1. Exposure/dose:

a. Define and discuss the significance and differences between exposure-response evaluation and dose-response assessment.

b. Give an example of how each would be used.

2. Define the following terms and describe how they are used.

a. RfD

b. RfC

c. NOAEL

d. LOAEL

e. MDD

3. Formaldehyde is a chemical that has been known to be present in certain types of flooring.

a. List the chemical properties of formaldehyde.

b. List the physical properties of formaldehyde

c. List the toxicological properties of formaldehyde.

d. What are the pathway(s) of exposure to formaldehyde as a result of its use in interior finishes and the risks that people may be exposed to, if any.

A 50 year old male is seen in his physician’s office for a routine checkup. His spleen shows enlargement and his blood work shows hemolytic anemia with bilirubinemia. His wife states the patient has been “off” lately for no apparent reason. He tends to have muscle pulsations in the afternoon to late evening that do not stop until he goes to sleep. Additional blood work is ordered along with a type and screen. His haptoglobin levels are decreased, and his physician orders two units of packed RBCs. His antibody screen results show he has a weakened expression of Kell antigens.

What is the most likely diagnosis?

You are given 5mL of 3mg/mL protein solution. You are asked to prepare samples for SDS-PAGE containing 250ng, 500ng, 750ng, and 1000ng. Your pipettes are calibrated to 2uL at the lower limit. Your total volume is 20uL, with 5uL being your loading buffer. How would you prepare these samples?

Why do you need to stimulate the nerve for longer at a lower stimulus intensity?

Young children tend to be “picky eaters.” This may lead to an imbalanced diet, poor intake of vitamins and minerals, and an increased risk of nutrient deficiencies. In this discussion you will gather and share ideas to help with this problem. Your first post should include the following three points.

1) Discuss toddlers/children. Briefly discuss the reason for your selection.

2) Using the HON website from Unit 1, research to find a reliable source for specific tips and strategies on how to encourage children to eat a well balanced diet. Include the web link to the specific article.

3) Using your research, describe at least one idea which might be used to support with eating/feeding challenges of children. Do you think the idea will work? Why or why not? Have you tried any of the ideas with your family or seen others use the suggestions?

Plasma membrane receptors must somehow let the inside of the cell “know” that a ligand/signal is present on the outside of the cell. In most cases, the ligand does NOT enter the cell. How does the inside of the cell “get the message”? Name two specific mechanisms for how this can be achieved. List and describe each mechanism. Then provide one example for each.  

Mechanism 1 (including example):

Mechanism 2 (including example):

You isolate nuclei from three different eukaryotic species. You treat the samples in exactly the same way (adding same amount of enzyme, buffer and time) to partially digest the chromatin with micrococcal nuclease, extract the DNA, and run it on a gel. You see the pattern below:

a-2pts) Knowing that the core-DNA in all cell types is the same what is your explanation for the difference in size in the patterns you observe (shown below):

b- 2pts) If you digested each of the three samples more thoroughly, what would the pattern look like? [Be specific and indicate what the size of the bands would be]

c-3pt) An explorer discovers a strange new species of plant and sends some of the plant tissue to a geneticist to study. The geneticist performs the kinds of experiments as described above in (b) except that: After digestion with nuclease 120-bp fragment of DNA are seen.
Analysis of the histone core reveals histones in the following proportions:

H2A 33.3%
H2B 33.3%
H3 0% [no histone H3 found]

H4 33.3%

On the basis of these observations, what conclusions could the geneticist make about the probable structure of the nucleosome in the chromatin of this plant? Be specific in describing the nature of the nucleosome: which histones form the core (1pt), how many of each are in there (1pt) and how much core-DNA is around it (1pt).

d-2pt) The geneticist also found H1 and a new histone H7 when histones were extracted from all of the chromatin (not just the nucleosome). What do you think the role of the new histone H7 would be in this new plant species?

After the discovery of DNA polymerase by Arthur Kornberg, the properties of the enzyme became quite well known. One of the most critical is that all known DNA polymerases synthesize DNA only: 5' to 3'. This fact led to a dilemma regarding how the semiconservative model would work for a DNA molecule. Reiji Okazaki a brilliant experimenter took on this problem. [An aside: Okazaki was born near Hiroshima, Japan, in 1930. He was a teenager there at the time of the explosion of the first of two nuclear bombs that the US dropped at the end of World War II. Reiji's scientific career was cut short by his untimely death from cancer in 1975 at the age of 44]

In the actual experiment: They cultured E. coli (at low temperatures to slow down replication process) in the presence of radioactive nucleotides. They did this for short pulses followed by the addition of excess nonradioactive nucleotides. This resulted in label (radioactivity) being present only in the DNA that was synthesized during the short period of the pulse. Soon after the pulse, they isolated the DNA and separated the individual strands from one another. The various pieces of DNA could then be sorted out by size: using a “sucrose gradient” and spun in an ultracentrifuge.

