During embryonic development, what event occurs on day six?
Implantation in the uterine wall
What is the gene that is expressed at the base of limbs in a zone of polarizing activity?
Sonic hedgehog (SHH) gene
The sonic hedgehog gene regulates patterning along the _____ (anterior-posterior or cranial-caudal) axis.
Name 2 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?
Which embryonic layer responds to products of the FGF gene?
How does the FGF gene cause limbs to lengthen?
It stimulates mitosis of the underlying mesoderm
What phenotype would be seen if there was a mutation in the homeobox gene?
There would be defects in segmental organization
Day 0 of fetal life is marked by the _____ of an ovum by a sperm.
What is formed when a sperm fertilizes an ovum?
At what stage of fetal development does implantation occur?
The blastocyst stage
The embryo exists as a _____ disk during the second week of development.
What two layers make up the bilaminar disk?
The epiblast and the hypoblast
During fetal development, the process of _____ occurs during the third week, which gives rise to a trilaminar disk.
If an embryo has a notochord and the neural plate is beginning to form, how many weeks old is the embryo?
3 weeks old
If an embryo has a primitive streak, how many weeks old is the embryo?
3 weeks old
During what part of embryonic development does organogenesis occur?
In an embryo, the neural tube forms from a neural plate between which days?
The embryo is most susceptible to teratogens during what time period?
During what week of development does the heart of an embryo begin to beat?
During what week of embryonic development do the upper and lower limb buds begin to form?
When is the first time the fetus begins to move and looks like a baby?
During what week of development do embryos first have genitalia with either male or female characteristics?
During embryonic development, what stage begins on day 2?
The zygote stage (2 haploid cells form a single diploid cell)
During embryonic development, what stage begins on day 3?
The morula stage (morula is latin for mulberry and occurs after the 16-cell stage)
During embryonic development, what stage begins on day 5?
The blastocyst stage (containing an outer layer of cells and an inner cell mass)
During embryonic development, what event occurs on day 6?
What embryonic structure implants itself into the uterine wall on day 6?
After the primitive streak, name three structures formed by neural precursor tissue.
Neural plate, neural crest, and neural tube