2B1 Molecular Biology Fundamentals Flashcards
Gain understanding of the central dogma of molecular biology and the roles of DNA and RNA.
What is the central dogma of biology?
The flow of genetic information from DNA to RNA to protein.
It demonstrates how DNA information leads to protein synthesis, emphasizing unidirectional flow.
What analogy helps understand the central dogma?
Baking a cake, where DNA is the recipe, RNA is the copy of the picture, and protein is the 3D cake.
Who proposed the central dogma theory?
James Watson and Francis Crick
This was in 1957.
What did Crick propose in his paper on the central dogma theory?
DNA is copied to RNA, which requires an intermediate (later identified as tRNA) to create proteins.
What evidence led to the expansion of the central dogma theory?
Discovery of reverse transcriptase by Howard Temin and David Baltimore in 1970.
What is reverse transcriptase and its significance?
It’s an enzyme that creates DNA from RNA, crucial in viral replication, including HIV.
Reverse transcriptase is also used in techniques like RT-PCR (Reverse Transcription Polymerase Chain Reaction), which is widely used in molecular biology and diagnostics.
What were the three original processes in the central dogma?
- DNA replication from DNA
- Transcription of DNA to RNA
- Translation of RNA to protein
Describe simply how DNA replication occurs?
DNA polymerase (enzyme) reads DNA and synthesizes a complementary strand of nucleotides.
What does transcription involve?
DNA is copied to RNA by RNA polymerase.
What is translation in the context of the central dogma?
RNA is read by ribosomes to synthesize proteins.
Compare the structure RNA to DNA?
- RNA is single-stranded, DNA is double stranded.
- RNA uses ribose sugar, DNA uses deoxyribose sugar.
- RNA contains uracil instead of thymine.
How did Watson and Crick describe DNA replication?
That it involves creating more copies using nucleotides A, G, C, and T.
Where does transcription occur in cells?
Nucleus
What is the role of ribosomes in the synthesis of proteins?
They translate RNA into proteins in the cytoplasm.
What does the central dogma propose about protein synthesis and DNA shape?
Proteins cannot be used to synthesize DNA, suggesting unidirectional flow.
Which 3 additional steps did the expanded central dogma include?
- RNA replication from RNA.
- DNA replication from RNA through reverse transcription.
- Direct translation of DNA to protein.
Describe another way that information is coded in the genome, other than direct coding sequences of DNA.
Non-coding RNA plays a role in gene regulation, protein functionality, and information transfer.
What is DNA responsible for in cells?
Carrying genetic information.
Where is DNA found in cells?
In the nucleus, condensed into chromatin.
Define a gene.
Genes are units of inheritance grouped within DNA.
What is the function of a gene?
By being expressed into proteins, vital for cellular functions and observable traits.
Describe the structure of DNA.
- A double stranded, double-helical structure.
- Made of nucleotides containing deoxyribose sugar, phosphate group, and nitrogenous base.
- The two strands twisted around each other.
What are the two types of nitrogenous bases in DNA?
- Purines (adenine and guanine)
- Pyrimidines (thymine and cytosine)
Describe how nitrogenous bases complementary base pair in DNA.
- Adenine pairs with thymine (2 hydrogen bonds)
- Cytosine pairs with guanine (3 hydrogen bonds)
What is DNA replication, and how does it occur?
- It’s the process of producing two identical copies of DNA.
- It involves unzipping the DNA double helix, synthesis of new DNA strands, and bonding them together.
What enzymes are involved in DNA replication?
- Helicase
- DNA polymerase
- RNA primase
- DNA ligase
What is meant by the ‘leading strand’ of DNA and how is it synthesized?
Runs in the 3’-5’ direction and is synthesized continuously by DNA polymerase.
What is the lagging strand, and how is it synthesized?
Runs in the 5’-3’ direction and is synthesized discontinuously in Okazaki fragments.
Define DNA sequencing.
A molecular genetic technology revealing the base pairing content of DNA, used in research and diagnostics.
Who developed the first DNA sequencing method, and what was it called?
Frederick Sanger developed the chain termination method or Sanger sequencing.
What has replaced the Sanger sequencing in modern laboratories and why?
Next-generation sequencing methods due to increased efficiency and reduced costs.
What is the human genome project, and when was it completed?
It was a project to sequence the entire human genome completed in 2003, revealing the sequence of bases in human DNA.
How long would the stretched DNA of a single cell be, and what compacts it?
Approximately 2 meters long.
Compaction is done by proteins called histones.
Which 3 scientists contributed to the discovery of DNA’s double helical structure?
- Rosalind Franklin
- James Watson
- Francis Crick
They discovered the structure using using X-ray diffraction.
What percentage of DNA comprises genes?
Only about 1%.
What are the non-coding segments called?
Introns
What are exons in DNA?
Coding segments responsible for the synthesis of proteins during gene expression.
What is the function of DNA polymerase in DNA replication?
Adds complementary nucleotides to the newly forming DNA strand during replication, ensuring accurate copying of the DNA template.
What is the significance of semi-conservative DNA replication?
Ensures that each newly formed DNA molecule contains one original (parental) strand and one newly synthesized (daughter) strand, maintaining genetic fidelity.
What is the role of histones in DNA compaction?
These are proteins that DNA wraps around to form nucleosomes, promoting compaction and organization of DNA into chromatin, allowing it to fit within the cell nucleus.
Histones also play a role in regulating gene expression by controlling access to the DNA.
How does DNA sequencing contribute to research and diagnostics?
Provides valuable information about the genetic makeup of organisms, aiding in understanding genetic diseases, evolutionary relationships, and personalized medicine.
What are the main stages of the cell cycle?
- Interphase (G1, S, and G2 phases)
- Mitosis (or M phase)
What is the difference between the composition of the sugar ribose and that of deoxyribose?
Ribose has an extra hydroxyl (OH) group attached to one of its carbon atoms.
Describe what happens during interphase.
It’s the phase where the cell grows, replicates its DNA, and prepares for cell division.
At what stage of the cell cycle does DNA replication occur?
S stage.
Why is the cell cycle important?
- It is essential for growth, development, and repair of organisms.
- It ensures accurate duplication and distribution of genetic material to daughter cells.
