False Genes Common: Sequencing of chromosome 7 has found a large chromosome with 1150 genes and 940 false genes. The telomere is in center of chromosome and there are few genes near it, but rather a lot of repeats. This means that when genetic material is lost when the cell divides that little important genetic material is lost until much later divisions.  This allows humans to live longer. 7/10/03 Nature, Wash U, St. Louis.

Inbreeding in Arabs Increases Deafness: Hereditary deafness is very common in the world’s Arab and Palestinian populations, because of the high rate of marriage between cousins, which passes on recessive genes from parents who are ill or asymptomatic carriers. Karen Avraham of Tel Aviv University. Some Palestinian villages one in 10 children are profoundly deaf. Some cases of hereditary deafness also occur among Jewish people. Over 130 genes involved in hearing problems are known, five of which occur in Israeli Jews and Palestinians, although only one of the genes is shared by both groups. At least 10 more genes are believed to cause hereditary deafness in the two populations. BMJ 8/2/03

Junk DNA Common: Junk DNA called LINE-1 elements can delete DNA when they jump to a new location – possibly knocking out genes or creating devastating mutations in the process. The value of this study is the unexpected knowledge that LINE-1 elements have the potential to cause broad-spectrum mutations in individual tumor cells," says John V. Moran, U-Michigan Medical School. Transposable LINE-1 or L1 elements make up 17 percent of human DNA. L1s "reproduce" by using RNA and a process called reverse transcription to make complementary DNA copies of themselves, as they integrate into other DNA sequences. Of 37 transposable events in our study, four resulted in deletions of genetic material. One of the deletions was more than 24 Kb in length [24,000 individual units of DNA called nucleotides] and potentially as large as 71 Kb. That's roughly equivalent to the size of BRCA1, a well-known gene that helps prevent the development of breast cancer. In cultured cells, we know that L1s can add to the genome by increasing its size, and now we've learned that they can decrease genome size by deleting genetic material. Cell 8/9/02

Large Scale Variations Affect Genetic Differences: Stretches of DNA sometimes hundreds of thousands of chemical bases (nucleotides) long are present or absent in the genomes of healthy individuals. These large-scale copy variations, or LCVs, frequently overlap with genes and could explain why people are different. The Human Genome Project indicates that the DNA in the genome of any two individuals is 99.9 per cent identical with the 0.1% variation arising primarily from some three million single nucleotide changes scattered amongst the chromosomes. There are at least 255 regions (comprising at least another 0.1%) of the genome where large chunks of DNA are present in different copy numbers between individuals. Over 50% of these alterations lead to changes in gene numbers and at least 14 regions overlapped with known sites associated with human disease. Some people may have 10 copies of a gene while others may have as much as 24 copies of the same gene. Stephen Scherer, Charles Lee. Harvard and University of Toronto. Nature Genetics 9/04 

Pseudogenes: 67 Deactivated Genes in Humans: Genes which no longer exproess functional protein are called pseudogenes. Researchers have found 67 in the human genome with originated in the time since humans split from chimps. One, CASP12, plays a role in suppressing the mammal immune sytems which function in all mammals except humans. Roughly 50,000 years ago, natural selection favored switching off the gene. This lowers the chance of severe sepsis, a disease where the body responds too strongly to an infaciton. Wang X, et al. PloS Biol 4:366-77, 2006.

Tetragametic Chimeras: A few people are made up from the fusion of two embryos in early fetal development. Thus, the cells of their bodies arise from two different sets of genes that are like non-identical twins to each other.  Some organs of their body, e.g. their blood cells, will all arise from only one set of the genes.  This situation was discovered when a woman in need of a kidney transplant found out that two of her three sons were not genetically related to her.  In fact, they were not genetically related to her blood cells, but were genetically related to some other parts of her body.  This situation also makes it possible for a true genetic father to test negative on a paternity test if he is a tetragametic chimera (from two eggs and two sperm). It is possible that his child came from a sperm from one set of DNA and his blood from the other set of DNA. New Scientist 11/15/03 pg 34-7.