Structure, function, History
Nucleotides are made up of...
pentose sugar, phosphate group, and nitrogenous bases (A, C, G, T).
The role of helicase in DNA replication
Unwind DNA
What is the purpose of transcription?
The purpose of transcription is to transcribe DNA into RNA, which is the first step in creating proteins.
What is the product of translation?
a polypeptide chain.
What is the difference between a missense and a nonsense mutation?
A missense mutation causes a change in the nucleotide sequence that results in a different amino acid being added to the polypeptide, while a nonsense mutation creates a stop codon, prematurely ending the protein and often making it nonfunctional.
A and G are ____. C and T are _____
Purines (A and G), Pyrimidines (C and T)
Why is DNA considered a semiconservative model
one strand is from the original parental molecule and the other strand is a new "daughter" strand, maintaining half of the original DNA.
What happens during the elongation stage of transcription, and how does the RNA strand separate from the DNA template?
During elongation, RNA polymerase adds RNA nucleotides to the growing RNA strand. As the RNA strand grows, hydrogen bonds between the RNA and DNA break, allowing the RNA strand to detach from the DNA template.
What is the role of tRNA in translation?
tRNA carries amino acids and pairs its anticodon with the mRNA codon during translation to ensure the correct amino acid is added to the polypeptide chain.
What causes silent mutations, and what is their impact on protein function?
Silent mutations occur when a nucleotide is substituted, but the amino acid sequence remains the same, so there is no effect on the protein function.
The 3 functions of DNA
Genetic instructions for making more DNA
Genetic instructions for making proteins
Genetic info passed from parent to offspring
Function of ligase
What is the purpose of RNA splicing, and how does it affect the final mRNA?
RNA splicing removes introns (non-coding regions) from pre-mRNA and joins exons (coding regions) together. This process ensures that only the coding regions are retained in the final mRNA, which is then used for protein synthesis.
How does complementary base pairing influence translation?
Complementary base pairing ensures that the correct codon on the mRNA is matched with the corresponding anticodon on the tRNA, dictating which amino acid is added to the growing polypeptide chain.
What is gene regulation, and why is it important for organisms?
Gene regulation is the process of turning genes on and off to control gene expression. It helps organisms respond to environmental changes and ensures that the right proteins are made at the right time.
Name at least 6 structural features of DNA
Two strands
Twisted double helix
Contains nitrogenous bases
Strands are oriented in opposite directions (antiparallel)
Bases held together by hydrogen bonds
Sugar phosphate backbone held together by phosphodiester bond (strong covalent bond)
Consistent diameter all the way down because 2 ring structure always pairs with single ring structure
Backbone is identical across every organism, bases hold the real genetic info.
A patient with a rare genetic disorder shows frequent mutations in DNA, particularly in areas important for cell division and growth. The mutations are not being repaired, and DNA replication appears faulty. Researchers suspect a malfunction in an enzyme involved in DNA replication. Which enzyme is malfunctioning?
DNA polymerase
What is the role of the 5' cap and poly-A tail in RNA modification?
The 5’ cap protects the mRNA from degradation, acts as a beacon for ribosomes, and helps with mRNA export. The poly-A tail at the 3’ end protects the mRNA from degradation and assists in mRNA stability and translation.
What happens during the initiation phase of translation?
The small ribosomal subunit attaches to the 5’ end of mRNA, the initiator tRNA (with anticodon UAC) pairs with the start codon (AUG) on mRNA, and the large ribosomal subunit clamps down to form a functional ribosome.
A frameshift mutation alters the reading frame of the DNA/RNA, changing the grouping of nucleotides into codons, which leads to an entirely different amino acid sequence and usually results in a nonfunctional protein.
Describe how Rosalind Franklin, Erwin Chargaff, James Watson, and Francis Crick contributed to the discovery of DNA
Rosalind Franklin used X-Ray crystallography to determine the location of sugar phosphate backbone and nitrogenous bases. She also discovered that DNA had a consistent diameter. Erwin Chargaff discovered that A%=T% and C%=G%. James Watson and Francis Crick used data from both of these discoveries to construct a DNA model.
Ribavirin is an antiviral medication used to treat viral infections like hepatitis C. It has been shown to inhibit the helicase of several viruses, including the hepatitis C virus (HCV). What effect would Ribavirin have on viruses like Hepatitis C?
By inhibiting helicase, Ribavirin prevents the viral RNA from unwinding properly, which halts the replication process. Without this critical step, the virus cannot replicate its genome, which reduces the viral load and helps in controlling the infection.
A researcher studying cancer finds a mutation in the promoter region of a gene that regulates the cell cycle, preventing RNA polymerase from binding and initiating transcription. How would this mutation affect gene transcription and the cell’s ability to regulate the cell cycle?
The mutation in the promoter region would prevent RNA polymerase from binding properly, hindering the initiation of transcription. As a result, the gene would not be transcribed into mRNA, leading to a lack of protein production. This could disrupt the regulation of the cell cycle, potentially causing uncontrolled cell division and contributing to the development or progression of cancer.
A researcher is investigating a drug that inhibits the elongation phase of translation. How would this drug affect protein synthesis, and what impact might this have on the cell?
The drug would halt the elongation phase of translation, preventing the addition of amino acids to the polypeptide chain. This would stop protein synthesis, leading to a lack of essential proteins in the cell, which could impair cell function, growth, and potentially result in cell death if critical proteins are not produced.
A patient is diagnosed with a genetic disorder where a specific gene contains a mutation that changes a codon from "GGC" (glycine) to "AGC" (serine). This mutation occurs in a crucial part of a protein involved in cell signaling. What type of mutation occurred, and how might it affect the protein?
The missense mutation changes the amino acid from glycine to serine, which may alter the protein’s shape and function, depending on the role of the specific amino acid.