Transcript Slide 1

BIOLOGICAL
BEGINNINGS
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Chapter 2
The Role of
Heredity on
Development
HEREDITY AND GENETICS
• Heredity
•
One’s nature based on biological transmission of traits and characteristics
• Genetics
•
Field within the science of biology that studies heredity
• Genetics Influence our
•
•
•
Physical traits
Behavioral traits
Psychological problems
THE COLLABORATIVE GENE
• The nucleus of each human cell contains
chromosomes
• Chromosomes: Threadlike structures made up of
deoxyribonucleic acid, or DNA
• DNA: A complex molecule with a double helix shape;
contains genetic information
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THE COLLABORATIVE GENE
• Genes: Units of hereditary information
composed of DNA
• Genes direct cells to reproduce themselves and
manufacture the proteins that maintain life
• Segments of DNA within chromosomes
• Regulate development of traits
• Transmitted by single gene or may be polygenic
• Approx. 20,500 genes in every cell (2008)
• Genome - The complete set of developmental
instructions for creating proteins that initiate the
making of a human organism
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FIGURE 2.2 - CELLS,
CHROMOSOMES, DNA, AND GENES
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GENES AND CHROMOSOMES
• Mitosis: Cellular reproduction in which the
cell’s nucleus duplicates itself with two new
cells being formed
• Strands of DNA break apart, duplicate and are rebuilt
• Each containing the same DNA as the parent cell, arranged
in the same 23 pairs of chromosomes
• Cell division by which growth occurs
• Mutations can develop throughout our lives
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GENES AND CHROMOSOMES
• Meiosis: A specialized form of cell division that
occurs to form eggs and sperm (or gametes)
• 23 chromosome pairs divide
• Result is a new cell with only 23 chromosomes
• 22 pairs are autosomes
• 23rd pair are sex chromosomes
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SOURCES OF VARIABILITY
• Meiosis
• Crossing Over
FERTILIZATION
• Fertilization: A stage in reproduction whereby
an egg and a sperm fuse to create a single cell,
called a zygote
• Zygote: A single cell formed through fertilization
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SOURCES OF VARIABILITY
• Monozygotic Twins (MZ)
• Derived from a single zygote that has split in two
• Identical twins
• Dizygotic Twins (DZ)
• Derived from two zygotes
• Probability of twins increases
• Maternal age
• Use of fertility drugs
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FIGURE 2.4 - THE GENETIC DIFFERENCE
BETWEEN MALES AND FEMALES
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SOURCES OF VARIABILITY
• Mutation
• DNA - A mistake by cellular machinery, or damage
from an environmental agent may produce a mutated
gene, which is a permanently altered segment of DNA
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SOURCES OF VARIABILITY
• Genotype: A person’s genetic heritage; the
actual genetic material
• Phenotype: The way an individual’s genotype is
expressed in observed and measurable
characteristics
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GENETIC PRINCIPLES
• Dominant-Recessive genes principle
• Recessive gene is influential only if both genes are
recessive
• Sex-Linked genes
• When a mutated gene is carried on the X chromosome,
the result is called X-linked inheritance
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GENETIC PRINCIPLES
• Genetic imprinting
• Occurs when genes have differing effects depending on
whether they are inherited from the mother or the father
• Polygenetic inheritance
• Occurs when most characteristics are determined by the
interaction of many different genes
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GENETIC PRINCIPLES
• Traits are determined by pairs of genes
• Each member of pair is an allele
• Homozygous
• Both alleles for a trait are the same
• Heterozygous
• Alleles for a trait are different
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FIGURE 2.5 - HOW BROWN-HAIRED PARENTS
CAN HAVE A BLOND-HAIRED CHILD
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TRANSMISSION OF DOMINANT AND
RECESSIVE TRAITS
FIGURE 2.5 – CHROMOSOMAL
ABNORMALITIES
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FIGURE 2.7 - SOME GENE-LINKED
ABNORMALITIES
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PRENATAL DIAGNOSTIC TESTS
