Chapter two biological beginnings (developmental)

Natural selection

an evolutionary process by which individuals of a species that are best adapted are the ones that survive and leave the most fit offspring

Adaptive behavior

• behavior that promotes an organism’s survival in the natural habitat because an organism possesses characteristics needed for survival

• ex. babies cry to make sure someone feeds them

Evolutionary psychology

• emphasizes the importance of adaptation and reproduction to ensure survival

• offspring that adapts, develops behaviors and possesses self-protective traits survive

• evolutionary selection benefits- how much biology has our back, goes down from 0-100

• need for culture- everything humans create to support life, goes up from 0-100

Evolutionary developmental psychology

• interest has grown in using the concepts of evolutionary psychology to understand human development

• psychological mechanisms are domain-specific

• for example, we developed sets of problem solving skills for recurring problems like finding food

Connecting evolution and life-span development

• the benefits conferred by evolutionary selection decrease with age

• natural selection primarily operates during the first half of life and during reproductive viability

• older adults weaken biologically and need culture based resources such as cognitive skills, literacy, medical technology and social support

Evaluating evolutionary psychology: criticisms include that it

• does not adequately value social/environmental factors

• relies on after the fact explanations

• cannot be tested scientifically

Evolution does not dictate behavior

• an alternative bidirectional view suggests environmental and biological conditions influence each other

• people have used their biological capacities to produce diverse cultures

Evolution occurs on a time scale that does not

• lend itself to empirical study

• the ideas coming out of evolutionary psychology are perhaps best tested by studying specific genes in humans and other species and their links to traits and behaviors

Human life begins as

a single cell

The nucleus of each cell contains

chromosomes

Chromosomes

• threadlike structures made up of deoxyribonucleic acid

• are like binders that hold all of our instructions for life

DNA

• a complex double-helix molecule that contains genetic code or information

• inside chromosomes

• body’s instruction manual

Genes

• units of hereditary information composed of DNA

• help cells to reproduce themselves

• manufacture the proteins that maintain life

• segments of DNA, specific chapters in that manual

• provide directions for building proteins that guide growth, development and functioning

The collaborative gene

• each gene has its own location-its designated place on a particular chromosome

• researchers today strive to discover the specific locations of genes that are linked to certain functions and developmental outcomes

• the Human Genome Project mapped the human genome-the complete genetic content of our cells

• in 2019, scientists concluded the human genome contains 19,969 protein- coding genes

• genes collaborate with each other and with nongenetic factors both inside and outside the body

Whether a gene is expressed-working to assemble proteins- as a matter of collaboration

• genetic expression is affected by their environment

• hormones in the blood can turn genes “on” and “off”

Certain genes are turned on or off as a result of exercise mainly through

• methylation

• tiny molecules attach themselves to the outside of a gene making the gene less capable of receiving and responding to biochemical signals from the body

• stress, exercise, nutrition, radiation, temperature and lack of sleep can negatively influence gene expression

All cells in the body except the sperm and egg

have 46 chromosomes in 23 pairs

Mitosis

• the cellular reproduction in which the cell’s nucleus duplicates itself into two new cells

• each contains the same DNA as the original cell

• how the skinned skin repairs itself

Meiosis

• cell division forming eggs and sperm (or gametes)

• sex cells form

• how eggs and sperm are made

• cuts the genetic material in half

Fertilization

the reproductive stage when egg and sperm fuse to create a zygote

Zygote

• a single cell formed through fertilization in which 23 unpaired chromosomes from the egg and 23 unpaired chromosomes from the sperm combine

• full set of instructions for a unique human being

Sources of variability

• combining the genes of two parents in offspring increases variability in the population

• the chromosomes are brought together in the zygote in a unique combination

In identical twins or monozygotic twins

a single zygote splits into two genetically identical replicas and becomes two individuals

In fraternal twins or dizygotic twins

two eggs fertilized by different sperm create two nonidentical zygotes as genetically similar as ordinary siblings

Mutated gene

a permanently altered segment of DNA

Susceptibility genes

genes that make the individual more vulnerable to specific diseases or accelerated aging

Longevity genes

genes that make the individual less vulnerable to certain diseases and more likely to live to an older age

Genotype

a person’s genetic material

Phenotype

how an individual’s genotype is expressed in observable and measurable physical and psychological characteristics

