Unit 6 Flashcards
What is a polymerase?
An enzyme that makes polymer DNA
DNA Replication process
1) Helicase unwinds DNA strands
2) Topoisomerase relaxes supercoiling in front of the replication fork
3) DNA polymerase requires RNA primers to initiate DNA synthesis
4) DNA polymerase synthesizes new strands of DNA continuously on the leading strand and discontinuously on the lagging strand
5) Ligase joins the fragments on the lagging strand
Is replication semiconservative?
Yes, replication is a semiconservative process where one strand serves as a template for a new strand of complementary DNA
What are the combinations in nucleotide base pairings for DNA?
T and A, C and G
What are the combinations in nucleotide base pairings for RNA?
A and U, T and A, C and G
Purines
G and A; double ring structure
Pyrimidines
C,T, and U; single ring structure
What direction is DNA synthesized?
5’ to 3’ direction
What are plasmids?
small extra-chromosomal, double stranded, circular DNA molecules
Where is genetic info stored?
its stored in and passed to subsequent generations through DNA molecules (in a minority of cases, through RNA molecules)
What is the difference between Prokaryotes and Eukaryotes?
Prokaryotic organisms typically have circular chromosomes and no nucleus. Eukaryotic organisms have multiple linear chromosomes and a nucleus.
What is transcription?
Writing something word for word
What is translation?
writing something word for word in a different language
What is transcription initiation?
When RNA polymerase binds to the DNA template strand to begin transcription
What is transcription elongation?
RNA polymerase adds RNA nucleotides (A, C, U, G) to the growing RNA strand
What is transcription termination?
RNA polymerase reaches a stop codon
What is translation initiation?
mRNA binds to a ribosome and translation begins at a start codon
What is translation elongation?
tRNA brings an amino acids to go bind an anticodon to a codon to mRNA; adds amino acid to growing polypeptide/protein
What is translation termination?
RNA polymerase reaches a stop codon
What is the central dogma of molecular biology?
DNA → RNA → Protein
Transcription: DNA is transcribed into messenger RNA (mRNA) in the nucleus.
Translation: mRNA is translated into proteins by ribosomes in the cytoplasm.
What are introns? Exons?
Introns are sections of a gene that do not code for proteins.
Exons are sections of a gene that code for proteins.
What is alternative slicing?
Excision of introns and slicing and retention of exons can generate different versions of the resulting mRNA molecule.
How does genetic information flow from RNA to DNA to proteins in a cell?
Genetic information flows from a sequence of nucleotides in DNA to a sequence of bases in a mRNA molecule to a sequence of amino acids in protein
Describe the function of the mRNA molecule and the tRNA molecule
mRNA molecules carry info from DNA to the ribosome. tRNA molecules bind specific amino acids and have anti-codon sequences that base pair with the mRNA
What are codons?
The sequence of nucleotides on the mRNA read as triplets
What are genes?
Genes are segments of DNA that contain the instructions for making proteins, which are essential for the structure, function, and regulation of the body’s tissues and organs.
How does gene expression affect differences in traits?
Gene expression affects differences in traits by controlling the production of proteins that determine an organism’s characteristics. The regulation of gene expression, genetic variation, environmental influences, and developmental stages all contribute to the diversity of traits observed in living organisms.
What are regulatory sequences and how to they control transcription?
Regulatory sequences are stretches of DNA that interact with regulatory proteins to control transcription.
They control transcription by expressing a subset of genes in each cell to save space.
What is cell differentiation?
The result of the expression of genes for tissue-specific proteins.
Describe the structure of DNA and RNA
DNA is double stranded and has the base pairs of A with T and C and G. RNA is single stranded and has the base pairings of A with U and C with G. Eukaryotic cells are more complex and larger than prokaryotic cells, which are simpler and smaller.
Step 1 of DNA replication
Unwinding the DNA: Helicase breaks the hydrogen bonds between base pairs, creating two single strands.
Step 2 of DNA replication
Priming: RNA primase synthesizes RNA primers to initiate DNA synthesis.
Step 3 of DNA replication
Synthesizing New Strands: DNA polymerase adds nucleotides to the growing DNA strand, following base-pairing rules.
Step 4 of DNA replication
Joining Fragments: DNA ligase joins the Okazaki fragments on the lagging strand.
Step 5 of DNA replication
Protecting Chromosome Ends: Telomerase extends telomeres to protect chromosome ends.
What is the role of helicase
Unwinds and separates double-stranded DNA into single strands.
Forms replication forks where new DNA strands are synthesized.
Allows DNA polymerase to access and copy the DNA templates efficiently.
What is the role of topoisomerase?
Relieving supercoiling and tension in DNA.
Preventing DNA tangling and knotting.
Facilitating smooth replication and transcription processes.
What is the role of DNA polymerase?
Synthesizing new DNA strands by adding nucleotides.
Proofreading and correcting errors to ensure the accuracy of replication.
Extending RNA primers to create complete DNA strands.
What is the role of RNA primers?
Initiating DNA synthesis by providing a starting point for DNA polymerase.
Serving as templates for the addition of DNA nucleotides.
Enabling the synthesis of both leading and lagging DNA strands.
What is the role of Okazaki fragments?
Allowing the lagging strand to be synthesized in short segments during DNA replication.
Ensuring that both the leading and lagging strands are accurately and efficiently replicated.
What is the role of ligase?
Joining Okazaki fragments during DNA replication to ensure a continuous DNA strand.
Repairing damaged DNA by sealing nicks in the DNA backbone.
Facilitating recombination processes by linking DNA segments.
