Let’s go through each question one by one, using the karyotype diagram provided.
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1.) How many pairs of chromosomes do you see?
In a human karyotype, chromosomes are arranged in 23 pairs. You can count them from pair #1 to pair #22 (autosomes), plus the sex chromosomes (X and Y or X and X). In this diagram, we see:
- Pairs numbered 1 through 22 → that’s 22 pairs
- Plus one more pair at the end labeled “X” and “Y” → that’s the 23rd pair
So total =
23 pairs
✔ Answer:
23
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2.) List some likenesses that you see among paired chromosomes:
When you look at each pair (like pair #1, pair #2, etc.), you’ll notice:
- They are about the same size.
- They have similar banding patterns (light and dark stripes).
- The centromere (the “waist” part) is in the same place on both chromosomes in a pair.
- They look like mirror images or twins — because they carry genes for the same traits (one from mom, one from dad).
✔ Example answer:
*They are the same size, have the same banding pattern, and the centromere is in the same spot.*
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3.) What is the sex of the organism?
Look at the last pair — the sex chromosomes. Here, it shows an
X and a
Y chromosome.
- XX = female
- XY = male
Since there’s an X and a Y, this is a
male.
✔ Answer:
Male
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4.) What do you think these “regions” of light and dark bands are?
These bands are created when chromosomes are stained during lab preparation. Each band represents a region where DNA is packed differently — some areas are tightly coiled (dark bands), others are looser (light bands). These help scientists identify specific parts of chromosomes and locate genes.
✔ Simple answer:
*They are regions where the DNA is packed differently — helping us tell chromosomes apart and find genes.*
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5.) If you start with chromosome number 1 and go until chromosome number 22, what trend in size correlation do you see?
Chromosome #1 is the largest. As you go up to #22, the chromosomes get progressively smaller.
✔ Trend:
*The chromosomes get smaller as the number increases — from biggest (#1) to smallest (#22).*
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6.) How does this trend affect the number of genes present on any particular chromosome?
Generally, bigger chromosomes hold more DNA, so they usually contain more genes. Smaller chromosomes have less DNA and fewer genes.
✔ Answer:
*Larger chromosomes (like #1) probably have more genes; smaller ones (like #22) likely have fewer genes.*
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7.) How many pairs of NUMBERED chromosomes do you see?
Numbered chromosomes are the autosomes — pairs #1 through #22. That’s 22 pairs.
The X and Y are not numbered — they’re sex chromosomes.
✔ Answer:
22
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Final Answer:
1.) 23
2.) Same size, same banding pattern, centromere in same location
3.) Male
4.) Regions where DNA is packed differently — helps identify chromosome parts and genes
5.) Chromosomes get smaller from #1 to #22
6.) Larger chromosomes likely have more genes; smaller ones have fewer
7.) 22
Parent Tip: Review the logic above to help your child master the concept of karyotypes worksheet.
