Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
The Cell Cycle consists of Interphase (divided into , , and phases) and the M-phase (Mitosis or Meiosis).
Mitosis is nuclear division giving rise to two genetically identical daughter cells. It is essential for growth, tissue repair, and asexual reproduction.
The stages of Mitosis are Prophase, Metaphase, Anaphase, and Telophase (). During the phase, DNA replicates so each chromosome consists of two sister chromatids.
Meiosis is a reduction division where the chromosome number is halved from diploid () to haploid (), resulting in four genetically different daughter cells (gametes).
Genetic variation in Meiosis is produced by 'Crossing Over' during Prophase I and 'Independent Assortment' of homologous chromosomes during Metaphase I.
Homologous chromosomes are pairs of chromosomes that have the same genes at the same loci, but potentially different alleles.
In humans, the diploid number is and the haploid number is .
📐Formulae
💡Examples
Problem 1:
A cell from an organism with a diploid number of undergoes meiosis. Calculate the number of chromosomes present in a cell at the end of Meiosis I and the total number of possible combinations of chromosomes in the gametes due to independent assortment.
Solution:
Chromosomes after Meiosis I: . Combinations: .
Explanation:
Meiosis I is the reduction division where homologous pairs separate, halving the chromosome number from to . The formula for independent assortment is , where is the haploid number.
Problem 2:
Compare the mass of DNA in a nucleus during phase versus phase of the cell cycle.
Solution:
If , then .
Explanation:
During the phase (Synthesis), which occurs between and , DNA replication doubles the amount of DNA in the nucleus. However, the chromosome number () remains the same as sister chromatids are still attached at the centromere.