BGM1004/L08 Eukaryotic Genes Flashcards
Give 4 characteristics than genomic DNA controls.
Development
Form and function
Behaviour
Interaction with environment
What is the relationship between complexity and gene number?
As complexity increases, gene number increases (not linearly)
What is the relationship between complexity and gene number called?
The C-value paradox
Approximately what percentage of the human genome does protein-coding make up?
2%
How many chromosomes do all eukaryotes have?
At least 2
What is mild proteolysis?
Breakdown of proteins
What is the process and banding pattern in G-banding ?
Mild proteolysis followed by GIEMSA
Dark bands are AT rich
What is the process and banding pattern in R-banding?
Heat denaturation followed by GIEMSA
Dark bands are GC-rich
What is the process and banding pattern in Q-banding?
Stain with quinacrine
Dark bands are AT-rich
What is the process and banding pattern in C-banding?
Barium hydroxide followed by GIEMSA
Dark bands are constitutive heterochromatin
When are chromosomes highly condensed and therefore visible?
During nuclear division in mitosis
What are mitotic chromosomes known as during mitosis?
Chromatids
When are chromosomes decondensed?
During interphase
How are chromosomes visualised via ‘painting’?
DNA sequences specific to one chromosome are fluorescently labelled and hybridised
What is the region in which decondensed chromosomes occupy?
Territories
What is a centromere?
A region where sister chromatids are held together
Where is the assembly site for the kinetochore?
Centromere
Describe the base sequence in the centromere.
Large arrays of repeated sequences
What is a metacentric chromosome?
A chromosome where p arm length = q arm length
What is a submetacentric chromosome?
A chromosome where p arms are slightly shorter than q arms
What is an arcocentric chromosome?
A chromosome where p arms are much shorter than q arms
What is a telocentric chromosome?
A chromosome where there are no p arms
What is a telomere?
A specialised region at the end of chromosomes with the repeating motif (5’-TTAGGG-3’)
Give the 2 major functions of the telomere.
Allow cell to distinguish real chromosome from unnatural end caused by DNA break
Solve problem that cells have replicating ends of a linear chromosome
Describe the End Replication Problem.
During DNA replication, the 3’ terminal portion of chromosome can’t be copied so ssDNA overhang is degraded
How does telomerase prevent chromosome shortening?
Uncopied region recognised by telomerase
Telomerase adds multiple copies of ‘TTAGGG’ repeat
Replication machinery synthesises other strand
Why do most cells turn off telomerase?
To reach ‘replicative cell senescence’
What is DNA wrapped around?
An octane of histones
What is the structure formed by DNA wrapped around histones called?
Nucleosomes
What is chromatin?
Protein complex of DNA wrapped around histones
What is euchromatin?
‘True chromatin’
Relatively uncondensed, associated with active genes
What is heterochromatin?
Condensed, repressive, inactive, repetitive gene poor regions
What are minichromosomes?
Chromosomes relatively short but rich in genes
What are B chromosomes?
Additional chromosomes possessed by some but not all individuals in a population
What are holocentric chromosomes?
Chromosomes without a single centromere but with multiple kinetochores throughout their length
What are polytene chromosomes?
Giant chromosomes made by larval cells of certain insects
