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Questions and Answers
What was the primary goal of Frederick Griffith's experiments in 1928?
What was the primary goal of Frederick Griffith's experiments in 1928?
Which strain of bacteria was found to be pathogenic in Griffith's experiments?
Which strain of bacteria was found to be pathogenic in Griffith's experiments?
What was the outcome of the fourth experiment where live R cells were mixed with heat-killed S cells?
What was the outcome of the fourth experiment where live R cells were mixed with heat-killed S cells?
Why did Griffith conclude that R cells did not mutate during the experiments?
Why did Griffith conclude that R cells did not mutate during the experiments?
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Which scientist is known for studying the patterns of genetics with plant phenotypes prior to Griffith's work?
Which scientist is known for studying the patterns of genetics with plant phenotypes prior to Griffith's work?
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What type of bond connects the nucleotides in the DNA backbone?
What type of bond connects the nucleotides in the DNA backbone?
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Which base pairs specifically bind together in DNA?
Which base pairs specifically bind together in DNA?
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Which of the following correctly identifies a difference between RNA and DNA?
Which of the following correctly identifies a difference between RNA and DNA?
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What effect does the incorrect pairing of two purines have on the structure of DNA?
What effect does the incorrect pairing of two purines have on the structure of DNA?
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What role does RNA serve in protein formation?
What role does RNA serve in protein formation?
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What process involves the migration of genes from the S strain to the R strain?
What process involves the migration of genes from the S strain to the R strain?
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Which method did Rosalind Franklin utilize to study DNA structure?
Which method did Rosalind Franklin utilize to study DNA structure?
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What was a significant finding from experiments involving dead cells of infectious strains?
What was a significant finding from experiments involving dead cells of infectious strains?
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What happens to cells when enzymes that digest DNA are added?
What happens to cells when enzymes that digest DNA are added?
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Which of the following components are nucleotides in DNA made of?
Which of the following components are nucleotides in DNA made of?
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Which statement about nucleic acids in viruses is true?
Which statement about nucleic acids in viruses is true?
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Why was Rosalind Franklin not awarded a Nobel Prize?
Why was Rosalind Franklin not awarded a Nobel Prize?
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What is the term for a sequence of three nucleotides that encodes one amino acid?
What is the term for a sequence of three nucleotides that encodes one amino acid?
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What is the outcome of a frameshift mutation?
What is the outcome of a frameshift mutation?
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Which of the following is NOT considered a common mutagen?
Which of the following is NOT considered a common mutagen?
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What significant observation was made regarding biodiversity in surface oceans?
What significant observation was made regarding biodiversity in surface oceans?
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How do mutations contribute to evolution?
How do mutations contribute to evolution?
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What was the result of the single point mutation in the fruit fly?
What was the result of the single point mutation in the fruit fly?
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What can result from the replication of genes within the genome?
What can result from the replication of genes within the genome?
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What role do mutations play in organism adaptation?
What role do mutations play in organism adaptation?
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Why do birds lack teeth?
Why do birds lack teeth?
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What role does the tRNA play in protein synthesis?
What role does the tRNA play in protein synthesis?
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Which of the following describes the function of ribosomes during translation?
Which of the following describes the function of ribosomes during translation?
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What happens during the initiation stage of translation?
What happens during the initiation stage of translation?
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Which process concludes when a stop codon is encountered during translation?
Which process concludes when a stop codon is encountered during translation?
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What is a silent mutation in the context of protein formation?
What is a silent mutation in the context of protein formation?
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What type of mutation occurs when one or more base pairs are added to the DNA sequence?
What type of mutation occurs when one or more base pairs are added to the DNA sequence?
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How do ribosomes facilitate the binding of mRNA and tRNA molecules?
How do ribosomes facilitate the binding of mRNA and tRNA molecules?
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What can result from point mutations in the genetic code?
What can result from point mutations in the genetic code?
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What is the main role of RNA Polymerase II?
What is the main role of RNA Polymerase II?
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What is a key difference between DNA and RNA in the context of nucleotides?
What is a key difference between DNA and RNA in the context of nucleotides?
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Which of the following statements about exons and introns is correct?
