i do not know why, topics regarding the control of developmental gene is just something that does not stick in my head, no matter how many time i read the information over and over again.
so can some help me and give me a easy and short explanation for the DAT.
I'm guessing that by developmental genes you're referring to the HOX genes. These are genes that control the development of specific body segments. For example, if you watch a time lap movie of Drosophila development, you'll realize that early on during development the embryo starts getting segmented. This segmentation is the result of expression of different Hox genes at different regions of the body. This expression determines what each segment of the body should become. Furthermore, after this general plan is laid out, other Hox genes within each segment are expressed, allowing the details of that segment to get developed. For example, if Hox gene#1 (Hypothetical gene) get's expressed in specific region of the body, it causes that region to develop into the head of the animal. Next, Hox gene#1 promotes the expression of Hox gene#2 in the head region. This 2nd gene allows the development of the antenas in the head region. Notice that if gene#1 doesn't get expressed, then gene#2 won't be expressed either, since Hox genes control each other's expression. The reason why we're confident that Hox genes control body segmentation and specialization is that if you expressed gene#2 in the abdomenal region of the body, then antenas start developing in that region, indicating that gene#2 is indeed in control of antena development. Interestingly, Hox genes' loci are arranged in the same order that they are expressed, on the DNA.
also i do not understand the following, so please help me with those if you could.
BIG THANKS.
pecking order>>refers to the social hierarchy within various groups of organisms. For example, you have the dominant alpha male at the top of the pecking order and more submissive males that fall underneath the alpha male.
DNA vectors (bacterial vs viral)>>DNA vectors are plasmids that are used to transfect a particular cell. Plasmids are essentially circular DNAs. Using restriction enzymes one can insert a particular gene into these plasmids. Once this is done, the plasmid can be forced into bacterial cells (via electrical shock and/or heat shock). Once inside, the cell's machinery will transcribe the gene located on that plasmid and produce the product. Viral vectors are essentially segments of viral DNA. Remember that viruses can have RNA as their genetic material as well (Retroviruse). Unlike plasmids that are transcribed independent of the host cells genome, viral vectros become incorporated into the host's genome. Then, they can either get transcribed along with the host's genome, or they can remain in a dormant state for long periods of time.
disruptive selection>>It's a form of selection that favores the two extreme genotypes within the population. Consider a population of rabbits. These animals can be White, Black, or anything in between. If the environment's background colors is comrprised of very bright and very dark colors, then individuals with white and black colors survive much better due to their superior camuflauge capabilities. Subsequently, the gene frequency corresponding to these two extremes rises within the population, while the frequency of the genes corresponding to the intermediate phenotypes drops significantly (rabbits with intermediate genotypes simply cannot camoflauge as well in such environment).
and impulse transmission.