Question

amoeba sisters video recap

1. the purpose of meiosis is to make gametes, also known as sperm and egg cells. in humans, your body cells have 46 chromosomes. how many chromosomes are in a sperm or egg cell if, when they come together to form a fertilized zygote, there are 46 chromosomes? write the correct number of chromosomes next to the sperm and egg.

images of sperm and egg cell

1. interphase must occur once before meiosis can happen. (same thing for mitosis). what would happen if interphase didn’t occur first?

image of a cell with interphase to-do list

1. a cell that begins meiosis has 23 chromosomes inherited from the mother (shown in green in the cartoon below) and 23 chromosomes inherited from the father (shown in blue in the cartoon below). in the process of meiosis, chromosomes begin to match up in homologous pairs. how would you know if two chromosomes were homologous?

image of homologous chromosomes

1. crossing over is a very important event in prophase i of meiosis! what happens during crossing over and what is the significance?

image of chromosomes crossing over

1. meiosis does pmat twice! that means there is a prophase i and a prophase ii. there is a metaphase i and a metaphase ii. etc... if the cartoon below has chromosomes in the middle of the cell, how would you know whether it was in metaphase i or metaphase ii?

image of a cell in metaphase

1. meiosis does not always occur without any difficulties. describe what occurs during nondisjunction and the effect on the resulting cells.

image of nondisjunction
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Explanation:

1. Meiosis halves chromosome number for fertilization; 46/2=23.
2. Interphase replicates DNA; no interphase = insufficient DNA for division.
3. Homologous chromosomes have same size/shape and carry matching genes.
4. Crossing over swaps DNA between homologs, increasing genetic diversity.
5. Metaphase I has paired homologs; Metaphase II has single chromosomes.
6. Nondisjunction = chromosomes fail to separate, causing abnormal chromosome numbers in gametes.

Answer:

1. Sperm: 23; Egg: 23
2. The cell would lack replicated DNA, so meiosis couldn’t produce viable gametes.
3. They have the same size, shape, and carry genes for the same traits (e.g., eye color).
4. Homologous chromosomes exchange DNA segments; increases genetic variation.
5. Metaphase I: Homologous pairs line up in the middle. Metaphase II: Single chromosomes line up.
6. Chromosomes don’t separate properly; gametes get extra/missing chromosomes, leading to genetic disorders.