A Closer Look at Conception

Introduction: The Genetic Package

▪Each of us inherits 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.

▪EX: asthma, diabetes, some cancers, cystic fibrosis

Making A Unique Person

▪Each sperm & egg cell contains a different

combination of genes.

▪Sperm: Male

▪Egg: Female

▪These cells combine during the fertilization

process and produce a unique individual.

Chromosomes

▪Tiny threadlike particles located in the nucleus of every

cell.

▪Chromosomes are what make up our genetic package

▪46 chromosomes = 23 pairs

Genes

▪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.

Genes

▪If both inherited genes are the same- then the child

will have that characteristic.

▪If they are different- the dominant gene will be

expressed in the child.

▪Dominant: STRONGER gene

▪Recessive: WEAKER gene

Let’s Understand Genes (eye color)

B= Brown Dominant b= Blue recessive

Dad (Bb)Mom (Bb)

Child 1 Child 2 Child 3 Child 4

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

Determining Sex

▪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

Multiple Births

▪Identical Twins: 1 egg divides in half soon after

fertilization. Each half grows and divides. 1

Zygote (the egg and sperm combined) becomes 2.

▪Fraternal Twins: 2 eggs are released and both

become fertilized

IdenticalFraternal

Infertility

▪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.

Infertility

▪More 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.

Videos about Infertility▪ In Vitro Fertilization:

http://video.nationalgeographic.com/video/ivf-sci

▪ Ovum Transfer:

https://www.youtube.com/watch?v=pGeIYV1HoP4

▪ Artificial Insemination:

https://www.youtube.com/watch?v=S6FmkzOf9ao

Let’s Review

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?