Question

_____ is an example of reproductive cloning. a. Somatic cell nuclear transfer (SCNT) b. Multiple offspring from the same pregnancy c. Artificial embryo splitting d. a and \(c\)

Short answer

d. a and c

Step-by-step solution

Understanding Reproductive Cloning

Reproductive cloning is a method used to create an organism that is genetically identical to the donor organism. This is achieved by creating a new organism from the cells of an existing organism.

Analyzing Option (a)

Somatic cell nuclear transfer (SCNT) involves transferring the nucleus of a somatic cell into an egg cell from which the nucleus has been removed. SCNT is a well-known method for reproductive cloning and was used to clone Dolly the sheep.

Analyzing Option (b)

Multiple offspring from the same pregnancy refers to the natural phenomenon of twins or triplets. This is not a method of creating genetically identical organisms through cloning but rather a natural occurrence.

Analyzing Option (c)

Artificial embryo splitting involves dividing an early-stage embryo to create multiple embryos. This process can produce clones, as each resulting embryo is genetically identical to the original. It is also considered a form of reproductive cloning.

Evaluating Combined Answer Option (d)

Option (d) states that both (a) and (c) are examples of reproductive cloning. From our previous analysis, SCNT and artificial embryo splitting are indeed both methods of reproductive cloning.

Key concepts

Somatic Cell Nuclear Transfer (SCNT)

Somatic Cell Nuclear Transfer, commonly abbreviated as SCNT, is a powerful technique used in reproductive cloning to create genetically identical organisms. It involves the removal of the nucleus from an egg cell and replacing it with the nucleus from a somatic (body) cell of the organism to be cloned. The egg cell now contains the DNA of the donor organism.
The process was famously used in the creation of Dolly the sheep, the first mammal cloned from an adult somatic cell.
After the somatic nucleus is introduced into the egg cell, it is stimulated to divide and develop into an embryo. This embryo is then implanted into a surrogate mother where it continues to develop until birth. This method ensures that the new organism shares the same genetic material as the donor organism, making it a clone.

• SCNT is crucial in veterinary and medical fields for research and the conservation of endangered species.
• This method also provides insight into genetic diseases and embryo development.

However, SCNT is complex and not always successful, as it requires precise conditions for the transferred nucleus to reprogram for embryonic development.

Artificial Embryo Splitting

Artificial Embryo Splitting is another reproductive cloning technique which mimics a natural process that occurs in the formation of identical twins. During early development, an embryo can be split into two or more distinct embryos, each capable of developing into a complete organism.
This splitting is done after fertilization but before significant cellular differentiation has occurred, which ensures each split section can grow independently.
In a controlled laboratory setting, scientists manually divide an embryo at the early stages of development. Each part of the divided embryo is then allowed to grow independently, resulting in two or more cloned embryos that are genetically identical to the original.

• Unlike SCNT, artificial embryo splitting does not involve transferring nuclei between cells.
• This technique is primarily used in animal breeding and scientific research to produce multiple identical specimens.

Artificial embryo splitting is less technologically demanding than SCNT, but it is limited by the need for a viable embryo to divide, making it less flexible than SCNT in some applications.

Genetically Identical Organisms

Genetically identical organisms, commonly known as clones, are the result of reproductive cloning processes which aim to replicate the DNA of a donor organism exactly. Both Somatic Cell Nuclear Transfer and Artificial Embryo Splitting are methods that achieve this goal by differing technological means.
In nature, identical twins are an example of naturally occurring clones, as they originate from the splitting of the same embryo. However, artificial cloning methods deliberately manipulate cells at the genetic level to create these copies.
Being genetically identical implies that the clone will share the same genetic traits, including both strengths and any potential genetic weaknesses of the original organism. This has powerful implications for research and applications such as:

• Conservation of endangered species by creating additional genetically similar animals.
• Studying genetic diseases by analyzing cloned organisms.

Despite their identical genetic coding, environmental factors can cause variations in the physical appearance and behavior of cloned organisms, demonstrating that genetics is only part of what determines an organism's development.