Meiosis: making egg and sperm cells with half the chromosomes

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   Use this

   Fruit fly card (real count: body cells have 8 chromosomes, in 4 matching pairs). One body cell completes meiosis. Cells made: ? Chromosomes in each: ?

2. 1.

   Ari reads that a fruit fly body cell has 8 chromosomes. One such cell completes meiosis. What does it make?

   • 8 cells, with 2 chromosomes each
   • 4 cells, with 4 chromosomes each
   • 2 cells, with 4 chromosomes each
   • 4 cells, with 8 chromosomes each

3. Meiosis in a fruit fly, counts per cell (real body-cell count, standard steps)

   stage	cells	chromosomes per cell	chromatids per cell
   before copying	1 cell	8 chromosomes	8 chromatids
   after copying	1 cell	8 chromosomes	16 chromatids
   after the first division	2 cells	? chromosomes	? chromatids
   after the second division	4 cells	4 chromosomes	4 chromatids

4. 2.

   Bo fills in the table for a fruit fly cell. What belongs in the blanks for one cell after the first division?

   • 4 chromosomes, 4 chromatids
   • 8 chromosomes, 16 chromatids
   • 8 chromosomes, 8 chromatids
   • 4 chromosomes, 8 chromatids
5. 3.

   a fruit fly body cell has 8 chromosomes and completes meiosis. Total chromosomes in all the finished cells together: ? A fruit fly body cell (8 chromosomes) completes meiosis. Esme adds up the chromosomes in all the finished cells together. What is the total?

   • 32 chromosomes
   • 8 chromosomes
   • 4 chromosomes
   • 16 chromosomes
6. 4.

   Jun reads picture T of a fruit fly cell in the first division. The pairs are being pulled toward the two ends. What goes to each end?

   • 8 X-shaped chromosomes, so both members of each pair
   • 4 X-shaped chromosomes, one from each pair
   • 8 single chromatids, from splitting each X
   • 2 X-shaped chromosomes, from two of the pairs

7. Count card (real count)

   The starting cell has 8 chromosomes. Each cell after the first division has 4 chromosomes, and each of those is still 2 sister chromatids joined. Each cell after the second division has 4 chromosomes.

8. 5.

   Luz asks which division lowers a fruit fly cell's count from 8 chromosomes to 4, and why. Which statement is best?

   • The second, because each cell divides again
   • The first, because the DNA is copied then
   • The second, because the sister chromatids go to different cells
   • The first, because the matching chromosomes go to different cells

9. Count card (human counts)

   Egg cell, 23 chromosomes. Sperm cell, 23 chromosomes. The two cells join to make a new cell (a zygote) with ? chromosomes.

10. 6.

    An egg cell and a sperm cell each have 23 chromosomes and join in fertilization. Which description of the new cell does Milo choose?

    • 46 chromosomes, with the egg cell supplying the whole set
    • 46 chromosomes, in 23 matching pairs
    • 23 chromosomes, one set from the egg cell
    • 92 chromosomes, in 46 matching pairs

11. Count card (model data, a model plant)

    The new cell formed at fertilization has 10 chromosomes in matching pairs. Chromosomes from the pollen cell: ? Chromosomes from the egg cell: ?

12. 7.

    A model plant's new cell has 10 chromosomes after a pollen cell and an egg cell join. Noah traces where they came from. Which is right?

    • 5 from the pollen cell and 5 from the egg cell
    • 4 from the pollen cell and 6 from the egg cell
    • 10 from the pollen cell and 10 from the egg cell
    • 10 from the egg cell, which holds the full set

13. Table (model data)

    Chromosomes per cell across two generations, columns cell and chromosomes. Row: parent 1 body cell, 12. Row: parent 1 sperm cell, 6. Row: parent 2 body cell, 12. Row: parent 2 egg cell, 6. Row: offspring zygote, 12. Row: offspring sperm cell, ?

14. 8.

    Pia fills in a table that follows chromosome counts for a model animal across two generations. What belongs in the last row?

    • 24 chromosomes
    • 6 chromosomes
    • 12 chromosomes
    • 18 chromosomes

15. Chromosome cards (model, pairs 1 and 2 are different chromosome pairs)

    The parent cell holds 4 cards. Pair 1: a card with A and a card with a. Pair 2: a card with B and a card with b.

16. 9.

    A parent cell has chromosome pair 1 with alleles A and a, and pair 2 with B and b. Ren deals the cards for one egg cell. Which cards can go to it?

    • A and b
    • Aa and Bb
    • A, a and B
    • A and a

17. Use this

    Pair 1 and pair 2 are different chromosome pairs. The parent cell has pair 1 with A and a, and pair 2 with B and b. Side edge, from the other parent (same alleles): AB, Ab, aB, ab. Top edge: ?

18. 10.

    Tala deals cards along the top edge of a Punnett grid. The parent cell has A and a on pair 1, and B and b on pair 2. Which cards go on the edge?

    • AB, Ab, aB, ab
    • AB and ab
    • A, a, B, b as single cards
    • Aa and Bb