Unit 1.6 Genetic Information is Copied and Passed On To
Daughter Cells
Chromosomes General Information
Chromosomes are made up of histones (proteins) and DNA.
As both of the above are seen as "chromosomes", so chromosomes are counted by the number of
centromeres present.
Haploid vs Diploid: Diploid (2n) are cells that have two sets of chromosomes (one from each parent),
human cells have 46 chromosomes in diploid cells (in 23 pairs). Haploid (n) cells have one set of
chromosomes, these are sperm and egg cells in human. Humans have 23 chromosomes in haploid cells (2n
= 46, so n=23).
, Homologues Chromosomes are a pair of matching chromosomes, so they are the same size/shape/have the
same gene loci (location), but they may have different alleles.
The Cell Cycle
This is the Cellular Events that repeat in order between 1 cell division and the next. The cell cycle has 3 main
stages;
1. Interphase- The Cell Spends most of it's time in this stage (but chromosomes can't be seen under a
microscope at this stage). Interphase goes from G1 to S-Phase to G2.
At G1 and G2 (known as "Gap" Phases):
Cell Increase in Size/Mass
New Organelles Made
ATP is made and built up.
At S-Phase (Synthesis Phase): DNA replicates, so mass/quantity doubles.
{Refer to Booklet showing Graph of Mass Increases Across Interphase}
2. Mitosis- This is Cell Division that produces 2 genetically identical daughter cells. With 4 Stages (Prophase,
Metaphase, Anaphase and Telophase- PMAT).
3. Cytokinesis- This is when the Cytoplasm divides to form two new cells.
Mitosis
Mitosis gives genetic stability- as 2 daughter cells are produced which are genetically identical to each
other, and the parent cell.
Mitosis is need for; Growth of Cells, Replacement of Cells and Repair of Tissues, and Asexual Reproduction.
Must be able to recognise 4 stages (PMAT) under a microscope (picture attached at end of document).
Mitosis in Animals:
1. Prophase
Chromosomes Condense (become shorter and thicker), so they're visible from microscopes.
Centrioles migrate to opposite poles of the cell and form spindles (protein microtubules), these spindle
fibres extend from pole to pole.
Nuclear Envelope Disintegrates.
Nucleolus Disappears.
2. Metaphase
Chromosomes attached to spindle fibres by their centromeres.
Chromosomes align along the equator (with the centromere on the equator).
3. Anaphase
Daughter Cells
Chromosomes General Information
Chromosomes are made up of histones (proteins) and DNA.
As both of the above are seen as "chromosomes", so chromosomes are counted by the number of
centromeres present.
Haploid vs Diploid: Diploid (2n) are cells that have two sets of chromosomes (one from each parent),
human cells have 46 chromosomes in diploid cells (in 23 pairs). Haploid (n) cells have one set of
chromosomes, these are sperm and egg cells in human. Humans have 23 chromosomes in haploid cells (2n
= 46, so n=23).
, Homologues Chromosomes are a pair of matching chromosomes, so they are the same size/shape/have the
same gene loci (location), but they may have different alleles.
The Cell Cycle
This is the Cellular Events that repeat in order between 1 cell division and the next. The cell cycle has 3 main
stages;
1. Interphase- The Cell Spends most of it's time in this stage (but chromosomes can't be seen under a
microscope at this stage). Interphase goes from G1 to S-Phase to G2.
At G1 and G2 (known as "Gap" Phases):
Cell Increase in Size/Mass
New Organelles Made
ATP is made and built up.
At S-Phase (Synthesis Phase): DNA replicates, so mass/quantity doubles.
{Refer to Booklet showing Graph of Mass Increases Across Interphase}
2. Mitosis- This is Cell Division that produces 2 genetically identical daughter cells. With 4 Stages (Prophase,
Metaphase, Anaphase and Telophase- PMAT).
3. Cytokinesis- This is when the Cytoplasm divides to form two new cells.
Mitosis
Mitosis gives genetic stability- as 2 daughter cells are produced which are genetically identical to each
other, and the parent cell.
Mitosis is need for; Growth of Cells, Replacement of Cells and Repair of Tissues, and Asexual Reproduction.
Must be able to recognise 4 stages (PMAT) under a microscope (picture attached at end of document).
Mitosis in Animals:
1. Prophase
Chromosomes Condense (become shorter and thicker), so they're visible from microscopes.
Centrioles migrate to opposite poles of the cell and form spindles (protein microtubules), these spindle
fibres extend from pole to pole.
Nuclear Envelope Disintegrates.
Nucleolus Disappears.
2. Metaphase
Chromosomes attached to spindle fibres by their centromeres.
Chromosomes align along the equator (with the centromere on the equator).
3. Anaphase
