Article 13. 1 Drug effects on the nervous system




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Male puberty

The initial sign of male puberty is testicular enlargement. The testes secrete testosterone, which stimulates many primary and secondary sexual characteristics. Testosterone causes the prostate gland and seminal vesicles to mature. The seminal vesicles begin to secrete fructose which is the primary nutrient sperm require. During puberty, primitive male germ cells begin to mature into primary spermatocytes. This early step in sperm maturation is testosterone-independent. However, the final stage of sperm maturation into spermatozoa is testosterone-dependent.


Female puberty

At the beginning of puberty, a girl's face rounds out, her hips widen, and her breasts begin to develop. Breast development can occur as early as eight but starts between 10 and 14 for most girls. Full breast development may take two to five years. Pubic hair begins to grow shortly afterwards, followed by the first menstrual period, or menarche. Like male puberty, female puberty is initiated by hypothalamic hormones.


Source Citation: Dickerson, Louise. "Puberty." Gale Encyclopedia of Science. Ed. K. Lee Lerner and Brenda Wilmoth Lerner. 3rd ed. Detroit: Gale, 2004. Science Resource Center. Thomson Gale. 25 February 2007


____ 14. Use Article 16.1 to answer the following question.


The major body puberty-controlling center is the

A.

adrenal glands.

B.

gonads.

C.

hypothalamus.

D.

pituitary gland.



____ 15. Use Article 16.1 to answer the following question.


Which of the following is the first sign of a female entering puberty?

A.

growth of pubic hair

B.

development of breasts

C.

increase in height

D.

menstruation



Article 16.3 Zygote

A zygote in animals is a fertilized egg or ovum. It is the first cell produced when a male gamete (sperm) unites with a female gamete (egg). Since it contains one set of chromosomes from each parent, the zygote will develop into a unique individual.


The act of fertilization brings together the sex cells of two different members of the same animal species. It eventually produces a fully developed offspring which begins as a one-celled fertilized egg called a zygote. Whether fertilization is external (as when a frog sprays his sperm over the female's eggs in the water) or internal (when a male mammal deposits them inside the body of the female), the moment an individual sperm makes physical contact with the egg, fertilization begins. The egg is surrounded by a jelly-like film called the "zona pellucida" that the sperm must break through. It does this by actually contacting the film, which causes the tip of the sperm head to rupture. This releases a chemical that opens a hole through the outer layers of the egg.


As the sperm head descends through the layers, tiny projections called "microvilli" emerge from both the sperm and the egg, and it is these that first fuse together. Following this, the actual membranes of both sperm and egg fuse and the cytoplasm (jelly-like fluid) of the egg engulfs the sperm. The sperm releases its genetic material into the egg as the nucleus (the cell's control center) of both merge into one new nucleus. At this point, the sperm and egg have fully merged. The sex of the new offspring and all the instructions needed to produce this new organism are already in place and are beginning to work. Because each parent has donated one set of chromosomes, the genetic information (or genome) of the offspring will represent a unique combination of deoxyribonucleic acid (DNA). The DNA contains the genetic instructions for each cell.


The zygote, therefore, is the first cell of this future offspring. As soon as the zygote is formed, a series of rapid cell divisions called cleavage begins. The zygote divides into two cells, then four cells, then eight, and so on. Each new cell has the same genetic make-up as the original zygote. As the cleavage process continues and the developing cell mass grows, it forms a berry-like, compact ball called a "morula." This ball soon develops different layers which eventually begin to form their own specialized cells. Some layers become muscle and bone while others become part of the different organs and systems. In humans, five days after fertilization and the creation of a zygote, the zygote has been transformed into the multicelled beginnings of an embryo, which will eventually become a fully developed offspring.


Source Citation: "Zygote." U*X*L Complete Life Science Resource. Ed. Leonard C. Bruno and Julie Carnagie. Detroit: U*X*L, 2001. Science Resource Center. Thomson Gale. 25 February 2007


____ 16. Use Article 16.3 to answer the following question.


When is fertilization considered to have started?

A.

when sperm is ejaculated from the penis

B.

when the sperm contacts the egg

C.

when the zona pellucida is penetrated

D.

when the sperm nucleus and the egg nucleus fuse



Article 16.2 Infertility

Infertility is the failure of a couple to conceive a child after trying to do so for at least one full year. In primary infertility, pregnancy has never occurred. In secondary infertility, one or both members of the couple have previously conceived, but are unable to conceive again after a full year of trying.


Male infertility can be caused problems with the sperm. A semen sample is examined under the microscope for four basic characteristics:

· The number of sperm present in a semen sample (the sperm count).

· Sperm motility (how well the sperm swim).

· The sperm's physical structure (A normal semen sample will contain no more than 25% abnormal forms of sperm.)

