Psychology Biological Foundations: Heredity, Prenatal Development, and Birth

What is the basic building block of the nature perspective

Gene

Genes

• are specific sequence of nucleotides and are recipes for making protein

• Proteins make up the structure of the cell and let it function.

• They’re the building blocks and machines of cells.

• Genes are the blueprints that let our bodies build those blocks and machine

DNA sequences

• Genes are DNA sequences

• There are about 20,500 genes for humans, made out of about 3 billion base pairs.

• If you unwound all of your DNA from a single cell and had it in a single double helix it would be about six feet long

• DNA is looped up into clumps called chromosomes

Chromosomes

• threadlike structures in the nuclei of cells that contain genetic material

• We have 23 pairs of chromosomes

Autosomes

• first 22 pairs of chromosomes

• These are matching pairs( should have 2 copies

Sex chromosomes

• 23rd pair of chromosomes; these determine the genetic sex of the child

Mitosis

• is defined as the cell’s nucleus making an exact copy of all the

chromosomes and splitting into two new cells

meiosis

• Gametes (sperm or ova), are formed

• . The gamete’s chromosomes duplicate, and then divide twice resulting in four cells containing only half the genetic material of a normal cell (23 unpaired chromosomes).

Gene

• group of nucleotide bases that provide a specific set of biochemical instructions

Genotype

person’s hereditary makeup

Phenotype

• physical, behavioural, and psychological features that result from the interaction between one’s genes and the environment

Alleles

• variations of genes

• Remember, genes come in pairs, you can have 2 different alleles of the same gene

Homozygous

• when the alleles in a pair of chromosomes are the same

Heterozygous

• when the alleles in a pair of chromosomes differ from each other

Dominant

• form of an allele whose chemical instructions are followed

Recessive

• allele whose instructions are ignored when it is combined with a dominant allele

Incomplete dominance

• situation in which one allele does not dominate another completely

Sickle Cell Anemia

• The gene that produces healthy round-shaped red blood cells is dominant.

• The recessive gene causes an abnormality in the shape of red blood cells; they take on a sickle form, which can clog the veins and deprive vital organs of oxygen and increase the risk of stroke.

• Those who have inherited only one recessive-gene are called carriers and should be unaffected by this recessive trait. Yet, carriers of sickle cell have some red blood cells that take on the c- shaped sickle pattern. Under circumstances of oxygen deprivation, such as high altitudes or physical exertion, carriers for the sickle cell gene may experience some of the symptoms of sickle cell

Genetic Disorders

• These can be inherited, in which a child inherits a gene for a disorder from one or both parents

• they can involve more or fewer chromosomes, as can happen when parents’ eggs or sperm do not form properly

• Most Dominant Disorders are not serious or debilitating.

• Recessive gene disorders are less common.

• Some disorders are ‘sex-linked’ which means the gene appears on the X chromosome but not the Y. Males only have one X chromosome so are much more likely to display the phenotypes for these defective genes.

Recessive Disorders( Homozygous)

• The individual inherits a gene change from both parents. If the gene is inherited from just one parent, the person is a carrier and does not have the condition

Examples of Recessive Disorders(homozygous)

• Sickle cells disease

• cystic fibrosis

• phenylketonuria

• Tay sachs disease

• Albinism

Cystic fibrosis(CF)

• is a condition that affects breathing and digestion due to thick mucus building up in the body, especially the lungs and digestive system. In CF, the mucus is thicker than normal and sticky

Phenylketonuria(PKU)

• Is a metabolic disorder in which the individual cannot metabolize phenylalanine, an amino acid. Left untreated intellectual deficits occur. PKU is easily detected and is treated with a special diet

Tay Sachs Disease

• is caused by enzyme deficiency resulting in the accumulation of lipids in the nerve cells of the brain. This accumulation results in progressive damage to the cells and a decrease in cognitive and physical development. Death typically occurs by age five

Albinism

• Is when the individual lacks melanin and possess little to no pigment in the skin, hair, and eyes. Vision problems can also occur

Autosomal Dominant Disorders( Heterozygous)

• In order to have the disorder, the individual only needs to inherit the gene change from one parent

Huntington’s Disease

• Is a condition that affects the individuals nervous system

• Nerve cells become damaged, causing various parts of the brain to deteriorate. The disease affects movement, behaviour and cognition. It is fatal and occurs at midlife

Tourette Syndrome

• Is a tic disorder which results in uncontrollable motor and vocal tics as well as body jerking

