Full summary of the Chromosomal Basis of Inheritance module covered in the BIO1000F course at UCT. Inclusive of content covered by lecture notes and slides as well as the relevant textbook sections.
, Chapter 12 - MITOSIS
Omnis cellula e cellula,” meaning “Every cell from a cell.”
PROKARYOTES EUKARYOTES
Small and simple Large and complex
unicellular Unicellular or multicellular
No de ned nucleus De ned nucleus
Ciruclar dna Linear dna
Single haploid chromosome Oaired dupoloid chromosome
Lack membrane bound organlles Has membrane bound organelles
Reproduuce both sexually and asexually Mostly sexually reproduction but can reproduce via
asexual reproduction
Binary ssion mitosis
Bacteria and archaea Eukarya
Has a cell membrane
has cytoplasm
Has ribosomes
Has dna
KEY ROLES OF CELL DIVISION
• Single celled organisms — create new organisms (exact copies)
• Multicellular organisms — embryonic development
• Renewal and repair in grown multicellular eukaryotes
• Distribution of identical genetic material to daughter cells
• Crux of mitosis — if produced cells were not identical they would not function
correctly
12.1 ORGANISATION OF GENETIC MATERIAL
• Genome = cell’s endowment of DNA/genetic information
• Prokaryotes have a single DNA molecule vs eukaryotes have multiple DNA molecules
• eukaryotic DNA molecules = packaged into chromosomes that carry 100s-1000s of
genes
• Each chromosome = one very long DNA molecule associated with many proteins
• Genes = units of information that specify an organism’s inherited traits
• Chromatin = entire complex of DNA and the proteins that form the building material
of chromosomes
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, • Eukaryotes have a characteristic chromosome number (eg. Humans 2n = 46)
• Somatic/body cells = diploid (2n)
• Full complement of chromosomal material of the parent cell
• Gametes/germ cells = haploid (n)
• When cell is not dividing — each chromosome = long, thin chromatin ber
• After replication, chromosomes condense, thicken and shorten (each ber becomes
densely coiled and folded)
• Each duplicated chromosome has two sister chromatids that are attached along
their lengths by cohesins (protein complexes)
• Attachment of the sister chromatids = cohesion
• Each sister chromatid has a centromere (a region of chromosomal DNA where
the chromatid is most closely attached to its sister chromatid)
• Centomere = point of attachment for spindle bres
• Mitosis = division of genetic material in the nucleus
• Cytokinesis = division of the cytoplasm to form two separate, genetically identical
daughter cells
12.2 MITOTIC PHASE ALTERNATES WITH INTERPHASE IN THE CELL CYCLE
Phases Of The Cell Cycle
• Interphase = G1, S, G2 phases (90% of the cell cycle)
• Mitotic Phase = mitosis and cytokinesis
• Mitosis = distribution of chromosomes into two daughter nuceli
• Cytokinesis = division of cytoplasm producing two daughter cells
INTERPHASE
• Cell grows by producing proteins and cytoplasmic organelles
First Gap (G1)
• Metabolic activity and cell growth
Synthesis (S Phase)
• Metabolic activity
• Growth
• DNA replication (each chromosome is now made of two sister chromatids)
Second Gap (G2)
• Metabolic activity
• Growth
• Preparation for cell division
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