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A new DNA strand elongates only in the 5' to 3' direction because?
Wiki User
∙ 14y ago
no DNA synthesis occurs in 5'-3' as well as in 3'-5' direction. only the difference is that ,that it is continuous in 5'-3' direction but discontinous in 3'-5' direction. this is because enzyme DNA polymerase III can synthesize DNA contionously in 5'-3' direction only.
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No DNA synthesis always occus in the 5' to 3' direction as there is no DNA polymerase that work in the other direction as it is too thermodynamically unfavourable. The cells solve the problem of having to synthesize in a 3' to 5' direction by synthesizing in reverse in discontinuous pieces. Technically there's never any direct 3' to 5' synthesis.
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DNA polymerase can add nucleotide to 3' end of primer or growing strand of DNA so in one direction it remains continuous ie leading strand while in in other strand it starts little later when it get enough space to grow in opposite direction then after synthesizing short strand it again goes to newly unwind strand and repeats the process, but the growth remains in 5' to 3' direction moving on template from 3' to 5' direction.
Wiki User
∙ 12y ago
Wiki User
∙ 14y agoDNA polymerase can only add to the free 3' end as it contains the OH group needed for binding.
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Why is replication on one strand of DNA continuous while on the other strand the replication must be discontinuous?
New strands of DNA can only be created in one direction - 5' to 3'. This is because only the 3' end of the DNA is able to join to a new nucleotide. The two strands of DNA are antiparallel - meaning they run in different directions. Therefore only one strand (called the leading strand) is running in the correct direction for continuous replication. The other strand (called the lagging strand) must first be looped around so that small sections can be replicated in the correct direction.
What is the direction of synthesis of the new strand?
The template strand (DNA) is read by RNA polymerase in the 3'-5' direction. First, RNA polymerase binds to an A-T rich promoter on the DNA which is upstream from the site of translation. Because A-T bonds are weaker than C-G bonds, the double helix opens up at this point and RNA polymerase begins translation. While translaing the DNA template strand, it creates a complementory mRNA strand and thus the Mrna will read 5'-3' with new bases being added at the 3' end.
Why can't DNA polymerase synthesize a new strand of DNA without the help of a RNA primer?
Because DNA Polymerase requires the OH on the 3' as an active site. It uses the OH on the 3' end of a nucleotide to attach a phosphate from the 5' end of the next nucleotide. It only works in this direction, and that is why DNA polymerase works 5' to 3'.
Which of the following statements best explains why the leading and lagging strands are synthesized using two different mechanisms?
The leading strand is created continuously, but the lagging strand is created as small fragments, known as Okazaki fragments. These fragments are later joined together to form one complete strand.
Describe the significance of Okazaki fragments?
Okazaki fragments are created during DNA replication because DNA Polymerase can only add nucleotides in a 5' to 3' direction. This means that one strand (the leading strand) can be continuously created, but the other strand (the lagging strand) runs in the opposite direction. This means that loops must be created and shorter parts of DNA replicated one at a time. This creates fragments on the lagging strand. The RNA primers on this strand are later replaced with DNA by DNA Polymerase I, and joined together with DNA ligase.
Why is replication on one strand of DNA continuous while on the other strand the replication must be discontinuous?
New strands of DNA can only be created in one direction - 5' to 3'. This is because only the 3' end of the DNA is able to join to a new nucleotide. The two strands of DNA are antiparallel - meaning they run in different directions. Therefore only one strand (called the leading strand) is running in the correct direction for continuous replication. The other strand (called the lagging strand) must first be looped around so that small sections can be replicated in the correct direction.
What is the direction of synthesis of the new strand?
The template strand (DNA) is read by RNA polymerase in the 3'-5' direction. First, RNA polymerase binds to an A-T rich promoter on the DNA which is upstream from the site of translation. Because A-T bonds are weaker than C-G bonds, the double helix opens up at this point and RNA polymerase begins translation. While translaing the DNA template strand, it creates a complementory mRNA strand and thus the Mrna will read 5'-3' with new bases being added at the 3' end.
