Lec 27: Development & Heredity

What is the first step in the process of development?

Fertilization (union of egg and sperm)

What are the two primary periods of development?

Prenatal development and postnatal development

What occurs during the pre-embryonic period?

Fertilization, cleavage, and blastocyst development (Weeks 0-2)

What major events occur during the embryonic period?

Gastrulation and organogenesis (Weeks 3-8)

What is the duration of the fetal period?

From Week 9 to birth (approximately 40 weeks)

What is cleavage in the context of embryonic development?

Rapid mitotic events after zygote formation, leading to smaller daughter cells.

What is a blastocyst?

A structure formed from the morula that contains an inner cell mass and a trophoblast.

What is the role of the trophoblast?

It forms the wall of the blastocyst and develops into the outer chorionic sac.

What is implantation?

The process where the blastocyst embeds in the endometrium, occurring around 6 days after fertilization.

What hormone does the blastocyst secrete to maintain pregnancy?

Human chorionic gonadotropin (HCG)

What are the four extraembryonic membranes?

Chorion, allantois, yolk sac, and amnion.

What is the function of the placenta?

It allows diffusion of gases, nutrients, and wastes between maternal and embryonic bloodstreams.

What is gastrulation?

The formation of three distinct germ layers (ectoderm, mesoderm, endoderm) around Day 15.

What does organogenesis refer to?

The development of major organs during the embryonic period.

What is neurulation?

The embryonic development of the central nervous system, forming the neural tube.

What are somites?

Blocks of mesoderm that form vertebrae, muscles, and connective tissues.

What significant changes occur during the 4th to 8th weeks of development?

All major organs develop, the embryo triples in size, and limbs begin to form.

What happens to the digits of hands by the end of the 8th week?

The digits are short and webbed, but the webbing dies through apoptosis.

What is the significance of the 12th week in placentation?

By this time, the placenta has two well-developed parts: fetal portion and maternal portion.

What physiological adjustments must a newborn make in the first hours of life?

The newborn must adapt to breathing air, feeding, and regulating body temperature.

What are the major impacts of STDs on development?

STDs can cause complications during pregnancy and affect fetal development.

What are the different patterns of inheritance?

Patterns include autosomal dominant, autosomal recessive, X-linked, and mitochondrial inheritance.

What is the role of progesterone during pregnancy?

It makes the endometrium suitable for implantation and maintains the pregnancy.

What is parturition?

The process of childbirth or delivery.

What is the average duration of gestation?

Approximately 266 days or 40 weeks.

What is the result of fertilization?

The formation of a single diploid zygote.

What are identical twins?

Twins that result from the complete splitting of the morula.

What are fraternal twins?

Twins that occur when two eggs are released and fertilized by different sperm.

What forms the maternal portion of the placenta?

Decidua basalis of the endometrium

What is the function of the umbilical arteries?

Carry deoxygenated fetal blood to the placenta

What does the umbilical vein do?

Carries oxygenated blood away from the placenta

What is the protective capability of the placenta?

Not a completely protective barrier; allows microorganisms, drugs, and alcohol to pass

What is the term for the detachment of the placenta after birth?

Afterbirth

What are the three stages of prenatal development?

Pre-embryonic period, Embryonic period, Fetal period

What occurs during the embryonic period?

Gastrulation and organogenesis (Weeks 3 to 8)

What significant development occurs around week 10 of the fetal period?

Differentiation of male structures begins

What is the anatomy scan, and when does it occur?

A detailed ultrasound scan to determine anatomical anomalies and sex, typically at week 20

What is allometric growth?

Body parts grow at different rates during the fetal period

What are the three shunts in fetal circulation?

Foramen ovale, Ductus arteriosus, Ductus venosus

What is the function of the foramen ovale?

Allows placental blood to bypass the lungs, going from the right atrium to the left atrium

What does the ductus arteriosus do?

Bypasses the lungs by sending blood from the pulmonary artery to the aorta

What is the role of relaxin during pregnancy?

Increases flexibility of the pubic symphysis and helps dilate the cervix during labor

What happens to maternal blood volume during pregnancy?

Increases by 30% to 50% to support the growing fetus and placenta

What hormone is involved in uterine contractions during labor?

Oxytocin

What are the stages of childbirth?

Dilation, Expulsion, Placental

What is the dilation stage of labor?

Starts with first contractions and ends when the cervix is fully dilated (10 cm)

What occurs during the expulsion stage of labor?

Ejection of the fetus, starting when the cervix is fully dilated

What is a cesarean birth?

A surgical procedure with an abdominal incision to remove the fetus and placenta

What are congenital disorders?

Birth defects affecting ~3% of babies born, causing 20% of infant deaths in the US

What is a teratogen?

A substance that can cause birth defects, such as drugs or infections

What is vanishing twin syndrome?

