. The DNA replicating enzymes will only add nucleotides to the 3' end of DNA or RNA, and thus an RNA primase must start replication. The DNA polymerases must correct errors or "proof read", a function that is not compatible with initiation.
In this diagram of the process of DNA replication at a replication fork, the strand labeled B is the:
http://www.biology.arizona.edu/molecular_bio/problem_sets/nucleic_acids/graphics/dnarep.gif
DNA Replication
The two antiparallel strands are replicated simultaneously in both directions.
RNA primers are used to initiate a new strand.
The parent strand at the 3' end of the template determines the daughter or leading strand in continuous replication.
The parent strand at the 5' end of the template produces the lagging strand as short pieces of DNA (100-200 nucleotides in eukaryotes and longer in prokaryotes).
The lagging strand fragments are called Okazaki fragments after their discoverer, Reiji Okazaki.
The RNA primers are removed by DNA polymerase and the fragments are joined by DNA ligase.
Direction of replication
http://www.biology.arizona.edu/molecular_bio/problem_sets/nucleic_acids/graphics/dna5.gif
New strands are always synthesized in the 5' to 3' direction. The 5' triphosphate can only be added to a free 3'OH of deoxyribose
The replication fork
http://www.biology.arizona.edu/molecular_bio/problem_sets/nucleic_acids/graphics/repfork1.gif
http://www.biology.arizona.edu/molecular_bio/problem_sets/nucleic_acids/graphics/repfork2.gif
ans:
1. C leading strand
The leading strand is the newly synthesized DNA with addition of nucleotides moving in the same direction as the replication fork. Since DNA replication is 5' to 3', this means that the leading strand will always have its 3' end towards the replication fork.
Other problems:
http://www.biology.arizona.edu/molecular_bio/problem_sets/nucleic_acids/graphics/dnarep.gif
2. In this diagram of the process of DNA replication at a replication fork, the newly synthesized DNA strand labeled C is the:
In this diagram of the process of DNA replication at a replication fork, the newly synthesized DNA strand labeled C is the:
A coding strand
B parental DNA
C leading strand
D lagging strand
ans: D lagging strand
The lagging strand is the newly synthesized DNA where addition of nucleotides is on the end opposite or away from the replication fork. This fragment has its 5' end near the replication fork, and must be synthesized as short Okazaki fragments to fill in the spaces created by unwinding the DNA.
3. In this diagram of the process of DNA replication at a replication fork, the black boxes labeled D and E are:
A RNA primers
B DNA template strands
C Okazaki fragments
D DNA polymerase
E Newly synthesized DNA strand
ans:
A RNA primers
The initiation of replication always starts with a short RNA piece. The DNA replicating enzymes will only add nucleotides to the 3' end of DNA or RNA, and thus an RNA primase must start replication. The DNA polymerases must correct errors or "proof read", a function that is not compatible with initiation.