Download BIOL100 Lecture 4

Cancer cells grow and divide when they should not
• Mitosis – an asexual cell division, that occurs in somatic cells
– “Soma” = body
• Cell cycle – the “lifecycle” of the cell
The Cell cycle: Interphase
• Interphase has three phases:
– G1: cell grows, organelles
duplicate
– S: DNA is replicated
– G2: cell makes proteins
needed to complete cell
division
DNA replication
• Produces exact copies of the cells
chromosomes
• Nucleotides are added by an enzyme called
DNA Polymerase
• semiconservative replication - each newly
replicated DNA molecule contains a
daughter and a parental DNA strand
Following replication, the DNA sequence ACCGTA
would be paired with a daughter DNA strand with the
sequence:
25%
A.
B.
C.
D.
25%
25%
B.
C.
25%
ACCGTA
TGGCAT
ATGCCA
UGGCAT
A.
D.
DNA replication duplicates chromosomes
• Chromosomes are
uncondensed before cell
division
• Duplicated chromosomes
are called sister chromatids
• They are held together at
the centromere
The Cell cycle: Mitosis
• Mitosis produces genetically-identical daughter nuclei
• Four stages:
– Prophase
– Metaphase
– Anaphase
– Telophase
• Mitosis is followed by cytokinesis, which splits the two nuclei
into two daughter cells
Mitosis : Prophase and Metaphase
Mitosis : Anaphase and Telophase