Achondroplasia

• is the most common form of disproportionate short stature. The individual has abnormal bone growth resulting in short stature, disproportionately short arms and legs, short fingers and a large head, and specific facial features

Sex linked disorders

• Whenthe X chromosome carries the mutated gene, the disorder is referred to as an x-linked disorder

• Males are more affected than females because they posses only one X chromosome without an additional X chromosome to counter the harmful gene

Fragile X syndrome

• Occurs when the body cannot make enough of a protein it needs for the brain to grow and problems with learning and behaviour can occur

• Fragile X syndrome is cause from an abnormality in the X chromosome which then breaks

• If a female has fragile X, her second X chromosome usually is healthy, but males with fragile X don’t have a second healthy X chromosome

• This is why symptoms of fragile X syndrome usually are more serious in males

Hemophilia

• Occurs when there are problems in blood clotting causing both internal and external bleeding

Duchenne Muscular dystrophy

• is a weakening of the muscles resulting in an inability to move, wasting away, and possible death

Chromosomal Abnormalities

• occurs when a child inherits too many or two few chromosomes.

• Some gametes do not divide evenly when they are forming. Therefore, some cells have more than 46 chromosomes. In fact, it is believed that close to half of all zygotes have an odd number of chromosomes. Most of these zygotes fail to develop and are spontaneously aborted by the mother’s body.

What is the most common chromosomal abnormalities

• One of the most common chromosomal abnormalities is on pair 21.

• Trisomy 21 or Down syndrome occurs when there are three rather than two 21st chromosomes.

• Other less common chromosomal abnormalities of live-born infants occur on chromosome 13, 18 and 23.

• When the abnormality is on 23rd pair the result is a sex-linked chromosomal abnormality.

Sex-linked chromosomal disorders

• The disorder occurs on chromosome pair #23 or the sex chromosomes

Turner Syndrome

• Is caused when all or part of one of the X chromosomes is list before or soon after concenption due to a random event. The resulting zygote has an XO composition

• Turner syndrome affects cognitive functioning and sexual maturation in girls. Infertility and a short stature may be noted

Klinefelter syndrome

• is caused when an extra X chromosome is present in the cells of a male due to a random event

• The Y chromosome stimulated the growth of male genitalia, but the additional X chromosome inhibits this development

• The male can have some breast development, infertility and low levels of testosterone

What are some possible genetic sexes and infant presentation

• XX will be assigned female at birth

• XY amab

• X0 afab

• XXY amab

Behavioural genetics

• the branch of genetics that studies the inheritance of behavioural and psychological traits and their interplay with the environment

• This would be relatively easy if most human traits fell into the simple categories often provided by single-gene inheritance (e.g., you can roll your tongue or you cannot)

Polygenic inheritance

• when phenotypes are the result of the combined activity of many separate genes

• most polygenic traits fall into normal distribution

Monozygotic twins

• result when a single fertilized egg splits to form two new individuals; also called identical twins

Dizygotic twins

• result of the fertilization of two separate eggs by two sperm; also called fraternal twins

• Both types share parents, homes, age, and prenatal environment, but monozygotic twins have 100% genetic overlap and dizygotic twins have 50%, the same as any other siblings would

What does Adoption studies involve

• Adoption studies involve comparing adopted children to

• Parents, both biological and adoptive

• Siblings, both biological and adoptive

• Some pitfalls include

• Monozygotic twins can be treated more similarly than dizygotic twins

• Despite sharing a family, children can have different environments

• The prenatal environment (linked to biological parents) won’t be controlled for

• Adoptive families are not necessarily a representative sample of the entire population

Passive genotype-environment correlation

• occurs when children passively inherit the genes and the environments their family provides.

• Certain behavioral characteristics, such as being athletically inclined, may run in families.

• The children have inherited both the genes that would enable success at these activities, and given the environmental encouragement to engage in these actions.

• Ex two athletes fall in love and raise their athletic children to enjoy athletic pursuits.

Evocative genotype-environment correlation

• refers to how the social environment reacts to individuals based on their inherited characteristics.

• For example, whether one has a more outgoing or shy temperament will affect how they are treated by others.

• The person’s genes evoke a reaction from the environment

Active genotype-environment correlation

• Active genotype-environment correlation occurs when individuals seek out environments that support their genetic tendencies.

• This is also referred to as niche picking.

• For example, children who are musically inclined seek out music instruction and opportunities that facilitate their natural musical ability

Genotype-Environment Interactions

• involve genetic susceptibility to the environment. Adoption studies provide evidence for genotype-environment interactions.