Expression is influenced by

• environmental factors

• for example a genetic potential for height may be stunted by lack of access to proper nutrition

Genetic principles determine how

a genotype is expressed to create a particular phenotype

Dominant-recessive genes principle

• one gene of a pair always exerts its effects overriding the potential influence of the other gene

• ex. eye color

Sex-linked genes

• when a mutated gene is carried on the x chromosome the result is called x-linked inheritance

• most x-linked inherited diseases manifest in males who have only one x chromosome

• ex. colorblindness

Genetic imprinting

• occurs when the expression of a gene has different effects depending on whether the gene is passed on by mother or father

• a chemical process prevents one member of the gene pair from expressing itself

• imprinting is normal but can go awry disturbing development and leading to growth disorders or cancer

Polygenic inheritance

many different genes interacting plus environmental influences determine a characteristic or developing disease

Gene-gene interaction

studies focusing on the interdependence of two or more genes in influencing characteristics, behavior, diseases and development

Down syndrome

• a form of an intellectual disability caused by the presence of an extra copy of chromosome 21

• can cause intellectual and physical issues

• most common chromosomal condition

Chromosomal abnormalities known as sex-linked involve

the presence of an extra X or Y chromosome or the absence of one X chromosome in females

Klinefelter syndrome

• a sex linked chromosomal disorder in which males have an extra x chromosome making them xxy instead of xy

• characteristics are underdeveloped testes, enlarged breasts and becoming tall

• lower fertility

• lower testosterone

• fertility/physical issues

Fragile X syndrome (FXS)

• a sex linked disorder involving an abnormality in the x chromosome which becomes constricted and often breaks

• can cause intellectual disability, learning disability or short attention span

• learning challenges, affect learning, behavior and attention

• most common inherited cause of intellectual disability

Turner syndrome

• a sex linked disorder in females in which either an x chromosome is missing or the second x chromosome is partially deleted

• can cause intellectual disability and sexual underdevelopment

• short stature, fertility issues, learning challenges

XYY syndrome

• a sex-linked disorder in which males have an extra Y chromosome

• can cause above-average height

• sometimes mild differences

Treatment and incidence for Down syndrome

• surgery, early intervention, infant stimulation and special learning programs

• 1 in 1900 births at age 20

• 1 in 300 births at age 35

• 1 in 30 births at age 45

Treatment and incidence for Klinefelter syndrome (XXY)

• hormone therapy can be effective

• 1 in 500 to 1000 male births

Treatment and incidence for Fragile X syndrome

• special education, speech and language therapy

• more common in males than in females

Treatment and incidence for Turner syndrome (XO)

• hormone therapy in childhood and puberty

• 1 in 2500 female births

Treatment and incidence for XYY syndrome

• no special treatment required

• 1 in 1000 male births

Gene-linked abnormalities are produced by

harmful genes

Phenylketonuria (PKU)

• a genetic disorder in which an individual cannot properly metabolize an amino acid called phenylalanine

• if left untreated it results in intellectual disability and hyperactivity

• special diet can result in average intelligence and normal life span

• 1 in 10,000 to 1 in 20,000 births

• can’t process protein

Sickle-cell anemia

• a genetic disorder that affects the red blood cells and occurs most often in blacks

• red blood cells become hook-shaped and cannot carry oxygen properly

• blood disorder that limits the body’s oxygen supply

• can cause joint swelling as well as heart and kidney failure

• penicillin, medication for pain, antibiotics, blood transfusion and hydroxyurea

• 1 in 400 black American children (lower among other groups)

Cystic fibrosis

• glandular disfunction that interferes with mucus production, breathing and digestion are hampered resulting in a shortened life span

• physical and oxygen therapy, synthetic enzymes and antibiotics, most individuals live to middle age

• 1 in 2000 births

• requires lifelong medical care

Diabetes

• body does not produce enough insulin which causes abnormal metabolism of sugar

• early onset can be fatal unless treated with insulin

• 1 in 2500 births

• affects both physical and mental health

Hemophilia

• delayed blood clotting causes internal and external bleeding

• blood transfusions/injections can reduce or prevent damage due to internal bleeding

• 1 in 5000 males

Huntington disease

• central nervous system deteriorates producing problems in muscle coordination and mental deterioration

• does not usually appear until age 35 or older, death likely 10-20 years after symptoms appear

