Friday, May 06, 2022
The 23rd Chromosome Match with SNPs; What Are SNPs?
Nadene Goldfoot
Our DNA (de-coxy-ribo-nucleic acid, is the blueprint of life: made up of a series of chemicals that defines unique us, except twins.
Pretend each of these blocks is one of 4 nucleotides.A=Adenine C=Cytosine
G=Guanine T=Thymine
Comparing Kit (Nadene Goldfoot) [Migration - F2 - F] and Kit [Migration - F2 - F] 1st cousins. My father is my cousin's mother's brother.
The last pair of 23 chromosomes is the 23rd which determines the sex of a child. Females have a matched XX pair and males carry an XY pair.
SNPs: Most commonly, SNPs are found in the DNA between genes. They can act as biological markers, helping scientists locate genes that are associated with disease. When SNPs occur within a gene or in a regulatory region near a gene, they may play a more direct role in disease by affecting the gene's function.
| Chr | B37 Start Pos'n | B37 End Pos'n | Centimorgans (cM) | SNPs |
| 23 | 9,455,754 | 40,868,188 | 51.8 | 4,292 |
| 23 | 107,092,263 | 115,362,823 | 9.9 | 696 |
Largest segment = 51.8 cM of a lot of SNPs
Total segments 61.6cM (32.429 Pct)
| Chr | B37 Start Pos'n | B37 End Pos'n | Centimorgans (cM) | SNPs |
| 23 | 22,835,253 | 52,067,217 | 46.2 | 3,405 |
| 23 | 62,038,249 | 119,045,617 | 41.9 | 4,317 |
Largest segment = 46.2 cM
Total segments 88.1cM (46.375 Pct)
Each SNP represents a difference in a single DNA building block, called a nucleotide. For example, a SNP may replace the nucleotide cytosine (C) with the nucleotide thymine (T) in a certain stretch of DNA.
SNPs occur normally throughout a person’s DNA. They occur almost once in every 1,000 nucleotides on average, which means there are roughly 4 to 5 million SNPs in a person's genome. These variations occur in many individuals; to be classified as a SNP, a variant is found in at least 1 percent of the population. Scientists have found more than 600 million SNPs in populations around the world.
SNPs differ from substitution variants, which replace one DNA building block (nucleotide) with another. Substitution variants usually cause disease and are generally not found in 1 percent of any population. Additionally, SNPs differ from copy number variants (CNVs), which occur when a whole gene (or other large section of DNA) is duplicated or deleted.
Most commonly, SNPs are found in the DNA between genes. They can act as biological markers, helping scientists locate genes that are associated with disease. When SNPs occur within a gene or in a regulatory region near a gene, they may play a more direct role in disease by affecting the gene’s function.
Most SNPs have no effect on health or development. Some of these genetic differences, however, have proven to be very important in the study of human health. SNPs help predict an individual’s response to certain drugs, susceptibility to environmental factors such as toxins, and risk of developing diseases. SNPs can also be used to track the inheritance of disease-associated genetic variants within families. Research is ongoing to identify SNPs associated with complex diseases such as heart disease, diabetes, and cancer.
Human DNA contains 3,147 million chemical nucleotide bases (A,G,C,T). The total length of DNA present in one adult himan is about 2 x 10meters, the distance from the earth to the sun and back. The DNA in an average chromosome is about 5cM long.
Almost all (99.9%) nucleotide bases are exactly the same in all people; and 997% are the same as the chimpanzee's.
As far as genealogy goes, we genealogist need not worry about SNPs, which show a health factor, and unless you are a nurse or doctor, would not be interested.
I was always hoping that SNPs would tell me some vital information about how many generations apart or such we would be, but will not fret about those numbers anymore.
Resource:
DNA & Genealogy by Colleen Fitzpatrick & Andrew Yeiser, 2005
https://medlineplus.gov/genetics/understanding/genomicresearch/snp/
Labels: dna, genealogy, health, nucleotides, SNPs
