Cell Cycle, Mitosis, Meiosis, and Genetics Review Guide:
Cell Cycle
1. What are the phases of the cell cycle? (G1, S, G2, M, C)
2. Know what each letter stands for, and what happens during each
phase.
G1 – Growth phase 1 – Cell matures – starts to get bigger
S – Synthesis – DNA Replicates
G2 – Growth phase 2 - Grows to double the size (Making 2 cells)
M – Mitosis – DNA form into chromosomes, sister chromatids (exact
copies) will separate into 2 identical cells
C – Cytokinesis – Cell splits into 2 cells
Mitosis:
1. What is Mitosis?
- Mitosis is the process where one cell divides into two cells (identical
– same copy of DNA)
2. What are the phases of Mitosis (in order) and what happens in each
phase?
Interphase – Stages G1, S, and G2 of the cell cycle.
A. Prophase – DNA forms chromosomes – Spindle fibers form –
Nucleus disappears.
B. Metaphase – Chromosomes line up in the middle of the cell
C. Anaphase – Sister chromatids separate to opposite ends of the
cell
D. Telophase – 2 Nuclei will form, one around each set of sister
chromatids. Cell starts to pinch.
Cytokinesis – cell splits – 2 identical cells
3. Why do cells go through mitosis?
Growth and Development, Repair damaged cells
Meiosis
1. What is Meiosis?
- The process of making sex cells (gametes) – cells have half the
amount of DNA
2. Why do we want to reduce the number of chromosomes in half?
- SO when we add a sperm and egg together – we make a complete
organism with a complete set of chromosomes
3. What are the stages of Meiosis? (Remember, Meiosis is mitosis
happening twice!!!)
- Meiosis I
- Meiosis II
4. What are the phases of Meiosis (Think about humans starting with
46 chromosomes)
Meiosis I
1. Prophase 1 – same as mitosis (look back definition) – Homologous
pairs (chromosomes that look like each other) pair up Tetrad forms (4
chromosomes together – 2 of each copy)
-Crossing over occurs – two homologous chromosomes exchange
DNA – Offspring are all genetically diverse (all different)
2. Metaphase 1 – Tetrads line up along the middle
3. Anaphase 1 – Tetrads separate or are pulled apart. Homologous
chromosomes separate
4. Telophase 1 and Cytokinesis 1 – Cell divides into 2 cells, each has
46 chromosomes.
Meiosis II
1. Prophase 2 – Chromosomes just float in the cell – NO MORE
CROSSING OVER
2. Metaphase 2 – Chromosomes line up in the middle
3. Anaphase 2 – Sister chromatids separate
4. Telophase 2 and Cytokinesis 2 – 4 total cells. Each cell now has 23 chromosomes
– half of what the original cell had.
Differences between the two (Mitosis and Meiosis)
Mitosis 2 cells, Meiosis 4
Mitosis 1 cycle, Meiosis 2 cycles
Mitosis – Growth and Development, Repair Meiosis - Reproduction
Meiosis has crossing over!!!!!
Mitosis – identical cells (full DNA) Meiosis – Different cells (half
DNA)
Genetics:
Know the important vocabulary: (Review the Fridge worthy genetics
sheet)
Genotype – The actual genes you get
Phenotype – Physical Traits you would see
Allele – one form of a gene
Dominant allele – gene that shows up more
Recessive allele – gene that shows up less
Homozygous dominant – two of the same alleles (both dominant) - BB
Heterozygous – Different alleles – one dominant, one recessive
- Bb
Homozygous recessive – two of the same alleles (both
recessive)
Brown is the dominant color in mice (B for brown allele).
White is a recessive color in mice (b for recessive allele).
Cross a homozygous dominant brown mouse with a
heterozygous mouse.
What are the genotypes and phenotypes of their offspring?