GizmosAnswerKey
Life ScienceGrade 9-11

Human Karyotyping Answer Key

Arrange human chromosomes into a karyotype and identify chromosomal abnormalities.

Prior Knowledge Questions

Q1.What is a karyotype?

Answer

A karyotype is an organized image of all chromosomes in a cell, arranged in homologous pairs by size.

Q2.How many pairs of chromosomes do humans have?

Answer

Humans have 23 pairs of chromosomes (46 total): 22 pairs of autosomes and 1 pair of sex chromosomes.

Q3.What determines biological sex in humans?

Answer

The sex chromosomes determine biological sex: XX = female, XY = male.

Activity A – Identifying Abnormalities

Q1.What is Down syndrome caused by?

Answer

Down syndrome (Trisomy 21) is caused by having three copies of chromosome 21 instead of two.

Q2.What is nondisjunction?

Answer

Nondisjunction is the failure of chromosomes to separate properly during cell division, resulting in cells with abnormal chromosome numbers.

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