What is A triplet in DNA replication?
What is A triplet in DNA replication?
Hidden within the genetic code lies the “triplet code,” a series of three nucleotides that determine a single amino acid. It was also known that there are only four nucleotides in mRNA: adenine (A), uracil (U), guanine (G), and cytosine (C).
What is found in both DNA and messenger RNA?
DNA and RNA each contain four different bases (see Figure 4-2). The purines adenine (A) and guanine (G) and the pyrimidine cytosine (C) are present in both DNA and RNA. The pyrimidine thymine (T) present in DNA is replaced by the pyrimidine uracil (U) in RNA.
What occurs during the stage of protein synthesis called translation?
Translation occurs at the ribosome, which consists of rRNA and proteins. In translation, the instructions in mRNA are read, and tRNA brings the correct sequence of amino acids to the ribosome. Then, rRNA helps bonds form between the amino acids, producing a polypeptide chain.
What is A promoter is it located at the upstream or downstream end of A transcription unit?
What is a promoter, and is it located at the upstream of downstream end of a transcription unit? The promoter is the region of DNA to which RNA polymerase binds to begin transcription, and it is at the upstream end of the gene (transcription unit).
Why genetic code is triplet?
Since there are only four nucleotides, a code of single nucleotides would only represent four amino acids, such that A, C, G and U could be translated to encode amino acids. When experiments were performed to crack the genetic code it was found to be a code that was triplet.
How does RNA work with DNA?
The portions of DNA that are transcribed into RNA are called “genes”. Cells make RNA messages in a process similar to the replication of DNA. The DNA strands are pulled apart in the location of the gene to be transcribed, and enzymes create the messenger RNA from the sequence of DNA bases using the base pairing rules.
What information is translated in the process of protein synthesis?
Translation is the process of translating the sequence of a messenger RNA (mRNA) molecule to a sequence of amino acids during protein synthesis. The genetic code describes the relationship between the sequence of base pairs in a gene and the corresponding amino acid sequence that it encodes.
Can promoters be downstream?
In molecular biology, a downstream promoter element (DPE) is a core promoter element. Like all core promoters, the DPE plays an important role in the initiation of gene transcription by RNA polymerase II. It is located about 28–33 nucleotides downstream of the transcription start site.
What is upstream promoter?
A promoter is a regulatory region of DNA located upstream (towards the 5′ region) of of a gene, providing a control point for regulated gene transcription. The promoter contains specific DNA sequences that are recognized by proteins known as transcription factors.
What are enzymes that are involved in DNA replication?
Enzymes that participate in the eukaryotic DNA replication process include: DNA helicase – unwinds and separates double stranded DNA as it moves along the DNA. It forms the replication fork by breaking hydrogen bonds between nucleotide pairs in DNA. DNA primase – a type of RNA polymerase that generates RNA primers.
How does helicase work at the replication fork?
Helicase opens up the DNA at the replication fork. Single-strand binding proteins coat the DNA around the replication fork to prevent rewinding of the DNA. Topoisomerase works at the region ahead of the replication fork to prevent supercoiling. Primase synthesizes RNA primers complementary to the DNA strand.
Why is RNA replication not the same at the end of chromosomes?
However, the process is not the same at the end of the chromosomes, where a replication fork can no longer progress due to the lack of bases. At the site of the lagging strand where the DNA primase places the last RNA primer, the DNA polymerase is no longer able to continue replication. The terminal DNA segment cannot be replicated.
How is new DNA synthesized at each replication fork?
New DNA complementary to each single strand is synthesized at each replication fork. The two forks move in opposite directions around the circumference of the bacterial chromosome, creating a larger and larger replication bubble that grows at both ends. Diagram based on similar illustration in Reece et al. .
