After DNA replication is completed, _____.

Here is the answer to the biology question: After DNA replication is completed, _. It’s collected as a biology test for preparing for the MCAT test.

After DNA replication is completed, _.

After DNA replication is completed, what does each DNA double helix consist of?

1. There are four double helices
2. Each of the four DNA strands consists of some old strand parts and some new strand parts.
3. Each new DNA double helix consists of one old DNA strand and one new DNA strand
4. One DNA double helix consists of two old strands and one DNA double helix consists of two new strands.

DNA

DNA is a type of nucleic acid, one of the four biological macromolecules contained in living cells.

DNA is a nucleic acid that carries the genetic information necessary for the synthesis of RNA and proteins in living cells and is a biomolecule essential for the development and proper functioning of living organisms.

DNA Molecular Structure

DNA consists of a large polymer of deoxyribonucleotides. Deoxyribonucleotides are composed of bases, deoxyribose, and phosphate. There are four of these bases: adenine (A), guanine (G), thymine (T), and cytosine (C).

In the DNA structure, two polydeoxyribonucleotide chains are coiled around a common central axis, forming a double helix structure. The deoxyribose-phosphate chain is on the outside of the helix structure, with the bases facing inward. The two polydeoxyribonucleotide chains are complementary in reverse and are linked by base-pairing formed by hydrogen bonds between the bases, forming a fairly stable assembly.

The order of the bases in the nucleotides in DNA constitutes genetic information. This genetic information can be formed into RNA through the process of transcription, and then the mRNA in it produces polypeptides through translation to form proteins.

Before cell division, the DNA replication process copies the genetic information. This avoids the loss of genetic information during transitions between cell generations.

In eukaryotes, DNA is found in structures called chromosomes in the nucleus of the cell. In other organisms that do not have a nucleus, DNA is found either in the chromosomes or in other tissues. Bacteria have single-loop, double-stranded DNA molecules, while viruses have DNA or RNA genomes.

In chromosomes, chromatin proteins such as histones, coexisting proteins, and cohesion proteins hold DNA in an ordered structure. These structures direct the interactions between the genetic code and the proteins responsible for transcription and help control the transcription of genes.

Types of DNA

Single-stranded DNA

Most DNA exists in a double helix structure. However, when treated with heat or alkali, it changes to a single-stranded state. Single-stranded DNA is the DNA that exists in this state.

Single-stranded DNA differs from double-stranded DNA in terms of molecular hydrodynamic properties, absorption spectra, and base reaction properties. Some phage particles contain single-stranded loops of DNA, and such phage DNA forms double-stranded DNA when it proliferates in the cell.

Closed circular DNA

Closed circular DNA is double-stranded circular DNA without a break, also known as superhelix DNA.

As each of the double strands with a helical structure closes, the entire DNA molecule is further twisted to form a tertiary structure.

In addition, if a break is created in a different part of one or two strands, it becomes an open-loop DNA molecule without a helix.

Plasmid or viral DNA extracted from cells contain both closed-loop and open-loop molecules. The two can be separated depending on their ability to bind to pigments.

Junk DNA

Junk DNA refers to DNA that is not translated into proteins in living organisms and used to be called junk DNA because they were considered useless.

Later, scientists discovered that junk DNA contains important regulatory mechanisms that can control basic biochemical reactions and developmental processes. This would help organisms to evolve more complex organisms. The more complex the organism, the more important junk DNA seems to be.

DNA replication

DNA replication is the process of replication of a DNA double-strand prior to cell division. If the replication process is normal, the result of replication is that one double-strand becomes two identical double strands.

Each double strand is identical to the original double strand. This process is successfully accomplished by a mechanism called semi-conserved replication.

Replication can be divided into the following phases.

1) Initiation phase

Unsplash locally unfolds the double-helical structure of the DNA molecule into a single strand. The primase recognizes the start site and uses the unraveled segment of DNA as a template to synthesize a short strand of RNA in the 5′ to 3′ direction. RNA primers are formed.

2) Generation of DNA fragments

On the basis of the 3′-OH end provided by the primer, DNA polymerase catalyzes the replication process of both strands of DNA simultaneously. Since the replication process can only be synthesized from the 5′->3′ direction, one strand can be synthesized continuously.

The other strand is synthesized in segments, where each short strand becomes Okazaki fragments.

3) Hydrolysis of RNA primers

After a certain length of DNA is synthesized, DNA polymerase hydrolyzes the RNA primers to fill in the gaps.

DNA ligase joins the DNA fragments together to form a complete DNA molecule. Finally, the newly synthesized fragments of DNA are re-formed into a helix with the help of rotamases.

DNA double helix

DNA double helix refers to a conformation of a nucleic acid. In this conformation, two opposite parallel polynucleotide chains are twisted around each other to form a right-handed double helix structure.

The bases of the DNA double helix are located on the inner side of the double helix, while the phosphate and sugar groups are on the outer side, linked by phosphodiester bonds to form the backbone of the nucleic acid.

The base plane is perpendicular to the hypothetical central axis, while the sugar loop plane is parallel to the axis, and both strands are right-handed helices.

The DNA molecular double helix model is an assembled structural model of the DNA molecule, which is made of high-quality colored plastic materials.

The model uses red, yellow, blue, and green color balls with special shape structures to represent A, T, G, and C nucleotides and brown sticks (representing phosphate P) five kinds of parts. Not only can the DNA molecular strands with double helix spatial structure be assembled, but also the self-replication function of DNA molecular strands can be expressed visually.

Correct Answer

Below is the correct answer to After DNA replication is completed, _.

After DNA replication is completed, each new DNA double helix consists of one new DNA strand and one old DNA strand.

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