Which of the following statements about exons and introns is correct?
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What is the function of mRNA in the cell?
What is the function of mRNA in the cell?
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Where does transcription start in the DNA structure?
Where does transcription start in the DNA structure?
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Which of the following is true about ribosomal RNA (rRNA)?
Which of the following is true about ribosomal RNA (rRNA)?
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During translation, which type of RNA carries specific amino acids?
During translation, which type of RNA carries specific amino acids?
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What role does the 5' cap serve in the final structure of mRNA?
What role does the 5' cap serve in the final structure of mRNA?
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What is the function of stop codons in translation?
What is the function of stop codons in translation?
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What occurs during the process of translation?
What occurs during the process of translation?
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Study Notes
DNA & Proteins
- DNA and proteins are fundamental to life.
- Early theories proposed a hereditary agent, but concrete macromolecules weren't identified.
- Darwin studied heredity, but lacked the mathematical tools to interpret his findings.
- Mendel's experiments on plant phenotypes exposed patterns of heredity.
Discovery of DNA's Purpose
- Frederick Griffith (1928) experimented with bacteria (streptococcus pneumoniae).
- He experimented with two types of bacterial cells:
- S strain bacteria (smooth): pathogenic
- R strain bacteria (rough): non-pathogenic
- A key finding was when heating-killed S strain bacteria and mixing it with live R bacteria, the R bacteria transformed into S bacteria.
- This suggested a transfer of genetic material.
Designed and ran 4 Experiments
- Four key experiments were conducted.
- Live R cells did not cause pneumonia
- Live S cells did cause pneumonia
- Killed S cells did not cause pneumonia
- Killed S cells plus live R cells DID cause pneumonia
What happened?
- The possibility of R cells mutating was discussed.
- The possibility of some S cells surviving was discussed.
- It was concluded that DNA transferred and changed the R cells.
Later Studies
- Further experiments used non-lethal forms of strains to infectious ones.
- Early belief was that proteins were hereditary.
- Biochemical experiments showed strains with protein digesting enzymes still developed more proteins.
- Experiments with DNA digesting enzymes showed cell functionality stopping.
- These affirmed DNA as the hereditary molecule.
Viruses
- In 1952, molecular biologists studied bacteriophages (viruses that infect bacteria).
- Electron micrographs showed viruses had protein coats and nucleic acids inside.
- When viruses infect cells, the protein coat remained outside, while nucleic acids entered.
The structure of DNA
- Rosalind Franklin used X-ray crystallography to study DNA structure.
- X-ray diffraction patterns revealed the DNA molecule's structure.
- Watson and Crick used Franklin's data and made significant deductions.
Fame and Fortune
- Watson and Crick received the Nobel Prize.
- Rosalind Franklin, who did much of the foundational work, was not recognized.
DNA
- DNA is a very stable molecule with a double helix structure that's more stable than RNA.
- Each gene codes for one protein.
- Genes are composed of 4 nucleotides: adenine, thymine, guanine, and cytosine.
- The sequence of nucleotides is the genetic code, determining protein structure.
- Nucleotides form codons of three, each specifying specific amino acids.
DNA Structure
- DNA is double-stranded and helical, adding stability.
- Base pairs (A-T, G-C) are complementary.
- Two hydrogen bonds link A and T.
- Three hydrogen bonds link G and C.
- The sugar-phosphate backbone forms the DNA’s structure.
Nucleotides
- Pyrimidines are single rings.
- Purines are double rings.
- DNA's structure is like a ladder — a pyrimidine pair bonded to a purine.
DNA Backbone Structure
- Nucleotides are bonded together via phosphodiester bonds.
- The phosphate groups of nucleotides form the DNA backbone.
- Phosphate groups are negatively charged, so the backbone aligns on opposite sides.
RNA
- DNA is the blueprint. RNA is the worker.
- Three main types of RNA:
- Messenger RNA (mRNA)
- Transfer RNA (tRNA)
- Ribosomal RNA (rRNA)
- All RNA is manufactured in the nucleus of eukaryotes or the nucleoid region of prokaryotes.
RNA and DNA Comparison
- DNA: Deoxyribose sugar, contains thymine, double-stranded double helix, genetic material for most organisms.
