BLGY1115 Cell BiologyDNA Replication and Cell Division

Dr. Glenn McConkey

Replication of the double helix

The chemistry of DNA replication

Steps to DNA replication-1

DNA is unwound

RNA primer is synthesised by DNA primase

Steps to DNA

replication-2

Exposed single-strand of DNA is bound with a protein

Steps to DNA

replication-3

Replication proceeds simultaneously on both strands-semidiscontinuous replication

Steps to DNA replication-4

The Structure of DNA with phosphate backbone and base pairing

What is semi-conservative replication?

During replication of DNA each parental strand serves as a template for replication of the new strand.

The site of active replication during the process of DNA replication

DNA replication in prokaryotes

Single origin of replication

Proceeds in both directions –bidirectional

Okazaki fragments are 1000-2000 nucleotides in length

Replication rate 1000 nucleotides/sec

Circular genome

DNA replication in eukaryotes

Very similar to prokaryotic replication

Multiple origins of replication

Okazaki fragments are 100-200 nucleotides in length

Telomeres or ends of linear chromosomes require telomerase

Late metaphase cell preparing to divide

Pushme-pullyu of chromosome movement

Animal vs plant

Cleavage furrow Cell plate formation

Plane of plant cell division and cell plates

Onion cells

Plane of division determines plant growth

The Relevance of Sexual Reproduction

Sexual life cycle is an alternation of haploid and

diploid stages

Higher eukaryotes only

replicate (by mitosis) in

diploid stages

Animal haploid stages are only for sexual stages

(e.g. clam egg with sperm bound)

Some lower eukaryotes only multiply during

the haploid stages

of their life cycle

Plants multiply during both haploid and

diploid stages(but the haploid

is very brief) Lily pollen spores in meiosis

Meiosis MITOsis

References

Molecular Biology of the Cell Chapter 5, 18, 20 free on-line

Molecular Cell BiologyChapter 12 free on-line

http://www.ncbi.nlm.nih.gov/sites/entrez?db=Books