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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
(BB)
Child 2 Child 3
(Bb)
(Bb)
Child 4
(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
Identical
Fraternal
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.
2.
3.
4.
List 3 traits that are inherited.
Explain how dominant and recessive genes work.
How is the sex of a baby determined?
What is the difference between identical twins and
fraternal twins?
5. What are some disadvantages of fertility drugs?