Development and Genetics Questions Part 2

Section I: Embryonic Disc and Germ Layers

• The embryonic disc consists of the epiblast and hypoblast.
• The amniotic cavity surrounds the developing embryo, creating a protective fluid bag.
• The ectoderm forms the epidermis and nervous system.
• The mesoderm forms the cardiovascular system and muscles.
• The endoderm forms the lining of the digestive and respiratory tracts.

Section II: Primitive Streak and Gastrulation

• The primitive streak is a band of migrating epiblast cells.
• The formation of the primitive streak signifies the start of germ layer differentiation.
• During gastrulation, the mesoderm lies between the ectoderm and endoderm.

Section III: Neural Tube and Somites

• The neural plate forms from the ectoderm.
• The neural crest differentiates into skeletal muscles and sensory neurons.

Section IV: Mesonephros and Gonadal Ridges

• The mesonephros is a precursor to permanent kidneys.
• The gonadal ridges give rise to testes or ovaries.
• Primordial germ cells migrate to the gonadal ridges.

Section V: Parturition

• The first stage of labor is the dilation stage.
• Uterine contractions are triggered by the release of oxytocin.
• The placental stage involves the expulsion of the placenta.

Section VI: Newborn Adaptations

• The foramen ovale is a structure that allows blood flow between the atria in the fetal heart.
• Meconium is a mixture of bile, cells, and mucus excreted by the newborn.

Section VII: Lactation

• Milk release during breastfeeding is stimulated by oxytocin.
• Prolactin stimulates additional milk production.

Section VIII: Genetics

• A phenotype represents the physical expression of a trait.
• A homozygous genotype has two identical alleles for a trait.
• Incomplete dominance is when the dominant allele does not completely mask the recessive allele.

Section IX: Types of Inheritance

• Codominance is a type of inheritance where both alleles are expressed equally.
• Eye color is an example of a polygenic trait.
• Sex-linked inheritance is associated with X-linked traits.

Section X: Additional Questions

• The placenta exchanges nutrients and oxygen between the mother and fetus.

Section X: Genetics (Continued)

• A karyotype is a representation of homologous chromosome pairing, a map of all chromosomes in an organism.
• An individual with one dominant and one recessive allele for a trait is heterozygous.

Section XI: Development and Birth

• The umbilical cord connects the fetus to the placenta, providing nutrients and removing waste products.
• The yolk sac helps in the development of the embryo and forms primordial germ cells and blood cells.

Section XII: Newborn and Lactation

• The ductus arteriosus closes after birth creating the ligamentum arteriosum.
• Colostrum is the initial milk produced by the mammary glands, rich in antibodies.

Section XIII: Aging and Death

• Mitochondrial DNA function declines with age, reducing energy production.
• Skeletal muscle loses fibers with age.

Section XIV: Additional Concepts

• Neural crest cells migrate to form sensory neurons and melanocytes.
• The ductus venosus allows blood to bypass the liver in the fetus.