• Early Growth and Development Study followed 360 adopted children and their adopted and biological parents in a longitudinal study.

• Children whose biological parents exhibited psychopathology, exhibited significantly fewer behavior problems when their adoptive parents used more structured parenting than unstructured.

• Elevated psychopathology in adoptive parents increased the risk for the children’s development of behavior problems, but only when the biological parents’ psychopathology was also high.

• The results show how environmental effects on behavior differ based on the genotype, especially stressful environments on genetically at-risk children.

Epigenetics studies

• modifications in DNA that affect gene expression and are passed on when the cells divide.

• Environmental factors, such as nutrition, stress, and teratogens are thought to change gene expression by switching genes on and off.

• These gene changes can then be inherited by daughter cells.

• This would explain why monozygotic or identical twins may increasingly differ in gene expression with age.

• For example, Fraga et al. (2005) found that when examining differences in DNA, a group of monozygotic twins were indistinguishable during the early years. However, when the twins were older there were significant discrepancies in their gene expression, most likely due to different experiences. These differences included susceptibilities to disease and a range of personal characteristics.

The human Genome project

Prenatal development

• the many changes that turn a fertilized egg into a newborn human

• On average, this takes about 38 weeks

• Divided into three periods:

• Germinal period (Zygote) (weeks 1–2)

• Embrionic Period (Embryo) (weeks 3–8)

• Fetal Period (Fetus) (weeks 9–38)

Zygote

• fertilized egg cell

• At ejaculation millions of sperm are released into the vagina, but only a few reach the egg and typically only one fertilizes the egg.

• Once a single sperm has entered the wall of the egg, the wall becomes hard and prevents other sperm from entering.

• The zygote begins cell division through mitosis. After five days of mitosis there are 100 cells, which is now called a blastocyst.

• The blastocyst consists of both an inner and outer group of cells. The inner group of cells, or embryonic disk will become the embryo, while the outer group of cells, or trophoblast, becomes the support system which nourishes the developing organism.

implantation

• During the first week after fertilization, the zygote travels down the fallopian tube toward the uterus

• Spends the second week in the process of implantation step in which the blastocyst burrows into the uterine wall and establishes connections with the body’s blood vessels

ectopic pregnancy,

• When the blastocyst implants in the fallopian tube and is no longer viable

Embryo

• term given to the zygote once it is completely embedded in the uterine wall

• The embryo is tiny, not generally visible to the naked eye in the case of a miscarriage

Cephalocaudal principle

• sequence of growth occurs from the head downward (head to caudal or tail region)

Proximodistal principle

• sequence of growth progresses from inner to outer parts of the body

• This means that those structures nearest the head develop before those nearest the feet, and those structures nearest the torso develop before those away from the center of the body (such as hands and fingers).

Embryonic Period (Weeks 3–8)

• The “head” develops in the fourth week and the cells which will turn into the heart begin to show rhythmic contractions by the 6th week

• In the early stages of the embryonic period, gills and a tail are apparent. However, by the end of this stage they disappear, and the organism takes on a more human appearance.

• Some organisms fail during the embryonic period, usually due to gross chromosomal abnormalities.

• As in the case of the germinal period, often the mother does not yet know that she is pregnant which can lead to the embryo being exposed to dangerous environmental influences

Fetal Period

• longest period of prenatal development, extending from the 9th until the 38th week after conception

• Great increase in size and weight during this period

• 4 months, about 120–240 grams

• From month 4 to month 9, a gain of about 3.4 kilograms more (or 7.5 lbs)

cerebral cortex

• wrinkled surface of the brain that regulates many functions that are distinctly human

• By the third month, the fetus has all its body parts. In the following weeks, the fetus will develop hair, nails, teeth and the excretory and digestive systems will continue to develop. The fetus is about 3 inches long and weighs about 28 grams at this point.

Month 3 of the fetal period

• In month 3, the testes in a male fetus secrete hormones (androgens) that causes development of a penis and scrotum

• Females don’t do this, and thus develop a vagina and labia as the “default human” structures

• In androgen insensitive genetic males, the secreted hormone has no or little effect which leads to female or mixed genitalia

Months 4-6 of fetal period

• During the 4th - 6th months, the eyes become more sensitive to light and hearing develops. The respiratory system continues to develop, and reflexes such as sucking, swallowing and hiccupping, develop during the 5th month.

• The fetus becomes more active, and develops regular cycles of activity and inactivity

• A more active fetus is somewhat more likely to be a “difficult,” fussy baby (change vs continuity!)

