The definition of genetics is the studying of genes
"Father of Genetics" A man named Gregor Mendel is considered the “Father of Genetics”. He spent his time as an Austrian monk who took care of the garden at the monastery where he resided. He began to observe the pea plants in the garden and would see how they would bloom as different colors. He began to get curious to find out why they bloomed as different colors. So his experiments began. He bred different flowers to see what kinds of colors and patterns could come about. He kept records of his experiments and soon noticed generations later of the repeating patterns that would take place in the offspring of the plants he would cross breed. This is basically how genetics was born and came to be.
Genetics is the study of traits being passed sexually from a parent to its offspring. This passing of traits is called heredity. A gene is the genetic information found in a person’s DNA. A gene is made up of two alleles that combine to form a gene. A set of alleles can either be made up of a recessive and a dominant allele, two dominant alleles, or two recessive alleles. If there is a recessive and a dominant allele, the gene’s phenotype will always be whatever the dominant allele is. If there is two dominant genes (homozygous dominant), the phenotype will also be whatever the dominant allele is. If there is two recessive genes (homozygous recessive), the phenotype will be whatever the recessive gene is.
Since there are so many different ways alleles can combine together, there were terms made to describe how the genes will come out when dominant, recessive, or both of the two are put together, One of the terms is the homozygous gene-which has the same exact types of alleles. The other term is heterozygous gene, which has one of each allele present. They can be remembered by their prefix, where homo means ‘same’ and hetero means ‘mixed’.
A set of alleles can either be made up of a recessive and a dominant allele, two dominant alleles, or two recessive alleles. If there is a recessive and a dominant allele, the gene’s phenotype will always be whatever the dominant allele is. If there is two dominant genes (homozygous dominant), the phenotype will also be whatever the dominant allele is. If there is two recessive genes (homozygous recessive), the phenotype will be whatever the recessive gene is.
Genotypes and Phenotypes
Each organism has a genotype and phenotype. The genotype is basically the genetic makeup of an organism and shows the patterns of our genes and alleles. The phenotypes is what we see physically. For example, if we are talking about someone's eye color and the genotype for their eye color is TT, then their phenotype would be described as brown eyes.
Punnett Square
The punnett square is used to determine the possibility of outcomes for genes when two alleles are crossed. It can be used to determine someone’s genotype and phenotype. It can also determine a person’s blood type and disabilities.
Example: A person who is tall has an offspring with someone who is short. The tall parent is heterozygous (Tt) and the short parent is homozygous recessive (tt).
Their children would have a 50% chance of being tall. ½: Tt heterozygous and a 50% chance of being short. ½: tt homozygous recessive.
Blood Types
Blood type can also be determined by a punnett square. There are four blood types: A, B, AB, O, all of which can be positive or negative. The genotype of blood type A is IAIA for heterozygous and IAi for homozygous. The genotype of blood type B is IBIB for heterozygous and IBi for homozygous. The genotype for blood type for AB is IAIB, there is no homozygous for this gene. The genotype for blood type O is ii, there is no heterozygous for this gene either.
Karyotypes are the profile or identity of a person(chromosomally). Chromosomes are lined up and arranged in their pairs according to their size. Putting the chromosomes in order helps geneticists figure out if there are any alterations or mutations that could lead to a genetic disorder. The way you make a karyotype is taking a photo of all the chromosomes found in a cell, then cutting them out and arranging them in the order they are supposed to go(smallest to largest)
So as we know, and organism’s genome is found on the chromosomes. Chromosomes come in two(one from mother, one from father). Only one of these pairs of chromosomes determines what sex the organism is. This are the sex chromosomes. All the rest of the chromosome are called autosomes.
Fun Fact: Human have 46 chromosomes, which is 23 pairs. Out of these, 2 chromosomes are sex chromosomes and the remaining 44 are autosomes.
Some disorders and diseases are passed through autosomes, and others are passed through sex chromosomes.
There is a disease called Phenotypic expression where it relies on if it is recessive or dominant. If a phenotypes of a gene is able to be looked at, even if it just has one copy of an allele, then it dominant. It does not matter if the individual is homozygous dominant or heterozygous (in terms of their genotypes(, the phenotype will still be observed.
If a phenotype can only be looked are when the person has two copies of an allele, then they are marked as autosomal recessive. This comes to be because of a homozygous recessive genotype.
If someone only gets one copy of this allele, and not two, then it will not show in their phenotype, but they still have the chance of passing the supposed to trait to future generations. If you are like this, then you are known as a carrier.
Pedigree Charts
There are charts that are similar to family trees that track inheritance patterns through the generations of families and show who currently possesses or possessed a certain trait that could be totally normal and common in a family or not. These are called pedigree charts, You can only see on trait on a chart at a time, so if you wanted to look at two different traits, you would have to make two charts.
Squares equal males and circles equal females
Traits being represented or found in the person are shown as shaded in and if a person does not possess the trait, then the shape will not be shaded in.
Traits that are found specifically just on the sex chromosomes are known as sex-linked traits. The chromosomes are different depending on your sex(female or male). Males have a XY sex chromosome combination and females have a XX sex chromosome combination. The way it works with genetics is that females can ONLY pass along an X chromosome to their offspring, but males can pass both X and Y. The male determines if the baby is a boy or a girl.
Another Fact is that males are more likely to have a sex linked trait shown or expressed than females because of their chromosomes. They Y chromosome does not have the extra segment or piece of genes that the X chromosome has.
Incomplete Dominance and Codominance
An incomplete gene is when two traits are blended together. For example, some people’s skin color is a golden color due to one parent having pale skin and the other having dark skin. A codominant gene is when two different dominant genes show through. For example, a horse that is half one color and half another color has a codominant gene.
Credits:
Created with images by Caroline Davis2010 - "DNA"