1. CHAPTER 4 PRENATAL DEVELOPMENT
Section 2- A Closer Look At Conception

2. THE GENETIC PACKAGE
People inherit many physical traits from their parents. These characteristics may include physical build; skin color; hair texture and color; eye color and shape; this size and shape of ears, hands, and feet; and blood type. Parents can pass on to their children a predisposition for certain talents, such as musical or athletic ability. Some of medical conditions are inherited as well. How does this happen? Scientists are continually we learning more and more about how heredity- the passing on of characteristics- works.

3. THE GENETIC PACKAGE (continued…)
At the moment of conception, every human baby receives 46 chromosomes, tiny threadlike structures in the nucleus of every cell. These chromosomes come in 23 pairs. The father’s sperm and mothers ovum each contribute one chromosome to each pair. Each chromosome has hundreds to thousands of genes, the units that determine a human’s inherited characteristics. The complete blueprint for the creation of a person is called a genome. Genes are made up of a complex molecule called DNA- deoxyribonucleic acid. A human’s 46 chromosomes form that person’s unique DNA. No two people, except identical twins, have identical DNA.

4. Dominant and recessive genes
At the moment of conception, every human baby receives 46 chromosomes, tiny threadlike structures in the nucleus of every cell. These chromosomes come in 23 pairs. The father’s sperm and mothers ovum each contribute one chromosome to each pair. Each chromosome has hundreds to thousands of genes, the units that determine a human’s inherited characteristics. The complete blueprint for the creation of a person is called a genome. Genes are made up of a complex molecule called DNA- deoxyribonucleic acid. A human’s 46 chromosomes form that person’s unique DNA. No two people, except identical twins, have identical DNA.
Most traits are influenced by most multiple genes. Height, weight, personality, and intelligence are examples of these. These traits are determined by a specific combination of genes that are brought together at conception.

5. Making a unique person
Heredity explains why people in the same family often resemble each other. You may have a friend who looks up a lot like his or her sibling. Heredity also explains why two people in the same family can look quite different. Every sperm and egg cell contains a different combination of genes. When these genes combined, they produce a unique individual. That is why one child in a family can have light brown hair and another to have black or blond hair. If each child in a family inherited the exact same genes from the father and the mother as his or her siblings inherited, all of the children in the family would look exactly the same.

6. Making a unique person (continued…)
The sex of the child is determined at conception. The sex chromosomes come in two types, X and Y. Each ovum in the woman’s ovaries carries an X chromosome. Each of sperm cells in the man’s body carries either an X or a Y chromosome. If the sperm that fertilize is the egg carries on X chromosome, the child receives an X chromosome from each parent. A child with the XX combination is a girl. If the sperm carries a Y chromosome, the child receives an X chromosome from the mother and a Y chromosome from the father. A child with the XY combination is a boy.

7. Multiple births
The number of children a woman will give birth to at one time is determined at conception or soon after. When a woman gives birth to more than one child at a time, it is called a multiple birth. The most common instance of multiple births is twins.
There are two types of twins, identical and fraternal. When a sperm fertilizing is a woman’s ovum, the cell begins to divide right away. As the cells continue to divide, demands of cells may split in half, creating two separate cell masses. Each cell mass continues to divide and grow into a separate embryo. The result is identical twins. Because only one ovum and sperm were involved in conception, identical twins have very similar characteristics and are always the same sex.

8. Multiple births (continued…)
Fraternal twins form when two eggs are released from the ovaries at the same time and are fertilized by two different sperm. Because of the different eggs and sperm, fraternal twins may not look any more alike than other siblings do. They just happen to be in the mother’s uterus at the same time. It is common for fraternal twins to be opposite sexes, but they can also be the same sex.
In a general population, three in 100, or about 3% of all births, are twins. The chances of having identical twins are less than that of fraternal twins. Out of 1,000 births, about 23 will be fraternal twins and about four will be identical twins .

9. Multiple births (continued…)
The birth of three or more babies is much more rare. However, a rise in the use of treatments to help women become pregnant has increased the frequency of multiple births. In fact, one potential drawback to some of these treatments is that they can cause more than one egg to be released at a time, making multiple births more likely. The more children a pregnant woman carries, the more difficult it is for all of them to survive.

10. Family planning
Any time a couple has sexual intercourse, a conception may take place. The only sure way to prevent pregnancy is abstinence- avoiding sexual
activity. There are various other methods of conception, which help prevent pregnancy.
Most methods do not prevent sexually transmitted diseases (STDs). Abstinence also prevents STDs.
Most family planning methods have possible side effects. These problems develop among some, but not all, users. The chart on the next slide compares various methods of family planning and indicates if there are side effects. Check medical reference books for complete listings of side effects.
Effectiveness is given in a percentage. A method that is 100% effective- such as abstinence- works all the time. If a method is 80% effective, there is a one in five chance that a pregnancy could occur when that method is used.