3a- 2pts) Describe what types of DNA fragments he would have observed after short pulses? Indicate in your answer:

1. What the difference is between the fragments in terms of size
2. Based on your understanding of the process of DNA replication what the source of those

fragments would be.

(Use accurate terminology. We will be using a Rubric that looks for the accurate use of terms needed to answer this question)

Assume Okazaki and his team were unaware that their bacteria had a mutation in the gene that codes for DNA Ligase. Also assume that the mutation rendered the protein DNA Ligase unable to carry out its enzymatic activity/function.

3b- 1pt) What kinds of fragments would be seen after a short pulse when carrying out the assay with such a mutant? (0.5pt) Why? (0.5pt) (Answer in complete sentences)

3c- 1pt) What kind of fragments would be seen after a long exposure to the radioactive label? (0.5pt) Why? (0.5pt) Answer in a complete sentence

Complete the genetic information (DNA base pairs, t-RNA and mRNA nucleotide bases, and the amino acids this gene codes for, in the following

DNA strand1 :    ATG     _____    _____   _____    _____     _____    CGC

DNA strand 2 : *_____    GCC    _____   _____    _____    AGT     _____   

mRNA : _____   _____    AUA    _____    UUU   _____    _____

   tRNA : _____    _____   _____     UAC     _____   _____    _____

Amino acids :   ______   ______   _____   _____   ______   ______   ______

(Remember which type of RNA actually carries the CODE as codons!)

* this is the DNA "sense strand" that will be transcribed to mRNA

Regression Trees​

Explain how classification trees works.

Given a classification tree, state the classification rule for a particular leaf.

List the two measures of impurities that were covered in class.

Why do we prune trees?

What are the advantages of single classification trees? The weaknesses?

One way to identify use of methamphetamine in a population is to monitor the waste water. Methamphetamine is excreted from the body up to 23% unchanged and can cause unintended environmental exposures. It has been detected in the sewage of all major cities, even after sewage treatment. Methamphetamine is organic base with a pKaof 10.0 [12].

a. Many sewage treatment facilities induce pH ranges from pH 5 to pH 10 to encourage degradation. Is methamphetamine charged at these extremes? Also, circle and name the functional group(s) predominately responsible for the pKa. Please provide your reasoning.

b. Methamphetamine is excreted in urine as a cation. Assuming it enters the environment as a cation, which of the four environmental compartments would you expect to find methamphetamine? Use chemical properties and environmental properties to justify your reasoning. (Hint: there are potentially two compartments.)

c. Assuming methamphetamine enters the environment as a cation through urine, what environmental properties determine which environmental compartment methamphetamine will be in?

d. Roughly three to six pounds of toxic waste is produced for each pound of

methamphetamine produced. Vapors created during production also cause further

environmental contamination, depositing the un-charged drug on surfaces near the

production site. The log Kow of methamphetamine is 2.07. What is the ratio of

methamphetamine in octanol:water?

i. What does this imply about BCF?

ii. What does it imply about K

d

?

iii. Also, what does all of this mean when we are talking about environmental

transport and potential persistence of methamphetamine in the environment?

You are studying a plant whose seed shape (round, disc or elongated) and seed color (yellow, green grey) are determined by two different gene loci. The R/r locus controls seed shape and the Y/y locus control seed color. You have some data from single-trait crosses that were carried out by a friend of yours:

-Yellow and green seed plants each breed true when self crossed, but grey seed plants produce offspring of all 3 color seeds.

-Round seed crossed with elongated seed plants produce only disc shaped seed plants.

When two plants having the same phenotype of seed shape and color were crossed, the offspring appeared in the following proportions.

1/16 round yellow 1/8 disc yellow, 1/8 elongated grey,

1/16 elongated yellow 1/8 round grey, 1/8 disc green,

1⁄4 disc grey 1/16 round green, 1/16 elongated green

A) in your cross: what are the (i) genotype of the parents (ii) genotypes of the offspring and (iii) the phenotype of the parents? Draw a Punnett Square to show your answer.

B) what type of allele interaction is occurring for (i) seed shape? What about (ii) seed color? Explain how you can tell.

C) Based on the data from these crosses – is there any sort of epistatic interaction between the genes? Explain why or why not.

Outline the roles played by restriction enzymes and vectors in cloning DNA.

Words to choose from: bacterial, eukaryotic, nucleotide, DNA, RNA, protein, palindrome,

nuclease, protease, phage, plasmid.

1. A restriction enzyme is a _________      ____________that recognizes specific _________ sequences in a ________molecule, often a __________, and cleaves or nicks the molecule at those sites.

2. A vector is an agent into which a foreign DNA segment is inserted and used to transform host cells. A vector can be created from a virus known as a __________ or a bacterial _________.