03 - Prenatal Development and Childbirth

Fertilization

Marks the beginning of development where sperm and ovum combine to create a zygote in the fallopian tube.

zygote

Single cell consists of DNA

Fertile Window

unpredictable time during which conception is possible

Maturation of sex cells

Must occur prior intercourse for conception to be possible

Menarche

Women first menstruation

Nocturnal Emission

Release of sperm at night

Ovulation

Rupture of a mature follicle which occurs every 28 days until menopause

Cell division

Zygote duplicates itself through the process of ___ to produce all cells that make up a baby

Death of both gametes

Unsuccessful fertilization results in the

Gametes

Sex cells that join during reproduction

White blood cells

Sperm cells are absorbed by the; body’s natural primary defense system

Ovum

Exits the body through the vagina; a mature female reproductive cell.

Dizygotic Twins

Fraternal twins; fertilization of 2 separate eggs by 2 sperms; Result of multiple eggs being released at one time

Monozygotic Twins

Identical twins; cleaving (splitting or cutting something apart) of 1 fertilized egg

Twin-to-twin Transfusion Syndrome

Nutrients are shared unequally as a result of an abnormal formation of blood vessels in the placenta

Mitosis

Somatic cell’s nucleus duplicates itself to form two new cells; Genetic identity of the parent cell is preserved, leading to minimal genetic variation among daughter cells; Formation of two identical diploid daughter cells

Diploid

Two complete sets (2n) of chromosomes

Meiosis

Specialized form of cell division that is involved in the production of gametes for sexual reproduction; Introduces genetic diversity results in genetically unique daughter cells; formation of four non-identical haploid daughter cells

Haploid

One complete set of chromosomes (n)

Gene

Segments of DNA that contain the instructions for building and maintaining an organism ; Help cells to reproduce themselves and help manufacture the proteins that maintain life

Chromosomes

Threadlike structures that come in 23 pairs and contain DNA

Deoxyribonucleic Acid (DNA)

Complex molecule that contains genetic information

Mutation

Permanent alteration in the DNA sequence of a gene

• Errors in DNA replication during cell division

• Exposure to mutagens or a viral infection

Results of mutation

Proteins

Building blocks of cells and regulators that direct the body’s processes

Human Genome

Reference point that shows the location of all human genes

Exciting or inhibiting genes

Genetic expression is also affected by their environment by

Methylation

Tiny atoms attach themselves to the outside of a gene resulting in certain genes becoming turned on or off

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

Sex-Linked Genes

Genes that determine an individual's sex / gender at birth; twenty-third pair of chromosomes

XX

Female sex chromosomes

XY

Male sex chromosomes

Autosomes

Chromosomes that are not related to sexual expression

X-linked Inheritance

When a mutated gene is carried on the X chromosome;

Because they lack a second X chromosome to mask the effects of the recessive allele

Why is X-linked Inheritance more commonly expressed in males?

Carriers

Females carrying one normal and one mutated X-linked allele are typically __ and may not express the disorder

Mendelian Genetics

Describes the inheritance of traits from one generation to the next.

Allele

Two or more alternative forms of a gene that occupy the same position on paired chromosomes and affect the same trait

Homozygous

Possessing two identical alleles for a trait

Heterozygous

Possessing two different alleles for a trait

Dominant Inheritance

Pattern of inheritance in which, when a child receives different alleles, only the dominant one is expressed

Dominant Gene

Allele that is expressed in the phenotype even when only one copy is present in the genotype (heterozygous condition)

Genotype

Organism's internal set of inherited genes; person’s genetic heritage; the actual genetic material

Phenotype

How those genes are observable, physical, and biochemical traits of an organism, shaped by both genetics and the environment

Recessive Inheritance

Pattern of inheritance in which a child receives identical recessive alleles, resulting in expression of a nondominant trait

Recessive Gene

An allele that is expressed in the phenotype only when two copies are present in the genotype (homozygous condition)

Polygenic Inheritance

Inheritance of traits that are controlled by multiple genes, each with a small additive effect.

Sample: Suppose a child has parents with different skin tones. The child may have a skin tone that is lighter, darker, or somewhere in between because many genes contribute to melanin production.

Multifactorial Transmission

Phenomenon by which environmental experience modifies the expression of the genotype for most traits

Sample: A child may inherit genes that make them more likely to gain weight. However, whether the child actually becomes overweight can also depend on diet, physical activity, lifestyle, and environment.

