Day 24-Genetics

Today we learned about genetics. We learned how genes are used to express a physical trait, which can either be dominant or recessive. There are two types of cells: a sex cell called a gamete, which is a sperm and an egg, and a somatic, which is a body cell. The two go through totally different processes to get to their chromosome. Gametes go through meiosis, where only 1 set of chromosomes is produced. Somatic go through mitosis, where an exact copy of the cell is produced.

We also learned how to solve genetics problems. Here are the steps:

1. Write down the info. For example, Dominant=A=trait.
2. Parenting genotype. Aa x Aa.
3. Law of segregation. For example, Aa splits up into A and a.
4. Punnett square. See example on the left.
5. Fill in the square. Below the empty is one that is filled in.
6. Create your ratios. For example, on the right, the phenotype ratio is 3 dominant :1recessive. The genotype ratio would be 1AA:2Aa:1aa.

Day 20-Handy Genes

Summary for Your Inner Fish CH3

Although it is interesting that we can trace homologous structure back to common ancestors, it is very interesting that we can trace back the gene frequencies, finding the small changes which result in easily visible differences between species today. Our bodies are formed from one single cell, which carries the plans for our entire body. Within this cell is all of the DNA which is passed from our parents, from their parents and so on. DNA makes up genes, which make up chromosomes, which make up cells, which turn into a body. Hands are very complex structures, which contain three different dimensions: thumb and pinky side, top and bottom, and tip and base. The million dollar question is what change in DNA causes these differences. The answer lies in the embryo, but is impossible to study this on human embryos, so the answer was chickens. A number of biologists did countless hours of work with chicken eggs to prove that each small change within the embryo causes a major difference in the mature body.