INHERITANCE OF TOOLS ANALYSIS

Pedigree chart question for biology assessment?

“Explain why pedigrees are particularly important tools in studying human genetics”

and the marking criteria says to mention these points
-Why must we use pedigrees to determine inheritance patterns and not other methods
-Time Restictions (??? i have no idea what this means in regard to pedigree charts)
- Offspring
- Analysis of past inheritance patterns.

in my opinion the marking criteria is really badly written but my teacher said to go by it to get full marks.

The first source I gave you answers your question about why pedigrees are particularly important tools in studying human genetics and why we must use pedigrees to determine inheritance patterns and not other methods:
“You cannot make humans of different types breed together so pedigree charts provide one of the few ethical ways of studying human genetics. Today genetic engineering has new tools to offer doctors studying genetic diseases …”.
However, I think your question is out dated because, as it says in the quote, “Today genetic engineering has new tools”, so I wouldn’t say that we “MUST we use pedigrees to determine inheritance patterns and not other methods” as long as the newer methods we have today are ethical.

When I studied genetics, the pedigree charts that were most talked about were the charts showing haemophilia in Royal families because Royal families kept detailed, extensive records. For most other families, pedigree charts do not go back far enough to see a pattern, and that is part of the answer to your question about “time restrictions”. Also, humans have such long lives, that seeing what transpires from one generation to another takes decades (especially in diseases like Huntington’s that show no symptoms until the patient is well into middle age). Time restrictions are less of a problem in shorter-lived animals like racehorses show dogs and fruit flies.

Offspring are children, grandchildren. Clearly, you have to see how phenotypes pass from parent to offspring when you use pedigree charts in order to study genetic inheritance patterns.

In humans, analysis of PAST inheritance patterns is one ethical way to use pedigree charts to study the pattern of phenotypes because it would be unethical to breed humans just to see what happens. To study FUTURE inheritance patterns, we can plan to cross specific phenotypes of fruit flies, dogs, horses, etc. to see what phenotypes appear, but it would be unethical to ask someone with a genetic disorder to have a child just to see if the child gets sick, too.

There are lots of people who are married to people who are known to have a genetic disorder. Some of these people know, at least one generation back, whether that disorder was present in one or both of their parents. And, some of these people CHOOSE to take a chance that the babies they produce will not inherit that genetic disorder. So, although it would be unethical to ASK anyone to produce a child that might be sick, it is ethical to collect the results of these VOLUNTARY genetic crosses. Still, it might take decades – longer than the career of most genetic researchers. Most genetic researchers don’t want to spend their time on research that won’t result in a published paper and/or a pay raise during their life times. It is much more fruitful to draw conclusions from pedigrees from the past.

EDIT: I was just reading about the life of the 4th Roman Emperor, Tiberius Claudius. He was physically disabled, perhaps by cerebral palsy, or maybe by Parkinson’s disease. He might also have been mentally disabled. Claudius lived during a time when people were deliberately poisoned. Some historians have suggested that Claudius merely pretended to be an imbecile so as to be ignored by whoever was poisoning the other people in line for the job of Emperor. He became Emperor and “… proved to be an able administrator and a great builder of public works. His reign saw an expansion of the empire, including the conquest of Britain. He took a personal interest in the law, presided at public trials, and issued up to twenty edicts a day …” So, Caludius was either very intelligent or had good handlers. Claudius was married four times and is said to have fathered children with his wives, but Romans of this time were not known for their fidelity. His third wife, Messalina was said to have been a nymphomaniac who secretly worked in a brothel under an assumed name. Claudius is an extreme example, but how can anyone trust anyone’s pedigree to be an accurate representation of the facts? How can anyone know that illnesses were correctly diagnosed in the past? You don’t have to go back to the days of the Roman Emperors to find adultery, secret adoptions and misdiagnosed illnesses. Pedigrees are important tools in the study of human genetics, but they have their limitations.

http://en.wikipedia.org/wiki/Claudius

http://www.youtube.com/watch?v=QNDpHtSL0dI&feature=related

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