Epigenesis

Mechanism that turns genes on or off and determines functions of body cells

TRUE

T or F: Genes are turned off or on as they are needed by the developing body or when triggered by the environment

Puberty and Pregnancy

Cells are particularly susceptible to epigenetic modification during critical periods such as

Genetic Imprinting

Occurs when the expression of a gene has different effects depending on whether the mother or the father passed on the gene

Gamete formation

Certain genes are "imprinted" or marked with chemical modifications during

Imprinting Disorders

Aberrations (departure from what is normal, usual, or expected) in genetic imprinting

Down Syndrome (Trisomy 21)

Extra copy of chromosome 21; Associated with intellectual disabilities, distinctive facial features, and an increased risk of certain health issues

Cri-du-chat Syndrome

Deletion on the short arm of chromosome 5; May have a distinctive cry resembling a cat

Edwards Syndrome (Trisomy 18)

Extra copy of chromosome 18; Associated with severe intellectual disabilities, congenital heart defects, and abnormalities in various organ systems

Patau Syndrome (Trisomy 13)

Extra copy of chromosome 13; Severe developmental and physical abnormalities, including intellectual disabilities, heart defects, and cleft lip and palate

Prader-Willi Syndrome

Genes on chromosome 15 are missing or inactive; intellectual disabilities, obesity, and behavioral issues

Alpha, Antitrypsin Deficiency

Mutation in chromosome 14; Enzyme deficiency that can lead to cirrhosis of the liver, emphysema, and degenerative disease in middle age

Alpha Thalassemia

Mutation in chromosome 16; Severe anemia that reduces the ability of the blood to carry oxygen, and all affected infants are stillborn or die soon after birth

Beta Thalassemia (Cooley’s Anemia)

Mutation in chromosome 11; Severe anemia resulting in weakness, fatigue, and frequent illness; usually fatal in adolescence or young adulthood

Cystic Fibrosis

Mutation in chromosome 7; Overproduction of mucus which collect in the lungs and digestive tract; children do not grow normally and usually do not live beyond the age of 30

Anencephaly

Influenced by a combination of environmental and genetic factors associated with the formation and closure of the neural tube during embryonic development

Absence of the cerebral hemispheres and the overlying skull and scalp; infants are stillborn or die soon after birth

Spina Bifida

Mutation in chromosome 11; the neural tube / spinal column fails to close properly

muscle weakness or paralysis, loss of bladder and bowel control, hydrocephalus, and mental retardation

Phenylketonuria (PKU)

Caused by the inability to metabolize the amino acid, phenylalanine; intellectual disability / hyperactivity if left untreated

Polycystic Kidney Disease

Infantile form: enlarged kidneys, leading to respiratory problems and congestive heart failure

Adult form: kidney pain, kidney stones, and hypertension resulting in chronic kidney failur

Sickle-cell Anemia

A recessive gene causes the red blood cell to become a hook-shaped “sickle” that cannot carry oxygen properly

Limits the body’s oxygen supply; joint swelling, and heart / kidney failure

Tay-Sachs Disease

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

Diabetes

Body doesn't produce enough insulin, which causes abnormal metabolism of sugar

Huntington’s Disease

Central nervous system deteriorates, producing problems in muscle coordination and mental deterioration

Angelman Syndrome

Absence or dysfunction of maternal genes on chromosome 15

developmental delays, seizures, and a happy demeanor

Turner Syndrome (XO)

Occurs in females with a single X chromosome (45, X)

short stature, webbed neck, and infertility

Klinefelter Syndrome (XXY)

Affects males with an extra X chromosome (XXY)

reduced fertility, gynecomastia (enlarged breasts), and other physical characteristics

Triple X Syndrome (XXX)

occurs in females with an extra X chromosome (47, XXX)

most individuals have no or mild symptoms, but some may experience learning difficulties, menstrual irregularities, and mental retardation

XYY Syndrome

Affects males with an extra Y chromosome (47, XYY)

tall structure, low IQ, especially verbal

Fragile X Syndrome

Expansion of a particular region on the X chromosome

Minor to severe mental retardation, delayed speech and motor development, speech impairments, and hyperactivity

Duchenne Muscular Dystrophy

Mutation in the X sex chromosome

Fatal disease usually found in males; marked by muscle weakness, minor mental retardation, respiratory failure and death in young adulthood

Behavior Genetics

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

Heritability

Statistical estimate of contribution of heredity to individual differences in a specific trait within a given population

Concordant

Tendency of twins to share the same trait or disorder

Sample: Two identical twins were raised in different families. Both twins develop similar height and physical characteristics.

