Flashcards in 1a.emvriologia-Important genes of embryogenesis-Early fetal development-Gastrulation Deck (26)
What is the gene that is expressed at the base of limbs in a zone of polarizing activity?
Sonic hedgehog gene
The sonic hedgehog gene regulates patterning along the ____ (anterior-posterior/cranial-caudal) axis
For a newborn with a known sonic hedgehog gene mutation, what is the most likely abnormal finding?
Name two genes expressed at the apical ectodermal ridge (the thickened ectoderm at the distal end of each developing limb).
Wnt-7 and FGF
What is the gene responsible for proper organization along the dorsal-ventral axis?
What gene is responsible for the lengthening of limbs?
You observe that there is insufficient mitosis of underlying mesoderm in an embryo, and the limbs are short. What gene could be defective?
FGF (it stimulates mitosis of the underlying mesoderm and provides limb lengthening)
You notice defects in segmental organization in the cranial-caudal direction in an embryo. What gene could be mutated?
Homeobox (Hox) genes
You observe an embryo that is notable for the presence of appendages in several wrong locations. Which gene is likely mutated?
Homeobox (Hox) genes
What is formed when a sperm fertilizes an ovum?
The zygote (formation of the zygote defined as day 0)
At what stage of development does implantation in the uterine wall occur? What important hormone secretion also begins at this time?
The blastocyst stage (it 'sticks' at day 6); hCG secretion
You observe that an embryo exists as a bilaminar disc. How many weeks old is the embryo?
2 weeks = 2 layers (bilaminar disc consists of the epiblast and the hypoblast)
You observe that an embryo exists as a trilaminar disc. How many weeks old is the embryo?
3 weeks = 3 layers
The neural plate of an embryo is starting to form. How many weeks old is the embryo?
You observe initial development of the notochord, primitive streak, and mesoderm and its organization. How many weeks old is the embryo?
In an embryo, the neural tube forms from the neuroectoderm and closes by how many weeks?
A patient asks at which time period is her baby most susceptible to teratogens. What do you tell her?
You observe heartbeat in an embryo. During what week of development does the heart of an embryo begin to beat?
You observe upper and lower limb buds appearing in an embryo. Approximately how many weeks old is the embryo?
Week 4 (4 weeks = 4 limbs)
When is fetal cardiac activity first visible by transvaginal ultrasound?
A patient wants to know the sex of her fetus. During which week of development can the first male/female characteristics be distinguished?
During embryonic development, what event occurs around days 6–10?
Implantation in the uterine wall
You observe that a zygote has divided into a morula. How many days after fertilization does this event occur?
In embryology, what is gastrulation?
Process that forms the trilaminar embryonic disc
Name the three germ layers established by the process of gastrulation.
Endoderm, mesoderm, and ectoderm