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What is the primary focus of genetic studies?
What is the primary focus of genetic studies?
According to Mendel's laws, a trait may not show up in an individual but can still be passed on to the next generation.
According to Mendel's laws, a trait may not show up in an individual but can still be passed on to the next generation.
True
What did Griffith hypothesize was transferred to the non-virulent r-strain bacteria?
What did Griffith hypothesize was transferred to the non-virulent r-strain bacteria?
Transforming principle
The _______ strain is virulent and has a smooth polysaccharide capsule.
The _______ strain is virulent and has a smooth polysaccharide capsule.
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Match the following scientists to their contributions to genetics:
Match the following scientists to their contributions to genetics:
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Which experiment demonstrated that DNA is responsible for genetic transformation?
Which experiment demonstrated that DNA is responsible for genetic transformation?
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The Hershey-Chase experiment used radioactive sulfur to label the DNA of bacteriophages.
The Hershey-Chase experiment used radioactive sulfur to label the DNA of bacteriophages.
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In the context of Mendel's experiments, what fraction of pea plants are expected to show purebred dominant traits?
In the context of Mendel's experiments, what fraction of pea plants are expected to show purebred dominant traits?
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What sugar is found in DNA?
What sugar is found in DNA?
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RNA is more stable than DNA.
RNA is more stable than DNA.
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Which base is found in RNA but not in DNA?
Which base is found in RNA but not in DNA?
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Adenine pairs with ______ in RNA.
Adenine pairs with ______ in RNA.
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Which of these statements about DNA pairing is true?
Which of these statements about DNA pairing is true?
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Match the types of RNA with their functions:
Match the types of RNA with their functions:
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DNA is found in the nucleus of a cell.
DNA is found in the nucleus of a cell.
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What is the process called by which mRNA copies genetic code?
What is the process called by which mRNA copies genetic code?
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What does a radioactive Sulphur label in bacteria indicate?
What does a radioactive Sulphur label in bacteria indicate?
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Rosalind Franklin identified three distinct configurations of DNA based on her x-ray crystallography work.
Rosalind Franklin identified three distinct configurations of DNA based on her x-ray crystallography work.
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What are the four types of nitrogenous bases in DNA?
What are the four types of nitrogenous bases in DNA?
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In DNA, adenine pairs with ______.
In DNA, adenine pairs with ______.
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Which structure was proposed by Watson and Crick?
Which structure was proposed by Watson and Crick?
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Match the following components of a nucleotide with their descriptions:
Match the following components of a nucleotide with their descriptions:
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In DNA, cytosine forms two hydrogen bonds with guanine.
In DNA, cytosine forms two hydrogen bonds with guanine.
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DNA consists of two ______-phosphate backbones.
DNA consists of two ______-phosphate backbones.
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What is the role of ribosomal RNA (rRNA) in protein production?
What is the role of ribosomal RNA (rRNA) in protein production?
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Supercoiling of DNA makes it less compact than relaxed DNA.
Supercoiling of DNA makes it less compact than relaxed DNA.
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What are the three steps of DNA replication?
What are the three steps of DNA replication?
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DNA topoisomerases regulate DNA supercoiling by _____ the winding and unwinding of DNA strands.
DNA topoisomerases regulate DNA supercoiling by _____ the winding and unwinding of DNA strands.
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Match the following classes of DNA topoisomerases with their functions:
Match the following classes of DNA topoisomerases with their functions:
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Which enzyme is responsible for strand separation during DNA replication?
Which enzyme is responsible for strand separation during DNA replication?
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DNA replication is a fully conservative process.
DNA replication is a fully conservative process.
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What is the 'origin of replication'?
What is the 'origin of replication'?
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What is the primary function of DNA polymerase III?
What is the primary function of DNA polymerase III?
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DNA replication is a continuous process with no interruptions.
DNA replication is a continuous process with no interruptions.
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What is the role of ligase during DNA replication?
What is the role of ligase during DNA replication?
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The single-stranded DNA binding protein (SSB) prevents the strands from _______.
The single-stranded DNA binding protein (SSB) prevents the strands from _______.
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Match the following components involved in DNA replication with their functions:
Match the following components involved in DNA replication with their functions:
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Which direction does DNA polymerase add nucleotides to the new strand?
Which direction does DNA polymerase add nucleotides to the new strand?
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The leading strand is synthesized discontinuously.
The leading strand is synthesized discontinuously.
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What is the purpose of the termination site sequence in DNA replication?
What is the purpose of the termination site sequence in DNA replication?
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Study Notes
Genetics
- The study of how traits are passed from parents to offspring.
- Genes are units of information about traits.
History of Genetics
-
Mendel's Laws of Inheritance:
- Inheritance of traits is determined by genes passed from parents.
- Individuals inherit one gene from each parent for each trait.
- Traits can be hidden but still passed on.
-
Griffith transformation experiment:
- Virulent (S-strain) bacteria have a smooth capsule, causing infection.
- Non-virulent (R-strain) lacks the capsule, not causing infection.