· Volume of the semen sample


Treatment of male infertility includes addressing known reversible factors first; for example, discontinuing any medication known to have an effect on spermatogenesis or ejaculation, as well as decreasing alcohol intake, and treating thyroid or other endocrine disease. Abnormally large veins in the testicles (varicoceles) can be treated surgically. Testosterone in low doses can improve sperm motility (ability to move).


The first step in diagnosing a woman's fertility problems is to make sure that she is producing an ovum each month. Luteinizing hormone (LH) is released just before ovulation. A simple urine test can be done to check if LH has been released around the time that ovulation is expected.


Treatment of ovulatory problems depends on the cause. If a thyroid or pituitary problem is responsible, simply treating that problem can restore fertility. Medication can also be used to stimulate fertility. Pelvic adhesions and endometriosis can cause infertility by preventing the sperm from reaching the egg or interfering with fertilization. However, both these conditions can be treated.


Some couple who are having trouble conceiving turn to assisted reproductive techniques, which include in vitro fertilization (IVF), gamete intrafallopian transfer (GIFT), and zygote intrafallopian tube transfer (ZIFT). These are usually used after other techniques to treat infertility have failed.


In vitro fertilization involves the use of a drug to induce the simultaneous release of many eggs from the female's ovaries, which are retrieved surgically. Meanwhile, several semen samples are obtained from the male partner, and the ova and sperm are then combined in a laboratory, where several of the ova may be fertilized. Cell division is allowed to take place up to the embryo stage. Three or four of the embryos are transferred to the female's uterus, and the wait begins to see if any or all of them implant and result in an actual pregnancy.


GIFT involves retrieval of both multiple ova and semen, and the mechanical placement of both within the female partner's fallopian tubes, where one hopes that fertilization will occur. ZIFT involves the same retrieval of ova and semen, and fertilization and growth in the laboratory up to the zygote stage, at which point the zygotes are placed in the fallopian tubes. Both GIFT and ZIFT seem to have higher success rates than IVF.


Source Citation: "Infertility." World of Health. Ed. Brigham Narins. Online. Detroit: Thomson Gale, 2007. Science Resource Center. Thomson Gale. 25 February 2007


____ 17. Use Article 16.2 to answer the following question.


Male infertility is caused by problems occurring in the

A.

zygote.

B.

Cowper’s glands.

C.

penis.

D.

inhibin.



____ 18. Use Article 16.2 to answer the following question.


What can prevent sperm from reaching the egg, if female infertility is the diagnosis?

A.

low levels of luteinizing hormone

B.

endometriosis

C.

a pituitary hormone imbalance

D.

extraembryonic coelom



Article 17.1 Muscular Dystrophy

Italian scientists have found human adult stem cells taken from blood vessels can regenerate muscle. This poses to be a breakthrough in the treatment of patients who have muscular dystrophy.


Giulio Cossu and colleagues from the Stem Cell Research Institute in Rome showed such cells isolated from young golden retrievers regenerated the muscles of dystrophic dogs when injected into their circulation. A new study by the same team demonstrates cells with similar properties can be isolated from human juvenile and adult blood vessels.


Muscular dystrophy is linked to a mutation in dystrophin, a gene required for muscle formation, and the authors genetically modified the stem cells to make them express the corrected version of the gene. After injection into the blood vessels of dystrophic mice, the cells found their way to skeletal muscle, which they were able to partly regenerate.


____ 19. Use Article 17.1 to answer the following question.


Upon insertion of a stem cell into the muscle tissue, the series of mitotic events it would pass through are

A.

prophase, anaphase, metaphase, telophase

B.

prophase, metaphase, anaphase, telophase

C.

anaphase, prophase, metaphase, telophase

D.

anaphase, metaphase, prophase, telophase



____ 20. Use Article 17.1 to answer the following question.


Once the muscle cells begin to divide, the chromosomes begin to condense and the nuclear membrane dissolves. This description is that of

A.

prophase

B.

metaphase

C.

anaphase

D.

telophase



____ 21. Use Article 17.1 to answer the following question.


A concern with the use of stem cells is that uncontrolled growth of the type of cells they produce may occur, resulting in

A.

non disjunction

B.

cancer

C.

mutation

D.

cloning



Article 17.2 Cloned Mules

It was nature vs. nurture when the University of Idaho's two mule clones Idaho Gem and Idaho Star took to the racetrack at Winnemucca, Nevada for the first leg of mule racing's triple crown. The mules became the first cloned athletes to participate in any sport.


The mules were cloned from mule fetal skin cells, so there is no adult animal with which to compare them. They will provide a unique test of whether genetics or environment, nature or nurture, is most important.


The mules' genetic heritage is from a racing line.


____ 22. Use Article 17.2 to answer the following question.


The amount of DNA that each of the cloned mules share with each other is

A.

100%

B.

50%

C.

25%

D.

0%



____ 23. Use Article 17.2 to answer the following question.


The amount of DNA each of these cloned mules share with the mule that gave birth to each of them is

A.

100%

B.

50%

C.

25%

D.

0%


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