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You are investigating how the number of nerve cells is regulated in a specific tissue of your favorite experimental organism. You isolate a mutant that contains almost none of these nerve cells in the adult animal, and you hypothesize that in this mutant the nerve cells are either not made or do not connect to their target cells and therefore fail to get the survival signals they need. You are surprised by the results of a developmental time course that you perform. You find that in the mutant more of the nerve cells are made than in controls, and they all connect correctly to their target cells. But then, at later times, nearly all of the nerve cells undergo apoptosis. What could be the explanation?

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Nelly Stracke
Nelly StrackeLv2
28 Sep 2019

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Related questions

________30. If you are investigating the inner structure of a new cell and see that it has a significantly larger amount of RER than other cells. You would conclude the cell does a great deal of____?
A. ATP synthesis

B. protein synthesis
C. DNA synthesis
D. active transport
E. polysaccharide hydrolysis

________31. If a cell comes in contact with a toxic substance such as H2O2, it could survive as long as it has a ___ to digest it.
A. DNA
B. peroxisome

C. mitochondria
D. phospholipids
E. intermediate filaments

________32. Some cells have structures to help them withstand osmotic pressure. For example,
A. Plant cells due to their walls
B. Animal cells due to the sodium/potassium pumps

C. Bacterial cell due to their swimming

D. Viruses due to their protein coats

________33. Evolution occurs only as a cell ____.

A. They undergo mitosis
B. Change in their gene pool
C. They move from one habitat to another

D. They begin to eat different foods

________34. Ribosomes are produced in the

A. nucleoli.
B. chromatin.
C. nuclear envelopes.

D. Golgi complex. E. cisternae.

________35. Algae are often green, but there are red and brown species also. What accounts for this difference in color?
A. The chlorophyll of chloroplasts
B. The pigments in other plastids

C. The presence of a mitochondria
D. The accumulation of cellular wastes

________36. The chloroplast and other like prokaryotes have which of the following that helps with photosynthesis?
A. They live in water based environments
B. They have chloroplasts in their cytoplasm

C. Change color in the dark vs. the sun
D. They have photoreceptor proteins in their membranes or mesosomes.

________37. Located in the membrane, we see a set of proteins called receptors that only connect with or bind to specific substances. This is called __.
A. ligand specificity.
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C. cell tonicity.
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________38. Of the following statements, we could say that ___ is false.
A. All organisms are composed of cells and cell products.
B. An organism's structure and all of its functions are due to the activities of cells.
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D. Cells come from preexisting cells.
E. Cells are made from nonliving components including the nucleus, cell membrane and cytoplasm.

________39. If it is really true that our cells are the smallest anatomical unit that meets all of the properties of life, then which of the following could imply otherwise?
A. vacuoles
B. centrioles

C. Golgi apparatus
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________40. Oxygen is an absolute need for animal and plant cells alike due to the ___.

A. RER
B. Mitochondria
C. Lysosomes

D. DNA

________41. In a plasma membrane, we expect to see the carb/protein structures to extend into the ___, but the secondary messengers to move within the __.
A. extracellular fluid; cytosol
B. cytosol; extracellular fluid

C. intracellular fluid; cytosol

D. cytosol; intracellular fluid

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________42. Bacteria are found in all of the following habitats:

A. Caves
B. Oceans
C. Animals

D. Everywhere on Earth

________43. Two solutions are separated by a selectively permeable membrane. Solution A has a higher concentration of an impermeable solute compared to solution B. Which of the following do you expect would happen?
A. solute will move from solution A to solution B

B. solute will move from solution B to solution A

C. water will more from solution A to solution B

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B. up; facilitated transport
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C. produce enzymes.
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A. Organs
B. Tissues

C. Cells

D. Nuclei

Question 2. Splicing is complicated. There isconstitutive splicing, and then there is regulated alternativesplicing, and these molecular events can occur in the same ordifferent tissues.

a. What is constitutive splicing?

b. What is alternative splicing?

c. Draw a gene with three exons and twointrons. In this example assume exons 1,2,3 are expressed in onetissue and exons 1,3 are expressed in another. Draw the alternativesplicing, and the resulting RNA from this gene.

d. Draw a model illustrating how sterichindrance can promote alternative splicing with in a gene.

e. An individual is heterozygous, one copy ofthe gene has a mutation in exon 1 and the other copy of the gen ehas a mutation exon 3. Draw their genes, with mutations. What RNAmolecules can be expressed from these alleles? Will thisheterozygote have a mutant or a wild - type phenotype? Explain.Assume the 1/3 variant and the 1/2/3 variant are required indifferent tissues

Question 3 . You haveidentified a 4 exon gene expressed in the nervous system of adiploid animal. Different splice variants are expressed in thenervous tissue at the same time. T he organism under study has agene, unc - 250 , that controls movement and has three differentrecessive mutant alleles: allele s a 1 , a2 , and a3 . All threemutations are nonsens e stop mutations. When a diploid organism ishomozygous for allele a 1 animals die. When homozygous for eitherallele a2 , or allele a3 , animals are very uncoordinated in theirmovement (unc). Alleles a2 and a3 fail to complement allele a1 ,that is to say a1 / a2 and a 1 / a3 heteroallelic animals are veryuncoordinated in their movement (unc). However, a2 / a3 animals arewild type, ie they complement. Using alternative splicingconstruct a logical model for these observations and show whereeach of the mutations would be located in the gene.

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