- Heat-killed S-strain mixed with live R-strain resulted in lethal infection.
- Transformation factor transferred from S-strain enabled R-strain to become virulent.
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Oswald Avery:
- Isolated a cell-free extract from S-strain.
- This extract transformed living R-strain into both S-strain and R-strain cells.
- Only DNase destroyed the "transforming principle", confirming DNA as the genetic material.
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Hershey-Chase Experiment:
- A phage is a virus containing DNA and a protein coat.
- Phages labeled with radioactive sulfur (protein) or phosphorous (DNA) infected bacteria.
- Radioactive phosphorous was found in infected bacteria, proving DNA carries genetic information.
-
Rosalind Franklin's X-ray Crystallography:
- Identified two DNA configurations (a and b forms).
- Proposed a double-helix structure with precise measurements for diameter, separation, and pitch.
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James Watson and Francis Crick:
- DNA is a double-stranded, helical molecule.
- The sugar-phosphate backbones form the outside of the helix.
- Nitrogenous bases (A, C, G, T) pair inside, held by hydrogen bonds (A-T, C-G).
- This structure is called the "genetic code".
Nucleic Acid Structure
- A nucleotide consists of a sugar, a phosphate group, and a nitrogenous base.
- Purine bases: adenine and guanine
- Pyrimidine bases: cytosine, thymine, and uracil
-
Double helix structure:
- Two sugar-phosphate backbones on the outside.
- Nitrogenous bases paired inside, held by hydrogen bonds.
- Strands run in opposite directions (antiparallel).
- This orientation is important for DNA replication and interactions.
Differences between DNA and RNA
- **Sugar:** DNA contains deoxyribose; RNA contains ribose.
- **Bases:** DNA has thymine; RNA has uracil.
- **Pairing:** DNA (A-T, C-G); RNA (A-U, C-G).
- **Location:** DNA in the nucleus; RNA forms in the nucleolus and moves to cytoplasm.
- **Reactivity:** DNA is more stable due to deoxyribose; RNA is reactive.
Types of RNA
- Messenger RNA (mRNA): Copies DNA code (transcription) and carries it to ribosomes for protein production.
- Transfer RNA (tRNA): Brings amino acids to ribosomes for protein synthesis.
- Ribosomal RNA (rRNA): A structural component of ribosomes.
DNA Supercoiling
- DNA folds up on itself to form tertiary structures.
- Supercoiling allows for compact packaging of circular DNA.
- Supercoiling changes the shape of DNA, making it more compact.
-
DNA topoisomerases:
- Regulate DNA supercoiling by winding and unwinding DNA strands.
- Class I: Break one strand of DNA helix.
- Class II: Break two strands of DNA helix.
The Flow of Genetic Information
- Replication (DNA synthesis): DNA makes a copy of itself.
-
Protein Expression:
- Transcription (RNA synthesis): DNA code is copied into RNA.
- Translation (protein synthesis): RNA code is used to create protein.
DNA Replication
- **Semi-discontinuous:** Occurs in both directions but at different rates.
- **Semi-conservative:** New DNA contains one original and one newly synthesized strand.
-
Three steps:
- Initiation: Begins at the origin of replication (oric).
- Propagation: Elongation of the new strand.
- Termination: Process ends at a specific termination sequence in the DNA.
Replication Step 1: Initiation
-
Enzymes:
- Helicase: Separates DNA strands, forming the replication fork.
- SSB protein: Binds to single strands to prevent them from rejoining.
- DNA polymerase III: Synthesizes the new strand, adding complementary nucleotides (5'-3' direction).
- DNA primase: Synthesizes short RNA primers to initiate DNA replication.
- Ligase: Joins Okazaki fragments.
Replication Step 2: Elongation
-
DNA Polymerase III functions:
- Adds nucleotides in 5'-3' direction.
- 3'-5' exonuclease activity: Proofreading for accuracy.
- 5'-3' exonuclease activity: Removes RNA primers or damaged DNA.
-
Semi-discontinuous replication:
- The leading strand is synthesized continuously in 5'-3' direction.
- Lagging strand is synthesized discontinuously, forming Okazaki fragments.
- DNA polymerase I replaces RNA primers, and ligase joins fragments.
Replication Step 3: Termination
- Replication is stopped at specific termination sequence in DNA.
- Termination involves:
- A termination site sequence.
- A protein binding to the sequence to stop replication.
IL 1
- DNA uses thymine (T) instead of uracil (U) because:
- Thymine is more stable than uracil, which is important for long-term storage of genetic information in DNA.
- Uracil is prone to deamination (loss of an amino group), which can lead to mutations if not properly removed.
- Thymine has a methyl group that helps protect it from deamination, ensuring the integrity of genetic code.
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Description
Explore the fundamental principles of genetics, including the inheritance of traits through Mendel's laws and landmark experiments by Griffith and Avery. Understand how genes function and their role in determining characteristics in organisms. This quiz covers key discoveries that shaped our understanding of genetics.
