Anaphase I begins when the two chromosomes of each bivalent (tetrad) separate and start moving toward opposite poles of the cell as a result of the action of the spindle. Notice that in anaphase I the sister chromatids remain attached at their centromeres and move together toward the poles.

5 0

3 years ago

Provide an adaptive and a nonadaptive hypothesis for the evolutionary loss of useless organs, such as eyes in many cave-dwelling

Zepler [3.9K]

In order to be able to Provide an adaptive and a non-adaptive hypothesis, the following is required

<h3>What is adaptation?</h3>

It refers to a trait or an integrated set of traits that increases the fitness of an organism. It is the process of improving the fit of phenotype to environment through natural selection.

<h3>What is non adaptation?</h3>

it refers to those traits that do not result in the better adaptation of the organism to its environment, and does not increase the genetic fitness of the organism.

Let us take the case of vain organs. There may be a metabolic value to constructing a vain organ, and subsequently the humans who have misplaced that organ might also have a selective advantage. Also, if the organ is useless, the mutations that disrupt the improvement of that organ would be evolutionarily neutral, and may want to unfold to fixation via genetic drift.

So an adaptive hypothesis as to why an organism may lose useless organs is energy trade offs. The organism may additionally be losing energy in growing and retaining a vain organ, whilst this strength can be higher used someplace else. So an organism that lives in a darkish cave might also sooner or later lose its eyes considering eyes are of no use inside a darkish cave.

A non adaptive hypothesis for the evolutionary loss of organs can be random mutation. If a random mutation occurs that causes an organism to lose its eyes, in a dark cave where it does not use its eyes anyway, it could still survive, reproduce and pass that mutation down.

For more information on adaptive hypothesis, visit

brainly.com/question/975242

3 0

2 years ago

Select the correct answer from each drop-down menu. rna interference is a mechanism of eukaryotic gene regulation. in this mecha

rosijanka [135]

The dicer enzyme processes dsRNA and forms siRNAs, which suppress the expression of target genes by cutting mRNA. 1) siRNA 2) RNA.

<h3>What are siRNA fragments?</h3>

siRNA means small interfering RNA. This is a silencing RNA molecule involved in the RNA interference mechanism, intervening in the expression of a specific gene.

siRNAs are complementary double-stranded RNA molecules composed of about 20-21 nucleotides. siRNA originates from a long double-stranded RNA (dsRNA).

The dicer enzyme cuts dsRNA molecules and produces siRNA. siRNAs suppress the expression of target genes when cutting messenger RNA.

siRNAs suppress the expression of target genes by cutting the complementary messenger RNA (mRNA) into two halves. This is accomplished by the interaction of the siRNA with the RISC complex (RNA-induced silencing complex).

The two mRNA halves are later degraded by the cellular machinery, leading to the suppression of the gene expression.

siRNAs also participate in other pathways related to RNAi, such as in antiviral defense or in the chromatin structure organization.

RNA interference is a mechanism of eukaryotic gene regulation. In this mechanism, the enzyme dicer cuts dsRNA into smaller fragments called (1) siRNA, which form a complex with RISC and degrade specific (2) RNA.

You can learn more about siRNA at

brainly.com/question/7508257

#SPJ1

5 0

1 year ago