Answer:
Immediately following the arrival of the stimulus at the axon terminal there is a short period called the latent period.
Explanation:
When a stimulus reaches the terminal of an axon, a period known as the latent period begins. This period has a short duration and during it it is possible to observe the blockage of new stimuli in the nerve fiber. Thus, the new stimuli fail to trigger an impulse and no muscle tension to be observed.
While the latent period is not finished, the neurotransmitter is released through the action of exocytosis that moves until it gets access to the receptor capable of activating the muscle cell.
Answer:
Empirical evidence of his ideas
Explanation:
The scientific process involves the formulation of hypotheses that enable to answer questions about the real world, and then to carry out experiments or observations that are used to confirm (or reject) such predictions. In the last 160 years, Darwin's ideas on 'descent with modification' have constantly been subjected to experimental assessment, and obtained data confirmed his observations. For example, molecular evidence based on the DNA and RNA -which constitute the genetic material of all living organisms- has shown the conservation of this process. In consequence, molecular evidence has been used to construct 'evolutionary' phylogenetic trees from DNA/RNA sequences. Moreover, evidence in genetics has shown the critical role played by mutations in the mechanism of natural selection proposed by Darwin, thus also confirming his theories. These are only some examples, and supporting evidence confirming Darwin's ideas has been collected from different research fields ranging from ecology to molecular biology.
Answer:
2% of the progeny will be double crossovers for the trihybrid test cross
Explanation:
By knowing the positions of genes, we can estimate the distances in MU between them per region.
- Genes A and B are 10 map units apart (Region I)
- Genes B and C are 20 map units apart (Region II)
- Genes A and C are 30 map units apart
----A-------10MU--------B-------------20MU-------------C---
Region I Region II
We can estimate the recombination frequencies by dividing each distance by 100.
• recombination frequency of A-B region = 10MU / 100 = 0.10
• recombination frequency of B-C region = 20MU / 100 = 0.20
Now that we know the recombination frequencies in each region, we can calculate the expected double recombinant frequency, EDRF, like this:
EDRF = recombination frequency in region I x recombination frequency in region II.
EDRF = 0.10 x 0.20 = 0.02
2% of the progeny will be double crossovers for the trihybrid test cross
Answer:
I, II, III
Explanation:
A threshold stimulus is a stimulus that is capable to produce a response in excitable tissues such as neurons and muscle fibers. At threshold potential, the outward movement of K+ and inward movement of Na+ become equal to each other. When the potential exceeds the threshold potential, more and more Na+ enter the cell to depolarize it and to allow the opening of Na+ channels. Therefore, to fire an action potential, the threshold must be exceeded.
Conduction of action potential is all or none phenomenon which means that either it occurs or it does not occur. As an impulse is passed by each successive part of an exon, it enters the refractory period during which there is no conduction of nerve impulse. It ensures the one-way conduction of impulse from the cell body to the axon terminal only.
