Genes contain the instructions for making proteins and passing traits from parents to children. During reproduction, genes from the mother and father combine in embryos to form unique genotypes. As embryos develop into fetuses and babies, environmental factors also influence how genes are expressed as physical and behavioral phenotypes. Genetic counseling can help parents understand potential genetic conditions in their future children based on family histories.

2. 2
8. Closing Thoughts
1. Introduction
2. Fact or Fiction?
3. The Genetic Code
4. The Beginnings of Life
5. From Genotype to Phenotype
6. Nature and Nurture
7. Chromosomal and Genetic Problems

3. Introduction
3
Video:
Genes and Development

4. 4
Fact or Fiction? Fiction Fact
1. No two cells of the human body
contain exactly the same material.
2. Not all individuals are born
genetically unique.
3. All the genes a person has show
up as observable traits.
4. Alcoholism is inherited.

5. What makes a child who he is?
The Beginnings of Life
5
gamete: A reproductive
cell (a sperm or ovum).

6. 6
The molecular beginnings of human development
Deoxyribonucleic Acid (DNA): The
chemical composition of the molecules
that contain genes.
chromosome: One of 46 molecules of
DNA (in 23 pairs) that virtually each
cell of the human body contains and
that, together, contain all the genes.
Other species have more or fewer
chromosomes.
gene: The basic unit for the
transmission of heredity.
Chromosome
DNA

7. What Genes Are
7
How are proteins made?
allele:
A variation that makes a
gene different in some
ways from other genes for
the same characteristics.

8. The chromosomes that make up
the 23rd pair are the sex
chromosomes.
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Genotype: an organism’s entire
genetic inheritance
THE BEGINNINGS OF LIFE

9. 9
Monozygotic (MZ) twins: Twins
who originate from one zygote
that splits apart very early in
development.
Dizygotic (DZ) twins: Twins who
are formed when two separate
ova are fertilized by two separate
sperm at roughly the same time.
THE BEGINNINGS OF LIFE

10. New Cells New Functions
How do genes work in
combination to build a person?
10
genome: The full set of genes;
instructions to make an individual
member of a certain species.
polygenic: A trait influenced by
many genes.
multifactorial: A trait affected by
many factors, both genetic and
environmental in expression.
FROM GENOTYPE TO PHENOTYPE

11. What are the possible gene combinations in a zygote?
Mother’stwogenes
Father’s two genes
F1M1
F1M2
F2M1
F2M2M2
M1
F1 F2
Gene-Gene Interactions
11
genotype: An organism’s
entire genetic inheritance,
or genetic potential.
phenotype: The observable
characteristics of a person.
FROM GENOTYPE TO PHENOTYPE

12. 23rd Pair Phenotype Genotype Next Generation
1. XX Normal woman Not a carrier No color blindness from mother
2. XY Normal man Normal X from mother No color blindness from father
3. XX Normal woman Carrier from father
Half her children will inherit her X. The girls with her X will be
carriers; the boys with her X will be color-blind.
4. XX Normal woman Carrier from mother
Half her children will inherit her X. The girls with her X will be
carriers; the boys with her X will be color-blind.
5. XY Color-blind man Inherited from mother
All his daughters will have his X. None of his sons will have his X.
All his children will have normal vision, unless their mother also had
an X for colorblindness.
6. XX
Color-blind
woman (rare)
Inherited from
both parents
Every child will have one X from her.
Therefore, every son will be color-blind. Daughters will be only
carriers, unless they also inherit an X from the father, as their
mother did.
How do x-linked genes affect heredity?
The 23rd Pair and X-Linked Color Blindness
More Complications
x-linked: Referring to
a gene carried on the
X chromosome.
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The X indicates an X chromosome with the X-linked gene for color blindness
FROM GENOTYPE TO PHENOTYPE

13. X-linked: Referring to a gene carried on the X chromosome.
What happens to behavior as alcohol
progresses from one brain part to another?
Addiction
13
Binge Drinking Among 14,000
Students in 119 Four-Year Colleges
44%
56%
Binge-drinking episode
No binge-drinking episode
44%
56%
NATURE AND NURTURE

14. What effect do college policies have on
the drinking behavior of college students?
Addiction
14
BAN NO BAN
abstinence
binge-drinking
39%
29%
48%
16%
NATURE AND NURTURE

15. 15
Baby’s eyes reflexively follow
the moving pattern
Baby’s eyes do not follow
the moving pattern
Visual Acuity
How are babies tested
for nearsightedness?
NATURE AND NURTURE

16. 16
Practical Applications
16
What do you know about
your biochemistry?
No
thanks
NATURE AND NURTURE

17. Not Exactly 46 Chromosomes
What is Down
syndrome?
Down syndrome (Trisomy-21):
A condition in which a person has 47 chromosomes instead of
the usual 46, with 3 rather than 2 chromosomes on the 21st
site, resulting in distinctive characteristics.
17
©DenysKuvaiev/Alamy

18. 18
Genetic Counseling and Testing
What do
prospective
parents learn
from genetic
counseling and
testing?
genetic counseling:
Consultation and
testing by trained
experts that enable
individuals to learn
about their genetic
heritage.
Video:
Prenatal Period: 3D ultrasound

19. Closing Thoughts
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What are some examples of how
genes and environment have
interacted to influence your
development or the development
of someone you know well?
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