[UNIT 5] THE MITOTIC CYCLE

Describe the structure of a chromosome:

• 1 chromosomes contain: 2 chromatids that are identical (sister chromatids) → 4 DNA molecules.

• each chromatid contains 2 strands of DNA

• DNA: contains gene

• Gene: nucleotide sequences in DNA that code for a polypeptide

• Sister of chromatids: identical chromatids in 1 chromosomes, formed by DNA replication

• Centromere: point where sister chromatids joined, constant position, point of attachment to spindle fibre during mitosis.

Describe the role of telomere:

• telomere: positioned at the ends of each chromatids, sealed the ends of chromatids

• short sequences of non-coding DNA(does not contain genes) made up of the same bases (mostly G and C)

• ensure the very ends of the DNA molecules are included in DNA replication during mitosis.

+ as the copying enzyme responsible for DNA replication is unable to run right to the very end of the DNA molecule. if these was a important piece → loss in genetic information during DNA replication

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