CHAPTER 3: FORMING A NEW LIFE

fertilization

- Union of sperm and egg

- Sperm and egg join to form a zygote.

- Union of sperm and ovum to produce a zygote; also called conception.

- A sperm cell from the father joins with an egg cell (ovum) from the mother.

- They combine to form a zygote, the first cell of a new human being.

zygote

- First cell of a new baby

- undergoes rapid division.

- the first cell of a new human being.

- one-celled organism resulting from fertilization

MONOZYGOTIC TWINS

- Twins resulting from the division of a single zygote after fertilization

- Identical twins

Identical twins

= they are genetically similar

DIZYGOTIC TWINS

- Twins conceived by the union of two different ova (or a single ovum that has split) with two different sperm cells

- Fraternal twins

Fraternal twins

- they are no more alike genetically than any other siblings

CHROMOSOMES

- thread-like structures inside our cells - Think of them as books that contain instructions for building the body.

- Is like a book

Human Genome

- the complete sequence of genes in the human body.

GENES

- are sections of DNA found on chromosomes

- They determine traits such as (eye color, hair color, height, blood type, some diseases)

- are the individual instructions inside the book.

SEX DETERMINATION

- The baby's sex depends on the father's sperm.

X chromosome

Mother always gives

→ Girl (XX)

Father gives either

Y

→ Boy (XY)

Father gives either

ALLELES

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 differing alleles for a trait

DOMINANT GENE

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

-Only one copy is needed for the trait to appear.

Example: Brown eyes usually dominate blue eyes.

RECESSIVE GENE

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

- Needs two copies to appear.

Example: Blue eyes appear only if both parents pass on the blue-eye gene

Alpha thalassemia

- Its condition is a severe anemia that reduces the ability of the blood to carry oxygen; nearly all affected infants are stillborn or die soon after birth

-Those who are at risk are primarily families of Malaysian, African, and Southeast Asian descent

- It can be done through frequent blood transfusions

Beta thalassemia (Cooley's anemia)

- Its condition is a severe anemia resulting in weakness, fatigue, and frequent illness; usually fatal in adolescence or young adulthood

- Those who are at risk are primarily families of Mediterranean descent

- It can be treated with frequent blood transfusions

Cystic fibrosis

- affects breathing and digestion

- its condition: overproduction of mucus, which collects in the lung and digestive tract; children do not grow normally, short life span; the most common inherited lethal defect among White people

- Those who are at risk are 1 in 2,000 White births

- It can be treated with Physical therapy to loosen mucus; antibiotics for lung infections; enzymes to improve digestion; lung transplant

Duchenne muscular dystrophy

- Its condition is a Fatal disease usually found in males, marked by muscle weakness and minor intellectual disability; respiratory failure and death usually occur in young adulthood

- Those who are at risk are 1 in 3,000 to 5,000 male births

- However, it cant be treated because there is no treatment.

Hemophilia

-Its condition is excessive bleeding, usually affecting males; in its most severe form, it can lead to crippling arthritis in adulthood

- The ones who are at risk are 1 in 10,000 families with a history of this defect or disorder

- It can be treated through Frequent transfusions of blood with clotting factors

Anencephaly

- Absence of brain tissues; infants are stillborn or die soon after birth

- Those who are at risk are 1 in 1,000

- However, it cant be treated because there is no treatment.

Spina bifida

- It's a condition that is an incompletely closed spinal canal, muscle weakness or paralysis, and loss of bladder and bowel control; often accompanied by hydrocephalus, an accumulation of spinal fluid in the brain, and intellectual disability

- Those who are at risk are 1 in 1,000

- It can be done through surgery, as this prevents further injury; a shunt placed in the brain drains excess fluid.

Phenylketonuria (PKU)

- Its condition is a metabolic disorder resulting in intellectual disability.

- Those who are at risk are 1 in 15,000 births

- It can be done or treated through special diet can prevent intellectual disability

Polycystic kidney disease

- It is conditioned as an Infantile form: enlarged kidneys, leading to respiratory problems and congestive heart failure.

- Those who are at risk 1 in 1,000

- It can be done through Kidney transplants

Sickle-cell anemia

- red blood cells become sickle-shaped

- can cause pain and anemia

- It is conditioned as deformed red blood cells that clog blooр vessels, depriving the body of oxygen; symptoms include severe pain, stunted growth, infections, leg ulcers, gallstones, pneumonia, and stroke

- those who are at risk are 1 in 500 African Americans

- it can be treated through painkillers, transfusions for anemia and to prevent stroke, and antibiotics for infections

Tay-Sachs disease

- It is conditioned as a degenerative disease of the brain and nerve cells, resulting in death before age 5

- Those who are at risk are primarily found in Eastern European Jewish families

- However, it cant be treated because there is no treatment.

EPIGENESIS

- mechanism that turns genes on or off and determines functions of body cells. - the idea that our genes provide the potential, but our environment and experiences influence how that potential develops.

