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Questions and Answers
What discovery did Griffith make in 1927?
What discovery did Griffith make in 1927?
- The phenomenon of bacterial transformation (correct)
- The structural composition of proteins
- The process of DNA replication
- The function of ribosomal RNA
What did Hershey and Chase's experiment demonstrate?
What did Hershey and Chase's experiment demonstrate?
- DNA is the genetic material (correct)
- Viruses cannot infect bacteria
- RNA is less stable than DNA
- Proteins carry genetic information
What is the role of tRNA during protein synthesis?
What is the role of tRNA during protein synthesis?
- To transcribe DNA into mRNA
- To carry specific amino acids to mRNA (correct)
- To synthesize DNA
- To form the structural components of ribosomes
How many chromosomes are found in human somatic cells?
How many chromosomes are found in human somatic cells?
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What is the primary function of DNA helicase during DNA replication?
What is the primary function of DNA helicase during DNA replication?
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Which of the following correctly describes the Watson and Crick model of DNA?
Which of the following correctly describes the Watson and Crick model of DNA?
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What happens during the process of transcription?
What happens during the process of transcription?
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Which base pairs are connected by double hydrogen bonds in DNA?
Which base pairs are connected by double hydrogen bonds in DNA?
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What is the function of ribosomal RNA (rRNA)?
What is the function of ribosomal RNA (rRNA)?
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What is a key characteristic of semiconservative DNA replication?
What is a key characteristic of semiconservative DNA replication?
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Which characteristic of RNA is true for messenger RNA (mRNA)?
Which characteristic of RNA is true for messenger RNA (mRNA)?
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What is the function of DNA ligase in the DNA replication process?
What is the function of DNA ligase in the DNA replication process?
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Which statement accurately describes the structure of DNA based on Watson and Crick's model?
Which statement accurately describes the structure of DNA based on Watson and Crick's model?
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What is the primary role of the start codon in protein synthesis?
What is the primary role of the start codon in protein synthesis?
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What do Meselson and Stahl's findings about DNA replication suggest?
What do Meselson and Stahl's findings about DNA replication suggest?
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Study Notes
Bacterial Transformation and Genetic Material
- Griffith (1927) identified bacterial transformation, where bacteria can change their genetic makeup by taking in foreign DNA from other bacteria.
- Avery's team provided experimental support that DNA is the genetic material.
DNA and Inheritance Studies
- Hershey and Chase (1952) demonstrated that DNA, not proteins, serves as the molecule of inheritance by tagging bacteriophages with radioactive isotopes 32P (DNA) and 35S (proteins).
- Rosalind Franklin utilized X-ray diffraction to show that DNA has a double helix structure.
- Meselson and Stahl (1953) confirmed that DNA replicates in a semiconservative manner, supporting Watson and Crick's model.
Types and Functions of RNA
- Messenger RNA (mRNA): synthesized from DNA during transcription, carries genetic information.
- Transfer RNA (tRNA): transports specific amino acids to the ribosome for polypeptide formation during translation.
- Ribosomal RNA (rRNA): structural component of ribosomes.
Chromosomes and Their Characteristics
- Chromosomes: Coiled DNA associated with histone proteins.
- Haploid (N): Contains one set of chromosomes found in sex cells (e.g., sperm and egg).
- Example: Sperm has 22 autosomes + X or Y chromosome; egg has 22 autosomes + X chromosome.
- Diploid (2N): Contains two sets of chromosomes in somatic (body) cells.
- Common examples: kidney, liver, brain, and skin cells.
- Humans have 46 chromosomes in somatic cells, arranged as follows:
- Females: 44 autosomes + XX sex chromosomes.
- Males: 44 autosomes + XY sex chromosomes.
- Karyotype: A visual representation of chromosomes arranged by size during metaphase.
Watson-Crick DNA Model
- DNA structure: Resembles a twisted ladder (double helix).
