Evidence [see P. G. Shiels, A. J. Kind, K. H. Campbell, et al. (1999),“Analysis of telomere lengths in cloned sheep,” Nature 399, 316–317] suggests that Dolly may have been genetically older than heractual age. As mammals age, the chromosomes in somatic cells tendto shorten from the telomeres. Therefore, older individuals haveshorter chromosomes in their somatic cells than do younger ones.When researchers analyzed the chromosomes in the somatic cells of Dolly when she was about 3 years old, the lengths of her chromosomeswere consistent with those of a sheep that was significantlyolder, say, 9–10 years old. (Note: As described in the chapter, thesheep that donated the somatic cell that produced Dolly was 6 yearsold, and her mammary cells had been grown in culture for severalcell doublings before one of the cells was fused with an oocyte.)A. Suggest an explanation why Dolly’s chromosomes seemedolder than they should have been.B. Let’s suppose that a female sheep (like Dolly), which wasproduced via reproductive cloning, was mated at age 11 to anormal male sheep and then gave birth to a lamb named Molly.When Molly was 8 years old, a sample of somatic cells wasanalyzed. How old would you expect Molly’s chromosomes toappear, based on the phenomenon of telomere shortening?Explainyour answer.C. Discuss how the observation of chromosome shortening, whichwas observed in Dolly, might affect the popularity of reproductivecloning.
Molecular Techniques
Molecular techniques are methods employed in molecular biology, genetics, biochemistry, and biophysics to manipulate and analyze nucleic acids (deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)), protein, and lipids. Techniques in molecular biology are employed to investigate the molecular basis for biological activity. These techniques are used to analyze cellular properties, structures, and chemical reactions, with a focus on how certain molecules regulate cellular reactions and growth.
DNA Fingerprinting and Gel Electrophoresis
The genetic makeup of living organisms is shown by a technique known as DNA fingerprinting. The difference is the satellite region of DNA is shown by this process. Alex Jeffreys has invented the process of DNA fingerprinting in 1985. Any biological samples such as blood, hair, saliva, semen can be used for DNA fingerprinting. DNA fingerprinting is also known as DNA profiling or molecular fingerprinting.
Molecular Markers
A known DNA sequence or gene sequence is present on a chromosome, and it is associated with a specific trait or character. It is mainly used as a genetic marker of the molecular marker. The first genetic map was done in a fruit fly, using genes as the first marker. In two categories, molecular markers are classified, classical marker and a DNA marker. A molecular marker is also known as a genetic marker.
DNA Sequencing
The most important feature of DNA (deoxyribonucleic acid) molecules are nucleotide sequences and the identification of genes and their activities. This the reason why scientists have been working to determine the sequences of pieces of DNA covered under the genomic field. The primary objective of the Human Genome Project was to determine the nucleotide sequence of the entire human nuclear genome. DNA sequencing selectively eliminates the introns leading to only exome sequencing that allows proteins coding.
Evidence [see P. G. Shiels, A. J. Kind, K. H. Campbell, et al. (1999),
“Analysis of telomere lengths in cloned sheep,” Nature 399, 316–
317] suggests that Dolly may have been genetically older than her
actual age. As mammals age, the chromosomes in somatic cells tend
to shorten from the telomeres. Therefore, older individuals have
shorter chromosomes in their somatic cells than do younger ones.
When researchers analyzed the chromosomes in the somatic cells of Dolly when she was about 3 years old, the lengths of her chromosomes
were consistent with those of a sheep that was significantly
older, say, 9–10 years old. (Note: As described in the chapter, the
sheep that donated the somatic cell that produced Dolly was 6 years
old, and her mammary cells had been grown in culture for several
cell doublings before one of the cells was fused with an oocyte.)
A. Suggest an explanation why Dolly’s chromosomes seemed
older than they should have been.
B. Let’s suppose that a female sheep (like Dolly), which was
produced via reproductive cloning, was mated at age 11 to a
normal male sheep and then gave birth to a lamb named Molly.
When Molly was 8 years old, a sample of somatic cells was
analyzed. How old would you expect Molly’s chromosomes to
appear, based on the phenomenon of telomere shortening?
Explainyour answer.
C. Discuss how the observation of chromosome shortening, which
was observed in Dolly, might affect the popularity of reproductive
cloning.
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