Chapter 16

Answer 1

Interphase (G1, S, G2):
-G1: Cell grows and checks if it’s ready to keep going.
-S: DNA Replication – makes copies of DNA (sister chromatids).
-G2: Cell grows more and checks DNA for damage before dividing.

M (Mitosis + Cytokinesis):
-DNA is split evenly into two cells (Prophase → Telophase).
-Metaphase Checkpoint: Makes sure DNA is lined up right.
-Cytokinesis: Splits the rest of the cell into two.

Question 2

Define mitosis and describe its purposes for organisms

Answer 2

Mitosis: A mother cell divides to produce 2 new daughter cells genetically identical to the original.

Functions:
-Tissue renewal and regeneration
-Asexual reproduction
-Embryonic development
-Growth

Question 3

Purpose in unicellular organisms:
Purpose in multicellular organisms:

Answer 3

Unicellular: to reproduce (make more of themselves)

Multicellular: For growth, repair, and replacing old or damaged cells.

Question 4

Define the term stem cell–what makes stem cells unique?

Answer 4

Stem cells are special cells that can:
-Become any kind of cell in the body
-Make more stem cells

What makes them unique?
-Haven’t chosen a job yet
-Can turn into different types of cells(differentiation)
-For development, growth, and repair

Question 5

Define the following terms

Answer 5

Autosome:
A regular chromosome (not a sex chromosome).

Sex Chromosome:
Decides if you’re male or female.

Diploid:
Cell with 2 sets of chromosomes (one from mom, one from dad).

Haploid:
Cell with 1 set of chromosomes.

Sister Chromatids:
Exact copies of a chromosome made during DNA replication

Question 6

Describe the role of the mitotic spindle apparatus

Answer 6

-helps sort and organize chromosomes during mitosis, ensuring each daughter cell gets the right number of chromosomes.

Kinetochore microtubules: attach to the centromere of each chromosome to move chromosomes and pull sister chromatids apart

Polar microtubules: Push against each other to stretch the cell and separate the two poles.

Question 7

Mitosis

Answer 7

1. Prophase:
   -Chromosomes condense into visible structures.
   -Nuclear membrane dissolves.
   -Centrosomes duplicate and move to opposite sides of the cell.
2. Prometaphase:
   -Mitotic spindle is fully formed.
   -Centrosomes are at opposite poles.
   -Spindle fibers attach to the chromosomes.
   -Chromosomes move towards the middle of the cell.
3. Metaphase:
   -Chromosomes line up in the middle (metaphase plate).
   -This is checked to make sure everything is aligned properly for an even division.
4. Anaphase:
   -Sister chromatids are pulled apart and move to opposite sides of the cell.
5. Telophase:
   -Chromosomes reach poles and decondense (spread out).
   -Nuclear membranes reform, creating two nuclei.

Cytokinesis:
-Cytoplasm divides to make two new cells.
-Animals: A cleavage furrow forms and “pinches” the cells apart.
-Plants: A cell plate forms between the cells, creating a new wall

Question 8

Meiosis

Answer 8

Meiosis is cell division that halves the chromosomes in daughter cells

Meiosis I:
-Prophase I: Homologous chromosomes pair up and exchange pieces (crossing over).
-Metaphase I: Homologous pairs line up.
-Anaphase I: Homologous chromosomes separate (sister chromatids stay together).
-Telophase I & Cytokinesis: Two haploid cells form.

Meiosis II:
-Prophase II: Chromosomes re-condense.
-Metaphase II: Chromosomes line up individually.
-Anaphase II: Sister chromatids separate.
-Telophase II & Cytokinesis: Four haploid cells are formed.

Meiosis reduces chromosome number and increases genetic variation

Question 9

Describe the three events that occur during meiosis I but not during meiosis II or mitosis.

Answer 9

Synapsis and Bivalent formation:
-Homologous chromosomes (mom and dad’s chromosomes) pair up to form a tetrad.

Crossing Over:
-Chromosomes swap pieces, creating new gene combinations (increasing genetic diversity).

Preparing to Separate:
-The homologous chromosomes stay together but get ready to separate in the next step.