HEREDITY PART ONE

Heredity is the passing of traits from a parent cell or organism to an offspring. The study of how these traits are passed on in living things is the science of genetics. One of the early problems with Darwin’s Theory of Evolution was an inproper understanding of how traits were acquired by organisms. We now know that the workings of genetics explains every aspect of evolution! The basic ideas for genetics were first discovered through the work of a monk - Gregor Medel in the late 1800’s. His work with peas uncovered the many principles of genetics understood today.

One set comes from your mother and another comes from your father! Chromosomes carry the “code” for traits and are passed on fully by one parent (asexual) or equally by two parents (sexual). Chromosomes are the small packages within the nucleus of a cell that hold DNA.. They are basically clusters of proteins “wrapped” with strands of DNA. The number of chromosomes found in a cell depends on the organism. For example, a human has 46 chromosomes in each cell – two complete sets of 23 unique chromosome pairs. Mosquitos have 6. Onions have 16. How many chromosomes do you think a has? 38 Why do you have two sets of chromosomes? Why are the pairs always even numbers? One set comes from your mother and another comes from your father!

A Karyotype is an image of the set of chromosome pairs in an organism. This is a karyotype from what organism? A Human because there are 23 sets shown…

Looking at the previous example: Is this a male or a female? We must focus on the 23rd pair of chromosomes. This set determines sex. Females have 2 longer “X” chromosomes here, were as males have one “X” and one “Y”. Therefore, the “Y” is referred to as the “sex determining” chromosome. This karyotype is that of a male human.

http://learn.genetics.utah.edu/content/begin/traits/ When this person participates in making a child, the child will receive one chromosome from each of these pairs (23 total) and one chromosome from each of the mother’s karyotype (23 total). The child’s karyotype will thus have a grand total of 46 chromosomes like all humans but they will be a mixture of both the mother’s and the father’s donated chromosomes. In summary, the child’s karyotype (set of paired chromosomes) will not look exactly like the father’s nor the mother’s – It can be any combination of the two. The child will thus not have the traits of only one parent. If another child is born, it too, will have a combination of the very same chromosomes, but a different combination than its older brother or sister…That is why siblings (apart from identical twins) look different and have different traits!

What on Earth is DNA? Simply put, DNA are the “instructions” included in the chromosomes in every cell that tell it how to live, grow, and what role to play. Fact File: - Short for: Deoxyribonucleic acid - How biological information is stored - Are a twisted ladder shape referred to as a double helix - Found mainly in the nucleus of eukaryote cells or in the cytoplasm of prokaryote cells - Organized into structures called chromosomes - Is replicated when a cell divides - Plays a lead role in evolution - Area where mutations occur - The same DNA is present in each cell of your body - DNA strands are unique, like a finger print for every individual (apart from identical twins) If you took all of the DNA strands in your body and lined them up end to end, it would stretch to the Sun and back….500 times! Fun Fact: