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Questions and Answers
During meiosis, which process leads to genetic variation by the exchange of DNA between homologous chromosomes?
During meiosis, which process leads to genetic variation by the exchange of DNA between homologous chromosomes?
What occurs during Prophase I of meiosis that contributes to genetic variability?
What occurs during Prophase I of meiosis that contributes to genetic variability?
Which stage of meiosis involves the alignment of homologous chromosomes for separation?
Which stage of meiosis involves the alignment of homologous chromosomes for separation?
In Griffith's Transformation Principle experiment, what was observed when heat-killed S strain bacteria were mixed with live R strain bacteria?
In Griffith's Transformation Principle experiment, what was observed when heat-killed S strain bacteria were mixed with live R strain bacteria?
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Which scientist proved that DNA was the genetic material responsible for transformation in bacteria?
Which scientist proved that DNA was the genetic material responsible for transformation in bacteria?
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What is the role of DNase in Avery's experiments on the transformation principle?
What is the role of DNase in Avery's experiments on the transformation principle?
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What did Chargaff's Rules establish regarding DNA base pairing?
What did Chargaff's Rules establish regarding DNA base pairing?
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In DNA replication, what is the function of DNA polymerase?
In DNA replication, what is the function of DNA polymerase?
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What is the role of telomeres in DNA replication?
What is the role of telomeres in DNA replication?
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How does semiconservative DNA replication work according to Meselson and Stahl's experiment?
How does semiconservative DNA replication work according to Meselson and Stahl's experiment?
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Which enzyme is responsible for producing an RNA primer during DNA replication?
Which enzyme is responsible for producing an RNA primer during DNA replication?
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What is the purpose of the sliding clamp in DNA replication?
What is the purpose of the sliding clamp in DNA replication?
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Study Notes
Meiosis
- Gametes are haploid (one set of chromosomes), while zygotes are diploid (two sets)
- Sexual life cycle: meiosis, gamete formation, and fertilization
- Meiosis has two stages: meiosis I (homologs separate) and meiosis II (sisters separate)
- DNA exchange occurs by crossing over, and random mixing of chromosomes produces variation
- Prophase I: homologs pair up (synapses) and crossing over occurs, forming chiasmata
- Metaphase I: homologs line up to separate
- Metaphase II: sisters line up to separate
- Stages of meiosis: interphase, meiosis I, and meiosis II
- Variation is introduced through independent assortment of chromosomes (2^23 = 8 million), random fertilization (2^23 x 2^23 = 64 trillion), and crossover (recombination) with 2-3 crossovers per chromosome
Discovery of Genetic Material
- Griffith (1928): discovered transformation principle, transforming R strain into S strain
- Avery (1944): proved DNA is the genetic material, using protease and RNase treatments
- Hershey and Chase (1952): proved DNA is the genetic material, using 32P-labeled DNA and 35S-labeled protein
- Chargaff (1952): discovered Chargaff's rules (A=T, G=C, and A+T/G+C ratio is variable)
- Watson and Crick (1953): solved the structure of DNA, a double helix with bases pairing in the center and backbones on the outside
Properties of DNA
- Nucleotide structure: phosphate, sugar, and base
- Nucleotides are strung together by phosphodiester bonds
- Double helix formation through H-bonding of bases
- Base pairing rules: complementation
- Denaturation and renaturation of DNA
- Antiparallel strands with 5' → 3' direction
DNA Replication
- Daughter strand is made from a template
- Semiconservative replication: Meselson and Stahl experiment shows half of DNA helix is a daughter, the other half is a template
- Dehydration synthesis and phosphodiester bond formation
- DNA polymerase is the enzyme, working in 5' → 3' direction
- Addition of free nucleotides according to base pairing rules
- Replication begins at a replication bubble, with each side being a replication fork
- Helicase opens the double helix like a zipper
- ssDNA binding protein helps keep DNA from base pairing
- RNA primer is required for DNA polymerase to work
- Sliding clamp helps keep DNA polymerase attached
- Leading and lagging strand synthesis, with different mechanisms
- Telomeres solve the "end replication problem" by providing a buffer zone for DNA loss
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Description
This quiz covers the overview of meiosis, including the haploid nature of gametes, the diploid nature of zygotes, and the comparison between mitosis and meiosis. It also includes information on the stages of meiosis, including DNA exchange through crossing over and random mixing of chromosomes for genetic variation.
