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# Chromosome Formulas

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I am having trouble writing the formulas. I know what each X and Y chromosome each possess but I don't know who to write a formula with that.

1. Write a formula for:
(a) a male with Down syndrome (due to the presence of an extra chromosome 21)
(b) a female with Turner syndrome (only one X chromosome)
(c) a female with cri du chat syndrome (deletion of a portion of p arm of chromosome 5)
(d) a male with Klinefelter syndrome (two X chromosomes and one Y chromosome)
(e) a female with a Philadelphia chromosome (tanslocation between chromosomes 9 and 22). People suffering from a form of leukemia (chronic myeloid leukemia) frequently harbor cells containing the Philadelphia chromosome.

2. Abnormalities in chromosome number are detrimental and usually lethal. Speculate as to why the impact of abnormal numbers in chromosome 21 and in sex chromosomes are relatively mild.

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#### Solution Preview

First of all, there are usually 22 pairs of somatic chromosomes and one pair of sex chromosomes (for 46 total chromosomes). You can write the formula for the karyotype of an individual by stating the total number of chromosomes in the followed by the sex chromosomes, then (if there is an abnormal number of chromosomes) what is extra or missing. So, the formula for a normal male is "46, XY" and for a normal female "46, XX".

1. Write a formula for:

(a) a male with Down syndrome (due to the presence of an extra chromosome ...

\$2.19

## Problems with a Single Chromosome

1) The genes GHI are on a single chromosome in the following order:

---G--------H-------------------------------------- I ------------------
5 mu 15 mu

The distance between G and H is 5 mu and the distance between genes H an I is 15 mu. What are the numbers of various progeny (assume a total of 4000 progeny are measured) in a GHI x ghi cross when:

1) c.o.c. = 1.0
2) c.o.c.= 1.5
3) c.o.c. = 0.5

Thank you! I really appreciate it!!

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