Genetics

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Before we even begin to talk about genetics and heredity, you must have a basic understanding of cells. Cells make up who we are; literally. Cells make up our body's tissue, which makes up our organs, which makes up our organ system. Every living thing has cells; both plants and animals have this. Cells are like little "bodies", as they have "organs", too. These organelles are what allow cells to function, which in turn allows us to function. Plant and animal cells have the same general organelles, though there are some differences, like the fact that plant cells have chloroplast, while animal cells do not. Now, there are plant and animal cells, right? Right; we established this. But there are deeper aspects of grouping cells, besides this.

Let's take a look at an animal system. This cell belongs to a... let's say dog. This mother is all grown up, but still, her cells divide and complete their routine functions. This describes interphase. But how do cells divide? How do her fur cells divide, making her furrier in the winter? Well, this is due to something called Mitosis. Mitosis is where any cell EXCEPT sex cells divide. Use PMAT to remember the order, but by now, you should already know this. If Mitosis is the generation of cells except from sex cells, then WHAT process produces sex cells? Well, unfortunately, it sounds quite similar! This results in diploid cells, which have two sets of chromosomes. This process is called Meiosis. This is how a female's egg and a male's sperm, are made; these are also known as Gametes. There are the same steps as PMAT though with slight differences, and the most important thing for you to remember is that it splits like Mitosis, but it occurs again, results in 4 haploid cells, meaning 4 cells that have 23 chromosomes. Actually, the PMAT steps are different; there are two processes: P1 M1 A1 T1 and P2 M2 A2 T2. Remember that mother dog? Well, she reproduced this way! Her egg was fertilized by her male counterpart's sperm, so she gave a successful birth to three little puppies. This means her puppies were produced sexually; with two parents. Asexual organisms reproduce with one parent. Some organisms can reproduce in both ways!

Now, finally, you are caught up. Let's go over genetics! Let's say there is a woman. She has red hair. She falls in love and gets married to a brown-haired man. They give birth to 4 children in total. 3 of the children have brown hair, and only one has their mother's red hair. Why wasn't there an equal ratio of children with brown and red hair? This is due to dominant and recessive traits. Dominant traits are common traits that most people have, that stand out. An example of this would be "DD", as capital letters represent dominant traits. But what if someone has a recessive trait as well? Well, then this person would have "Dd", lowercase letters representing recessive traits. But what even ARE recessive traits?! Recessive traits are more uncommon traits that are masked if a dominant trait is present, like the case with Dd. That person would have brown hair. But what if they have two recessive traits, or "dd"? Then, this child would have red hair, in this example. The traits given and the letters vary, on questions. If someone has two dominant traits this is "homozygous dominant" as homo = same. If some has two recessive traits, they are "homozygous recessive" and for the same reason. If they have a dominant AND recessive trait, then they are just "heterozygous". This information can be plotted into a Punnett Square; look it up! They are squares in which you graph these traits to predict offspring, in a way, by recording the mother's and father's genotype. What's a genotype? Genotype is simply those letter combinations we were discussing, like "Dd". Those letters represent alleles which are a variation of a gene. The genotype represents the phenotype, or the physical trait. The phenotype of the parents and children would be red and brown hair.

Punnett Squares are simple; hopefully, you have learned how to solve them. Another chart-type thing you will see in your genetics unit is pedigrees. In a pedigree, you solve problems regarding the chart. You have a circle (female) and a square (male). If they have a horizontal line between them, they are married -- this is the marriage line. If there is a line below this, connecting to more females and males, those are their children. The lines connected to the children represent being of relation (siblings) but there is also a marriage line for when they reproduce. And when this happens, they have children, too. If a shape is colored in fully, they fully have the trait. If it is half shaded, then the person is a carrier of the trair