All categories

2 years ago

During which stage of interphase do cells copy their chromosomes?

Biology

1 answer:

Step2247 [10]2 years ago

8 0

Answer:

The S phase (Synthesis phase)

DNA replication takes place during the S-phase of interphase, creating two identical sets of DNA. The DNA coils and condenses into units known as chromosomes during the start of mitosis. The two identical sister chromatids that make up each chromosome are joined by a centromere.

<h2>How does DNA replication work?</h2>

The biological process of creating two identical copies of DNA from a single original DNA molecule is known as DNA replication.

A double helix of two complementary strands makes up DNA. These strands are split apart in the replication process. The method of semi-conservative replication uses each strand of the original DNA molecule as a template to create its counterpart.

Several enzymes that carry out this process are given below, along with their activities.

____________

DNA Dependent DNA POLYMERASE is a class of enzymes that is responsible for all organisms' DNA replication processes. It accelerates DNA replication in the 5′ to 3′ range.
The enzyme known as TOPOISOMERASE is involved in the over- or under-winding of DNA.
HELICASE—Using the energy from ATP hydrolysis, which is characterized by the breakdown of hydrogen bonds between annealed nucleotide bases, helicases are frequently employed to separate the strands of a DNA double helix or a self-annealed RNA molecule.
DNA GYRASE, a particular kind of topoisomerase, relieves strain caused by DNA helicase's unwinding action.
DNA LIGASE- Joins the OKAZAKI FRAGMENT of the lagging strand and re-anneals the semi-conservative strands.
PRIMASE - Primase catalyzes the production of a short primer, which is a ssDNA template-specific piece of RNA (or DNA in other species).

REPLICATION FORK -(Attachment #1)

_________________

REPLICATION PROCESS -

INITIATION - The beginning of DNA replication takes place at certain locations in the DNA molecule known as ori-sites or regions. Enzymes often recognize these locations and initiate the process. As opposed to C-G base pairs, which produce three hydrogen bonds, A-T base pairs only form two hydrogen bonds, making them easier to strand split. As a result, these sites are typically "AT-rich" (rich in adenine and thymine bases). Following the discovery of the origin, enzymes create a pre-replication complex that unzips the double-stranded DNA. The enzyme topoisomerase is involved in this process.
Elongation - The 5'-3' activity of the DNA polymerase enzyme. Now, a new strand was created by DNA polymerase enzymes in the direction of 5′ to 3′ (note: the DNA template is read in 3' to 5' direction). RNA primers were simultaneously created by the primase enzyme and utilized by the polymerase to create new strands of RNA.

As DNA polymerase enzyme has 5′ - 3′ direction so two types of strand are form -

LEADING STRAND - A DNA polymerase with high processivity that has the direction 5′ - 3′ (template strand 3′-5′) extends the continuous strand from the primer in the same direction as the replication fork that is expanding. One RNA primer is applied to the leading strand.

LAGGING STRAND - It is the discontinuous strand whose synthesis is going in the opposite direction of the replication fork that is developing. Each primer extends the lagging strand intermittently to create Okazaki fragments. A low processivity DNA polymerase that is different from the replicative polymerase enters to fill the gaps after RNase eliminates the priming RNA pieces. Multiple primers are applied to the lagging strand, and then the Okazaki fragments are joined by the ligase enzyme, filling in the gaps.

TERMINATION - Replication forks meet and end at several locations throughout the chromosome because eukaryotes start DNA replication at various locations; it is unknown how these are controlled. Termination necessitates the halting or blocking of the DNA replication fork's forward motion. When termination occurs at a particular locus, it includes the interaction of two elements: (1) a DNA sequence known as a termination site sequence, and (2) a protein that binds to this region to actually cease DNA replication.

#SPJ2

You might be interested in

What is the symbol for carbohydrates

Mariana [72]

The answer is none. carbon has a symbol (c) but there is no symbol for carbohydrates because its not a chemical compound.for example fats or vitamins or minerals

8 0

3 years ago

A force has direction and contact true or false

Assoli18 [71]

Answer:

Because a force is a vector that has a direction, it is common to represent forces using diagrams in which a force is represented by an arrow. In physics, a force is any interaction that, when unopposed, will change the motion of an object. A force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate. ... A force has both magnitude and direction, making it a vector quantity.

Therefore, yes

8 0

3 years ago

Which of the following is necessary for the light-independent reactions to proceed?

Yanka [14]

Answer;

C) ATP

Explanation;

-Photosynthesis can be divided into two parts: the light-dependent reactions and the light-independent reactions (also referred to as the "dark" reactions).

-The two products of the light-dependent reactions of photosystem are ATP and NADPH. The movement of high energy electrons releases the free energy that is needed to produce these molecules. The ATP and NADPH are used in the light-independent reactions to make sugar.

-The light-independent reactions, or dark reactions, of photosynthesis are chemical reactions that convert carbon dioxide and other compounds into glucose. These reactions occur in the stroma, the fluid-filled area of a chloroplast outside the thylakoid membranes.

8 0

3 years ago

Fermentation is an anaerobic biochemical pathway with truly one simple intent.

larisa86 [58]

Answer:

We are losing Earth's greatest biological treasures just as we are beginning to appreciate their true value. Rainforests once covered 14% of the earth's land surface; now they cover a mere 6% and experts estimate that the last remaining rainforests could be consumed in less than 40 years.

One and one-half acres of rainforest are lost every second with tragic consequences for both developing and industrial countries.

Rainforests are being destroyed because the value of rainforest land is perceived as only the value of its timber by short-sighted governments, multi-national logging companies, and land owners.

Nearly half of the world's species of plants, animals and microorganisms will be destroyed or severely threatened over the next quarter century due to rainforest deforestation.

Experts estimates that we are losing 137 plant, animal and insect species every single day due to rainforest deforestation. That equates to 50,000 species a year. As the rainforest species disappear, so do many possible cures for life-threatening diseases. Currently, 121 prescription drugs sold worldwide come from plant-derived sources. While 25% of Western pharmaceuticals are derived from rainforest ingredients, less that 1% of these tropical trees and plants have been tested by scientists.

Most rainforests are cleared by chainsaws, bulldozers and fires for its timber value and then are followed by farming and ranching operations, even by world giants like Mitsubishi Corporation, Georgia Pacific, Texaco and Unocal.

There were an estimated ten million Indians living in the Amazonian Rainforest five centuries ago. Today there are less than 200,000.

In Brazil alone, European colonists have destroyed more than 90 indigenous tribes since the 1900's. With them have gone centuries of accumulated knowledge of the medicinal value of rainforest species. As their homelands continue to be destroyed by deforestation, rainforest peoples are also disappearing.

Most medicine men and shamans remaining in the Rainforests today are 70 years old or more. Each time a rainforest medicine man dies, it is as if a library has burned down.

When a medicine man dies without passing his arts on to the next generation, the tribe and the world loses thousands of years of irreplaceable knowledge about medicinal plants.

Explanation:

3 0

3 years ago

How do scientist today usually communicate their results and conclusions

Rudiy27

Scientists publish their results and conclusions in scientific journals.

8 0

3 years ago