1
Biological Beginnings
From Genes to Babies
Lecture 3
Outline
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Genes and environment
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Prenatal development
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Effects of the prenatal environment
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Assessing and caring for babies at risk
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Genotype
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A particular set of
genes a person
inherits from his
or her parents
Genes and Environment
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Phenotype
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The visible
expression of the
genotype
Chromosome: threadlike
structure that contains the
genetic information
DNA: the genetic substance
in chromosomes
Genes: segments of
DNA
The Process of Genetic Transmission
The Process of Genetic Transmission
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Ovum
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Largest human cell
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The female germ cell
(egg)
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Sperm
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Smallest human cell
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The male germ cell
The Process of Genetic Transmission
Ovum and sperm Unite to form a
single cell= the
Zygote
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2
Genetic Influences on Development
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A gene has 2 alleles
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Allele=An alternate form of a gene (
A
or
a
)
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One from the mother
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One from the father
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Alleles combination
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Same alleles=homozygous (
AA, aa
)
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Different alleles=heterozygous (
Aa, aA
)
1.
Blend to form intermediate trait
2.
Codominance: Both are simultaneously expressed
3.
One dominant and one recessive
Sickle-Cell Anemia
Genetic Influences on Development
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The sex chromosomes
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Y chromosome does not
have equivalent genes to
match the X chromosome
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Recessive X-linked genes
will automatically be
expressed in males
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Recessive X-linked genes
in female will be
expressed only if the other
X-chromosome has the
recessive allele as well
Genetic Influences on Development
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Genetic disorders
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Gene level
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- Fall '08
- lagatutta
- Genetics, low birth weight, prematurity, environment Prenatal development Effects
-
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