Download Looking at karyotypes

Activity AB1.8 Looking at karyotypes
To answer
1. Why do individuals have 2 copies of each chromosome?
2. What is a karyotype?
3. In a karyotype chromosomes are arranged according to size and which 2
other factors are considered?
4. What difference is there between the male and the female karyotype?
The karyotype of a person with Klinefelter’s syndrome is shown below.
5. Describe how the Klinefelter’s karyotype is different.
Klinefelter’s syndrome produces a sterile male with female features and small
testes.
6. Explain why a person with Klinefelter’s syndrome is male, not female, even
though they have two X chromosomes.
7. Half of all miscarriages are due to chromosome abnormalities. This means
that parts of chromosomes are missing or duplicated. Using your
knowledge of how genes affect development, suggest why chromosome
abnormalities usually cause serious symptoms in an individual.
Answers
1. One from each parent
1
2. Diagram showing the chromosomes possessed by an individual
1
3. Shape and banding
1
4. Pair 23 is either XX female or XY male
1
5. Have an extra sex chromosome (X) chromosome – XXY
1
6. Y chromosome carries the SRY gene;
produces testosterone – male hormone;
embryo develops into a male
2
7. genes code for a protein;
if a gene is missing then a particular protein is not made or an enzyme
is missing;
if the chromosome is duplicated then too much of the protein / enzyme
is produced
3