11. Family Planning Method
Characteristics
Abstinence
Only method that is 100% effective.
Birth Control Pills
Some side effects; 95-98% effective.
Cervical Cap
Small latex thimble must remain in place 8 hours; increased risk of infection; 60-91% effective.
Condom
Available for females, but more frequently used by males. Helps reduce spread of STDs. Effectiveness 86% to 97%; should be used with spermicide.
Diaphragm
Diaphragm is used with spermicide; increases risk of urinary infections; 80-94% effective.
Hormonal Implants
Capsules placed under skin of upper arm; 99% effective for up to 5 years.
Hormonal Injections
Hormones given by physician monthly or once every 3 months; may cause irregular bleeding; up to 99% effective.
Hormonal Patch
Thin patch worn on skin 3 weeks each month; similar side effects to birth control pills; 99% effective.
Intrauterine Device (IUD) and Uterine Implant
May cause discomfort and side effects first 3 months of use; up to 99% effective.
Natural Family Planning
Known as the rhythm method, 53% to 80% effective.
Spermicide
Foams, creams, gels may cause allergic reactions; 72% effective; should be used with condom, diaphragm, cervical cap.
Vaginal Implant
Ring worn internally for 3 weeks each month, 95-99% effective.

12. infertility
Not all couples who want to become parents are able to conceive. These couples are considered infertile. There are many causes of infertility- the inability to become pregnant- in both men and women. Male infertility is the major factor in about 40% of infertility cases, while about 40% are due to female infertility. The rest have unknown causes or are linked to both partners.
Male Infertility (3:20)

13. Infertility On Infertile Ground- The Documentary (5:22)
People with infertility problems often feel isolated and abnormal. There are support groups available to help couples in this situation. In addition, advance’s in medicine have helped couples overcome infertility. The treatments used to depend on the cause. For example, a doctor can prescribe medication when a woman’s ovaries do not release an ovum each month. Some fertility medications, however, can cause uncomfortable are potentially serious side effects, and require the careful supervision of a doctor. As time passes, researchers are improving the safety and effectiveness of a variety of infertility treatments.

14. Options for infertile couples
After attempts to treat infertility, some couples who still cannot conceive a child. There are several options they may discuss with each other and their doctors:
Adoption. By adopting a child, a couple legally takes on all responsibilities and rights for raising, loving, and caring for a child in need of a permanent home.
Artificial insemination. In this process, a doctor injects sperm into a woman’s uterus. This procedure is timed to take place when a woman’s ovaries releases an ovum. Often, the sperm is from the woman’s husband. If the spouse has a genetic disorder that prevents his sperm from being used, a sperm from a male donor can be used.

15. Options for infertile couples (continued…)
In vitro fertilization. This process is used to treat many causes of infertility, including when a woman has damaged fallopian tubes that will not allow an ovum to pass through to the uterus. With the help of a microscope, the doctor combines a mature for ovum from the woman with sperm from her husband. If the ovum becomes fertilized, the doctor places the new zygote in the woman’s uterus. If the zygote attaches itself to the uterus, pregnancy takes place.
Ovum transfer. This procedure is similar to In Vitro fertilization, except an ovum has been donated by another woman. The ovum is fertilized in a laboratory and placed in the mother’s uterus. This procedure is an option for women who lack of working ovaries, have poor ovum quality, or who have inherited disorders.

16. Options for infertile couples (continued…)
Surrogate mother. A surrogate, or substitute, mother is a woman who becomes pregnant to have a baby for another woman. This option requires legal arrangements the need for all of the people involved, including the child. Each state has laws regarding the surrogate motherhood that must be followed.
IVF, Fertility Treatment, Assisted Conception, pregnancy, Test Tube Baby (2:11)

17. Questions raised
As technology and knowledge continue to advance, other options to the treatment of infertility may become available. However, personal beliefs may limit a couple’s options. Not everyone believes that these alternatives are acceptable. For example, the use of surrogate mothers and sperm and ovum donors is considered controversial. These practices raise many ethical questions, as will new procedures in the future.
Sophisticated medical procedure for infertile couples require access to specialists. Not all couples can afford the costs involved. Most medical insurance plans glued or limit coverage for infertility treatment, which is often very expensive.

18. List of at least five traits that are inherited. What is a genome?
Section 4-2 review
List of at least five traits that are inherited.
What is a genome?
Explain how dominant and recessive genes work.
What is the difference between fraternal and identical twins?
What is one potential drawback to fertility treatments?
Explain one of the options an infertile couple has if infertility treatment does not work.

19. Discovery Health The Ultimate Guide: Pregnancy (49:58)