1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Zinaida [17]
3 years ago
15

Explain how we know that DNA breaks and rejoins during recombination.

Biology
1 answer:
alisha [4.7K]3 years ago
8 0

Answer:

It occurs through homologous recombination

Explanation:

GENERAL RECOMBINATION OR HOMOLOGIST

           Previously we defined its general characteristics. We will now describe a molecular model of this recombination, based on the classic Meselson and Radding, modified with the latest advances. Do not forget that we are facing a model, that is, a hypothetical proposal to explain a set of experimental data. Not all points of this model are fully clarified or demonstrated:

           Suppose we have an exogenote and an endogenote, both consisting of double helices. In recombination models, the exogenote is usually referred to as donor DNA, and the endogenote as recipient DNA.

1) Start of recombination: Homologous recombination begins with an endonucleotide incision in one of the donor double helix chains. Responsible for this process is the nuclease RecBCD (= nuclease V), which acts as follows: it is randomly attached to the donor's DNA, and moves along the double helix until it finds a characteristic sequence called c

Once the sequence is recognized, the RecBCD nuclease cuts to 4-6 bases to the right (3 'side) of the upper chain (as we have written above). Then, this same protein, acting now as a helicase, unrolls the cut chain, causing a zone of single-stranded DNA (c.s. DNA) to move with its 3 ’free end

2) The gap left by the displaced portion of the donor cut chain is filled by reparative DNA synthesis.

3) The displaced single chain zone of the donor DNA is coated by subunits of the RecA protein (at the rate of one RecA monomer per 5-10 bases). Thus, that simple chain adopts an extended helical configuration.

4) Assimilation or synapse: This is the key moment of action of RecA. Somehow, the DNA-bound RecA c.s. The donor facilitates the encounter of the latter with the complementary double helix part of the recipient, so that in principle a triple helix is formed. Then, with the hydrolysis of ATP, RecA facilitates that the donor chain moves to the homologous chain of the receptor, and therefore matches the complementary one of that receptor. In this process, the chain portion of the donor's homologous receptor is displaced, causing the so-called "D-structure".

It is important to highlight that this process promoted by RecA depends on the donor and the recipient having great sequence homology (from 100 to 95%), and that these homology segments are more than 100 bases in length.

Note that this synapse involves the formation of a portion of heteroduplex in the double receptor helix: there is an area where each chain comes from a DNA c.d. different parental (donor and recipient).

5) It is assumed that the newly displaced chain of the recipient DNA (D-structure) is digested by nucleases.

6) Covalent union of the ends originating in the two homologous chains. This results in a simple cross-linking whereby the two double helices are "tied." The resulting global structure is called the Holliday structure or joint.

7) Migration of the branches: a complex formed by the RuvA and RuvB proteins is attached to the crossing point of the Holliday structure, which with ATP hydrolysis achieve the displacement of the Hollyday crossing point: in this way the portion of heteroduplex in both double helices.

8) Isomerization: to easily visualize it, imagine that we rotate the two segments of one of the DNA c.d. 180o with respect to the cross-linking point, to generate a flat structure that is isomeric from the previous one ("X structure").

9) Resolution of this structure: this step is catalyzed by the RuvC protein, which cuts and splices two of the chains cross-linked at the Hollyday junction. The result of the resolution may vary depending on whether the chains that were not previously involved in the cross-linking are cut and spliced, or that they are again involved in this second cutting and sealing operation:

a) If the cuts and splices affect the DNA chains that were not previously involved in the cross-linking, the result will be two reciprocal recombinant molecules, where each of the 4 chains are recombinant (there has been an exchange of markers between donor and recipient)

b) If the cuts and splices affect the same chains that had already participated in the first cross-linking, the result will consist of two double helices that present only two portions of heteroduplex DNA.

You might be interested in
How did the development of the brain contribute to hominid evolution?
Phoenix [80]

The brain is most of the ape's main gimmicks, aside from the opposable thumb. It allows us to not die without claws, fangs, and other evolutionary benefits.

6 0
3 years ago
Which of these is an example of inside lag in monetary policy?
FrozenT [24]
<span>The correct answer is C. The Fed lowers interest rates several months into a recession. It's a lag because they could've done it sooner and helped with the recession sooner but decided not to and thus they created a lag in monetary policy of a federation. It's like if the congress refused to help with the recession for no reason for a few months.</span>
7 0
3 years ago
Read 2 more answers
what structure is found outside of the cell membrane of a plant cell which gives the cell its strength and shape
pychu [463]

Answer: the cell wall

Explanation:

6 0
3 years ago
Read 2 more answers
Witch statment best compares and contrast two physical properties of matter
marta [7]
What are the statement choices?
4 0
3 years ago
What is a part of the central dogma? A.RNA is a single stranded molecule. B.DNA is used as a template to make RNA. C.RNA contain
arsen [322]
<span>"DNA is used as a template to make RNA" is a part of the central dogma of molecular biology.</span>
7 0
3 years ago
Read 2 more answers
Other questions:
  • The _____ sends out an electrical impulse that regulates the heartbeat.
    9·2 answers
  • What sets of instructions in each human cell that determine inherited traits called?
    6·1 answer
  • Which statement is true?
    6·2 answers
  • Sound waves can only travel through fluids<br> TRUE or FALSE
    8·2 answers
  • Evolution by ___ ____ is the theory that maintains that population inherited traits change over time
    10·1 answer
  • Explain what occurs during the process of each type of artificial selection technique. Cloning, Artificial Insemination, In vitr
    14·1 answer
  • Starch digestion begins in the mouth. what specifically occurs during starch digestion?
    11·1 answer
  • Can someone please answer quick and correctly all three questions btw thxs I will give brainliest
    15·1 answer
  • Unlike the cell membrane, the cell wall is a
    14·1 answer
  • Removal of water from plants bodies in form of vapour is called ____​
    15·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!