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 (9th Edition)
- The following diagram outlines how the process of cloning a sheep was accomplished. Cloning is the process of creating a genetically identical copy of another individual. With Dolly, the first cloned mammal, an egg cell was removed from a donor (B) and the nucleus was removed from the egg cell. Then cells from a sheep's mammary gland were removed from a second donor (A). The nucleus of one of the cells from the mammary gland was fused with the enucleated egg cell using an electrical pulse. The fused cell underwent cell division and at the blastocyst stage was implanted into a surrogate mother sheep. The fused cell is cultured and is implanted as a multi-celled embryo. During the step where the fused cell begins dividing normally, the cells of the future clone undergo Select one: a. fertilization b. meiosis c. mitosis d. gene splicingarrow_forwardFor each of the following scenarios, indicate YES (it is cloning) or NO (it is not cloning). 6. ___________ Sperm taken from a male goat is combined with a female's egg in a petri dish. The resulting embryo is implanted into the female's uterus to develop 7. ___________ A sheep embryo, composed of 16 cells, is removed from the mother's uterus and separated into individual cells. Each cell is allowed to multiply, creating 16 separate embryos, which are then implanted in different female sheep to develop to maturity. 8. ___________ A cow with many desirable traits is stimulated with hormones to produce a number of egg cells. Each of these eggs is fertilized and implanted into a surrogate mother. 9. ___________ Cell nuclei from a recently deceased dog are placed into enucleated egg cells from another female dog. These egg cells are then placed into the uterus of an additional female surrogate dog, where it grows into a puppy.arrow_forwardUnneeded genes in an adult animal cell are permanently inactivated,making it impossible for most specialized cells to turn into any othercell type. How does this arrangement save energy inside a cell? Whydoes the ability to clone an adult mammal depend on techniques forreactivating these “dormant” genes?arrow_forward
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