Genome Structure Flashcards
What is the DNA?
What is it composed of?
- DNA is a deoxyribonucleic acid
- It is a macromolecule consisting of a linear strand of nucleotides
- The single linear strands bind to it’s complementary strands forming a double stranded DNA
What is the Nucleotide made up of?
- A sugar molecule
- Nitrogenous base
- Phosphate group
Describe the single stranded DNA
- The Nucleotides attach to eachother from the Carbon 3 of one molecule to the Carbon 5 of another molecule
- 5’ and 3’ carbons are indicated
- The sequence is 5’ -> 3’ by convention
Describe the DNA in three dimensions
- Has 2 anti parallel strands of DNA
- The bases are stacked
- Has two grooves = Major/minor
How big is the human genome?
The human genome is about 3 x 10^9 base pairs - 3Gbp
How many genes does the human genome contain?
Contains about 20 000 genes
Describe the trend in genes in regards to the human genome
- The simpler the organism, the fewer genes they have. For e.g. flies have 10 000, yeast have 4000, bacteria 1000
- However the genome size is not always strongly related to the complexity of the organism
What is the problem with DNA in the body?
- The body has about 2 meters of DNA in a nucleated cell with about 37.2 trillion cells in the body.
- That’s about 7.44 x 10^13 meters of DNA
- The average cell is 50 ùm in diameter so how does the DNA fit
How is this problem resolved?
- Solved through a type of protein called Histone proteins
- They’re basic positively charged proteins that bind DNA
- Eight histones 2x(H2A+H2B+H3+H4) form the nucleosome
- Histone 1 binds to the linker DNA
Describe the Chromosome structure
- The metacentric has a short arm and long arm
- The Submetacentric has a centromere (At centre), Telomeres at the bottom ends and chromatids at the top ends
- The acrocentric has Satellites on the centromeres
Describe the primary DNA sequence
- The primary DNA sequence encodes all the gene products necessary for a human
- Also includes a large number of regulatory signals
- Much of the DNA sequence does not have an assigned function as yet
Describe the Exome
- The exome is made up of gene sequences
- Some definitions use all the coding sequences ( -37 Mbp about 1.2% of genome)
- Some definitions use all of the gene sequences (~60Mbp – 2% of genome)
What is a gene?
- The gene is all of the DNA that’s transcribed into RNA including the Cis linked regions
- Cis linked regions ensure quantitatively appropriate tissue specific expression of the final protein
- It is not just the bits that encode the final protein, Regulation of the gene is very important
Describe the gene structure (View diagram on slide)
Has a 2 gene region at the start of the gene followed by the inter gene region followed by another gene region. (These genes can often be very different in size)
Describe the interagency region
Intervened regions contain sequences which have no known functions such as repetitive DNA, endogenous retroviruses, pseudo genes. They can contain many regulatory elements.