Complete Dominance

One trait completely hides the other (e.g., brown eyes over blue eyes).

Incomplete Dominance

The traits blend to produce an intermediate appearance (e.g., red + white flowers = pink flowers).

Codominance

Both traits are fully expressed at the same time (e.g., AB blood type).

SEX-LINKED INHERITANCE

- Pattern of inheritance in which certain characteristics carried on the X chromosome inherited from the mother are transmitted differently to her male and female offspring.

- Because males (XY) have only one X chromosome, they are more likely to express X-linked disorders

XYY

- Its characteristics are Male; tall stature; tendency toward low IQ, especially verbal

-Its incidence are 1 in 1,000 male births

- No special treatment

XXX (triple X)

- Its characteristics are a Female, normal appearance, menstrual irregularities, learning disorders, and intellectual disability

- Its Incidence 1 in 1,000 female births

- Its treatment is Special education

XXY (Klinefelter)

- Its characteristics are Male; sterility, underdeveloped secondary sex characteristics, small testes, and learning disorders

- its incidence 1 in 1,000 male births

- Its treatments are Hormone therapy, special education

XO (Turner)

- Its characteristics are Female; short stature, webbed neck, impaired spatial abilities, no menstruation, infertility, and underdeveloped sex organs

- Its incidence is 1 in 1,500 to 2,500 female births

- Its treatment is hormone therapy and special education

Fragile X

- Its characteristics: Minor-to-severe intellectual disability, more severe in males; delayed speech and motor development, hyperactivity; the most common inherited form of intellectual disability

- Its incidence: 1 in 1,200 male births; 1 in 2,000 female births

- Its treatment Educational and behavioral therapies when needed

Passive Correlation

Example: Parents who love reading pass on genes related to verbal ability and also fill the home with books.

Evocative Correlation

Example: A naturally cheerful baby receives more smiles, attention, and positive interactions from adults.

Active Correlation (niche-picking)

example: A child with a natural musical talent joins the school choir and practices music in their free time.

DOWN SYNDROME

- the most common chromosomal abnormality

- characterized by moderate-to-severe intellectual disability

- also called trisomy-21

CEPHALOCAUDAL

- ("Head to Toe")

- Development occurs from the head downward to the feet.

- Control and movement develop earlier in the head and neck.

- Later development occurs in the trunk, arms, and legs.

- Example: A baby can hold up their head before they can control their legs.

PROXIMODISTAL

- ("Center to Extremities")

- Development occurs from the center of the body outward to the hands and feet.

- Large muscles and central parts develop before smaller, outer parts. Example: A baby can move their upper arm before they can move their fingers.

GERMINAL STAGE (0-2 WEEKS)

- PERIOD OF THE ZYGOTE

What happens?

• Fertilization occurs.

• Zygote divides rapidly.

• Travels to the uterus.

• Implants in the uterine wall.

Think of it as: The beginning of life.

EMBYONIC STAGE (2-8 WEEKS)

- PERIOD OF THE EMBRYO

- Most vulnerable period to teratogens

- This is the most critical stage.

Major organs begin to develop:

• Brain , Heart, Eyes, Arms, Legs

- Because organs are forming, the embryo is highly vulnerable to

harmful substances.

FETAL STAGE (9 wks - birth)

- PERIOD OF THE FETUS

- Rapid growth and functional development

The fetus:

• Grows rapidly

• Gains weight

• Organs mature

• Begins moving

• Can hear sounds

• Practices breathing

- Most physical growth occurs during this stage.

IMPLANTATION

The blastocyst implants in the uterine lining.

EMBRYONIC STAGE 3 WEEKS

The neural tube, heart, and major organs begin to form.

EMBRYONIC STAGE 5 WEEKS

- Heart starts beating.

- Limb buds and facial features appear.

EMBRYONIC STAGE 8 WEEKS

- All major organs are present.

- Embryo is about 2.5 cm long.

FETAL STAGE 12 WEEKS

- Fetus is active.

- Fingernails, eyelashes and external organs are developed.

FETAL STAGE 20 WEEKS

- Mother may feel "quickening".

- Fetus can hear and suck thumb.

FETAL STAGE 28 WEEKS

- Body systems continue to mature.

- Higher chance of survival.

Prenatal development

begins at fertilization and continues until birth.

embryo

forms the body structures.

Arms and legs

- appear by 4-5 weeks.

- Organs continue to develop and mature.

TERATOGENS

- (Substances/Factors that may harm the developing baby)

- Harmful substance affecting prenatal development

alcohol

smoking

drugs

certain medications

infections

radiation

(6) types of TERATOGENS

Heredity

Traits inherited from parents

Environment

External influences on development

Embryo

Developing baby from 2-8 weeks

Fetus

Developing baby from 9 weeks until birth

Prenatal Care

Medical care during pregnancy