Concept explainers
Cloning can be done by somatic cell nuclear transfer (SCNT) (see Figure 20-12). Some conservation biologists have proposed using SCNT technology to preserve highly endangered animal species. What might be some of the genetic disadvantages of this approach?
Figure 20-12 Dolly, the First Mammal Cloned from an Adult Cell. (a) Dolly was cloned from a serum-starved mammary (udder) cell that was fused with an egg cell from which the nucleus had been removed. (b) Dolly as an adult.
To explain: The genetic disadvantages of cloning done by Somatic Cell Nuclear Transfer (SCNT).
Introduction: In sexual reproduction, genetic information from both the parents is combined together to produce the offspring. A cell having two sets of chromosomes is known as diploid whereas, a cell having a single copy of chromosomes is known as haploid. Sperms are the gametes produced by males and eggs are the gamete produces by females, these gametes fuse together to form a zygote.
Explanation of Solution
An offspring which is the identical copy of the parent is known as its clone. Asexual reproduction is a method to produce clones naturally. Clones can also be produced artificially in the laboratories. Somatic cell nuclear transfer is a method of producing clones artificially. In the somatic cell, nuclear transfer nucleus from a somatic cell is implanted into an enucleated oocyte to produce an embryo. Therefore, SCNT can be used for cloning experiments. Dolly the sheep was the first clone produced by the technique.
Following are the genetic disadvantages of cloning done by SCNT to preserve highly endangered animals:
- As the clones are identically similar to the parents, genetic diversity will decrease in producing a clone through SCNT and as a resulting susceptibility to a particular genetic disease carried by the parent will increase in the next generation.
- Producing clones will also increase homozygosity and decrease the chances of evolution.
- Incomplete reprogramming of the cells can also produce abnormal phenotypes.
Thus, SCNT has certain genetic disadvantages such as production of abnormal phenotypes, an increase in homozygosity, an increase in susceptibility to genetic diseases.
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Chapter 25 Solutions
BECKER'S WORLD OF THE CELL-W/ACCESS
- If you knew the mRNA sequence for the human insulin gene could you know what size cDNA fragment you would find on your DNA gel when you ran it against a size standard (a “molecular ruler”)? Would you continue with your insulin cloning experiment, if the DNA from your PCR was very different in size from that predicted by the insulin mRNA? Why or why not? Primers can sometimes bind and target the wrong gene, especially if the primers are allowed to bind to the DNA strands at a low temperature. PCR also preferentially amplify short segments of DNA. Would it be important to actually run the cDNA after the PCR on a DNA gel in order to check for a PCR product of the predicted size for the insulin gene? Why or why not?arrow_forwardWoolly mammoths have been extinct for about 10,000 years, but we often find their well- preserved remains in Siberian permafrost. Research groups are now planning to use SCNT to resurrect these huge elephant- like mammals. No mammoth eggs have been recovered so far, so elephant eggs would be used instead. An elephant would also be the surrogate mother for the resulting embryo. The researchers may try a modified SCNT technique used to clone a mouse that had been dead and frozen for sixteen years. Ice crystals that form during freezing break up cell membranes, so cells from the frozen mouse were in bad shape. Their DNA was transferred into donor mouse eggs, and cells from the resulting embryos were fused with mouse stem cells. Four healthy clones were born from the hybrid embryos. What are some of the pros and cons of cloning an extinct animal?arrow_forwardDo a few cells created by therapeutic cloning of your own somatic cells constitute life? If these cells do constitute life, do they have the same rights as a human being conceived naturally? If it were possible, should someone be allowed to grow his or her own therapeutic clone into an adult?arrow_forward
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