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behavior geneticists capitalize on the basic by 3h3eq06L


									 Chapter 3

                        Biological Beginnings

The Evolutionary     Genetic            Reproduction     Heredity-
  Perspective      Foundations           Challenges    Environment
                                        and Choices     Interaction

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          The Evolutionary

Natural Selection                  Evolutionary
 and Adaptive                      Psychology

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Natural Selection

• Natural selection is the
  evolutionary process that
  favors individuals of a
  species that are more
  adapted to survive and
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 Charles Darwin
• Observed that most organisms
  reproduce at tremendous rates, yet
  populations remain nearly constant.
• Reasoned that an intense, constant
  struggle for food, water, and resources
  must occur among the numerous
  young born.
• Those that survive pass on their genes
  to the next generation.
• Believed that those who survive are
  superior to those who do not.
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Adaptive Behavior
• Adaptive behavior is behavior that promotes an
  organism’s survival in the natural habitat.
• It involves the organism’s modification of its
  behavior to include its likelihood of survival.
• All organisms must adapt to particular places,
  climates, food sources, and ways of life.
• Natural selection designs adaptation to perform a
  certain function.
• Attachment is a system designed by natural
  selection to ensure a human infant’s closeness to
  the caregiver for feeding and protection from
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    This branch of psychology emphasizes the
  importance of adaptation, reproduction, and
  “survival of the fittest” in explaining behavior.
• It focuses on conditions that allow individuals
  to survive or to fail.
• It believes natural selection favors behaviors
  that increase organisms’ reproductive success
  and their ability to pass their genes on the next
• David Buss believes that evolution shapes both
  our physical features and pervasively
  influences how we make decisions, how
  aggressive we are, our fears, and our mating
  patterns.    Black Hawk College               7
Evolution and Life-
Span Development
 • Developmentalist Paul
   Baltes believes that the
   benefits of evolutionary
   selection decrease with age.
 • He also believes that the
   need for culture increases
   with age.
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      The Benefits of
   Evolutionary Selection
    Decrease with Age
• Selection operates mainly during the
  first half of life during the period of
  reproductive fitness.
• Given the much shorter life span in
  early human evolution, selection
  pressure could not function often in the
  later years of life.
• This results in older adults having a
  higher number of deleterious genes and
  dysfunctional gene expressions, such
  as Alzheimer’s.
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The Need for Culture
 Increases with Age
  • As older adults weaken biologically, they
    need culture-based resources, such as
    cognitive skills, motivation, socialization,
    literacy, and medical technology.
  • Baltes stresses that a life span shift in the
    allocation of resources takes place away
    from growth and toward maintenance
    and the regulation of loss.

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• Albert Bandura
• Steven Jay Gould
• Theodore Dobzhansky
• The Bidirectional View

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Albert Bandura
• Acknowledges the important
  influence of evolution on human
  adaptation and change
• Rejects “one-sided evolutionism”—
  defining social behavior as the
  product of evolved biology
• Believes the pace of social change
  gives testimony that biology permits
  a range of possibilities
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Steven Jay Gould
 • Concluded that in most
   domains of human functioning,
   biology allows a broad range of
   cultural possibilities

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Theodore Dobzhansky
   • Points out that the human
     species has been selected for
     learnability and plasticity,
     allowing us to adapt to diverse
     contexts rather than have our
     behavior be biologically fixed

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The Bidirectional View
• States that evolutionary pressures created
  changes in biological structures for the
  use of tools.
• This enables organisms to manipulate,
  alter, and construct new environmental
• Environmental innovations of increasing
  complexity, in turn, produced new
  selection pressures for the evolution of
  specialized biological systems for
  consciousness, thought, and language.
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What Are   Mitosis and    Genetic         Behavior   Molecular   Chromosome
Genes?      Meiosis      Principles       Genetics   Genetics     and Gene-

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Genetic Foundations
  • Each of us carries a genetic
    code that we inherited from our
  • This code is located within
    every cell in our bodies.
  • The code is the mechanism for
    transmitting characteristics
    from one generation to the next.
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Genetic Building
• Genes
• Chromosomes

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Definition of DNA

 • Deoxyribonucleic acid
   is a complex molecule,
   shaped like a double
   helix, that contains
   genetic information.
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What Are Genes?
• The units of hereditary
  information—short segments
  composed of DNA—that act
  as a blueprint for cells to
  reproduce themselves and
  manufacture the proteins that
  maintain life.
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 Definition of
• Threadlike structures
  comprised of thousands
  of genes, that come in 23
  pairs, one member of
  each pair coming from
  each parent
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Mitosis and Meiosis
  • Mitosis is the process by which
    each chromosome in the cell’s
   nucleus duplicates itself.
  • Meiosis is the process by which
    cells divide into gametes
    (testes/sperm in males, ovaries/eggs
    in females), which have half the
    genetic material of the parent cell.
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   The Difference
Between Mitosis and
  • Mitosis                       • Meiosis
    – Focus is on cell             – Involves sexual
      growth and repair
    – The number of
      chromosomes                  – The
      present remains the            chromosomes
      same (the                      are halved
      chromosomes copy
      themselves)                  – Four daughter
    – Two daughter cells             cells are
      are formed                     produced

