Download Name

Name ANSWER KEY___________ Block:
Digenis v4/13
What Can Our Chromosomes Tell Us?
A Web-based Activity
In your internet browser, go to: learn.genetics.utah.edu/content/begin/traits/
Read through the site and answer the following questions. Also be sure to complete the activities on
each of the pages, including the Try-It-Yourself Karyotype. These are fair game for your next quiz or
test.
What is a chromosome? (watch the movie)
1. A. How long is all the DNA in one of your cells, stretched out end-to-end? __3 meters_______
B. How many chromosomes do Carp have? ___104_____
How Do Scientists Read Chromosomes?
2. What three chromosomal characteristics are compared in karyotype analysis?
• length, banding/staining pattern (size & location of bands), centromere position
3. What is the centromere position on chromosome 1? What does this mean?
• metacentric = in the center of the chromosome
4. What are the other two types of centromere positions? Draw and label them below.
• submetacentric = positioned so one arm is longer than the other
• acrocentric = positioned very close to one end
Do the mini-activity in the right margin before going back to the main page!
Make A Karyotype
5. What is a karyotype? An organized picture/profile of all the chromosomes in a cell.
6. How is a karyotype made? By breaking open a metaphase cell, taking a picture of the
chromosomes and then arranging and numbering the chromosomes by size from longest
to shortest (except for sex chromosomes).
Do the activity before going back to the main page. Turn on the hints if you are having trouble. Is the
karyotype you made from a male or a female person? ___male_________
Using Karyotypes to Predict Genetic Disorders
7. What three things do scientists look for when analyzing a human karyotype? (3 differences that
could exist?)
• too many or too few chromosomes
• missing pieces of chromosomes
• mixed up pieces of chromosomes
Watch the movies for MEIOSIS, FERTILIZATION, ABNORMAL MEIOSIS, and TRISOMY.
8. An event during meiosis called nondisjunction can lead to the production of egg or sperm that
have an extra copy of a particular chromosome (two copies instead of one). When one of these
eggs or sperm is combined with a normal gamete (with just one copy of said chromosome), the
resulting zygote is said to have what condition? (indicating that is has total of 3 copies of a
particular chromosome)
Trisomy
Watch the movies for MONOSOMY, DELETIONS and TRANSLOCATIONS.
9. What is monosomy?
When a zygote is missing a copy of a chromosome – has only one copy of a
chromosome instead of the normal two copies of that chromosome.
10. In your own words describe translocation.
Translocation is when a chromosome breaks and one of the pieces attaches to a different
type of (non-homologous) chromosome.
Reciprocal translocation: a swap of DNA between non-homologous chromosomes
Robertsonian translocation: the long arms of the two chromosomes fuse together and
the short arm is lost
11. What are the three disorders listed on this web site that are caused by an abnormal number of
chromosomes? (do the QUIZ to help you if you are unsure)
• Klinefelter’s syndrome (47 chromosomes total, due to an extra sex chromosome)
• Down syndrome (47 chromosomes total, due to an extra chromosome 21)
• Turner’s syndrome (45 chromosomes total, due to a missing sex chromosome)
Name: _______________________________ Block: ___
Web Karyotyping Simulation
Go to: http://www.biology.arizona.edu and click on Karyotyping in top left corner.
(or go to http://www.biology.arizona.edu/human_bio/activities/karyotyping/karyotyping.html)
Read the Introduction and answer the following question:
1. How many genes do the Giemsa or G-bands on chromosomes really represent?
Potentially 100’s of genes
Now go on to the patient histories. Start with Patient A. Follow the instructions on-screen to
complete Patient A’s karyotype. When you have completed Patient A’s karyotype, a screen will
appear with information on Notation and Diagnosis. Answer the following questions after you finish
Patient A’s karyotype!
2. Explain what information can be learned from the notation method typically used in karyotyping.
For example, what does 47, XY, +18 mean?
• total # of chromosomes (in this example, 47 chromosomes total)
• the sex or gender of the person (in this example, XY = male)
• the type of extra or missing chromosome/s (in example, an extra copy of chromosome 18)
3. What most commonly happens to a fetus with an extra or missing chromosome?
(careful here – if you see a word in the answer you don’t understand, look it up!)
An extra or missing chromosome usually causes the embryo or fetus to be inviable (fails to
develop/survive, results in a very early stage miscarriage).
Now you are ready to record each patient’s chromosomal condition and diagnosis. Using the
information on-screen, answer the following:
Patient A
A1. ___47, XY, +21_______ (notation)
A2. ___Down Syndrome____ (diagnosis)
Patient B
B1. ____47, XXY______ (notation)
B2. ____Klinefelter’s Syndrome____ (diagnosis)
Patient C
C1. ___47, XY, +13____ (notation)
C2. ___Trisomy 13 Syndrome (aka Patau Syndrome)____ (diagnosis)
Human Chromosomal Abnormalities
Use the chart you were given in class AND any reputable & reliable web resources to answer
the following questions.
1. Which types of chromosomal abnormalities seem more severe, those involving autosomes or
those involving sex chromosomes? What specific information leads you to conclude this?
AUTOSOMES. Examples (like Edwards Syndrome & Cri du Chat) have more severe
symptoms and deformities, including many autosomal disorders with greatly shortened
lifespans.
2. Which chromosomal abnormalities cause sterility or infertility (unable to have children)?
Turner’s and Klinefelter’s Syndromes, with Down Syndrome, males are usually infertile and
females have greatly reduced fertility.
3. Which chromosomal abnormalities don’t have any (or many) unusual or severe symptoms?
Triple X or Metafemale
4. Which chromosomal abnormality is most common among live births? ___Down Syndrome___
5. Identify the following:
a. Trisomy 13
__Patau Syndrome___
b. Monosomy X
__Turner’s Syndrome__
c. Trisomy 21
__Down Syndrome__
d. Trisomy X
__Triple X Syndrome__