• 1 in 20,000 births

• fatal disorder

Spina bifida

• neural tube disorder that causes brain and spine abnormalities

• corrective surgery at birth, orthopedic devices and physical/medical therapy

• 1 in 500 births

Tay-Sachs disease

• deceleration of mental and physical development caused by an accumulation of lipids in the nervous system

• medication and special diet are used but death is likely by 5 years of age

• 1 in 30 American Jews is a carrier

Dealing with genetic abnormalities

• every individual carries DNA variations that predispose the person to serious physical disease or mental disorder

• genes that are missing, nonfunctional or mutated can contribute to disorders

Identifying genetic flaws enables medical professions to

• predict an individual’s risks

• recommend healthy practices

• prescribe the safest and most effective drugs

A number of tests can indicate whether a fetus is developing normally

• ultrasound sonography

• brain imaging techniques

• chronic villus sampling

• amniocentesis

• maternal blood screening and cell-free DNA

• noninvasive prenatal diagnosis (NIPD)

• fetal sex determination

Infertility

the inability to conceive a child after 12 months of regular intercourse without contraception

In vitro fertilization (IVF)

• a process in which eggs and sperm are combined in a laboratory dish by experts

• one or more of the resulting zygotes will be transferred into the woman’s uterus

• multiple zygotes can increase health risks

• IVF success rate depends on the mother’s age and other factors

Adoption

a social and legal process that establishes a parent-child relationship between persons unrelated at birth

U.S. couples are adopting a wide diversity of children

• from other countries

• from other ethnic groups

• children with physical and/or mental problems

• children who had been neglected or abused

• increased diversity has also characterized adoptive parents

Types of adoption

• domestic adoption from the public welfare system, often older children who may have been in foster care, many children in the U.S.

• domestic infant adoption through private agencies and intermediaries

• international adoption

Outcomes for adopted children

• adolescents who were adopted face challenges in their identity development

• adopted children fare much better than children raised in long-term foster care

• children who are adopted at a very early age are more likely to have positive outcomes

Behavior genetics

the field that seeks to discover the influence of heredity and environment on individual differences in human traits, development and behavior

Twin study

the behavioral similarity of identical twins is compared with the behavioral similarity of fraternal twins

Adoption study

• seeks to discover whether behavioral and psychological characteristics of adopted children are more like those of their adoptive parents or biological parents

• adoptive parents provided the home environment

• biological parents contributed their heredity

Passive genotype-environment correlations

occur because biological parents provide a rearing environment for the child

Evocative genotype-environment correlations

occur because a child’s genetically influenced characteristics elicit certain types of environments

Active (niche-picking) genotype-environment correlations

occur when children seek out environments that they find compatible and stimulating and suited for their genetically influenced abilities

Epigenetic view

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

• the epigenetic mechanisms involve the actual molecular modification of the DNA strand as a result of environmental inputs in ways that alter gene functioning

Conclusions about heredity-environment interaction

• the relative contributions of heredity and environment are not additive

• genes produce proteins-or not- in many different environments throughout the life span

• complex behaviors are influenced by genes and environments in a way that gives people a propensity for a particular developmental trajectory

• we can also author a unique developmental path by changing the environment

Biological determinism

idea that genes or evolution completely explain a client’s behavior

Bidirectional view

biology and environment influence each other

Fight

push back against stress or threat

Flight

avoid or escape

Freeze

shut down or go numb

Fawn

appease or please to stay safe

Errors in imprinting

growth or developmental disorder

Prader Will syndrome

• certain gene on chromosome 15 missing from dad

• impacts growth, appetite and behavior challenges

Angelman syndrome

• certain gene on chromosome 15 missing from mom

• developmental delays, speech and movement differences

Ultrasound sonography

• routine imaging of fetus/placenta

• most routine, safe, uses sound waves

Brain imaging (MRI)

detailed look at structures

Chorionic villus sampling (CVS)

• placenta tissue sample

• 10-12 weeks

• carry some risk

Amniocentesis

• amniotic fluid sample

• 15-20 weeks

• test for chromosomal and metabolic disorders

• carry some risk

Maternal blood and cell free DNA

• noninvasive screening for abnormalities

• can indicate risk for conditions

Noninvasive prenatal diagnosis (NIPD)

• uses fetal DNA in maternal blood

• can sometimes reduce the need for invasive procedures

Fetal sex determination

ultrasound or blood based tests