- Nitrogen bases pair through weak hydrogen bonds:
- Adenine (A) pairs with Thymine (T) through double hydrogen bonds.
- Cytosine (C) pairs with Guanine (G) through triple hydrogen bonds.
- The two DNA strands are complementary and anti-parallel.
DNA Replication
- Process of DNA duplication involves several enzymes:
- DNA Helicase: Unwinds DNA by breaking hydrogen bonds between strands.
- DNA Polymerase: Synthesizes new DNA strands by adding nucleotides in a 5' to 3' direction; also repairs DNA.
- DNA Ligase: Joins nucleotides together to form a continuous DNA strand.
Protein Synthesis
- Transcription: Process where DNA is transcribed into RNA.
- RNA polymerase binds to a promoter, assembling nucleotides to form mRNA.
- Codons: Three-nucleotide sequences in mRNA that code for specific amino acids; the start codon is AUG.
- Stop codons: UAA, UAG, UGA signal termination of protein synthesis.
- Splicing: Involves removing introns (non-coding regions) from pre-mRNA to produce mature mRNA.
Bacterial Transformation and Genetic Material
- Griffith (1927) identified bacterial transformation, where bacteria can change their genetic makeup by taking in foreign DNA from other bacteria.
- Avery's team provided experimental support that DNA is the genetic material.
DNA and Inheritance Studies
- Hershey and Chase (1952) demonstrated that DNA, not proteins, serves as the molecule of inheritance by tagging bacteriophages with radioactive isotopes 32P (DNA) and 35S (proteins).
- Rosalind Franklin utilized X-ray diffraction to show that DNA has a double helix structure.
- Meselson and Stahl (1953) confirmed that DNA replicates in a semiconservative manner, supporting Watson and Crick's model.
Types and Functions of RNA
- Messenger RNA (mRNA): synthesized from DNA during transcription, carries genetic information.
- Transfer RNA (tRNA): transports specific amino acids to the ribosome for polypeptide formation during translation.
- Ribosomal RNA (rRNA): structural component of ribosomes.
Chromosomes and Their Characteristics
- Chromosomes: Coiled DNA associated with histone proteins.
- Haploid (N): Contains one set of chromosomes found in sex cells (e.g., sperm and egg).
- Example: Sperm has 22 autosomes + X or Y chromosome; egg has 22 autosomes + X chromosome.
- Diploid (2N): Contains two sets of chromosomes in somatic (body) cells.
- Common examples: kidney, liver, brain, and skin cells.
- Humans have 46 chromosomes in somatic cells, arranged as follows:
- Females: 44 autosomes + XX sex chromosomes.
- Males: 44 autosomes + XY sex chromosomes.
- Karyotype: A visual representation of chromosomes arranged by size during metaphase.
Watson-Crick DNA Model
- DNA structure: Resembles a twisted ladder (double helix).
- Nitrogen bases pair through weak hydrogen bonds:
- Adenine (A) pairs with Thymine (T) through double hydrogen bonds.
- Cytosine (C) pairs with Guanine (G) through triple hydrogen bonds.
- The two DNA strands are complementary and anti-parallel.
DNA Replication
- Process of DNA duplication involves several enzymes:
- DNA Helicase: Unwinds DNA by breaking hydrogen bonds between strands.
- DNA Polymerase: Synthesizes new DNA strands by adding nucleotides in a 5' to 3' direction; also repairs DNA.
- DNA Ligase: Joins nucleotides together to form a continuous DNA strand.
Protein Synthesis
- Transcription: Process where DNA is transcribed into RNA.
- RNA polymerase binds to a promoter, assembling nucleotides to form mRNA.
- Codons: Three-nucleotide sequences in mRNA that code for specific amino acids; the start codon is AUG.
- Stop codons: UAA, UAG, UGA signal termination of protein synthesis.
- Splicing: Involves removing introns (non-coding regions) from pre-mRNA to produce mature mRNA.
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