Age of viability

• The first chance of survival outside the womb, at about 23 weeks

• it depends on birthweight, health, and availability of appropriate medical care. In low- income countries, 32 weeks has a 50% survival rate

• The majority of the neurons in the brain have developed by 24 weeks

• Senses begin to function

• A fetus can hear, smell, and taste stimuli from the uterine environment

7th and 9th month

• Between the 7th - 9th months, the fetus is primarily preparing for birth. It is exercising its muscles and its lungs begin to expand and contract.

• The fetus gains about 5 pounds and 7 inches during this last trimester of pregnancy, and during the 8th month an insulating layer of fat develops under the skin.

• The fetus stores some basic memories that will be accessible after birth

• Babies prefer Mom’s voice, prefer to hear books Mom read out loud during pregnancy, prefer tastes of foods Mom consumed during pregnancy

Weeks 36-37

• At around 36 weeks the fetus is almost ready for birth. It weighs about 6 pounds and is about 18.5 inches long (47 cm).

• By week 37 all of the fetus’s organ systems are developed enough that it could survive outside the mother’s uterus without many of the risks associated with premature birth.

• The fetus continues to gain weight and grow in length until approximately 40 weeks.

• By then the fetus has very little room to move around and birth becomes imminent

stem cells

• Prenatal brain development begins in the third gestational week with the differentiation of stem cells, which are capable of producing all the different cells that make up the brain.

Neural Plate

• The location of these stem cells in the embryo is referred to as the neural plate.

neural tube

• By the end of the third week, two ridges appear along the neural plate first forming the neural groove. These ridges fold and merge to form the neural tube by the end of week 4. The open region in the center of the neural tube forms the brain’s ventricles and spinal canal.

By the End of the embryonic period what has the neural tube differentiated into?

the forebrain, midbrain, and hindbrain.

Neurogenesis,

• the formation of neurons (8.5 billion of them!) is largely completed after five months of gestation.

• The hippocampus continues to develop throughout life, though

• Neural migration is mostly completed in the cerebral cortex by 24 weeks

• Neurons begin to produce dendrites and axons that begin to form the neural networks responsible for information processing

gray matter

• Regions of the brain that contain the cell bodies

• gray in appearance.

White Matter

• The axons that form the neural pathways because they are covered in myelin, a fatty substance that is white in appearance.

• Myelin aids in both the insulation and efficiency of neural transmission.

• Although cell differentiation is complete at birth, the growth of dendrites, axons, and synapses continue for years, with final myelination only occurring in the early 20s.

What are the 3 general risk factors for prenatal development

• Nutrition

• stress

• mothers age

Nutrition

• Food intake should be adequate to maintain a healthy weight, usually involving about 25– 35 pounds of weight gain if Mom started at a healthy weight

• Mom must also eat the right types of foods, ensuring adequate vitamins, minerals, and other nutrients

Spina Bifida

• disorder in which the embryo’s neural tube does not close properly

• Leads to problems with spinal cord and nervous system

• Can result from a diet lacking in folate

• Prenatal multivitamins are generally designed to provide optimal levels of proteins, vitamins, and minerals that are essential to a child’s healthy development

What are some foods that have a high risk of causing damage during pregnancy

• Raw fish*

• Undercooked meat

• Raw or lightly cooked eggs

• Unpasteurized milk products or juices

• Raw sprouts

Stress

• physical and psychological responses to threatening or challenging conditions

• Experiencing intense stress leads to:

1. Stress hormones that reduce the flow of oxygen to the fetus

2. The immune system is weakened, making the parent more susceptible to illness, which can damage fetal development

3. Parent is more likely to smoke or drink alcohol and less likely to rest, exercise, and eat properly

4. High levels of stress hormone are linked to the baby having attentional difficulties and anxiety issues

Mothers age

• If the mother is still in her teens, there is increased risk of

• Poor nutrition and lack of prenatal care

• Incomplete maternal education, poverty, family instability

• Correlates with high stress, drug and alcohol use

• Marital/relationship difficulties for the mother are common

• Teen mothers are at a higher risk of complications like anemia, high blood pressure, and low birth weights for their babies, as well as premature births

• About 25% of teen mothers under age 18 have a second baby within 2 years after the first baby’s birth.

