In the genetics lab, we used a simulation and defined what a chromosome is, and we took a look at its structure and the copying and distribution of chromosomes during cell division.
INSTRUCTIONS
In this lab, we want to take a closer look at human chromosomes and the concept of non-disjunction by looking at actual photos of human chromosomes. These photos are called karyotypes and these are used in clinical medicine. Karyotypes from a single cell are used in the hospital clinic to determine genetic abnormalities due to non-disjunction. Samples are taken from parents or unborn children and cells are cultured (grown in the lab) and then analyzed to see if the full complement of chromosomes are in each cell. Here is a quote from a fertility clinic website describing the karyotyping procedure:
“A karyotype can be performed on any tissue but most often it is done from a blood sample, a sample of amniotic fluid or a piece of placenta obtained through chorionic villi sampling. Karyotyping is a complex process that involves growing the cells, obtaining the chromosomes, staining and analyzing the chromosomes and reporting the results. A karyotype is an actual photograph of the chromosomes from one cell.”
Why do the cells have to be cultured? Think about it and see the answer at the bottom of page 2. Since in some cases individual genetic abnormalities are due to non-disjunction of certain chromosomes, each of the 23 pairs of chromosomes is observed so that abnormalities can be detected. A complete set of chromosomes is determined by locating each pair of the 23 chromosomes. How can this be done if they all look the same? They can be the same because each pair of chromosomes is actually very different from all other pairs. For instance, chromosomes can differ in appearance by their length, the position of their centromere, and their banding pattern.
The banding pattern on a chromosome is a series of stripes seen on chromosomes and is the result of the way the DNA is packed into the chromosome. Chromosome pairs show identical (or nearly identical) banding patterns. In this activity, you will be completing an actual karyotype by observing and arranging chromosomes in clinically-derived karyotype samples.
In the genetics lab, we used a simulation and defined what a chromosome is, and we took a look at its structure and the copying and distribution of chromosomes during cell division.
INSTRUCTIONS
In this lab, we want to take a closer look at human chromosomes and the concept of non-disjunction by looking at actual photos of human chromosomes. These photos are called karyotypes and these are used in clinical medicine. Karyotypes from a single cell are used in the hospital clinic to determine genetic abnormalities due to non-disjunction. Samples are taken from parents or unborn children and cells are cultured (grown in the lab) and then analyzed to see if the full complement of chromosomes are in each cell. Here is a quote from a fertility clinic website describing the karyotyping procedure:
“A karyotype can be performed on any tissue but most often it is done from a blood sample, a sample of amniotic fluid or a piece of placenta obtained through chorionic villi sampling. Karyotyping is a complex process that involves growing the cells, obtaining the chromosomes, staining and analyzing the chromosomes and reporting the results. A karyotype is an actual photograph of the chromosomes from one cell.”
Why do the cells have to be cultured? Think about it and see the answer at the bottom of page 2. Since in some cases individual genetic abnormalities are due to non-disjunction of certain chromosomes, each of the 23 pairs of chromosomes is observed so that abnormalities can be detected. A complete set of chromosomes is determined by locating each pair of the 23 chromosomes. How can this be done if they all look the same? They can be the same because each pair of chromosomes is actually very different from all other pairs. For instance, chromosomes can differ in appearance by their length, the position of their centromere, and their banding pattern.
The banding pattern on a chromosome is a series of stripes seen on chromosomes and is the result of the way the DNA is packed into the chromosome. Chromosome pairs show identical (or nearly identical) banding patterns. In this activity, you will be completing an actual karyotype by observing and arranging chromosomes in clinically-derived karyotype samples.
Short Answer (30 pts):
- According to your analysis of patient A’s karyotype, you believe that this patient has the
genetic condition known as ____________ 21. (1 word answer) - According to your analysis of patient B’s karyotype, you believe that this patient has the
genetic condition known as ____________ syndrome. (1 word answer)
According to your analysis of patient C’s karyotype, you believe that this patient has the genetic
condition known as Trisomy ___. (1 number answer)
Short Essay (30 pts):
Use internet and book resources to determine the circumstances under which karyotyping is done
in a health clinic setting. Also, share your thoughts regarding whether you or one of your family
members would choose to undergo a karyotype test. The short essay must be 100–140 words and
demonstrate course-related knowledge, and it must include 1 citation from the Bible and 1 from
an outside source other than your course textbook. Sources must be cited in current Turabian
format. (References are not included in the final word count.)
Answer: Remember that chromosomes are only condensed in their classic “X” shape during cell
division, so cells must be cultured or grown so that they proceed through the cell cycle. This
allows the clinician ttHBAo find cells with condensed chromosomes.