Cell Cycle Basics
What is the phase of the cell cycle when the cell grows and performs normal functions before DNA is replicated?
G1 (growth and normal function).
What is the primary purpose of mitosis in multicellular organisms?
To produce two genetically identical daughter cells for growth, repair, and asexual reproduction.
What is the main outcome of meiosis in terms of chromosome number relative to the parent cell?
Meiosis produces haploid cells with half the chromosome number of the diploid parent.
Give one biological process that requires mitosis and one that requires meiosis
Mitosis: skin cell replacement. Meiosis: formation of sperm or egg.
What is a chromosome?
A structure of DNA and proteins carrying genetic information; visible during cell division.
During which phase does DNA replication occur?
S phase
During which mitotic phase do sister chromatids separate and move toward opposite poles?
Anaphase.
During which meiotic stage does crossing over (recombination) occur?
Prophase I (specifically during pachytene of prophase I).
Why is meiosis necessary for sexual reproduction?
Meiosis reduces chromosome number so fusion of gametes restores species’ chromosome number and increases genetic variation.
Define diploid and haploid.
Diploid (2n): two sets of chromosomes; Haploid (n): one set.
Name the checkpoint that ensures all chromosomes are properly attached to the spindle before anaphase.
The spindle assembly checkpoint (metaphase checkpoint).
Explain the role of the mitotic spindle and name the protein structure that organizes microtubules in animal cells.
The mitotic spindle segregates chromosomes; centrosome (with centrioles in animal cells) organizes microtubules.
Define homologous chromosomes and explain how they differ from sister chromatids.
Homologous chromosomes are matching chromosome pairs (one from each parent) with same genes but possibly different alleles; sister chromatids are identical copies formed during DNA replication.
Explain how mitosis contributes to growth and repair using a specific example in humans.
Example: bone fracture repair — mitosis produces new osteoblasts to rebuild bone tissue.
What is a kinetochore, and what is its function during cell division?
Kinetochore: protein complex at centromere where spindle fibers attach to move chromosomes.
Describe the difference between G0 and G1 phases.
G0 is a nondividing/resting state; G1 is the first gap/growth phase preparing for DNA synthesis.
Compare cytokinesis in plant cells versus animal cells (what structure forms in each).
Animal cells: cleavage furrow forms via contractile ring; Plant cells: cell plate forms building a new cell wall.
Explain how independent assortment during meiosis increases genetic variation.
Independent assortment: homologous pairs line up randomly at metaphase I, producing different combinations of maternal and paternal chromosomes in gametes.
Discuss how errors in cell division can contribute to cancer (mention whether mitosis or meiosis is involved).
Errors like uncontrolled mitotic divisions or mutations affecting cell-cycle checkpoints can cause tumors/cancer; meiosis errors cause gamete abnormalities (not cancer).
Define synapsis and state when it occurs.
Synapsis: pairing of homologous chromosomes during prophase I of meiosis.
List the stages of the cell cycle in order and give one major event that occurs in each stage. A cell with 16 chromosomes enters mitosis. After mitosis and cytokinesis, how many chromosomes will each daughter cell have? Explain.
Order: G1 (growth), S (DNA replication), G2 (preparation/checks), M (mitosis: nuclear division) and cytokinesis (cytoplasm divides).
A cell with 16 chromosomes enters mitosis. After mitosis and cytokinesis, how many chromosomes will each daughter cell have? Explain.
Each daughter cell will have 16 chromosomes (same as parent).
Describe nondisjunction and predict one possible chromosomal result in human gametes if nondisjunction occurs during meiosis I.
Nondisjunction: failure of homologs or sister chromatids to separate; result could be gametes with an extra chromosome (n+1) or missing one (n-1) — e.g., trisomy 21 (Down syndrome) if fertilization involves an n+1 gamete.
Compare and contrast the genetic similarity between parent and daughter cells after mitosis versus after meiosis (address chromosome number and genetic identity).
After mitosis, daughter cells are diploid and genetically nearly identical to the parent (barring mutation). After meiosis, daughter gametes are haploid and genetically unique due to crossing over and independent assortment.
Explain the terms "crossing over," "chiasma," and "recombination," and describe their significance for offspring.
Crossing over: exchange of chromosome segments between homologs; chiasma (plural chiasmata): visible site of crossover; recombination: result of crossing over that creates new allele combinations — increases genetic diversity.