Chapter 6- Embryology

All embryos start from a single parent cell pairing, which becomes a blastocyst, which then attaches to (hopefully) the right place in a mother's uterus, and a flat disk with two layers forms. The disk rolls into a double tube, and three layers of tissue differentiate. The top layer forms the ectoderm, the middle the mesoderm, and the inner the endoderm. The inner tube becomes our guts and inner organs, the outer tube becomes our skin and nervous system, and the middle layer becomes our skeleton and muscles. At one point, there exists a region of tissue can Organize cells into all three layers. Hilde Mangold was responsible for grafting a piece of such tissue onto a newt embryo, creating a twin out of the graft. Organizers from animals can be placed into different species and function properly.

Sex linked and pedigree

Some genes are sex linked, which means that they occur on an X chromosome such that only when there is no other x chromosome, the trait will show. Which means males are more likely to show the trait than females.
when doing problems on sex linked genetics, always label whether the genes are on an X chromosome, and whether the individual has a y chromosome.

this is useful in pedigrees because we can easily see all the genders and genetic identities of individuals. We can then find whether the trait is dominant, recessive, sex linked, or not.

More Complexity

You can have two or three traits going on at the same time. 

all you need to do is either create gametes and do a big chart

or cross the two traits separately and multiply each combination. 

both ways work, but I personally prefer separating traits and multiplying because it's fast and you can choose to only determine a couple of phenotypes. for the big chart it's necessary to finish the chart, which sometimes gives you excess information.