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
Which of the following is not a piece of molecular evidence supporting the endosymbiotic theory?
Alchen [17]
A. the mitochondria and chloroplasts are much different in structure than bacteria
6 0
3 years ago
2 Describe List three devices that produce
agasfer [191]

Answer:

list of three devices are 1st phone 2nd doorbell 3rd alarm clock

Explanation:

if these devices will not produce sound then we can not do our work properly these are very useful for everyday life

5 0
2 years ago
Which of the following is the correct haploid number of chromosomes in humman?
Dima020 [189]

Answer: 23 chromosomes

In humans, gametes are haploid cells that contain 23 chromosomes, each of which a one of a chromosome pair that exists in diplod cells. The number of chromosomes in a single set is represented as n, which is also called the haploid number. In humans, n = 23.

HOPE THIS HELPS

4 0
2 years ago
Read 2 more answers
What two things can you tell from each word of an air masses' name?
olchik [2.2K]

Answer:

<em>Option</em><em> </em><em>A)</em><em> </em><em>humidity</em><em> and</em><em> </em><em>temperature</em>

3 0
3 years ago
What are the 3 laws of inheritance?
nikdorinn [45]

The three laws of inheritance are :

Law of Dominance. Law of Segregation. Law of Independent Assortment.

what is law of dominance?

First, according to the Law of Dominance and Uniformity, some alleles—variants of a specific gene located at the same chromosomal locus or location—are dominant over other alleles for that gene.

As it relates to genetics, the term "inherited" describes a feature or variation that is encoded in DNA and passed from parent to child during reproduction. The laws of Mendelian genetics govern inheritance. A will needs to be admitted to probate in order for the inheritance procedure to start. The probate court examines the will, approves an executor, and formally distributes assets to recipients in accordance with the terms. The executor will pay off any outstanding obligations of the deceased prior to the transfer

To learn more about inheritance,click below link

brainly.com/question/15078897

#SPJ4

3 0
1 year ago
Read 2 more answers
Other questions:
  • If a person cuts his finger eventually the cut will heal and the skin will be whole again how does the gap created by the cut ge
    9·1 answer
  • Why are hippos endangered
    14·2 answers
  • The reason that there are Okazaki fragments during DNA replication is ultimately because:
    14·1 answer
  • Our planet has changed overtime by?
    13·2 answers
  • Junipers, hemlocks, and cedars belong to which group of gymnosperms?
    8·2 answers
  • What are the three components of a nucleotide
    13·1 answer
  • How did land whales eventually became aquatic?
    13·1 answer
  • Van Helmont did experiments on
    6·1 answer
  • Read the descriptions ..
    13·1 answer
  • The offspring of crosses between parents with different traits are called:.
    5·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!