Solved MITOSIS - Chromosome Worksheet 1. In the MITOSIS | Chegg.com - Free Printable

Let’s work through this step by step.

We’re looking at a mitosis worksheet for a hypothetical (non-human) cell. The key is to understand how chromosomes behave during mitosis — and remember: mitosis makes identical copies of the parent cell, so chromosome number stays the same throughout, except temporarily doubled in S phase due to replication.

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Step 1: Look at the Parental Cell (Top Circle)

It shows 4 chromosomes labeled 1, 2, 3, 4.

- Chromosome 1: big, dark
- Chromosome 2: small, light
- Chromosome 3: medium, dark
- Chromosome 4: medium, light

Notice:
- Big dark (1) and big light? No — wait, actually, let’s pair them by size and shape.
Actually, looking again:
→ Chromosome 1 (big, dark) and Chromosome 4 (medium-light but similar length?) — no, better to look at pairing.

Wait — in diploid cells, homologous pairs are same size/shape, one from each parent. So likely:

- Pair A: #1 (big, dark) and #4 (big, light) → they’re both long, just different shading.
- Pair B: #2 (small, light) and #3 (small, dark) → both short, different shading.

So yes — two homologous pairs → meaning the cell is diploid (2n).

Total chromosomes = 4 → so 2n = 4 → n = 2.

✔ Haploid or diploid? → Diploid (2n)
✔ Homologous pair example: #1 and #4 OR #2 and #3

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Step 2: S Phase of Interphase

In S phase, DNA replicates → each chromosome becomes two sister chromatids joined at centromere.

But — we still count chromosomes by centromeres! So even though each chromosome now has 2 chromatids, it’s still counted as 1 chromosome until they separate.

So:

- Number of chromosomes = still 4
- Still diploid (2n)
- Single or duplicated? → Duplicated (each has 2 chromatids)

The image already draws them as X-shaped (duplicated), which matches.

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Step 3: Prophase of Mitosis

Chromosomes condense, nuclear envelope breaks down, spindle forms.

No change in chromosome number yet.

- Number of chromosomes = 4
- Still diploid (2n)
- Tetrad formation? → NO — that’s meiosis I (homologs pair up). In mitosis, homologs don’t pair.
- Independent assortment? → NO — that’s also meiosis I (random alignment of homologs). Not in mitosis.
- Crossing over? → NO — that’s prophase I of meiosis. Not in mitosis.

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Step 4: Metaphase of Mitosis

Chromosomes line up single file at the equator.

Still 4 chromosomes, each with 2 chromatids.

- Number of chromosomes = 4
- Diploid (2n)

Draw them lined up in the middle — keep their shapes and shadings consistent.

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Step 5: Anaphase of Mitosis

Sister chromatids split apart → now called individual chromosomes.

Each pole gets 4 chromosomes (since each original chromosome splits into 2).

Wait — important: When sister chromatids separate, each is considered a full chromosome.

So total chromosomes in the cell momentarily doubles to 8? But we usually say “number of chromosomes per nucleus” — and since nuclei haven’t reformed yet, some texts say 8, others say 4 moving apart.

BUT — standard teaching: At anaphase, when chromatids separate, you have 8 distinct chromosomes in the cell (but not yet in two nuclei). However, many worksheets simplify and say “still 4 chromosomes being pulled apart” — but technically, after separation, each chromatid is a chromosome.

Let’s clarify:

Before anaphase: 4 chromosomes, each with 2 chromatids → total 8 chromatids.

After separation: 8 chromosomes (each single-chromatid), 4 going to each pole.

But the question says: “Number of chromosomes = ?”

In most high school biology contexts, they consider the number based on centromeres. Before anaphase: 4 centromeres → 4 chromosomes. After anaphase: 8 centromeres → 8 chromosomes.

However, some curricula teach that the chromosome number doesn’t change until cytokinesis completes — but that’s incorrect biologically.

To be precise:

At anaphase start: 4 chromosomes (each with 2 chromatids)

At anaphase end: 8 chromosomes (each with 1 chromatid), 4 at each pole.

But the worksheet probably expects:

“Number of chromosomes = 8” (because chromatids are now independent chromosomes)

And “Haploid or diploid?” → This is tricky. Since the cell hasn’t divided yet, and all 8 chromosomes are present, but they are in two sets of 4 (identical), it’s still functionally diploid — but technically, the ploidy refers to sets of homologs. Since there are no homologous pairs being separated (like in meiosis), and all 8 are just copies, we might still call it diploid because the genetic content is equivalent to 2n=4, but doubled.