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The Process of Human
 • Reproduction begins when a
   female gamete (ovum) is fertilized
   by a male gamete (sperm).
 • This produces a zygote—a single
   cell formed through fertilization.
 • In the zygote, two sets of unpaired
   chromosomes combine to form
   one set of paired chromosomes.
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Genetic Principles
 • Dominant-recessive genes
 • Sex-linked genes
 • Polygenically inherited
 • Reaction range
 • Canalization
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  Genes Principle
  • If one gene of a pair is dominant
    and one is recessive, the
    dominant gene exerts its effect,
    overriding the potential
    influence of the other, recessive
  • A recessive gene exerts its
    influence only if the two genes
    of a pair are both recessive.
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Sex-Linked Genes
 • Two of the 46 chromosomes
   human beings normally
   carry are sex chromosomes.
   Ordinarily females have two
   X chromosomes and males
   have an X and a Y.

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Polygenic Inheritance
   • The genetic principle that
     many genes can interact to
     produce a particular
   • There are more than 50,000
     genes, imagine the possible
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  Genotypes and
    Phenotypes genetic
• Genotype - an individual’s
  heritage, the actual genetic material.
• Phenotype - the way an individual’s
  genotype is expressed in observed and
  measurable characteristics.
   – Physical traits: height, weight, eye
   – Psychological characteristics:
     intelligence, creativity, personality
• For each genotype, a range of
  phenotypes can be expressed.
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Reaction Range
• Reaction range is the range
  of possible phenotypes for
  each genotype, suggesting
  the importance of an
  restrictiveness or richness.

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• Canalization is the term chosen
  to describe the narrow path, or
  developmental course, that
  certain characteristics take.
• Preservative forces help protect
  or buffer a person from
  environmental extremes.

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Behavior Genetics
 • This is the study of the degree and
   nature of behavior’s hereditary
 • It assumes that behaviors are jointly
   determined by the interaction of
   heredity and environment.
 • Behavior genetics often uses twins
   or adoption situations to study the
   influence of heredity on behavior.
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       Twin Studies
• The behavioral similarity of identical twins
  is compared with the behavioral similarity
  of fraternal twins.
• Identical twins (monozygotic twins) develop
  from a single fertilized egg that splits into
  two genetically identical replicas, each of
  which becomes a person.
• Fraternal twins (dizygotic twins) develop
  from separate eggs and separate sperm,
  making them genetically no more similar
  than ordinary siblings.
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 Issues with Twin
• By comparing groups of identical and
  fraternal twins, behavior geneticists
  capitalize on the basic knowledge that
  identical twins are more similar genetically
  than are fraternal twins.
  – However, adults might stress the similarities of
    identical twins more than those of fraternal
• Identical twins might perceive themselves
  as a “set” and play together more than
  fraternal twins.
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Adoption Studies
• Investigators seek to discover
  whether, in behavior and
  psychological characteristics,
  adopted children are more like their
  adoptive parents, who provided a
  home environment, or more like
  their biological parents, who
  contributed their heredity.
• Another method is to compare
  adoptive and biological siblings.
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Molecular Genetics
 • There is now a great deal of
   enthusiasm about the use of
   molecular genetics to discover
   the specific locations on genes
   that determine an individual’s
   susceptibility to many diseases
   and other aspects of health and
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• The term used to describe the
  complete set of instructions for
  making an organism
• Contains the master blueprint for all
  cellular structures and activities for
  the life span of the organism
• The human genome consists of
  tightly coiled threads of DNA

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The Human Genome
 • Began in the 1970s
• In the process of mapping the human genome
• Has located the genes for Huntington disease,
  some forms of cancer, and many others
• May possibly be used to transplant healthy
  copies of missing/defective genes into affected
• May lead to the development of drugs that
  will alter the genetic makeup of the
  affected cells

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    Chromosome and
• Chromosome
  Abnormalities                        • Gene-Linked
  – Down Syndrome                        Abnormalities
  – Klinefelter                          – Phenylketonu
    Syndrome                               ria
  – Fragile X Syndrome                   – Sickle-Cell
  – Turner Syndrome                        Anemia
  – XYY Syndrome