Twin Study

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

Adoption Study

Seek to discover whether the behavior and psychological characteristics of adopted children are more like those of their adoptive parents or more like those of their biological parents

Reaction Range

Range of potential expressions of a hereditary trait; Depends on environmental opportunities and constraints and a person’s behavior

Sample: A child is born with genes that give them the potential to become very good at reading and language.

However, the child grows up in a home with few books and receives little educational support. Because of the limited environment, the child may not reach their full genetic potential.

Canalization

Illustrates how heredity restricts the range of development for some traits; Strongly programmed by genes and there is little opportunity for variance in their expression; It would take an extreme change in environment to alter their course

Sample: A baby is born with genes that strongly program the development of basic motor abilities, such as walking. Whether the child grows up in a quiet home, a busy household, or with different parenting styles, the child will most likely develop the ability to walk around the typical developmental period.

Genotype-Environment Interaction

Genetically similar children often develop differently depending on their home environments

Sample: Two children have different genetic predispositions for athletic ability.

• Child A has genes that give them a high potential for physical strength and coordination. They grow up in a family that encourages sports, enrolls them in basketball training, and provides proper nutrition. As a result, their athletic ability becomes highly developed.

• Child B has a similar genetic potential but grows up in an environment with little opportunity for sports or physical activity. Their athletic abilities may not develop to the same extent.

Genotype-Environment Correlations

Tendency of certain genetic and environmental influences to reinforce each other

Sample: Child A is naturally energetic and has a genetic predisposition for good physical coordination and athletic ability. Because of these characteristics, their parents notice that the child enjoys running and playing sports. The parents then enroll Child A in basketball training and provide opportunities to practice.

As a result, the child's genetic characteristics influence the type of environment they experience.

Passive

When an individual’s environment is correlated with the genetic makeup they inherit from their parents

Sample: A child is born into a family where both parents are highly intelligent and enjoy reading. The parents pass on genes associated with cognitive abilities to the child. At the same time, because the parents themselves love reading, they naturally create a home filled with books, educational materials, and intellectual discussions.

Evocative

When an individual's genetically influenced characteristics evoke specific responses from others in their environment

Sample: A child is naturally outgoing, talkative, and socially confident because of their genetic predispositions. Because the child frequently talks to others, asks questions, and enjoys interacting, teachers and classmates respond positively. The teacher may give the child more opportunities to participate in class, lead activities, or interact with other students.

Active

When individuals seek out or create environments that are compatible with their interests (niche-picking)

Sample: A teenager has a genetically influenced tendency toward high curiosity and a strong interest in music. As they grow older, they actively choose to spend time in environments that match these interests. They join the school choir, learn guitar, watch music tutorials, and seek out friends who also enjoy music.

Nonshared Environment

Unique environment in which each child in a family grows up; Consists of distinctive influences or influences that affect one child differently than another; Children’s genetic differences may lead parents to react to them differently and treat them differently

Sample: Two siblings, Anna and Mia, grow up in the same family with the same parents and attend the same school. However, Anna is encouraged by her teacher to join the debate club, while Mia becomes close friends with classmates who enjoy sports and joins the basketball team.

Over time, Anna becomes more confident and interested in public speaking, while Mia becomes more athletic and socially outgoing.

1. Obesity

2. Intelligence

3. Temperament and Personality

4. Schizophrenia

Characteristics Influenced by Heredity and Environment

Prenatal Development

Gestation that takes place in three stages

1. Germinal

2. Embryonic

3. Fetal

Three stages of Prenatal Development

Gestation

Period of development between conception and birth

Gestational Age

Age of an unborn baby dated from the first day of an expectant mother’s last menstrual cycle

Cephalocaudal Principle

dictates that development proceeds from the head to the lower part of the trunk

Sample: A newborn baby first gains control over their head and neck. After developing head control, the baby gradually gains control over their upper body and arms, and later develops control over their legs and feet, eventually learning to walk.

Proximodistal Principle

Dictates that parts of the body near the center develop before the extremities

Sample: A baby may first learn to control their shoulders and arms, then use their hands to grasp objects, and eventually develop the fine motor skills needed to pick up a small piece of food using their thumb and index finger.

First Trimester — Conception to 4 weeks

• Less than 1/10 inch long

• Beginning development of spinal cord, nervous system, gastrointestinal system, heart, and lungs

• Amniotic sac envelopes the preliminary tissues of entire body

• Called “zygote”