Genealogy and DNA: Part One
Deoxyribonucleic Acid (DNA) testing can be confusing! Because of that I want to share what I have learned about DNA testing. First though it is important to understand just what DNA is, so part one of this series of articles defines DNA.
Deoxyribonucleic Acid (DNA) Structure and Function
Deoxyribonucleic acid is the genetic material that all living things carry in their cells. The cell’s nucleus and mitochondria contain the DNA. In essence, DNA can be thought of as a set of instructions that every cell in your body has and uses, it is essential for the synthesis of proteins and the division of cells.
Figure Credit: Magnus Manske Wiki Commons
Because you can’t see DNA it is an abstract concept, yet the structure of DNA is complex. To help understand how DNA is structured and functions it can be thought of as a computer file. Similar to a computer file, DNA is located in a specific place and contains specific information related to a particular purpose.
Deoxyribonucleic acid is made up of small units of base pairs of nucleic acids.[1] Nucleic acids are formed when nucleotides bond.[2]
Each nucleotide has three parts:
A five carbon sugar
A nitrogenous base
A phosphate (PO43-)[3]
When nucleotides bond, they are polymerized into something similar to a long chain. With DNA this chain takes the form of a double helix that is held together by nitrogen bases.
DNA can also be likened to a spiral staircase whose mainstay is a sugar phosphate structure. The ‘steps’ are nitrogen bases that are composed of either adenine (A) and thymine (T), or cytosine (C) and guanine (G).[4] According to Brennan and Demand, “The types and sequence of nucleotides in DNA determine the types and sequence of nucleotides in ribonucleic acid (RNA). This in turn determines the types and order of amino acids included in proteins.[5]”
Three nucleotides make up a codon. How base pairs are organized and structured in the condon, along with ribonucleic acid, informs the cell as to how to make new proteins that in turn determine our biological traits.[6] Both DNA and RNA have condons. The codons specify which amino acids (building blocks of protein) will be used in this process of protein building. [7] Like DNA, RNA is also a chain of nucleotides. However, RNA forms a single chain, not a double chain, and thymine is replaced by uracil (u).[8] The figure below represents a strand of RNA with its condons:
Figure Credit: Graham Beards Wiki Commons
RNA Structure and Function
Ribonucleic acid has three different types of structures:
Messenger RNA
Transfer RNA
Ribosomal RNA
Though the types of structure vary, each type is engaged with the synthesis of protein.[9] Simply put, when a cell wants to make protein, the enzyme helicase assists the DNA double helix in unwinding, so that DNA nucleotides are transcribe to a developing ‘thread’ of RNA.[10] This process is called transcription. After transcription, the DNA strand rewinds, and messenger RNA (mRNA) exports the DNA from the nucleus to the ribosomes.[11] Ribosomal RNA (rRNA) then decodes and uses the information from the condons “to add amino acids to a developing protein. chain.”[12] This continues until all of the mRNA has been decoded and the protein is fully synthesized.[13]
DNA: Generation to Generation
DNA carries its genetic code from one generation to the next through the chromosomes. In all, a person has 46 chromosomes that result in 23 chromosomal pairs, each pair consists of one chromosome from each parent. The chromosomes are thread-like structures that contain the DNA.[14] They can be thought of as hereditary ingredients that are passed from parents to offspring. It is during these processes that genetic materials flow from one generation to the next as a new life is formed from the genetic material of its parents.
Look for Part Two next month.
Kim
[1] David N. Finegold, “Genes and Chromosomes”, mmwebsite, 2013, (http://www.merckmanuals.com/home/fundamentals/genetics/genes_and_chromosomes.html?qt=dna%20&alt=sh: 2015)
[2] Larry Weiskirch, “Nucleotides and Nucleic Acids”, Sunyoccwebsite, 2002, (http://myhome.sunyocc.edu/~weiskirl/nucleotides_nucleicacid.htm: 2015).
[3] Finegold, Genes and Chromosomes.
[4] Amit Jain, “The Structure of DNA”, BoiseStatewebsite, 2005, (http://cs.boisestate.edu/~amit/teaching/342/lab/structure.html: 2015)
[5]John Brennan & Demand Media, “Relationship Between DNA Bases Genes, Proteins and Traits”, Sciencewebsite, 2012, (http://science.opposingviews.com/relationship-between-dna-bases-genes-proteins-traits-2074.html).
[6] Ibid.
[7] Thomas Baldwin & Madeleine Lapointe, The Chemistry of Amino Acids, The Biology Project, ASUwebsite, 2002, (http://www.biology.arizona.edu/biochemistry/problem_sets/aa/aa.html: 2015).
[8] Weiskirch, Nucleotides and Nucleic Acids.
[9]Frank Lee, “Molecular Biology: RNA Structure and Function”, BSONwebsite, n.d. (http://www.web-books.com/MoBio/Free/Ch3C.htm: 2015).
[10] Amanda Norick, “The Double Helix”, FHCwebiste, 2007, (http://www.foothill.edu/attach/psme/Norick.30B.26Continue.pdf: 2015).
[11] Ibid.
[12] Bruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, & Peter Walter; “Molecular Biology of the Cell”, 4th edition, NCBRwebiste, 2002, (http://www.ncbi.nlm.nih.gov/books/NBK26829/: 2015).
[13] Ibid.
[14]The Genetic Science Learning Center at The University of Utah, “What is a Chromosome?”, UniversityofUtahwebsite, 2015, (http://learn.genetics.utah.edu/content/chromosomes/intro/: 2015).
