Transcript X-linked: Referring to a gene carried on the X

1. Introduction
2. Fact or Fiction?
3. The Genetic Code
4. From One Cell to Many
5. From Genotype to Phenotype
6. Chromosomal and Genetic Abnormalities
7. Closing Thoughts
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Introduction
[Video: Heredity and Environment
Introduction]
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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.
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The molecular beginnings of human development
Deoxyribonucleic Acid (DNA): The
chemical composition of the molecules
that contain genes.
Chromosome
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.
DNA
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What Genes Are
allele:
A variation that makes a
gene different in some
ways from other genes for
the same characteristics.
How are proteins made?
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The Beginnings of Life
What makes a child who he is?
gamete: A reproductive
cell (a sperm or ovum).
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New Cells New Functions
How do genes work in
combination to build a person?
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.
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Gene-Gene Interactions
What are the possible gene combinations in a zygote?
Father’s two genes
Mother’s two genes
F1
M1
F1M1
F2
F2M1
genotype: An organism’s
entire genetic inheritance,
or genetic potential.
phenotype: The observable
characteristics of a person.
M2
F1M2
F2M2
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x-linked: Referring to
a gene carried on the
X chromosome.
More Complications
How do x-linked genes affect heredity?
The 23rd Pair and X-Linked Color Blindness
The X indicates an X chromosome with the X-linked gene for color blindness
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.
Color-blind man
All his daughters will have his X. None of his sons will have his X.
Inherited from mother All his children will have normal vision, unless their mother also had
an X for colorblindness.
5. XY
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.
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Addiction
X-linked: Referring to a gene carried on the X chromosome.
Binge Drinking Among 14,000
Students in 119 Four-Year Colleges
No binge-drinking episode
44%
44%
56% 56%
Binge-drinking episode
What happens to behavior as alcohol
progresses from one brain part to another?
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Addiction
What effect do college policies have on
the drinking behavior of college students?
48%
39%
29%
BAN
16%
NO BAN
abstinence
binge-drinking
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Visual Acuity
How are babies tested
for nearsightedness?
Baby’s eyes reflexively follow
the moving pattern
Baby’s eyes do not follow
the moving pattern
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Practical Applications
What do you know about
your biochemistry?
No
thanks
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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.
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Genetic Counseling and Testing
What do
prospective
parents learn
from genetic
counseling and
testing?
[Video: 3D ultrasound]
genetic counseling:
Consultation and
testing by trained
experts that enable
individuals to learn
about their genetic
heritage.
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Genetic Counseling and Testing
[Audio: Fetal Heartbeat]
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Closing Thoughts
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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