A type of miscarriage in multiple pregnancies where one twin stops developing and is absorbed

What is the age of viability?

The age at which a fetus can survive outside the womb, typically around 22-24 weeks

What percentage of babies born in the US are premature?

Over 12% are born before 38 weeks

What is the significance of the 20-week anatomy scan?

It helps determine anatomical anomalies and the sex of the fetus

What is the medical term for miscarriage?

Spontaneous Abortion

What is abstinence in the context of birth control?

Refraining from sexual activities, which protects from STDs.

What is sterilization in birth control?

Cutting or sealing the reproductive tract, which provides no STD protection.

What is a vasectomy?

A surgical procedure that cuts the vas deferens, sometimes reversible soon after.

What is tubal ligation?

A surgical procedure that seals the fallopian tubes, usually not reversible.

What is hormonal contraception?

Using hormones to affect ovulation and the uterus.

What hormones are commonly used in combination contraception?

Estrogen and progesterone.

What is the purpose of estrogen and progesterone in birth control?

To prevent the surge in estrogen that triggers LH/FSH release.

What is progesterone-only contraception?

Uses synthetic progesterone to thicken cervical mucus and may prevent ovulation.

What is the function of spermicide?

Kills sperm before fertilization can occur.

How long do foams, creams, and jellies spermicide last?

Approximately 1 hour.

What is the duration of effectiveness for Copper IUDs?

Up to 10 years.

What is YCT-529?

A male birth control pill currently in human clinical trials.

What are barrier methods of birth control?

Methods that prevent sperm and egg contact, such as condoms and diaphragms.

What is the rhythm method in birth control?

Also called fertility awareness, it avoids the days when fertilization is most likely.

What are emergency contraceptive pills?

Hormonal pills taken after unprotected intercourse to prevent pregnancy.

What is colostrum?

The first milk produced after birth, rich in nutrients and antibodies.

What hormone stimulates milk production?

Prolactin.

What initiates the milk ejection reflex?

Oxytocin, stimulated by suckling or hearing a baby cry.

What is the Apgar score?

A score calculated to evaluate the physical status of a newborn at 1 and 5 minutes after birth.

What are the stages of human life?

Infancy (birth - 12 mo), Childhood (13 mo - 12/13 yrs), Adolescence (puberty - late teens), Adulthood (remainder of life).

What are some causes of aging?

Reduction of cell division, DNA damage, and various genetic, environmental, and lifestyle factors.

What is the current life expectancy in the US?

Approximately 79 years.

What is the definition of homozygous?

Individuals with two copies of the same allele.

What is the definition of heterozygous?

Individuals with different alleles of a given gene.

What is a dominant allele?

An allele whose effects are detected regardless of the alternative allele.

What is a recessive allele?

An allele whose effects are masked in the heterozygous condition.

What is the difference between genotype and phenotype?

Genotype refers to the alleles present for a gene, while phenotype refers to observable traits.

What is an allele?

Different forms of a gene that produce different versions of a trait.

What is a karyotype?

A karyotype shows 46 chromosomes arranged in pairs by size and centromere position.

How many pairs of autosomes do humans have?

Humans have 22 pairs of autosomes.

What are the sex chromosomes for females?

XX

What are the sex chromosomes for males?

XY

What is nondisjunction?

Nondisjunction is the failure of chromosomes to separate during meiosis or mitosis.

What can result from nondisjunction?

It can result in gametes that are polypoid or nullisomic (no chromosomes).

What is Turner's syndrome?

Turner's syndrome (X0) is a condition characterized by a missing or incomplete X chromosome.

What is Klinefelter syndrome?

Klinefelter syndrome (XXY) is a condition characterized by the presence of an extra X chromosome.

What is De la Chapelle syndrome?

De la Chapelle syndrome occurs when an individual is born with XX chromosomes but develops male characteristics.

What is Swyer syndrome?

Swyer syndrome occurs when an individual is born XY but develops female characteristics.

What is a chromosomal deletion?

A chromosomal deletion is the loss of a piece of a chromosome.

What is cri-du-chat syndrome?

Cri-du-chat syndrome is caused by a deletion of a piece of chromosome 5.

What is a chromosomal duplication?

A chromosomal duplication is the addition of a piece of a chromosome.

What is Fragile X syndrome?

Fragile X syndrome is caused by a duplication of a region on the X chromosome.

What is the purpose of prenatal genetic testing?

Prenatal genetic testing is recommended when a defective gene runs in the family or if the mother is older than 35.

What is amniocentesis?

Amniocentesis is an invasive procedure that samples amniotic fluid to examine fetal cells for chromosomal abnormalities.

What is chorionic villi sampling (CVS)?

CVS is an invasive procedure that samples a small piece of chorionic villi to examine chromosomes.