Actually, best approach: In mitosis, ploidy doesn’t change. Even at anaphase, the cell is still considered diploid because it contains two complete sets of chromosomes — even if those sets are temporarily in one cell.

But let’s check common textbook answers:

Most sources say: During anaphase of mitosis, the number of chromosomes doubles temporarily because sister chromatids become individual chromosomes.

Example: Human cell (46 chromosomes) → at anaphase, 92 chromosomes (46 moving to each pole).

So here: 4 → 8.

Ploidy: Still diploid? Technically, since there are 4 homologous pairs worth of genes, but duplicated — but ploidy is about unique sets. Actually, after duplication, before division, it’s still 2n, but with duplicated chromosomes. After separation, each pole will get 4 chromosomes — which is 2n.

I think the safest answer for school level:

→ Number of chromosomes = 8 (because chromatids are now separate chromosomes)

→ Haploid or diploid? → Diploid (because each future daughter cell will be diploid, and the cell hasn't divided yet)

Separating: Sister chromatids

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Step 6: Telophase & Cytokinesis

Two daughter cells form.

Each gets 4 chromosomes (single chromatid each).

So:

- Two daughter cells
- Each has 4 chromosomes → diploid (2n)
- Genetically identical to parent and each other

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Now, drawing instructions:

You need to draw missing chromosomes in each circle, making sure to show:

- Light vs dark (shading)
- Big vs small (size)
- Shape (rod-like, X-shaped where appropriate)

Parental cell: Already drawn — 4 chromosomes: 1(big-dark), 2(small-light), 3(small-dark), 4(medium-light? Wait, earlier I said 4 is big-light — let me recheck the image description.

Looking back at user’s text:

"1 2 3 4" — and descriptions:

From typical such worksheets:

Usually:

- Chromosome 1: large, black
- Chromosome 2: small, white (light)
- Chromosome 3: small, black
- Chromosome 4: large, white (light)

So homologous pairs: 1&4 (both large), 2&3 (both small)

Yes.

So in drawings:

- S phase: Each chromosome duplicated → so 1 becomes two black rods connected; 2 becomes two white small rods connected; etc. Image already shows this.

- Prophase: Same as S phase — condensed, duplicated. Draw the same 4 X-shaped chromosomes, scattered in nucleus.

- Metaphase: Line them up in center — order doesn’t matter, but keep sizes and shades correct.

- Anaphase: Pull sister chromatids apart — so for each chromosome, split the X into two V-shapes going to opposite poles. You’ll have 8 chromosomes total: 4 going left, 4 going right. Make sure each pair going to a pole includes one from each homologous pair — e.g., one big black, one big white, one small black, one small white per pole.

- Telophase: Two circles, each with 4 chromosomes (single chromatids): big black, big white, small black, small white.

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Final Answers Summary:

Hypothetical Parental Cell
Number of chromosomes = 4
Haploid (1n) or diploid (2n)? → Diploid (2n)
Example of homologous pair: #1 and #4 (or #2 and #3)

S Phase of Interphase
Number of chromosomes = 4
Haploid or diploid? → Diploid (2n)
Single or duplicated? → Duplicated

Prophase of Mitosis
Number of chromosomes = 4
Haploid or diploid? → Diploid (2n)
Tetrad formation? → No
Independent assortment? → No
Crossing over? → No

Metaphase of Mitosis
Number of chromosomes = 4
Haploid or diploid? → Diploid (2n)

Anaphase of Mitosis
Number of chromosomes = 8
Haploid or diploid? → Diploid (2n)
Separating: Sister chromatids

Telophase of Mitosis & Cytokinesis
Two or four daughter cells? → Two
Number of chromosomes / daughter cell = 4
Haploid or diploid? → Diploid (2n)
Genetically different or identical? → Identical

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Final Answer:

Parental Cell: 4 chromosomes, diploid, homologous pair e.g. #1 and #4
S Phase: 4 chromosomes, diploid, duplicated
Prophase: 4 chromosomes, diploid, no tetrad/independent assortment/crossing over
Metaphase: 4 chromosomes, diploid
Anaphase: 8 chromosomes, diploid, separating sister chromatids
Telophase: Two daughter cells, 4 chromosomes each, diploid, genetically identical