Questions and Answers
What phenomenon did Griffith discover in 1927?
Who provided direct experimental evidence that DNA is the genetic material?
What type of RNA carries specific amino acid molecules to mRNA?
What is the correct chromosomal number in human somatic cells?
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What does a karyotype represent?
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What did Hershey and Chase prove about inheritance?
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Which type of RNA is primarily involved in the process of transcription?
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What is the shape of DNA as determined by Rosalind Franklin's work?
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Which statement is correct regarding haploid cells?
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During which phase do chromosomes duplicate before division?
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What are the two copies of chromosomes found in diploid somatic cells called?
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Which researcher used X-ray techniques to demonstrate the helical structure of DNA?
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What does mRNA do during protein synthesis?
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In terms of chromosomal composition, how do male somatic cells differ from female somatic cells?
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What type of RNA forms part of the structural component of ribosomes?
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Study Notes
Bacterial Transformation and Genetic Material
- Griffith (1927) discovered bacterial transformation, allowing bacteria to change their genetic composition by absorbing foreign DNA.
- Avery provided experimental evidence identifying DNA as the genetic material.
Evidence of DNA as Genetic Material
- Hershey and Chase (1952) demonstrated that DNA is the molecule of inheritance by marking bacteriophages with radioactive isotopes (32P for DNA and 35S for proteins).
Structure of DNA
- Rosalind Franklin utilized X-ray diffraction to confirm that DNA has a double helix structure.
- Meselson and Stahl (1953) supported Watson and Crick’s semiconservative model of DNA replication.
Types of RNA
- Messenger RNA (mRNA) is synthesized from a DNA template during transcription.
- Transfer RNA (tRNA) transports specific amino acids to mRNA at the ribosome for polypeptide synthesis during translation.
- Ribosomal RNA (rRNA) forms part of the ribosomal structure, essential for protein synthesis.
Chromosome Structure and Composition
- Chromosomes consist of coiled DNA wrapped around histone proteins.
- Chromosomal number varies:
- Haploid (N) cells, such as sperm and egg cells, have one set of chromosomes (e.g., sperm: 22+X/22+Y).
- Diploid (2N) somatic cells possess two sets of chromosomes (e.g., kidney, liver, brain, skin).
Chromosome Number in Humans
- Humans have 46 chromosomes in somatic cells.
- Female genetic composition: 44 autosomes and 2 sex chromosomes (XX).
- Male genetic composition: 44 autosomes and 2 sex chromosomes (XY).
Karyotype and Chromosome Behavior
- Karyotype refers to the organized profile of an individual’s chromosomes arranged by size during metaphase.
- Before cell division (interphase), chromosomes exist in a single shape; they are duplicated during division.
- Following fertilization, one chromosome from each parent combines, featuring the same size, shape, and genes.
Bacterial Transformation and Genetic Material
- Griffith discovered bacterial transformation, where bacteria can change their genetic traits by absorbing foreign DNA.
- Avery’s work provided evidence that DNA is the genetic material, reinforcing the role of DNA in heredity.
- Hershey and Chase demonstrated through experiments that DNA, not proteins, carries genetic information, using radioactive isotopes 32P (DNA) and 35S (proteins).
Structure and Replication of DNA
- Rosalind Franklin utilized X-ray diffraction to confirm that DNA has a double helix structure.
- Meselson and Stahl confirmed the semiconservative nature of DNA replication, supporting Watson and Crick's model.
Types of RNA
- Messenger RNA (mRNA) is synthesized from a DNA template during transcription and carries genetic information from DNA to ribosomes.
- Transfer RNA (tRNA) transports specific amino acids to the ribosome during translation to build polypeptides.
- Ribosomal RNA (rRNA) is a key structural component of ribosomes, facilitating protein synthesis.
Chromosomal Structure and Number
- Chromosomes consist of coiled DNA wrapped around histone proteins.
- The haploid number (N) represents one copy of each chromosome, found in sex cells like sperm (22 + X or 22 + Y) and egg cells (22 + X).
- The diploid number (2N) refers to two copies of chromosomes in somatic cells, such as those in kidneys, liver, brains, and skin.
Human Chromosome Information
- Humans have 46 chromosomes in somatic cells, consisting of 44 autosomes and 2 sex chromosomes.
- Female chromosome composition includes 44 autosomes and XX sex chromosomes.
- Male chromosome composition includes 44 autosomes and XY sex chromosomes.
Karyotype and Chromosome Behavior
- A karyotype is a systematic arrangement of chromosomes by size and shape observed at metaphase.
- During interphase (before cell division), chromosomes exist in a single condensed form.
- Following fertilization, chromosomes are homologous, with one from each parent, exhibiting similar size, shape, and genetic content.
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Description
Explore the fascinating world of DNA and RNA in this biology quiz. Learn about bacterial transformation, the evidence supporting DNA as genetic material, and the roles of different types of RNA. Test your knowledge on historical experiments and the structure of genetic material.
