Day 25: Using Microscopes/Chapter 6

Today we learnt how to properly use  microscopes while learning about cells. We looked at some really cool things. We looked at our cheek cells, plant cells, and cells from the creatures from our aquarium.

Here is a picture from the digital microscope we have and it shows the chloroplast in the plant cells.

Chapter 6 from Your Innner Fish was about how scientists like von Baer and Haeckel studyed embroylogy. embroyology is the study of embroyos whic we briefly discussed in the study of evolution and how embryos at an early stage in a lot of life forms shows the close links between us and pigs for example. There can be three layers to an embroy the endoderm, the mesoderm, and the ectoderm. Each layer is where diferrent organs start to develop from that starts at four weeks after
conception.

A embryologist named Spemann later experimented with embryos and found something really
intresting.He split an embryo of a newt and sepreated it and found that in both pieces a complete viable newt grew. Later his student Mangold cut a piece off of an embroyo that contained the important three germ layer. Mangold moved it and a newt  was formed with two heads. This patch was known as the organizer. People then later looked at DNA especially in flies and saw that the DNA was organized. There was points where there is DNA for devleopment like for the head and then the body all in an order. They looked at this sequence and it was nearly identical in every species and the sequence is called homeobox and the eight genes that contain this homeobox are called hox genes. Scientists were looking for these hox genes in a frog and noticied a gene in the organizer that affect embryo development. Another gene was found called Noggin that did what the organizer did and duplicated a head on a species. Noggen and the hox genes play a role in the organizer.

This is what the newt can look like after the organizer gene is transplanted:

Day 24: Unit 4 Test

We took a test today that included:

• mendelian genetics
• monohybrid crosses 
• dihybrid crosses
• pedigrees
• sex-linked genetics 
• meiosis (brief)

Day 23: Pedigrees

We learned how to analyze the pedigrees of generations to discover whether a condition is sex-linked or autosomal.

This is an example of a pedigree they use roman numerals on the side for each generation and numbers left to right. This pedigree is autosomal because the number affected is not higher than 50% in offspring of the a certain sex. It is also recessive because none of the II offspring showed this trait.

Day 22: Sex-linked genetics

Sex-linked genetics is when an gene is passed on thru the male or female parent (linked to the chromosomes) to the new generations and can be found on the X chromosome for example when a black female (X^B X^B) and an orange male cat (X^bY) are crossed. The result would be a tortoise shell female or a black male because of this offspring possibilities produced:

XBXb	XBXb
XBY	XBY

Day 21: Dihybrid in Genetics

Dihybrid crossing of alleles is when there are two traits that each parent has. For example in flies there can be a yellow body color that is dominant allele( B) or a black color that is recessive (b) and there can be a red eye color that is dominant (E) and a black eye color that is recessive (e). This picture is the cross of the F1 generation of parents with heterozygous mixes of the body color and eye colors BbEe and BbEe.

Monohybrid crosses in Mendelian Genetics

Today in class we practiced monohybrid crosses of genes and alleles. They can look like this:

or like this:

It doesn't really matter which direction this four square is turned the outcomes will be the same. In these two examples the cross was between heterozygous genes which are a mix of a dominant and a recessive allele (this is review from the Hardy-Weinberg). This monohybrid cross of genes however can be between homozygous recessive (aa) and dominant (AA) as well.

There are phenotype ratios which are 3:1 for the heterozygous examples shown above because three displayed a purple flower or a smooth pea and one did not.

The genotype ratio, however was 1:2:1 this means there are one set homozygous for dominant alleles and there is two heterozygous and one for a set of homozygous recessive alleles.