Explain why DNA needs to be replicated both continuously and discontinuously?
DNA is replicated both continuously and discontinuously because of the presence of a leading strand and a lagging strand.
When DNA needs to be replicated, it is in the form of a double helix that is separated through DNA helicase. The bonds
are broken between the base pairs. As the 2 strands are being separated, there is a fork being created. DNA polymerase III
then starts to add bases to the 2 strands that have been partly separated from the original DNA double helix. Primers are
used on both ends and the bases attach themselves in the 5' to 3' direction. Since DNA is a double helix, the second strand
follows the 3' to 5' direction. Because there are 2 strands, one (5' to 3' strand) is the leading strand while the other strand is
the lagging strand. The leading strand is replicated continuously because DNA can only be replicated in the 5' to 3' end.
The lagging strand is replicated discontinuously, which means that it's replicated in small pieces called Okazaki fragments,
because it needs to start from the other direction to have it replicate from 5' to 3'. Then, DNA ligase can join those
fragments to form another continuous strand. Because of this, DNA needs to be replicated in both ways at the same time
so that both strands of the original DNA double helix can form new strands of DNA. If DNA were only replicated
continuously, the second strand or the lagging strand would not be able to replicate in the first place.
Why are errors in DNA replication more impactful compared to errors in transcription? What mechanisms are used to
prevent errors in DNA mutations?
Errors in DNA replication in other words mutations can cause permanent change in the nucleotide sequence of cell's
DNA. When these errors are not proofread and not corrected it can cause the replication of continuous and wrong
information to the daughter cells during the S phase during Interphase. In comparison to the effects of errors with DNA
replication to transcription is that transcription uses RNA Polymerase to add the complementary RNA nucleotides to
create mRNA. If any mistake was made, a protein is not made with that particular mRNA and the process and start again
to make another mRNA. It does not impact daughter cells. Mutations in DNA impacts all the proteins that will be made
since mRNA is made from DNA.
You have learned that there is a stop codon that signals the end of an amino acid chain. Why is it important that a signal to
stop translation be part of protein synthesis?
Protein synthesis is the process responsible for making proteins and enzymes. More specifically, in the ribosome tRNA is
responsible for the formation of amino acid chains when it makes base pairs by combining codons with anti-codons. The
stop codon signals for the forming of an amino acid chain to stop when it has reached the appropriate length. Without this
the amino acid chain would not be the correct length. This would mean that when the amino acid chain has folded, the
enzyme that it makes will not be the proper shape – this impacts its function since it can change the active or the allosteric
site.
Mutations are often just a single changed nitrogenous base in DNA/mRNA that affects the synthesis of proteins. Explain
why mutations do not always lead to ineffective proteins or have the same effects?
Mutations do not always lead to ineffective proteins because a single changed nitrogenous base does not always affect
amino acid being coded. During protein synthesis, mRNA is transcribed from the template strand of the DNA. The mRNA
is then made up of codons which are read in groups of three and determine the amino acid sequence made from the
mRNA. If there is a single changed nitrogenous base in the DNA, this means that there is one incorrect nucleotide on the
mRNA. However, this does not always lead to an ineffective protein because there are numerous codons for each amino
acid. If the incorrect codon still codes for the correct amino acid, there will be no effect on the protein. This is called a
silent mutation.
A medication for a bacterial infection prevents DNA ligase from functioning properly in bacteria. Explain why this is an
effective treatment?
In DNA replication, a double helix of DNA is separated into 2 strands (leading and lagging strand). Since DNA can only
be replicated in the 5' to 3' direction, the leading strand is replicated continuously while the lagging strand is replicated
discontinuously (since lagging strand is 3' to 5'). The lagging strand is still replicated with the primer and DNA
polymerase III, however it replicates in smaller fragments (Okazaki fragments). The function of DNA ligase is then to
close those fragments (gaps) to form a continuous strand and form a new strand of DNA. Since we don't want harmful
DNA is replicated both continuously and discontinuously because of the presence of a leading strand and a lagging strand.
