Let's go through the
Karyotype Worksheet step by step and solve each question with explanations.
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Question 1:
> Look at the karyotype in Figure 1 below. Notice the two sex chromosomes, pair number 23, do not look alike. They are different because this karyotype is of a male, and a male has an X and a Y chromosome. Circle the Y chromosome in the Karyotype below.
Answer:
In
Figure 1, the 23rd pair (the last pair) consists of two
different-sized chromosomes: one is larger (the
X chromosome) and one is smaller (the
Y chromosome). The
Y chromosome is significantly smaller than the X.
✔ Circle the smaller chromosome in pair 23 — that’s the
Y chromosome.
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Question 2:
> Notice the center point of each chromosome. This is called a centromere. Is there a line running through each centromere in the picture above? Circle YES or NO.
Answer:
Yes, in the karyotype, each chromosome has a
centromere, which appears as a
constriction or
break in the middle of the chromosome. In the image,
a line runs through the centromere of each chromosome to indicate its position.
✔ Circle: YES
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Question 3:
> How many chromosomes does a normal person have? Circle: 23 or 46
Answer:
A normal human being has
46 chromosomes —
23 pairs (22 pairs of autosomes + 1 pair of sex chromosomes).
✔ Circle: 46
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Question 4:
> Look at the karyotype labeled Figure 4. Do you see any chromosomal abnormalities? YES or NO
Answer:
Look at
Figure 4. Compare each chromosome pair. You’ll notice that in
pair 21, there are
three chromosomes instead of two — this is a trisomy.
This condition is known as
Trisomy 21, or
Down syndrome.
✔ Circle: YES
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Question 5:
> What chromosomes are abnormal? AUTOSOME or SEX
Answer:
The abnormality is in
chromosome pair 21, which is an
autosome (not a sex chromosome). Autosomes are chromosomes 1–22.
✔ Circle: AUTOSOME
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✔ Final Answers:
1.
Circle the smaller chromosome in pair 23 (the Y chromosome).
2.
YES – a line runs through each centromere.
3.
46 – normal human chromosome count.
4.
YES – there is a chromosomal abnormality (trisomy 21).
5.
AUTOSOME – the abnormal chromosome is an autosome (chromosome 21).
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🔍 Summary:
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Figure 1 shows a
normal male karyotype (XY).
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Figure 4 shows a
karyotype with Trisomy 21, a common genetic disorder caused by an extra copy of chromosome 21.
Let me know if you'd like a visual explanation or help identifying specific chromosomes!
Parent Tip: Review the logic above to help your child master the concept of karyotype activity worksheet.
