WK 5: Prenatal Development, Birth, and Infancy

Genotype

the genetic makeup of an individual, consisting of alleles inherited from both parents

Phenotype

• the outward expression of a trait (ex: hair color and height)

• determined by the genotype

Homozygous

having two identical alleles for a particular gene (ex: AA or aa)

Heterozygous

having two different alleles for a particular gene (ex: Aa)

Chromosomes

rod-shaped portions of DNA that are organized in 23 pairs

Sex chromosome

• a chromosome that determines the biological sex of an individual

• either XX for females or XY for males

• is the 23rd pair of chromosomes

DNA

• stands for deoxyribonucleic acid

• contains a bunch of genes

• function: determines the nature of every cell of the body and how it will function

Genes

• segments of DNA that contain genetic information

• they determine individual traits and characteristics

____ are the basic unit of genetic information.

genes

Zygote

a fertilized egg formed from the union of sperm and egg

What determines the gender of a child?

the X or Y chromosome that a Father’s sperm carries

Mendelian law of Inheritance

explains how traits are passed from parents to offspring through dominant and recessive alleles

Dominant trait

a genetic trait that is expressed phenotypically when two competing traits are present

Recessive trait

a trait that is present within an organism, but not expressed phenotypically (unless two copies of the recessive allele are present)

What are the two types of twins?

• identical (monozygotic) twins

• fraternal (dizygotic) twins

When does identical (monozygotic) twins result?

when a single zygote separates and develops into two embryos

When does fraternal (dizygotic) twins result?

when two separate ova are fertilized and form two embryos

Phenylketonuria

• A genetic disorder caused by the inability to metabolize the AA phenylalanine, leading to potential neurological damage if not managed.

• the person has to be on a strict diet for life

Sickle Cell Anemia

• a blood disorder that affects African Americans

• RBC shape is distorted and forms a crescent, leading to a variety of health problems

Tay-Sachs Disease

• a fatal neurological disease

• most people diagnosed don’t live past early childhood

• causes blindness, muscle degeneration, and death

X-linked Disorders

• are caused by genes only located on the X chromosome

• men have a higher risk of being affected (bc they only have one X chromosome)

What are some examples of X-linked disorders?

• Hemophilia: a bleeding disorder due to low levels of clotting factor

• Fragile X Syndrome: occurs when a particular gene is injured on the X chromosome

What is Down Syndrome caused by?

the presence of an extra 21st chromosome

What are examples of diseases caused by sex chromosome abnormalities?

• Klinefelter syndrome: caused by an extra X chromosome in males (XXY)

• Turner syndrome: results from a missing or partially missing X chromosome in females (X)

• Intersex: a condition where a person possesses both male and female characteristics

What is the purpose of genetic counseling?

to discuss a couple’s risk for having a child with hereditary disorders

Prenatal Testing

uses a variety of techniques to assess the health of an unborn child

Examples of prenatal tests

• Ultrasound

• Aminocentesis

• Chronic Villus Sampling (CVS)

Ultrasounds

use high frequency sound waves to create images of the unborn baby, measure its growth, and detect any abnormalities

Aminocentesis

• examines amniotic fluid to test for genetic abnormalities and fetal health

• performed around week 15-20 of pregnancy

Chronic Villus Sampling (CVS)

• a procedure that involves taking a sample of tissue from the placenta to test for genetic disorders and other fetal health issues

• performed between weeks 10-13 of pregnancy

CRISPR

a gene editing tool

Why might individuals respond differently to the same environmental stimuli?

bc of differences in genetic makeup

Epigenetics

the study of how environmental factors (such as diet, stress, and toxins) can influence gene expression

When does fertilization occur?

when a sperm and ovum combine to form a zygote

What are the stages of prenatal development?

• Germinal Stage

• Embryonic Stage

• Fetal Stage

Germinal Stage

• duration: fertilization to 2 weeks

• What happens? The zygote undergoes rapid cell division, the egg implants itself in the uterus lining, the cells form a protective layer, and the placenta provides nourishment and O2

Embryonic Stage

• duration: 2-8 weeks

• child is now considered an embryo

• What happens? the embryo’s major organs develop

• this is the sensitive period

Fetal Stage

• duration: 8 weeks until birth

• What happens? the fetus continues to grow and mature

• fetal movements can be felt

• sex determination is possible

When can a fetus’s sex be determined using NIPT, Ultrasounds, and Amniocentesis?

• NIPT: 10 weeks (2.5 months)

• Ultrasound: 12-14 weeks (3-3.5 months)

• Amniocentesis: 15-16 weeks (abt 4 weeks)

When is life outside the uterus possible / childbirth?

around 22-24 weeks

When is the age of viability?

22-24 weeks, the point at which life outside the uterus is possible

Teratogens

an environmental agent (such as a drug, chemical or virus) that causes a birth defect

Harm done by teratogens is affected by what?

• drug use and dosage

• genetics

• Mother’s age

Examples of teratogenic substances

• drugs (including prescription, non-prescription, and illegal)

• tobacco

• alcohol

• radiation

• environmental pollution

• infectious diseases

What are maternal factors that can affect prenatal development?

• a mother’s nutrition

• emotional stress

• age

• Rh factor incompatibility

• and lack of prenatal care

Older mothers have a ___ risk for a variety of pregnancy and birth complications than younger women.

greater

How can mothers’ maximize their chance of having a healthy baby?

by eating healthy, maintaining a healthy weight, and exercising

What are the steps of labor?

1. oxytocin is released

2. the cervix dilates

3. baby is born

4. placenta is delivered

A baby has high levels of stress hormones during labor. Why is this beneficial?

• it helps the baby withstand O2 deprivation

• prepares the baby to breathe

• and arouses the baby into alertness

Apgar Scale

a standard measuring system healthcare providers use to evaluate the health of an infant when they are first born

Pre-term

• occurs when an infant is born several weeks or more before their due date

• their weight may be appropriate for current length of pregnancy

What type of care is recommended if a baby is born prematurally?

Kangaroo care

Kangaroo care

a method of holding a premature infant close to the caregiver's chest for warmth and emotional bonding (it promotes health and weight gain)

Small-for-date

• is a term used to describe an infant whose birth weight is lower than expected for the gestational age

• baby may be pre-term or full-term

Hormones that facilitate caregiving:

• oxytocin

• prolactin

• estrogens

Hormonal effects of childbirth may depend on ___.

experience

What are some challenges new parents face?

adjusting to new roles and changed schedules (they lose sleep)

What is meant by the gene-environment interaction?

It refers to the complex interplay between genetic predispositions and environmental factors that shape an individual's development and behavior