Dna Replication Flashcards
Who discovered the evidence for the structure of DNA ?
Watson & Crick
What did Watson & Crick state ?
Dna replicates either conservatively or semi - conservatively
State the definition for ‘ Semi - Conservative Replication ‘
Each replicated Dna contains
One original DNA strand
One newly synthesised strand
Who tested for semi - conservative replication ?
Messelson & Stahl
Explain the role of bacteria in the ‘ Messelson & Stahl ‘ Experiment.
Bacteria takes in Nitrogen isotopes (Nitro bases)
For new DNA nucleotides
So bacteria in a N 14 isotope medium will be less dense than bacteria in a N 15 medium
How does meiosis produce 4 haploid daughter cells ?
- Dna is replicated semi-conservatively
2.Two nuclear divisions
3.Chromosomes are halved via independent segregation during meiosis 1
4.Crossing over also occurs (Genetic Variation) - New combination of alleles
How does crossing over occur ?
Homologous chromosomes associate
Forms chiasmata
Chromatids equally exchanged
Forming new combinations of alleles.
State the differences between meiosis and mitosis
One for growth, one for reproduction
One produces 2 diploid cells, one produces 4 haploid cells
Mitosis has 1 stage, meiosis has 2
What is the biggest contributor for genetic variation ?
Independent segregation
How doe ‘Independent Segregation ‘ lead to genetic variation ?
- The random shuffling of homologous chromosomes.
- Each homologous pair is separated and paternal and maternal will move to opposite poles.
- Products of that first division will have many variations on the make-up of how many maternal/paternal chromosomes there are.
What is formed by a dna molecule and its associated proteins ?
Chromosome
Describe binary fission in bacteria
Replication of dna
Replication of plasmids
Replication of cytoplasm
Producing daughter cells
What can errors in the DNA cause ?
The growth and production of tumours
