Exam 2 Developmental Psychology

A. Genetics

1. Chromosomes

a. Number of chromosomes and pairs for each (autosomes and sex chromosomes)
Humans have 46 chromosomes in total, arranged in 23 pairs. These are divided into:

• Autosomes: 22 pairs of chromosomes (numbers 1-22), responsible for most traits and genetic functions.

• Sex chromosomes: 1 pair of chromosomes (X and Y) that determine biological sex. Females typically have two X chromosomes (XX), and males have one X and one Y chromosome (XY).

b. Chromosomal variations
Chromosomal variations can occur due to structural changes or the number of chromosomes. Some examples include:

• Down syndrome: Caused by an extra copy of chromosome 21 (trisomy 21).

• Turner syndrome: Females with only one X chromosome (45,X).

• Klinefelter syndrome: Males with an extra X chromosome (47,XXY).

• Fragile X syndrome: Caused by a mutation in the X chromosome, often leading to intellectual disabilities.

2. Genotype and Phenotype

• Genotype: The genetic makeup of an individual, consisting of all the alleles inherited from both parents. For example, having one allele for brown eyes and one for blue eyes would give a genotype of "Bb."

• Phenotype: The observable traits or characteristics of an individual, which are influenced by the genotype and the environment. This includes things like eye color, height, or susceptibility to certain diseases.

3. Additive genes vs. dominant-recessive heredity

• Additive genes: These genes contribute to the phenotype in a cumulative way. For example, skin color or height can be influenced by multiple genes, each contributing a small amount to the overall trait.

• Dominant-recessive heredity: In this pattern of inheritance, one allele is dominant (will express its trait even if only one copy is present) and the other is recessive (will express its trait only if both copies are recessive). For example, the allele for brown eyes (B) is dominant over the allele for blue eyes (b). A person with the genotype "Bb" will have brown eyes.

4. Epigenetics

Epigenetics refers to changes in gene expression that do not involve alterations in the DNA sequence itself. These changes can be influenced by environmental factors such as diet, stress, and toxins. Epigenetic modifications can be heritable and affect how genes are turned on or off, influencing development, health, and disease susceptibility.

B. Prenatal Development and Birth

1. From gamete to zygote to blastocyst

a. Fertilization time and place
Fertilization typically occurs within 24 hours of ovulation in the fallopian tube when a sperm meets an egg. This forms a single-celled zygote, the first stage of human development.

b. Implantation: where and when
The zygote divides and forms a blastocyst (a hollow ball of cells). The blastocyst implants itself into the uterine lining (endometrium) about 6-10 days after fertilization.

c. Cell division and differentiation
After implantation, cells continue to divide and differentiate into various types of cells (such as skin, muscle, or nerve cells) as the embryo develops. This is essential for forming all the body systems.

2. Periods of prenatal development

a. Germinal Period (Weeks 1-2)
The germinal period starts with fertilization and ends with implantation in the uterus. During this time, the zygote rapidly divides and forms a blastocyst, which embeds itself into the uterine wall.

b. Embryonic Period (Weeks 3-8)
This period involves the development of the major organ systems. By the end of the embryonic period, the embryo has a human-like appearance with recognizable features such as a beating heart, limb buds, and facial characteristics.

c. Fetal Period (Weeks 9-38)
The fetal period involves growth and maturation of the organs and systems. The fetus grows larger, gaining weight, and its organs become more functional. By the end of the fetal period, the baby is ready for birth.

3. Cephalocaudal and proximodistal growth principles

• Cephalocaudal principle: This principle describes the tendency for development to proceed from head to tail. The head and brain develop first, followed by the rest of the body.

• Proximodistal principle: This principle states that development starts at the center of the body and moves outward toward the limbs. For example, the torso develops before the hands and feet.

4. Age of viability

The age of viability refers to the point in fetal development (around 24 weeks of gestation) when the fetus has a chance of surviving outside the womb, with medical support. At this stage, the lungs and other critical organs are developed enough for the baby to potentially survive if born prematurely.

5. Effects of teratogens on the embryo/fetus and considerations for likelihood of harm

Teratogens are harmful substances or agents that can cause birth defects if a mother is exposed to them during pregnancy. The likelihood of harm depends on the timing of exposure, the dose, and the genetic vulnerability of the fetus. Examples of teratogens include:

• Alcohol: Can cause fetal alcohol syndrome, leading to cognitive and physical developmental delays.

• Drugs: Certain medications, illicit drugs, or tobacco use can harm the fetus.

• Infections: Viruses like Zika can cause birth defects.

• Environmental factors: Exposure to harmful chemicals or radiation.

C. Birth and the Newborn

1. 3 stages of childbirth and how labor is initiated

Labor stages:

• Stage 1 (Dilation): This stage involves the cervix dilating to allow the baby to pass through the birth canal. It consists of early labor (cervical effacement and dilation) and active labor (rapid dilation and stronger contractions).

• Stage 2 (Delivery of the baby): This stage involves pushing and the actual delivery of the baby.

• Stage 3 (Delivery of the placenta): The placenta is delivered after the baby is born.

Labor initiation: Labor is initiated when the body releases hormones like oxytocin, which trigger uterine contractions. This process also involves the release of prostaglandins and a decrease in progesterone, which help to soften the cervix.

2. Newborn assessment: Apgar scale

The Apgar scale is a quick assessment tool used to evaluate the newborn's health immediately after birth. It measures five criteria on a scale from 0 to 2, with a total score out of 10:

• Appearance (skin color)

• Pulse (heart rate)

• Grimace response (reflexes)

• Activity (muscle tone)

• Respiration (breathing rate)

Scores of 7-10 indicate good health, while scores below 7 suggest the need for medical intervention.

3. At-risk newborns

a. Low birthweight classifications
Low birthweight is defined as a baby weighing less than 5.5 pounds (2500 grams) at birth. It can be due to premature birth or intrauterine growth restriction.

b. Small for gestational age (or small-for-date)
A small-for-date baby is one whose birth weight is significantly below the average for their gestational age, often due to factors like poor maternal health, placental insufficiency, or genetic factors.

c. Kangaroo care
Kangaroo care is the practice of holding a newborn skin-to-skin, which helps regulate the baby’s temperature, promotes bonding, and improves overall health outcomes, particularly for preterm infants.

4. Breastfeeding benefits and challenges

Benefits:

• Provides ideal nutrition for the newborn, including antibodies that boost the immune system.

• Promotes mother-baby bonding.

• Reduces the risk of infections and illnesses in infants.

• Can benefit the mother's health, reducing the risk of breast cancer and promoting postpartum recovery.

Challenges:

• Some mothers may experience difficulties with latch, milk supply, or discomfort.

• Workplace or social barriers can make breastfeeding challenging.

• Some medical conditions may prevent breastfeeding.