Explain the similarities between mRNA, tRNA, and rRNA
mRNA, tRNA, and rRNA are all RNA molecules involved in the process of protein synthesis. They are transcribed from DNA and work together to translate genetic information into functional proteins. While mRNA serves as the template, tRNA brings the amino acids, and rRNA forms part of the ribosome where protein assembly takes place.
Explain the differences between mRNA, tRNA, and rRNA
mRNA: Carries genetic information from DNA to ribosomes; single-stranded with 5’ cap and poly-A tail.
tRNA: Transports specific amino acids to ribosomes; cloverleaf structure with anticodon and amino acid attachment site.
rRNA: Forms the core of ribosomes and catalyzes peptide bond formation; part of ribosome’s large and small subunits.
What is the role of GTP caps?
Protecting mRNA from degradation.
Facilitating the initiation of translation.
Regulating the export of mRNA from the nucleus.
Assisting in RNA splicing and processing.
What is the role of the poly-A-tail?
Stabilizing mRNA and protecting it from degradation.
Facilitating the export of mRNA from the nucleus to the cytoplasm.
Enhancing the efficiency of translation by aiding in ribosome recruitment.
Regulating translation by controlling the length of the poly-A tail.
What are the similarities between translation in prokaryotic and eukaryotic cells?
both prokaryotic and eukaryotic cells share fundamental similarities, including the use of the universal genetic code, ribosomes, tRNA, and the overall steps of translation (initiation, elongation, and termination). These conserved mechanisms ensure that proteins are accurately synthesized in both types of cells.
How is the flow of information in a retrovirus different than the central dogma of molecular biology?
In retroviruses, the flow of information starts with RNA, which is reverse transcribed into DNA and then follows the central dogma path of DNA to RNA to protein. This contrasts with the central dogma’s one-way flow from DNA to RNA to protein, highlighting the unique mechanisms retroviruses use to integrate and propagate their genetic material within the host.
How is gene expression regulated by regulatory sequences, epigenetic modifications, transcription factors, or operons?
Regulatory Sequences: Promoters, enhancers, and silencers control the initiation and efficiency of transcription.
Epigenetic Modifications: DNA methylation and histone modifications influence chromatin structure and gene accessibility.
Transcription Factors: Activators and repressors bind to specific DNA sequences to modulate transcription.
Operons: Coordinated regulation of gene clusters in prokaryotes in response to environmental signals.
How is gene regulation different in prokaryotes and eukaryotes?
Prokaryotes: Gene regulation involves operons, simple regulatory networks, repressor/activator proteins, and simultaneous transcription-translation.
Eukaryotes: Gene regulation is more complex, involving chromatin structure, multiple regulatory sequences, a variety of transcription factors, epigenetic modifications, and separation of transcription and translation.
What are some factors that cause mutations?
Mutations can arise from spontaneous errors during DNA replication, exposure to chemical or physical mutagens, biological factors like viruses and transposable elements, and environmental pollutants and toxins.
How do errors in cell division cause genetic disorders like Down’s Syndrome or Turners syndrome?
Errors during cell division, particularly nondisjunction during meiosis, can lead to genetic disorders such as Down syndrome and Turner syndrome.
How do the following increase genetic variation: transformation, transduction, conjugation, transposition?
Transformation: Uptake of free DNA from the environment increases genetic diversity by introducing new genes.
Transduction: Transfer of DNA by bacteriophages spreads genetic material between bacteria, enhancing genetic variation.
Conjugation: Direct transfer of plasmids through pili increases genetic diversity by spreading beneficial genes.
Transposition: Movement of transposons within and between genomes causes genetic rearrangements and introduces new genetic traits.
Describe how gel electrophoresis works and give an example
How it works:
Gel electrophoresis is a technique used to separate DNA, RNA, or proteins based on their size and charge.
The samples are loaded into wells in a gel matrix (usually agarose or polyacrylamide).
An electric current is applied, causing the molecules to migrate through the gel. Smaller molecules move faster and farther than larger ones.
The separated molecules can be visualized using a staining dye or fluorescent markers.
Ex. DNA fingerprinting- By comparing the banding patterns of DNA fragments, forensic scientists can identify individuals with high accuracy.
Explain how PCR works and give an example
PCR: used to amplify a specific DNA segment, making millions of copies from a small initial sample.
Ex. Since PCR is used to detect the presence of specific pathogens, PCR is commonly used to diagnose COVID-19 by detecting the viral RNA.
Explain how transformation works and give an example
How it works:
Transformation is the process of introducing foreign DNA into a bacterial cell.
The bacterial cells are made competent to take up DNA by chemical treatment or electroporation (using an electric field).
The foreign DNA, often in the form of a plasmid, is mixed with the competent cells and taken up by some of them.
The transformed cells can then express the new genetic material.
Ex. Transformation is used to produce recombinant proteins, such as insulin. The gene for human insulin is inserted into a plasmid and introduced into bacteria, which then produce insulin that can be purified and used for medical treatments.
Explain how DNA sequencing works and give an example
How it works:
Fragmentation: Cutting the DNA into smaller pieces.
Amplification: Using PCR to amplify the fragments.
Labeling: Adding fluorescently labeled nucleotides to the fragments.
Separation and Detection: Running the fragments through a capillary gel and detecting the fluorescent labels to determine the sequence.
Ex. DNA sequencing is used to study the genomes of organisms, providing insights into genetic variations, evolutionary relationships, and the functions of genes. For example, sequencing the human genome has led to a better understanding of genetic diseases and personalized medicine.