- RNA: Ribose sugar, contains uracil, instead of thymine, single-stranded, genetic material for some viruses.
Basic DNA to Protein Scheme
- DNA—Transcription—RNA—Translation—Protein
Transcription
- DNA information is converted into RNA information.
- The "alphabet" is the same -- just the "letters" (nucleotides) differ (Thymine → Uracil)
Translation
- mRNA's information is converted to protein.
- Codons on mRNA are converted into amino acids form the protein by translating the genetic alphabet.
mRNA
- Messenger RNA carries genetic information from DNA to ribosomes
- Accounts for 5-10% of the total RNA in a cell at any given point
- Consists of a chain of nucleotides
- Used for protein production but is temporary.
rRNA
- Used in constructing ribosomes.
- Ribosomes contain primarily rRNA and some proteins;
- rRNA makes up 60-65% of the ribosome mass and proteins make up roughly 35-40%.
- rRNA constitutes 75-80% of the total RNA in a cell at any given moment.
Ribosome Structure
- Ribosomes have a small and a large subunit
- Involved in assembling amino acids according to mRNA instructions.
Promoter
- Transcription begins at a region called a promoter
- RNA polymerase recognizes the specific promoter region to start transcription
- Promoters are found upstream (before) the gene to be transcribed.
RNA Polymerase
- Responsible for mRNA synthesis, based on a DNA template
- There are specific RNA polymerases for different RNA types:
-RNA Polymerase I (rRNA)
-RNA Polymerase II (mRNA)
-RNA Polymerase III (tRNA)
Construction of RNA
- RNA polymerase uses a DNA template and environmental nucleotides to build RNA molecules.
- The template is a particular strand of DNA, selected with a promoter.
mRNA
- Post-transcriptional processing adds a "cap" and "tail" to the finished mRNA.
- This modified mRNA is transported outside the nucleus toward ribosomes for protein synthesis.
- "Tail" protects the mRNA from enzymatic degradation.
Junk DNA
- DNA contains portions that are not coding for protein.
- Exons code for proteins.
- Introns are non-coding regions that are spliced out.
- Introns can create alternative mRNA versions allowing for many proteins from a single gene.
Genetic Code
- The genetic code uses triplets of nucleotides (codons) to specify amino acids.
- AUG codes for methionine (start codon).
- UAA, UAG, and UGA are stop codons.
tRNA
- tRNA molecule carries amino acids to the ribosome.
- They contain specific anti-codons that recognize mRNA codons.
- The anticodon sequence determines which amino acid is attached to the tRNA.
Ribosomes
- Ribosomes are the protein synthesis machinery, binding mRNA and tRNA molecules
- The ribosome functions to orient the mRNA and tRNA in relation to one another so they can bond effectively, effectively acting as an enzyme.
Translation (Stages)
- Initiation: start codon, mRNA and tRNA, assembly of ribosomal units.
- Elongation: tRNA brings in amino acids to each codon on mRNA.
- Termination: stop codon reached, release of amino acid chain.
Mutations and Proteins
- Changes in DNA sequences (mutations) may affect protein formation.
Point Mutations
- Changes in one or a few base pairs.
- Substitution mutations: replacing one nucleotide with another.
- Insertion/deletion mutations: adding or removing nucleotides, which causes a major structural change.
Mutagens
- External factors causing mutations (U/V light, chemicals).
- Recent research shows high diversity in surface oceans and organisms.
- Limited diversity in deep-earth organisms, suggestive of a slower rate of evolution in such an environment.
Mutations important for evolution
- Mutations introduce variation, which allows organisms to adapt over generations and develop useful metabolic processes and body structures.
- Gene replication in the genome allows for multiple copies of genes to evolve over generations without interfering with the primary function.
Some Examples of Mutations
- Single base-pair changes can lead to significant differences, as evidenced in the evolution of birds' beaks and fruit flies' development.
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Description
Explore the fundamentals of DNA and proteins, and how early theories of heredity evolved over time. Learn about key experiments by Frederick Griffith that unveiled the role of DNA in genetic material transfer and its implications for understanding heredity.
