Biology Forums - Study Force

I just realized my physioex 9.0 exercise 12 sheet is due tomorrow and I don't think I have time to finish it because I have a million other things for school I have to do tonight. If anybody has any of the answers and could help I would greatly greatly appreciate it! I really need to get it done. I'm usually very good at staying on top of my work but this week has been hectic and this assignment completely slipped my mind! Here are the questions..

Activity 1
1. Describe the importance of the washing steps in the direct antibody fluorescence test.
2. Explain where the epitope (antigenic determinant) is located.
3. Describe how a positive result is detected in this serological test.
4. How would the results be affected if a negative control gave a positive result?

Activity 2
1. Describe how you were able to determine what antigen is in the unknown well.
2. Why does the precipitan line form?
3. Did you think human serum albumin and bovine serum albumin would have epitopes in common?

Activity 3
1. Describe how the direct and indirect ELISA are different.
2. Discuss why a patient might test indeterminate.
3. How would your results have been affected if your negative control had given an inderterminate result?
4. Briefly describe the basic structure of antibodies.

Activity 4
1. Describe why the HIV Western blot is a more specific test than the indirect ELISA for HIV.
2. Explain the procedure for a patient with an indeterminate HIV Western blot result.
3. Briefly describe how the nitrocellulose strips were prepared before the patient samples were added to them.
4. Describe the importance of the washing steps in the procedure.

A positive result is detected when fluorescently labeled antibodies bind to the epitope regions found on the elementary bodies when they are present.


A patient that is indeterminate would be retested and monitored.

Good luck.

Thank you  :) if anyone else has any other answers and could help that would be great!

It is very important to following the washing steps in the direct antibody fluorescence test in order to remove any non specific binding that may have occurred.

Using Direct Fluorescent Antibody Technique to Test for Chlamydia
1. Describe the importance of the washing steps in the direct antibody fluorescence test.
This is done to wash off excess antibodies and prevent nonspecific binding of the antigen and antibody

2. Explain where the epitope (antigenic determinant) is located.

The epitopes are located in the antigens so that the antibodies can bind to them

3. Describe how a positive result is detected in this serological test.

The elementary bodies of the Chlamydia trachomatis stains green inside the red host cell, and the presence of ten or more elementary bodies in a field of view with a diameter of 5mm is considered a positive result.

4. How would the results be affected if a negative control gave a positive result?

This would be a false positive which would invalidate all other results

A C T I V I T Y 2
Comparing Samples with Ouchterlony Double Diffusion
1. Describe how you were able to determine what antigen is in the unknown well.

The results between well 2 & 5 were the same results as 3 & 4. Human serum albumin was placed in 4, so that must have been placed in 5 to achieve the same result

2. Why does the precipitin line form?
The precipitin line occurs when the antigen and antibody are in optimal proportions and cross-linking occurs forming an insoluble precipitate.

3. Did you think human serum albumin and bovine serum albumin would have epitopes in common? How well did the results compare with your prediction?

   yes
results showed they have partial identity

A C T I V I T Y 3

Indirect Enzyme-Linked Immunosorbent Assay (ELISA)

1. Describe how the direct and indirect ELISA are different.
   Direct ELISA is directly looking for the foreign substance
The microtiter plate is coated with homologous antibodies made against the antigen of interest If the antigen is present, a sandwich of antibody, antigen and secondary antibody will form
Indirect ELISA is designed to detect antibodies that the patient has made against the antigen
The microtiter plate is coated with antigens



2. Discuss why a patient might test indeterminate.
The patient might test indeterminate if they have not yet seroconvert or it they have not yet produced enough antibodies to yield a positive result

3. How would your results have been affected if your negative control had given an indeterminate result?
If the negative control is positive this invalidates the results It could be due to not enough washing in the washing steps to remove nonspecific binding


4. Briefly describe the basic structure of antibodies.
A C T I V I It is composed of four polypeptides linked by disulfide(-S-S-) bonds.
The two heavy chains are about 400 amino acids long, and the two light chains about half that long. Each heavy chain has a hinge region where the antibody is bent, giving the monomer a T or Y shape Y 4
   



 Western Blotting Technique
1. Describe why the HIVWestern blot is a more specific test than the indirect ELISA for HIV.

The HIV Western blot has a discrete protein band that represents the specific antigen the antibody is recognizing, while the ELISA uses a well that corresponds to a mixture of antigens.

2. Explain the procedure for a patient with an indeterminate HIVWestern blot result.

Patients that are deemed indeterminate after multiple tests should be monitored and tested again at a later date.  They are deemed indeterminate if bands are present but do not match the criteria for a positive result. For results to be positive there must be bands in gp160, gp120 and either p31 or p24.


3. Briefly describe how the nitrocellulose strips were prepared before the patient samples were added to them.
Electrical current is used to separate proteins on the basis of their size and charge.  This technique uses gel electrophoresis to separate the proteins in a gel matrix, the proteins are then transferred to a nitrocellulose membrane.
   

4. Describe the importance of the washing steps in the procedure.

The washing steps remove any nonspecific binding of secondary conjugated antibodies so they do not react incorrectly with the substrate to give a false positive.

Thanks for this!(:

thanku so much..

The proteins separated on the nitrocellulose in this activity are _______.
The proteins separated on the nitrocellulose in this activity are _______.
    Lyme disease antibodies
    HIV antigens
    Lyme disease antigens
    HIV antibodies

In this activity, _______________ was used to detect a positive result.
In this activity, _______________ was used to detect a positive result.
    immunofluorescence
    Ouchterlony technique
    an indirect ELISA
    a direct ELISA
HELPPPPP!!!!

The sample(s) from which of the following tested positive for reverse transcriptase?
The sample(s) from which of the following tested positive for reverse transcriptase?
    patient B and the positive control
    the positive control
    patient C and the positive control
    patient B



HElP PLEASE!!!!

Antigens with epitopes in common _______.
Antigens with epitopes in common _______.
    can have partial identity and can be identical
    can have partial identity
    can be identical
    can have nonidentity
    can have partial identity, can be identical and can have nonidentity

My students - I found this site.  Don't even think about copying - you'll get a zero.  Thanks to the students who copied for leading me straight here!  (If you can Google it, so can I).

Boo to teachers with no life