4.3 REPRODUCTIVE STRATEGIES AND TECHNOLOGIES

AGRICULTURESelective breeding:

breeding plants and animals for desirable traits

imprecise but produces many varieties of plants and animals.

Artificial insemination:

transfer of semen into a female’s reproductive tract

breeders make high-quality sperm from choice males, stock improves.

Embryo transfer:

fertilizing an egg artificially and then transferring it into a recipient female.

Embryos shipped more easily than animals.

ASSISTIVE REPRODUCTIVE TECHNOLOGIES FOR HUMANS

1. Artificial insemination: sperm is collected and concentrated, then introduced into a woman’s vagina.

2. In vitro fertilization (IVF): immature eggs are retrieved, joined with sperm in the lab, and embryos are inserted into the woman’s uterus. This is an option for women with blocked Fallopian tubes.

3. Pre-implantation genetic diagnosis: As an additional step to IVF, one of the cells of an embryo is removed and tested for specific genetic disorders before it is implanted in the uterus.

After the sperm and egg are put together in

laboratory glassware, they are incubated together

for about 18 hours to allow fertilization.

CLONING – GENE CLONINGmanipulate DNA to produce multiple copies of a gene or another segment of DNA in foreign cells.

Eg. production of the protein insulin

1. Isolate the insulin gene segment.

2. Choose an appropriate vector, such as a bacterial plasmid.

3. Create recombinant DNA by inserting the insulin gene into the vector, using molecular agents to cut and join pieces together.

4. Treat the bacterial cells so that they take in the recombinant DNA in a process called transformation. Cells now make many copies of the gene and thus produce a large amount of the protein.

5. Harvest the insulin.

CLONINGA gene or piece

of DNA can be

cloned. Many

copies of it or

the protein

product that the

gene codes for

can be

produced and

isolated.

CLONINGTherapeutic cloning: produces genetically identical cells that are used to treat various diseases. The cloned cells are then used to grow new tissues and organs.

Reproductive cloning: produces cell clones, but with the aim of producing a genetically identical organism. Reproductive cloning in animals is rarely successful.

Both use a process called somatic cell nuclear transfer (SCNT). In this technique, an egg cell’s nucleus is removed and replaced with the nucleus of a somatic cell of a donor.

CLONING

Therapeutic and

reproductive

cloning involve

inserting the

nucleus from a

somatic cell of

the donor into an

egg cell that has

had its nucleus

removed.

CLONING CONTROVERSYboth therapeutic and reproductive cloning

people are unsure how the processes will be applied.

Two issues arise with the process of therapeutic cloning (somatic cell nuclear transfer or SCNT) because:

1. the process produces stem cells that could potentially be used to create a human clone

2. in some cases, the original cells used are embryonic stem cells

solution to the second issue: use specialized adult (pluripotent) cells that have been induced into a stem-cell-like state.

CLONING CONTROVERSYStem cells can be

stimulated to

differentiate into

specific tissue types

under the right

conditions.

Potential

applications for

stem cells include

treating diseases

and in regenerative

medicine.

TRANSGENIC PLANT APPLICATIONS

transgenic organism, genetically modified organism, GMO

has DNA from another species inserted into its genetic material.

many applications in the plant kingdom:

increase plant’s resistance to herbicides, insects, or viruses

produce medicinal proteins such as insulin from the safflower plant for humans

increase nutritional value of a plant such as golden rice

TRANSGENIC PLANT APPLICATIONS

This transgenic

product, golden

rice, contains four

different foreign

genes. Three of

these genes come

from other plants,

and one comes

from a fungus.

TRANSGENIC ANIMAL APPLICATIONS

some applications in the animal kingdom:

• transgenic milk-producing animals can produce medical proteins like human growth hormone

• milk-producing animals can be modified to secrete silk for commercial use

• transgenic animals could successfully serve as organ donors for humans

TRANSGENIC ANIMAL APPLICATIONS

Genetic

engineering can

create transgenic

animals that

secrete human

proteins or other

substances in

their milk.

GMO CONCERNSMany people have reservations about GMOs despite thorough review processes. These concerns include:

•creation of super-weeds as species cross-reproduce, due to their herbicide genes

• herbicide-resistant plants could encourage the use of stronger herbicides

• not enough is known about the long-term effects of human consumption of transgenic foods and medicine

• the amount of money spent may be greater than the overall benefit

HOMEWORK

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