BIOL 101 Chapter 11: Study Notes at South Carolina
Chapter 11- Mitosis
• Cell Division
o The process by which cells make more cells
o Cell division occurs for:
▪ Growth
▪ Cell Replacement
▪ Healing
▪ Reproduction
• Binary Fission
o 1. The circular bacterial DNA molecule is attached by proteins to the inner
membrane (red)
o 2. DNA replication begins at a specific location and proceeds bidirectionally
around the circle.
o 3. The newly synthesized DNA molecule is also attached to the inner membrane,
near the attachment site of the initial molecule
o 4. As replication proceeds, the cell elongates symmetrically around the midpoint,
separating the DNA attachment sites.
o 5. Cell division begins with the synthesis of new membrane and wall material at
the midpoint.
o 6. Continued synthesis completes the constriction and separates the daughter cells.
o End up with 2 cells that have the exact same copy as the original and can happen
again and again
• Mitotic Cell Division
o Eukaryotes
▪ Genome large and linear
▪ DNA in nucleus
o Prokaryotes
▪ Genome small and circular
▪ DNA in cytoplasm
• Cell Cycle (Eukaryotes)
o After the cell has divided
▪ Interphase
• G0 Phase (Cells that aren’t actually dividing)
o Cells are performing normal functions
• G1 Phase (Gap 1)
• S Phase (DNA synthesis)
• G2 Phase (Gap 2)
▪ M Phase
• Mitosis and Cytokinesis
o Double-stranded DNA wraps around histone proteins to form nucleosomes that
have the appearance of “beads on a string.” The nucleosomes are coiled into a 30-
nm chromatin fiber. When a cell undergoes mitosis, the chromosomes condense
even further
• Centromeres/ Chromatids
o Homologous Chromosomes
▪ Same genes
o Centromere
▪ In the middle
o Chromatids
▪ Sister chromatids
▪ Pairs above and below centromere
• IPMAT or I Propose Men Are Toads
o Interphase- not very Interesting
o Prophase- chromosomes first a Ppear
o Metaphase- chromosomes line up in the middle
o Anaphase- chromosomes move Away
o Telophase- now you have Two
o ****Prometaphase****
• Prophase
o Chromosomes condense. Centrosomes radiate microtubules and migrate to
opposite poles
o Organizing DNA so that you can get an exact copy
o Double membrane all around it
• Prometaphase
o Microtubules of the mitotic spindle attach to chromosomes
o Football shaped
• Metaphase
o Chromosomes align in center of cell
o Chromosomes tugged in both directions by microtubules
o 46 chromosomes line up in the middle of the cell
• How do the chromosomes move?
o Motor proteins at the kinetochore pull the chromosomes along the microtubules
o Motor proteins at the spindle poles pull the microtubules toward the poles
o Microtubules also shrink
• Motor proteins between the overlapping polar microtubules cause the microtubules to
slide past each other pushing the poles apart
• Motor proteins on the astral microtubules also help to pull the poles apart
• Telophase
o Nuclear envelope re-forms and chromosomes decondense
• Meiosis
• Meiotic Cell Division
o Results in 4 daughter cells
o Specifically to produce egg and sperm cells
o Each daughter cell contains half the number of chromosomes as the parent
o Each daughter cell is genetically unique
• Asexual vs. Sexual Reproduction
o Asexual Reproduction- the generation of offspring from a single parent without
the fusion of gametes. In most cases, the offspring are genetically identical to the
parent
o Sexual Reproduction-occurs when 2 parents give rise to offspring that have
unique combinations of genes inherited from both parents
• Asexual Reproduction
o Single cell organisms reproduce asexually by cell division
o Some multicellular organisms can reproduce asexually
▪ Budding
▪ Vegetative Reproduction (Plants)
o A Clone is a group of genetically identical individuals
• Sexual Reproduction
o In contrast to clones produced by asexual reproduction, offspring produced by
sexual reproduction are different genetically from both
• Genetics
o Genetics- the study of heredity and hereditary variation
o Heredity- the transmission of traits from one generation to the next. (Inheritance)
o Variation- the differences between parents and offspring or differences between
members of the same species
• Genes
o Hereditary traits are passed from one generation to the next in the form of genes
o Gene-a discrete unit of hereditary information consisting of a specific sequence in
DNA
o Genes are located in the same spot on chromosomes
o Locus- a gene’s specific location along the length of a chromosome
• Gametes
o Gametes- plants and animals that reproduce sexually produce specialized cells
called gametes that are the vehicles that transmit genes from one generation to the
next (sperm and egg)
o Germ-Line Cells- produce gametes
o Somatic cells- all of the other cells in the body (or plant)
• Karyotype
o A karyotype is an ordered display of all the chromosomes in a cell
o All somatic cells have two copies of each chromosome
▪ Each pair has the same length, centromere position, and staining pattern
o Two chromosomes that are the same are called homologous chromosomes
• X and Y Chromosomes
o Two homologous chromosomes that are not equal in length are the X and Y
chromosomes
o Only a small region of homology shared between X and Y
o Important for determining the sex of an individual
o Sex Chromosomes
o Rest of the chromosomes are called autosomes
• Alleles
o The order of genes is the same on two homologous chromosomes
o Each homologous chromosome can have different versions of the same gene. The
position of that gene on the chromosome is the locus
o Different versions of the same gene are called alleles
• Ploidy
o Ploidy- refers to the number of sets in a chromosome (23 in humans)
o Diploid- two sets of each chromosome
▪ One set from mother and one set from father
