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discuss cytokinesis

discuss cytokinesis

 

Explain and discuss cytokinesis
Biology
Cytokinesis-the actual process of cell division-has attracted theorists for well over 100 years. It has been said that all possible explanations of cytokinesis have been proposed; the problem is to decide which one is correct.

Consider the following three hypotheses:

1. Chromosome signaling: When chromosomes split at anaphase, they emit a signal to the nearby cell surface to initiate
furrowing.

2. Polar relaxation: Asters relax the tension in the region of the cell surface nearest the spindle poles (the polar region),
allowing the region of the membrane farthest from the poles (the equatorial plane) to contract and initiate furrowing.

3. Aster stimulation: The asters stimulate contraction in the region of the cell surface where oppositely oriented spindle fibers
overlap (that is, the equatorial region), thereby initiating furrowing.

These hypotheses have been tested in a number of ways, One particularly informative experiment involved pressing a glass ball
onto the center of a dividing sand dollar egg so as to deform it into a torus (donut shape). As illustrated in Figure 17-35, the egg
divided into a single sausage-shaped cell at the first division; at the second division, it divided into four cells.

A. What does the chromosome-signaling hypothesis predict for the result of this experiment? Do the predictions match the experimental observations?

B. What does the polar-relaxation hypothesis predict for the experimental out-come? Do the predictions match the experimental observations?

C. What does the aster-stimulation hypothesis predict? Do the predictions match the experimental observations?

Predict salt concentration the protein would come off

Predict salt concentration the protein would come off

Predict salt concentration the protein would come off

Biology

Suppose you are purifying a protein on a weak cation exchanger (pH 7.5) and it comes off at 300mM salt. predict what salt concentration (lower, same, higher) the protein would come off if you used a strong cation exchanger. explain the logic behind your prediction in terms of the differences between a weak and strong exchange

What is the mechanism of diversity in translation

What is the mechanism of diversity in translation

 

What is the mechanism of diversity in translation

Biology

Many of the larger DNA viruses are able to enhance viral protein translation by coding for ribosomes that selectively translate viral proteins?

 

a. True b. false

Question 2: A viral messenger RNA has the following sequence:

AUG AGU GGG GCC CAU GGG AAA CCC AGG UUU

The following proteins are produced:

MetAsnGlyAlaHisGlyLysProArgPhe

MetGlyAsnProGly

What is the mechanism that generates this diversity?

A. Polyprotein Synthesis

B. Leaky Scanning

C. Suppression of Termination

D. Ribosomal frameshift

Question 3: Some viruses are able to initiate translation at sites other than AUG(Methionine)?

a. True b. false

Question 4: A viral messenger RNA has the following sequence:

AUG AGU GGG GCC CAU GGG AAA CCC AGG UUU

The following proteins are produced:

MetAsnGlyAlaHisGlyLysProArgPhe…

MetAsnGlyAlaProTrpGluThrGlnVal…

What is the mechanism of diversity in translation of this viral mRNA?

Question 5: The genomes of (+) RNA viruses can be translated immediately upon cellular entry, even though they do not possess a 5′ 7-methylguanosine cap due to the presence of this structure at the 5′ end of the genome [x].

Question 6: Most viral infections induce activation of the eIF2a kinase PKR which halts protein translation in an infected cell. Which of the following mechanism enable viruses to evade the antiviral effects of PKR (Select all that apply)?

A. Viral protein inhibits eIF2a phosphatase.

B. Viral proteins inhibit dsRNA binding to PKR

C. Virus produces its own kinase that phsophorylates eIF2a.

D. Viral protein binds to PKR dsRNA binding site and activates PKR autophosphorylation.

E. Viral proteins act as pseudo-substrates that inhibit PKR kinase activity

 

Calculate the percentage of the bacterial genome

Calculate the percentage of the bacterial genome

Calculate the percentage of the bacterial genome
Biology
Sequencing of a new bacterial genome revealed a circular genome of 2.9 x 106 base pairs. Open reading frame (ORF) analysis indicated the presence of 2,120 ORFs that encode proteins with a median length of 270 amino acids (aa) and an average length of 360 aa. Based on this information and assuming that all of the predicted ORFs actually encode proteins, calculate the percentage of the bacterial genome that encodes the cell’s complete proteome.

An action-potential signal to a postsynaptic neuron

An action-potential signal to a postsynaptic neuron

An action-potential signal to a postsynaptic neuron

Biology

It is known that calcium plays diverse roles in cellular processes. Upon increases in cytotoxic calcium concentration, calcium binds to proteins that have calcium binding sites, leading to the conformational change of the protein as well as changes in its biological activity. For in case, it is well established that in presynaptic neurons, the elevation of cytosolic calcium triggers the fusion of exocytotic vesicles that contain neurotransmitters to the plasma membrane.

A.) How does calcium trigger the fusion of exocytotic vesicles to the plasma membrane?

B.) How does the presynaptic neuron transducer an action-potential signal to a postsynaptic neuron

How many genes are involved in determination of fruit shape

How many genes are involved in determination of fruit shape

 

How many genes are involved in determination of fruit shape

Biology

The fruit in summer squash may have different shapes. When two true breeding plants with disc-shaped fruit were crossed to true breeding plants with long fruit, all the F1 plants had disc fruits. In the F2 progeny there were 110 plants with disc-shape fruits, 70 plants with sphere-shape fruits and 12 plants with long fruits.

How many genes are involved in determination of fruit shape in summer squash?

Mutational event to the frameshift mutant

Mutational event to the frameshift mutant

 

Mutational event to the frameshift mutant

Biology

Some amino acids are post-translationally removed from the C-terminal end of the b-lactamase enzyme from B. imaginarium (i.e. – after translation and release from the ribosome, a protease chews off a few amino acids). The purified wildtype enzyme is 327 amino acids in length and the sequence of its C-terminal amino acids is shown below aligned with the C-terminal amino acids found in a mutant strain of B. imaginarium, which contains of a frameshift mutation that abolishes processing if its C-terminus. This frameshift mutant was caused by insertion or deletion of a single nucleotide. Use this information to answer the questions below.

AA# 327

wild-type: Ser Asn Ala Lys Asp Trp

mutant: Ser Asn Ala Ile Arg Leu Asp Trp Gln Met Lys

A. What was the mutational event that gave rise to the frameshift mutant? Determine precisely where the single nucleotide insertion or deletion occurred in the b-lactamase coding sequences.

B. What is the length of the wildtype enzyme prior to processing (how many amino acids)?

C. Deduce, as far as possible, the actual sequence of the C-terminus of the wild-type enzyme prior to processing.

 

What relationship to the allele for yellow seeds

What relationship to the allele for yellow seeds

What relationship to the allele for yellow seeds

Biology

Mendel crossed yellow-seeded and green-seeded pea plants and then allowed the offspring to self-pollinate to produce an F2 generation. The results were as follows: 6022 yellow and 2001 green (8023 total). The allele for green seeds has what relationship to the allele for yellow seeds?

dominant
incomplete dominant
codominant