What are some risks about having child over age 35

• Fertility problems

• High blood pressure

• Diabetes

• Miscarriage

• Placenta Previa

• Cesarean section

• Premature birth

• Stillbirth

• A baby with a genetic disorder or other birth defects

What are some upsides to being an older parent

• More confident

• Less stressed

• Typically higher family stability

• Children tend to perform higher in school, less prone to injuries & emotional issues

• Older women tend to be more stable, educated, wealthier, and live longer (though that might be caused by good health in general: longevity and reproductive ability)

• For every year a woman delays motherhood, she makes 9% more in lifetime earnings.

Gestational Diabetes

• 7% of pregnancies cause this. It can lead do preeclampsia (high blood pressure and kidney/liver failure).

High blood pressure

• 8% of pregnancies. Can cause low birth weight, premature birth, placental abruption, and preeclampsia.

Rh disease

• When a Rh- mother has a Rh+ fetus her body can form antibodies against the Rh protein, which can affect subsequent Rh+ babies of hers.

Weight gain

• gaining too much or too little weight during pregnancy can harm the mother or baby. 25-35lbs is a common amount to put on.

Depression

• Feelings of sadness, worthlessness, guilt, and fatigue interfere with daily functioning. Depression can occur before, during, or after pregnancy, and 1 in 7 women is treated for depression sometime between the year before pregnancy and year after pregnancy. Some antidepressants (especially SSRIs) are linked with increased chance of birth defects

Preeclampsia

• is characterized by a sharp rise in blood pressure, a leakage of protein into the urine as a result of kidney problems, and swelling of the hands, feet, and face during the third trimester of pregnancy

• Preeclampsia is the most common complication of pregnancy. It is estimated to affect 5% to 10% of all pregnancies globally (less in Canada and the US) and accounts for 40% to 60% of maternal deaths in developing countries.

• Also the most common cause of fetal complications and stillbirth.

• Preeclampsia occurs most frequently in first pregnancies, and it is more common in women who are obese, have diabetes, or are carrying twins.

eclampsia

• When preeclampsia causes seizures

Postpartum Depression

• Occurs in about 10–15% of new mothers

• Symptoms include

– Irritability

– Feelings of low self-worth

– Disturbed sleep

– Poor appetite

– Apathy

What are some contributors to postpartum depression

• Particularly high levels of hormones during the later phases of pregnancy

• Depression before pregnancy

• Other life stresses

• Unplanned pregnancy

• Lack of other adults (e.g., the father) to support adjustment

• Breastfeeding is protective against it, in some studies

Dangers of postpartum depression

• Lack of warm mothering

• Less touching, cuddling, talking to the baby

• Less effectiveness in dealing with feeding and sleep routines

• In mothers’ long-term depression, increased risk of children’s insecure attachment and later antisocial behaviour

Paternal Impact

• As with women, babies of men over 40 face an increased risk of miscarriages, autism, birth defects, achondroplasia (though the increase in risk is small).

• Men are more likely to work with hazardous materials which could have a teratogenic effect, and are also more likely to be a source of secondhand smoke during pregnancy.

• Family stability and spousal support are both beneficial to the mother and child’s health

Teratogen:

• agent that causes abnormal prenatal development

• Three major categories

  • Drugs

  • Diseases

  • Environmental hazards

How can the effects be moderated

• The timing of the exposure (later is better)

• The amount of the exposure (less is better)

• The number of teratogens (less is better)

• Genetics – some mothers may be more resistance to some teratogens compared to others

• Genetic sex of baby – Males are more likely to be damaged by teratogens, possibly because of the less robust Y chromosome

Drugs

• Thalidomide, a drug used to treat morning sickness in the 1950s, caused babies to develop serious abnormalities, sometimes including missing limbs

• We now know that many drugs, both legal and illegal, are potential teratogens

Aspirin

• particularly with heavy use, linked with deficits in intelligence, attention, and motor skills

Caffeine

• with heavy use, lower birth weight, decreased muscle tone

Marijuana

• lower birth weight, less motor control

Nicotine

• delayed growth, possible cognitive impairments

• Nicotine constricts blood vessels, reducing the oxygen and nutrients that can reach the fetus

• Smoking is linked to low birth weight, ectopic pregnancy, placenta previa, placental abruption, preterm birth, stillbirth, SIDS, birth defects, learning disabilities and early puberty in girls.

• Even third hand smoke (residue on clothes or furniture) results in a negative impact on infants’ lung development.

Cocaine and heroin

• delayed growth, lack of nutrition and prenatal care, irritability in newborns, addiction in newborns, SIDS, and future developmental, emotional and behavioural problems including addiction

Neonatal abstinence syndrome

• when a newborn is in withdrawal from an addictive drug the mother was using while pregnant