Why can't DNA polymerase synthesize a new strand of DNA without the help of a RNA primer?
Because DNA Polymerase requires the OH on the 3' as an active site. It uses the OH on the 3' end of a nucleotide to attach a phosphate from the 5' end of the next nucleotide. It only works in this direction, and that is why DNA polymerase works 5' to 3'.
Which of the following statements best explains why the leading and lagging strands are synthesized using two different mechanisms?
The leading strand is created continuously, but the lagging strand is created as small fragments, known as Okazaki fragments. These fragments are later joined together to form one complete strand.
Describe the significance of Okazaki fragments?
Okazaki fragments are created during DNA replication because DNA Polymerase can only add nucleotides in a 5' to 3' direction. This means that one strand (the leading strand) can be continuously created, but the other strand (the lagging strand) runs in the opposite direction. This means that loops must be created and shorter parts of DNA replicated one at a time. This creates fragments on the lagging strand. The RNA primers on this strand are later replaced with DNA by DNA Polymerase I, and joined together with DNA ligase.
At each replication fork one new strand of DNA is made of many small pieces. what is the strand of DNA called?
When the two parent strands of DNA are separated to begin replication, one strand is oriented in the 5' to 3' direction while the other strand is oriented in the 3' to 5' direction. DNA replication, however, is inflexible: the enzyme that carries out the replication, DNA polymerase, only functions in the 5' to 3' direction. This characteristic of DNA polymerase means that the daughter strands synthesize through different methods, one adding nucleotides one by one in the direction of the replication fork, the other able to add nucleotides only in chunks. The first strand, which replicates nucleotides one by one is called the leading strand; the other strand, which replicates in chunks, is called the lagging strand. The lagging strand replicates in small segments, called Okazaki fragments. These fragments are stretches of 100 to 200 nucleotides in humans (1000 to 2000 in bacteria).
The continually elongating strand of new dna at one side of a replication fork during dna replication is known as?
The strand of DNA that is being continually created is known as the leading strand. The strand that is being created in sections/loops is known as the lagging strand. The reason that these two strands are created differently is because the two strands of DNA run in different directions (they are anti-parallel). This means that because new nucleotides can only be added in a 5'-3' direction, the two strands cannot be created in the same method.
Does DNA have a specific direction?
In a way Yes!, but also, in the same way no. Each strand of DNA is polymerized in the 5' to 3' direction. Meaning that to copy the strand of DNA, the enzyme used to do this (DNA polymerase) can only flow in this direction. However, the complimentary base paired strand also goes in the 5' to 3' direction, but it is opposite of what the other strand is. So basically you have one strand going 5' to 3' and one strand in the same direction going 3' to 5'Here is an example....Letters indicate basesA- adenineG- guanineC- cytosineT- thymine5'-AATTCGGTCCGTTCCGGCTAATCG-3'3'-TTAAGCCAGGCAAGGCCGATTAGC-5'The 5' or 3' direction basically indicates that there is a hydroxy group attached to the end of each sugar phosphate backbone so that the next nucleotide can be added by a hydrolysis reaction. In this way, the nucleotides can only be added from 5' to 3' making DNA a perfect molecule for enzymatic replication!Hope this helps!
Why can't you see the double helix Dna strand?
Only because it is invisible to the 'naked' eye.
Why is the leading strand considered continuous?
The leading strand is the correct orientation, so it can be replicated continuosly - meaning the DNA Polymerase can continue to add new nucleotides without stopping. New DNA strands can only be created in a 5' to 3' direction. This is different to the lagging strand - which must be looped and copied in small, non-continuos segments. These segments are known as Okazaki fragments.
Why transcription is unidirectional?
Transcription is unidirectional because you are copying only ONE side of the DNA. Remember that DNA is a double stranded helical structure. One strand of DNA is complementary to the other strand.
What does the first nucleotide attach to because DNA polymerase can only add nucleotides to a pre-existing strand?
An RNA primer.