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Down Syndrome
• Caused by the presence of an extra
• Characterized by:
  –   round face
  –   flattened skull
  –   extra fold of skin over the eyelids
  –   protruding tongue
  –   short limbs
  –   retardation of motor and mental abilities
• Women younger than 18 and older than
  38 are more likely to have Down
  syndrome babies.
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Klinefelter Syndrome
  • Sex-linked chromosome abnormality
  • Males have an extra X chromosome,
    making them XXY instead of XY
  • Characterized by:
    – undeveloped testes
    – enlarged breasts
    – become quite tall

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Fragile X Syndrome
  • Sex-linked chromosome abnormality
  • The X chromosome becomes
    constricted and often breaks
  • Characterized by:
    – mental deficiency (varied in form from
      mental retardation to short attention
  • Occurs more frequently in males

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Turner Syndrome
• Sex-linked chromosome abnormality
• Females are missing an X
  chromosome, making them XO
  instead of XX
• Characterized by:
  –   shortness of stature
  –   webbed neck
  –   possible mental retardation
  –   possible sexual underdevelopment
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XYY Syndrome
• Sex-chromosome linked abnormality
• The male has an extra Y
• Early belief surrounding the
  syndrome was that the extra Y
  chromosome contributed to male
  aggression and violence.
• Researchers have since found that
  XYY males are no more likely to
  commit crimes than are XY males.
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• Gene-linked abnormality
• The individual cannot properly
  metabolize an amino acid
• Currently easily detected
• Treated by diet to prevent an excess
  accumulation of phenylalanine.
• If left untreated it can result in mental
  retardation and hyperactivity.

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Sickle-Cell Anemia
• Gene-linked abnormality
• Occurs most often in African
• Affects the shape of red blood
  cells, hindering their ability to carry
  oxygen to the body’s cells
• Results in anemia and early death
  of the individual

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     Other Genetic
•   Cystic Fibrosis
•   Diabetes
•   Hemophilia
•   Huntington Disease
•   Spina Bifida
•   Tay-Sachs Disease
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       Reproduction Challenges
            and Choices

 Prenatal     Infertility         Adoption

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Prenatal Diagnostic
  •   Amniocentesis
  •   Ultrasound Sonography
  •   Chorionic Villi Sampling
  •   Maternal Blood Test

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• A prenatal medical procedure in which
  a sample of amniotic fluid is withdrawn
  by syringe and tested to discover if the
  fetus is suffering from any
  chromosomal or metabolic disorders
• Performed between the 12th and 16th
  weeks of pregnancy
• There exists a small risk of
  miscarriage (one in every 200-300)

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• A prenatal medical procedure in
  which high frequency sound waves
  are directed into the pregnant
  woman’s abdomen
• Echo from the sounds is
  transformed into a visual
  representation of the fetus’s
  inner structures
• Able to detect such disorders as
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 Chorionic Villi
• A prenatal medical procedure in
  which a small sample of the
  placenta is removed
• Performed between the 8th and 11th
  weeks of pregnancy
• Provides information about the
  presence of birth defects
• Has a slightly higher risk of
  miscarriage than amniocentesis
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        Maternal Blood Test

• Called the alpha-fetoprotein (AFP)
• A prenatal diagnostic technique
  used to asses blood alphaprotein
  level, which is associated with
  neural-tube defects
• Administered between the 14th and
  20th weeks of pregnancy
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• Infertility is the
  inability to conceive a
  child after 12 months
  of regular intercourse

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 Causes of Infertility
• Women                 • Men
 – Ovulation                 – Low sperm
   problems                    count
 – Antisperm
                             – Immobile
 – Blocked
   fallopian tubes           – Antibodies
 – Endometriosis               against sperm

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Infertility Treatment
   •   In vitro fertilization (IVF) - Egg and sperm are combined in a
       laboratory dish and resulting fertilized embryo is transferred
       into the woman’s uterus. (Success rate slightly less than 20%)
   •   Gamete intrafallopian transfer (GIFT) - A doctor inserts eggs
       and sperm directly into a woman’s fallopian tube. (Success
       rate almost 30%)
   •   Intrauterine insemination (IUI) - Frozen sperm—of the husband
       or an unknown donor—is placed directly into the uterus.
       (Success rate 10%)
   •   Zygote intrafallopian transfer (ZIFT) - Eggs are fertilized in the
       laboratory then any resulting zygotes are transferred to a
       fallopian tube. (Success rate approximately 25%)
   •   Intracytoplasmic sperm injection (ICSI) - A single sperm is
       injected by pipette into an egg and the zygote is returned to
       the uterus. (Success rate approximately 25%)

