Genomes Flashcards
How many base pairs are in the human genome?
3 million
What is the only somatic cell that doesn’t have the same genes as the rest?
B lymphocyte
Define transcriptome
Entire set of mRNA Hexpressed from the genes of an organism
Define proteome
Entire set of proteins expressed by an organism
What are housekeeping genes?
Genes that are expressed in all cell types
How many pairs of autosomes do humans have?
22 pairs
How many chromosomes does a human have?
46/ 23 pairs
What is a telomere?
specialised nucleotide sequence at the end of a linear chromosome that is repeated
What enzyme replenishes the telomere after each division?
Telomerase
What does telomerase do?
Adds copies of the end sequence - dynamic equilibrium
What is the point of a telomere?
They act as protective caps –> prevent chromosomes from being degraded during replication
Also prevents chromosomes from sticking to each other
3 main structural components of a chromosome
Telomere, Centromere and origin of replication
What is a centromere?
Specialised, repetitive DNA sequences to which the mitotic/meiotic spindle is attached during cell division. Allows chromosome segragation
What do centromeres facilitate?
Chromosome attachment to the spindle via the kinetochore
What is a kinetochore?
“Landing pad” for microtubules to attach to centromere
What is an origin of replication?
Located within DNA molecules and creates 2 replications forks that move away from each other
How many origins of replication are there?
Eukaryotic cells may have multiple origins of replication in order to replicate chromosomes quicker
DNA replication in E. coli
Bidirectional replication
Initiator prettiness bind to specific DNA regions in the origin of replication
This wraps the DNA around the proteins to form a complex that destabilise the adjacent double helix
The complex attracts two DNA helices, each bound to a helices loader which keeps helices inactive
The DNA helicases are then properly loaded onto the replication fork and the loaders dissociate and helices unwinds the double helix
This exposes enough ssDNA for DNA primes to synthesise RNA primers…
Where is the E. coli genome contained?
Contained in a single circular chromosomal DNA molecule
Where is DNA replication regulated in E. coli?
At initiation stage
How is DNA replication regulated in E. coli?
- Make sure there are sufficient nutrients for an entire round of replication
- Only one round of DNA replication occurs for each cell division…after replication, initiator protein deactivated by hydrolysis of bound ATP
How is the initiator protein deactivated in DNA replication?
Hydrolysis of bound ATP
Are genome sizes larger in more complex organisms?
Yes
How does the number of introns and exons differ ion larger more complex organisms?
More introns but similar number of exons as smaller organisms
