Gene Organization Flashcards
About how many genes are in the human genome?
20,000
Describe chromosomes
Made of proteins and DNA, if unbroken each double-stranded DNA helix would stretch out to be 1.8m in length
Describe histones
Every 200 nucleotides, the DNA is coiled around a core group of eight positively charged stabilizing proteins. Since they are positive, they are very attracted to DNA (slightly positive due to phosphate background).
Describe nucleosomes
The combination of coiled DNA and histones
Describe supercoiling
DNA folded into a higher level of coiling than is already present in nucleosomes
Describe VNTRs
Variable number tandem repeats. Also known as microsatellites, they are repetitive non-coding sequences of DNA, such as telomeres and centromeres (ex. TAGTAGTAGTAGTAG)
Describe centromeres
Constricted region of chromosomes that holds two replicated chromosome strands together
Describe pseudogenes
They have similar sequences to functioning genes but are never transcribed. Their origin and function are unclear
LINEs: long interspersed nuclear elements, they are repeating sequences from 5000 to 7000 base pairs in length
SINEs: short interspersed nuclear elements, they are repeating sequences from 300 base pairs in length
Describe epigenome
The outside flag of the genome that shows how DNA changes over time. They include leftover viruses, chemicals, mutagens, and environmental differences.
Describe the genome components of humans
All the protein coding sequences occupy less than 2% of the genome. Introns are non-coding regions which occupy 24% of the genome.
The rest of the DNA (almost 75% of the genome) occupies spaces between the genes, some of which can be functional and will have regulatory sequences such as promoters. However, much of it (more than 50%) is repeated sequences that are non-functional.
