In the karyotype of a person with Down syndrome, or trisomy 21, an extra copy of chromosome 21 is apparent. This abnormality affects roughly 1 of every 700 children born and is the most common serious birth defect in the United States. People affected by Down syndrome often have cognitive difficulties, heart defects, and shortened life spans. Based on this scenario and your understanding of meiosis, what is the most likely explanation for the extra chromosome 21 in people with Down syndrome? 

In a typical human body (somatic cell, how many total chromosomes are there? 

All of the following may be found in a DNA nucleotide EXCEPT: 

If the DNA of a certain organism has guanine as 30% of its bases, then what percentage of its bases are adenine? 

If meiosis did NOT occur in sexually reproducing organisms: 

A cell with 10 chromosomes undergoes mitosis and complete cell division. How many daughter cells are produced, and what number of chromosomes do they have? 

Background Carbon dioxide moves across the plasma membrane by simple diffusion, meaning it travels from an area of higher concentration to an area of lower concentration without requiring energy or transport proteins. Question What primarily determines the rate at which carbon dioxide enters the cell?

Background Sulfa drugs are a type of antibiotic that interfere with how bacteria make the building blocks of their DNA. These Sulfa antibiotics work by targeting a bacterial enzyme that is essential for the bacteria’s survival. These antibiotics mimic a normal substrate the bacteria needs; they bind to the enzyme’s active site and block the real substrate from entering. As a result, the bacteria cannot produce nucleotides, which are necessary for their reproduction and survival. Question Identify the name of this ‘bacteria-building blocking’ process and describe the specific mechanism by which these drugs prevent bacterial growth. Then, explain how these antibiotic drugs function at the molecular level.

What is the functional difference between DNA polymerase and RNA polymerase.  Be specific and thorough.

Scenario You have an artificial cell with a selectively permeable membrane that allows water to pass through but not sugar. Inside the cell: 1% sugar solution Outside the cell: 2% sugar solution Question How do these concentrations immediately effect the movement of water, and why? Be specific about the direction of water flow and the reasoning behind it.