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shutvik [7]
3 years ago
14

Where does gas exchange occur between the blood and tissues?

Biology
1 answer:
BartSMP [9]3 years ago
7 0

jjj

idk

Explanation:

vete al hospital porque me voy de la casa nunca se me olvido

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A diploid somatic ("body") cell has 2n=20 chromosomes. At the end of mitosis, each daughter cell would have ______ chromosomes.
Nostrana [21]

Answer:

1. 20 chromosomes

2. 10 chromosomes

3. 10 chromosomes

Explanation:

1. The process of mitosis results in the two daughter cells from the same parental cell with exactly the same genetic material. Thus the two cells contain the same number of chromosomes as the parent cell. Therefore if a cell with 20 chromosomes undergoes mitosis will result in the 20 chromosomes.

2. During meiosis I two daughter cells are formed with different ploidy levels as the number of the chromosome reduces to half. Therefore the cell with 20 chromosomes results in two cells with 10 chromosomes.

3. During meiosis II, the two daughter cells formed from meiosis I result in the formation of two more daughter cells with an exact number of chromosome number that is 10 chromosomes.

7 0
3 years ago
QUESTION 8 In pea plants, purple (P) is dominant for flower color and white (p) is recessive. In a cross between a plant that is
Leviafan [203]
Your answer is actually all correct. Great job! A heterozygous combination would just implicate greater power to the 'dominant' dominant allele.
8 0
3 years ago
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Which statement describes how pioneer species and climax communities are different?
Lorico [155]

Answer: D). Primary species have large numbers of offsprings, and climax communities contain species that have small numbers of offsprings.

An ecological succession is a process of gradual changes occurs in a biological community with respect to changes in the non-living abiotic factors  (water, air and sunlight) and with respect to time until the ecosystem attains stability. Primary or pioneer species are the species which invade the previously barren and primitive landmass for their survival. These species make the environment suitable for the growth of other species. These grow and develop in the initial stages of succession. These species are simple organisms which reproduce asexually and produces large number of offsprings. Examples are lichen and moss. Lichen grows on the surface of rocks and acids released by them causes withering of rocks into soil which facilitate the growth of mosses and other plants. Climax community develops in an ecosystem after replacing many previously inhabiting species. Climax community develops in the end of the ecological succession. It contains species which are highly complex and uses sexual reproduction for the production of offsprings which are less in number as compared to those produced by pioneer species by asexual reproduction.  

8 0
3 years ago
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Why does prolonged exposure to UV light from the sun or tanning beds increase the risk for getting skin cancer?
Lilit [14]
B. Increased exposure to UV light increases the risk of mutation occurring.
7 0
2 years ago
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Explain how we know that DNA breaks and rejoins during recombination.
alisha [4.7K]

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.

8 0
3 years ago
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