When DNA needs to be replicated, it is in the form of a double helix that is separated through DNA helicase. The bonds
are broken between the base pairs. As the 2 strands are being separated, there is a fork being created. DNA polymerase III
then starts to add bases to the 2 strands that have been partly separated from the original DNA double helix. Primers are
used on both ends and the bases attach themselves in the 5' to 3' direction. Since DNA is a double helix, the second strand
follows the 3' to 5' direction. Because there are 2 strands, one (5' to 3' strand) is the leading strand while the other strand is
the lagging strand. The leading strand is replicated continuously because DNA can only be replicated in the 5' to 3' end.
The lagging strand is replicated discontinuously, which means that it's replicated in small pieces called Okazaki fragments,
because it needs to start from the other direction to have it replicate from 5' to 3'. Then, DNA ligase can join those
fragments to form another continuous strand. Because of this, DNA needs to be replicated in both ways at the same time
so that both strands of the original DNA double helix can form new strands of DNA. If DNA were only replicated
continuously, the second strand or the lagging strand would not be able to replicate in the first place.
Why are errors in DNA replication more impactful compared to errors in transcription? What mechanisms are used to
prevent errors in DNA mutations?
Errors in DNA replication in other words mutations can cause permanent change in the nucleotide sequence of cell's
DNA. When these errors are not proofread and not corrected it can cause the replication of continuous and wrong
information to the daughter cells during the S phase during Interphase. In comparison to the effects of errors with DNA
replication to transcription is that transcription uses RNA Polymerase to add the complementary RNA nucleotides to
create mRNA. If any mistake was made, a protein is not made with that particular mRNA and the process and start again
to make another mRNA. It does not impact daughter cells. Mutations in DNA impacts all the proteins that will be made
since mRNA is made from DNA.
You have learned that there is a stop codon that signals the end of an amino acid chain. Why is it important that a signal to
stop translation be part of protein synthesis?
Protein synthesis is the process responsible for making proteins and enzymes. More specifically, in the ribosome tRNA is
responsible for the formation of amino acid chains when it makes base pairs by combining codons with anti-codons. The
stop codon signals for the forming of an amino acid chain to stop when it has reached the appropriate length. Without this
the amino acid chain would not be the correct length. This would mean that when the amino acid chain has folded, the
enzyme that it makes will not be the proper shape – this impacts its function since it can change the active or the allosteric
site.
Mutations are often just a single changed nitrogenous base in DNA/mRNA that affects the synthesis of proteins. Explain
why mutations do not always lead to ineffective proteins or have the same effects?
Mutations do not always lead to ineffective proteins because a single changed nitrogenous base does not always affect
amino acid being coded. During protein synthesis, mRNA is transcribed from the template strand of the DNA. The mRNA
is then made up of codons which are read in groups of three and determine the amino acid sequence made from the
mRNA. If there is a single changed nitrogenous base in the DNA, this means that there is one incorrect nucleotide on the
mRNA. However, this does not always lead to an ineffective protein because there are numerous codons for each amino
acid. If the incorrect codon still codes for the correct amino acid, there will be no effect on the protein. This is called a
silent mutation.
A medication for a bacterial infection prevents DNA ligase from functioning properly in bacteria. Explain why this is an
effective treatment?
In DNA replication, a double helix of DNA is separated into 2 strands (leading and lagging strand). Since DNA can only
be replicated in the 5' to 3' direction, the leading strand is replicated continuously while the lagging strand is replicated
discontinuously (since lagging strand is 3' to 5'). The lagging strand is still replicated with the primer and DNA
polymerase III, however it replicates in smaller fragments (Okazaki fragments). The function of DNA ligase is then to
close those fragments (gaps) to form a continuous strand and form a new strand of DNA. Since we don't want harmful
