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DNA replication is controlled by enzymes. 1)____________“unzips” the double helix by breaking hydrogen bonds, 2)___________ adds new nitrogenous bases to the exposed single strands, and 3) ____________ bonds short sequences together that are formed from the lagging strand (the strand that is “read” in the opposite direction).

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? 

Assume it is possible to remove continuous cores of rock from Earth that are 3,000 feet long and contain fossils. What would the theory of evolution by natural selection predict about the fossils found in such cores as they are examined from top to bottom?

What is the ratio of expected phenotypes in the offspring produced by the cross Aa × Aa? Assume complete dominance for the trait. 

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.

List all possible gametes of an organism that is AaBb.  HINT:  FOIL

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? 

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

Patau Syndrome is a chromosomal condition known as Trisomy 13 and is caused by a translocation. Surviving children with this condition have several developmental disabilities, polydactyly, and multiple organ defects among other issues. Explain what Trisomy 13 means, what a translocation is, and when it might occur during meiosis.

In mink, black is completely dominant to brown.  The allele designated B causes the black color, and b when homozygous, results in brown.  What would be the expected phenotypes in the offspring of a cross of two brown minks?