• Ultrasound sonography –
• A prenatal medical procedure in which high frequency
sound waves are directed into the pregnant woman’s
abdomen
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PRENATAL DIAGNOSTIC TESTS
• Amniocentesis
• Prenatal medical
procedure in which a
sample of amniotic
fluid is withdrawn by
syringe and tested for
chromosomal or
metabolic disorders
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PRENATAL DIAGNOSTIC TESTS
• Chorionic villi
sampling
• Prenatal medical
procedure in which a
small sample of the
placenta is removed
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PRENATAL DIAGNOSTIC TESTS
• Maternal blood or triple screening
• Identifies pregnancies that have an elevated risk for
birth defects such as spina bifida and Down syndrome
• Noninvasive prenatal diagnosis (NIPD)
• Focuses on the isolation and examination of fetal cells
circulating in the mother’s blood and analysis of cellfree fetal DNA in maternal plasma
• Fetal sex determination
• Noninvasive techniques have been able to determine the
sex of the fetus at an earlier point by assessing cell-free
DNA in maternal plasma
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INFERTILITY AND REPRODUCTIVE
TECHNOLOGY
• Infertility
• Inability to conceive after 12 months of regular
intercourse without contraception
• In vitro fertilization (IVF)
• Eggs and a sperm are combined in a laboratory dish
• Adoption
• Social and legal process by which a parent-child
relationship is established between persons unrelated at
birth
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CONCEPTION
Against All
Odds
FERTILIZATION
1
5
14
• Egg is viable for
24 hours
• Sperm is viable for
3 to 5 days
• “Unsafe period” is from
day 9 to 15 if ovulation occurs on day 14
day 7 to 17 could be unsafe
28
FEMALE REPRODUCTIVE ORGANS
Figure 2.8
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CONCEPTION
• Ova
• Begin to mature at puberty
• Monthly release of mature egg into Fallopian tube
• Egg is propelled by cilia
• If not fertilized, egg is discharged in the menstrual
flow
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CONCEPTION
Figure 2.9
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CONCEPTION
• Sperm
• Self propelled and smaller than ova
• Sperm with “Y” chromosome swim faster than sperm with “X”
chromosome
• From 200 to 400 million in ejaculate; only 1 in 1,000 arrive in
vicinity of ovum
• Sperm are attracted by chemical odor secreted by ova
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BEHAVIOR GENETICS
• The field that seeks to discover the influence of
heredity and environment on individual
differences in human traits and development
• Twin study: A study in which the behavioral
similarity of identical twins is compared with
the behavioral similarity of fraternal twins
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BEHAVIOR GENETICS
• Adoption study: A study in which investigators
seek to discover whether, in behavior and
psychological characteristics, adopted children
are more like their adoptive parents or more like
their biological parents
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FIGURE 2.11 - EXPLORING HEREDITYENVIRONMENT CORRELATIONS
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SHARED AND NONSHARED
ENVIRONMENTAL EXPERIENCES
• Shared environmental experiences: Siblings’
common experiences, such as their parents’
personalities and intellectual orientation, the
family’s socioeconomic status, and the
neighborhood in which they live
• Nonshared environmental experiences: The
child’s own unique experiences, both within the
family and outside the family, that are not
shared by another sibling
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THE EPIGENETIC VIEW AND GENE X
ENVIRONMENT (G X E) INTERACTION
• Epigenetic view: Emphasizes that development
is the result of an ongoing, bidirectional
interchange between heredity and environment
• Gene x Environment (G x E) interaction: The
interaction of a specific measured variation in
the DNA and a specific measured aspect of the
environment
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CONCLUSIONS ABOUT HEREDITYENVIRONMENT INTERACTION
• The relative contributions of heredity and
environment are not additive
• Complex behaviors have some genetic loading
that gives people a propensity for a particular
developmental trajectory
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