Tutor profile: Lauren T.
Subject: Natural Sciences
Define natural selection, and describe one example of how a deleterious trait has remained in the gene pool despite reducing fitness.
Natural selection is the process in which organisms that are fit for their environment tend to survive and reproduce more than those who are unfit. Throughout generations of this tendancy for the fittest to survive and reproduce, a population's gene pool will trend towards the best alleles for that particular organism's environment. This is the primary driver of evolution. One example of a deleterious trait remaining in the gene pool is Huntington's Disease, which is caused by a single nucleotide mutation. One might wonder how this mutation has lasted in humans throughout thousands of years since it ultimately results in death, but Huntington's is a good example of a delayed fitness disadvantage. This is because the worst symptoms of Huntington's do not arise until after the normal reproductive age, so individuals with the disease survive long enough to reproduce and pass on their genes despite the deleterious mutation.
Subject: Basic Chemistry
What are intermolecular forces and what role do they play in the state of a substance?
Intermolecular forces are the attractive forces between molecules in a bond. These are different than INTRAmolecular forces, which are the forces between atoms in an individual molecule. A chemical bond is an intramolecular force. INTERmolecular forces determine the strength of molecular bonds. The stronger the intermolecular forces in a molecular bond, the more likely a substance is in a solid or liquid state due to the attractive forces condensing its molecules closer together.
Briefly describe the process of transcription and translation of a gene into its protein product within a Eukaryotic cell.
Transcription of a gene begins with initiation, where an RNA polymerase and its corresponding transcription factors binds to the promoter region of the gene. Then, during elongation, the RNA polymerase begins to transcribe the DNA into messenger RNA (mRNA), which undergoes RNA processing. After processing, the mature mRNA migrates to the ribosome in order to undergo translation. During translation, the ribosome "reads" the mRNA three nucleotides at a time. These groups of three nucleotides are called codons, and each one corresponds to an amino acid. The first codon is a start codon, which initiates the start of translation. With each codon, a tRNA binds to the ribosome-mRNA complex and adds the correct corresponding amino acid. This continues to occur until the chain of amino acids is complete and a stop codon is reached.
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