Each of us inherit many personal characteristics from our parents.

EX: physical build, skin color, hair color & texture, eye color & shape.

Just as personal traits can be passed on, so can medical conditions.

Tiny threadlike particles located in the nucleus of every cell.

46 chromosomes = 23 pairs

Each chromosome contains several genes.

Genes- the unit that determine the child's inherited characteristics.

Genes makeup chromosomes as beads make up a necklace.

For every inherited characteristic, a person receives 2 copies- 1 from mom and 1 from dad.

If both inherited genes are the same- then the child will have that characteristic.

If they are different- the dominant gene will be expressed.

Dominant- stronger gene. Recessive- weaker gene.

Ex: B= Brown Dominant, b= Blue recessive.

Dad (Bb) Mom (Bb)

Child 1 Child 2 Child 3 Child 4

(BB) (Bb) (Bb) (bb)

Each sperm & egg cell contains a different combination of genes.

These cells combine during the fertilization process and produce a unique individual.

The sex of a child is determined at conception.

Every egg cell contains an X chromosome.

Each sperm cell will contain either an X or a Y chromosome.

The sex of the child is determined by the chromosome carried by the sperm that fertilizes the egg.

XX= baby girl XY= baby boy

Identical Twins= 1 egg divides in half soon after fertilization. Each half grows and divides. 1 Zygote becomes 2.

Fraternal Twins= 2 eggs are released and both becomes fertilized

Infertile- inability to conceive a child.

There are many causes of infertility in both men and women.

Options for Infertile Couples:› Adoption- 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- doctor injects sperm into the uterus. Sperm may be the husband’s or from a donor.

Options for Infertile Couples:› In Vitro Fertilization- Doctor combines a

mature ovum from the woman with sperm from her husband. If the ovum becomes fertilized then the doctor places it in the uterus.

› Ovum Transfer- Similar to In Vitro, except that the ovum is donated by another woman. It is fertilized in the laboratory and placed in the uterus.

› Surrogate Mother- A surrogate mother is a substitute woman who becomes pregnant to have a baby for another woman.

1. List 3 traits that are inherited.2. Explain how dominant and

recessive genes work.3. How is the sex of a baby

determined?4. What is the difference between

identical twins and fraternal twins?5. What are some disadvantages of

fertility drugs?

Heredity in the Works Worksheet