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• Adoption is the social
  and legal process by
  which a parent-child
  relationship is
  established between
  persons unrelated at
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Research Findings on
 • Adopted children and adolescents often
   show more psychological and school-
   related problems than nonadopted
 • Adopted adolescents are referred to
   psychological treatment 2-5 times as
   often as their nonadopted peers.
 • Early adoption often has better child
   outcomes than later adoption.
 • Adoptees show higher levels of prosocial
   behavior than nonadopted peers.
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Adoption Related
• Research findings have implications for
  social policy regarding the foster care
• Clinical psychologists report that sometimes
  adoptive parents try to make life too perfect
  for adoptive children, and thus the children
  feel that they can’t release any angry feelings
  or openly discuss problems.
• Consensus among psychologists is that
  adopted children should be told they are
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                         Heredity - Environment

Intelligence   Heredity-Environment Shared and Nonshared Conclusions about
                   Correlations        Environmental Heredity-Environment
                                         Influences         Interaction

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• Arthur Jensen sparked a debate theorizing that intelligence
  is primarily inherited.
• He believed that standardized IQ tests are a good indicator
  of intelligence.
• Jensen supported his theory with findings from twin
   – IQs of identical twins yielded an average correlation of
   – IQs of ordinary siblings yielded an average correlation
      of .50
   – IQs of identical twins reared together yielded a
      correlation of .89
   – IQs of identical twins reared apart yielded a correlation
      of .78
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Criticisms of Jensen’s
   • IQ tests tap only a narrow range of
     intelligence, excluding important aspects
     such as everyday problem solving, work,
     and social adaptability.
   • Most investigations of heredity and
     environment don’t include environments
     that differ radically.
   • Developmentalists believe intelligence is
     influenced by heredity, but such a strong
     relationship has not been found.

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     The Bell Curve:
 Intelligence and Class
Structure in Modern Life
 • Highly controversial book written in 1994 by
   Richard Herrnstein and Charles Murray.
 • States IQ test scores vary across ethnic groups:
    – Asian Americans score several points higher
      than Whites.
    – African Americans score about 15 points lower
      than Whites.
 • IQ differences are partly due to heredity.
 • Believes government funding for projects such as
   Head Start is wasted.

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Criticisms of The Bell
   • While experts agree that African
     Americans tend to score lower on IQ
     tests, they question the ability of the
     tests to accurately measure
   • The U.S. Supreme Court endorsed
     this criticism by ruling that tests of
     general intelligence are
     discriminatory and cannot be used
     for determining employment.
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  • Relates to the concept that
    individuals’ genes influence the
    types of environments to which
    they are exposed.
  • Behavior-geneticist Sandra Scarr
    described three ways that heredity
    and environment are correlated:
    – Passively
    – Evocatively
    – Actively
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   Passive Genotype-
Environment Correlations
   • Occur when biological parents, who
     are genetically related to the child,
     provide a rearing environment for
     the child.
   • Example:
     – Parents who have a genetic
       predisposition to be intelligent and read
       skillfully, provide their children with
       books to read. The children, in turn,
       become skilled readers due to both
       their inherited predispositions and
       environmental influences.
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  Evocative Genotype-
Environment Correlations
   • Occur because a child’s genotype
     elicits certain types of physical and
     social environments.
   • Examples:
     – Active, smiling children receive more
       social stimulation than passive, quiet
       children do.
     – Athletically inclined youth tend to elicit
       encouragement to engage in school

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Active (Niche-Picking) Genotype-
    Environment Correlations
   • Occur when children and adolescents
     seek out environments they find
     compatible and stimulating.
   • Niche-picking refers to finding a setting
     that is suited to one’s abilities.
   • Active selection of environments is
     related to one’s genotype.
   • Example:
     – Teens who are musically inclined select
       musical environments in which they can
       successfully perform their skills.
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Shared and Nonshared
   • Even though children live under
     the same roof with the same
     parents, often their
     personalities are very different.
   • Robert Plomin found that
     common rearing, or shared
     environment, accounts for little
     of the variation in children’s
     personality or interests.
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Shared Environmental
   • Children’s common
     experiences such as:
     – their parents’ personalities
       and intellectual orientation
     – the family’s social class
     – the neighborhood in which
       they live

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• Children’s unique experiences, both
  within the family and outside the
  family, that are not shared with
  another sibling.
• Experiences occurring within the
  family can be part of the “nonshared
• Parents often interact differently
  with each sibling, and siblings
  interact differently with parents.
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  Conclusions about
• Both genes and environment are necessary for a
  person to exist.
• Heredity and environment operate together, or
  cooperate, to produce:
   – intelligence           -weight
   – temperament             -ability to pitch a
   – height                 -ability to read
• The emerging view is that genes give people a
  propensity for a particular developmental
  trajectory that is ultimately realized through
  environmental circumstances.

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