Organisation Of Euk Genome✅

• 2nm -ve charged DNA molecule coils around +ve charged histone octamer to form nucleosomes joined by linker DNA. - Many nucleosomes form a 10nm nucleosome fibre _______________________________________ . • 10nm nucleosome fibre coils further to form a 30nm solenoid structure _______________________________________ . • 30nm solenoid struc associates with scaffolding proteins to form 300nm looped domains _______________________________________ . • 300nm looped domains coil further to form one of the two 700nm sister chromatids during PROPHASE chromosome are NOT visible normally or even during interphase

• lower gene denstity in euk genome • due to large proportion of introns in euk DNA • which are non-coding

• no • bcuz the no of base pair in each gene can vary • while having more genes does increase genome size, it shouldn’t be assumed that organisms w more genes have a larger genome size

• no • bio complexity is also dependent on regulation of gene expression • bcuz a single gene can be expressed differently to give rise to diff proteins . • multicellular org generally also more complex than unicellular org

• introns • promoter • enhancer • silencer • 5’ / 3’ UTR • centromere • telomeres

• DNA that is not transcribed into RNA OR • DNA that is transcribed BUT NOT translated to form protein

S1 - Non-coding tandem repeats 5’-TTAGGG-3’ found at both ends of linear chromosomes . F1 - Telomeres protect the critical coding genes near the ends of the chromosome from being eroded - due to the end replication problem in each round of DNA replication - (by shortening in place of the genes) . - (counting mechanism) to allow for replicative cell senescence where the cell stops dividing once telomeres have shortened to critical length _______________________________________ . S2 - _ 3’ overhang_ - which is single stranded and unreplicated - folds back on itself AND forms H bonds w an earlier complementary repeat to form a T loop - stabilised by telomere binding proteins . Functions ● Stabilises chromosomes so that their single-stranded overhangs do not fuse with each other by complementary base pairing forming H bonds . ● Protect 5’ end and single stranded 3’ overhang from being recognised as damaged DNA - and protect from degradation by exonucleases . ● Allows for its own extension as 3’ overhang provides a specific binding site for telomerase

1) Telomerase’s RNA template complementary base pair with 3’ overhang of the telomere, - by forming H bonds - aligning telomerase reverse transcriptase (TERT) with respect to the DNA _______________________________________ . 2) telomerase reverse transcriptase (TERT) catalyses formation of phosphodiester bond - between the growing 3’ overhang and the incoming DNA nucleotides - which complementary base pair with the unpaired ribonucleotides of the RNA template _______________________________________ . 3) Telomerase translocates to the end of the 3’ overhang to continue elongating it with tandem repeat sequence 5’-TTAGGG-3’ _______________________________________ . 4) the (OPPOSITE) 5’ unreplicated daughter strand is extended using the 3’ lengthened parental strand overhang as a template to sythesise primers - DNA pol synthesises a complementary strand in the 5’ to 3’ direction

S1 - short tandem repeats of A-T rich seqs . F1 - allow for attachment of kinetochore proteins to form the kinetochore protein complex - kinetochore microtubules can attach to the kinetochore of the centromere so sister chromatids and be lined up along the metaphase plate and be evenly separated during meiosis . F2 for S1 - is acts as a non-coding region allowing two sister chromatids to join

SIM - Both contain tandem repeats - Both are non-coding _______________________________________ . diff 1. location T: at extreme ends of chromosome C: at a specific point of a DNA molecule, but never at the ends (not necessarily at the centre) . 2. Shortens after DNA rep? T: shortens after each round C: doesn’t shorten . 3. proteins associated T: telomere binding proteins C: kinetochore proteins . 4. ss or ds? T: ss segment aka the 3’ overhang C: ds with no ss segments . 5. FUNCTION T: to protect critical genes near the ends from erosion due to end rep problem C: attachment site for kinetochore microtubules