1) After analyzing several karyotypes, you have just found an interesting chromo
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Question
1) After analyzing several karyotypes, you have just found an interesting chromosome variation at 5p15.2. Explain how you would describe the location of this variation to someone who is not a geneticist. Be sure to explain what each number/letter means.
2) Complete the karyotyping activity listed in the Task List. Write a short paragraph summarizing how you came up with your diagnosis for Patient A, B and C.
https://www.biologycorner.com/worksheets/karyotyping_key.html
http://www.biology.arizona.edu/human_bio/activities/karyotyping/karyotyping.html
3) After initial prenatal screening, you are told that you are at risk for delivering a child with Down Syndrome. You are sent to the genetic counselor and they inform you of your options for further testing. State your reasons for proceeding with testing or not testing. regardless of whether or not you decide to test, what genetic tests could be done. Which test would you choose and why?
Explanation / Answer
Answer 1) 5p15.2 is a Cri-Du-Chat syndrome. Cri-du-chat syndrome is a chromosomal disorder caused by a deletion of the short arm of chromosome 5. The disease severity, levels of intellectual and developmental delay, and patient prognosis have been related to the size and position of the deletion.
Edit
Cri du chat syndrome is due to a partial deletion of the short arm of chromosomenumber 5, also called "5p monosomy" or "partial monosomy." Approximately 90% of cases result from a sporadic, or randomly occurring, de novo deletion. The remaining 10-15% are due to unequal segregation of a parental balanced translocation where the 5p monosomy is often accompanied by a trisomic portion of the genome. These individuals may have more severe disease than those with isolated monosomy of 5p. A recent study suggests this may not be the case where a trisomy of chromosome 4q is involved.
Most cases involve total loss of the most distant 10-20% of the material on the short arm. Fewer than 10% of cases have other rare cytogenetic aberrations (e.g., interstitial deletions, mosaicisms, rings and de novotranslocations). The deleted chromosome 5 is paternal in origin in about 80% of de novocases. Loss of a small region in band 5p15.2 (cri du chat critical region) correlates with all the clinical features of the syndrome with the exception of the catlike cry, which maps to band 5p15.3 (catlike critical region). The results suggest that 2 noncontiguous critical regions contain genes involved in this condition's cause. Two genes in these regions, Semaphorine F (SEMA5A) and delta catenin(CTNND2), are potentially involved in cerebral development.
Answer 2) Its a spam question, its against the chegg policy to answer this question.
Answer 3)
There are two basic methods of screening for Down's syndrome - the ultrasound scan and biochemical serum screening:
Nuchal translucency ultrasound scan (also called the NT scan): this is a special ultrasound scan that is done between 11 weeks and 2 days and 14 weeks and 1 day of pregnancy. It may be done at the same time as your early dating scan and is carried out in the same way. It measures the fluid collection under the skin at the back of the baby's neck (the nuchal translucency (NT)).
All babies have a collection of fluid here but babies with Down's syndrome tend to have more fluid in this area. The fluid measurement, your age, the size of the baby and other details such as your weight, ethnicity and smoking status are then put into a computer program to give the risk of the baby having Down's syndrome.
Sometimes it may be difficult to obtain an accurate measurement of the NT. This may be due to the position of the baby or because the pregnant woman is overweight.
Blood tests (also called biochemical serum screening): blood tests may be done to measure levels of various hormones and proteins in your blood. These hormones and proteins are produced by the placenta or the developing baby.
Examples include pregnancy-associated plasma protein A (PAPP-A), beta human chorionic gonadotrophin (beta-hCG) and alpha-fetoprotein (AFP). If the baby has Down's syndrome, the levels of these substances can be affected.
Again, a computer program is used to give the risk of the baby having Down's syndrome, based on the blood test results, your age, the stage that you are at in your pregnancy, your weight, ethnicity and smoking status. The blood test used in Down's syndrome screening is also sometimes called serum screening.
The two main screening tests used for Down's syndrome using the above methods are:
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