Structure Of Eukaryotic Genome Flashcards
What does the c value paradox mean
The genome size doesn’t determine gene number - could have a big genome but few genes
Why is gene density lowest in humans
Genome has many sequence repeats which don’t code for proteins
Many introns
Protein coding genes =2% of genome
How do eukaryotic genome differ from prokaryote
Linear chromosomes
Multiple regions of ORIC (origins of rep)
Mostly diploid
What is formed at many oric sites on eukaryotic genome
Replication bubbles
What does the karyote show
The 23 homologous pairs of chromosomes and 23rd being the 2 sex chromosomes
What are Bandung patterns on chromosomes
Due to stains which attach to specific base sequences
The centromere which holds sister chromatids is made of repeated sequences. What are these called in humans
Alpha satellite
Name the 4 types of chromatids based on centromere location
Metacentric - centromere in middle
Submetacentric - shorter P arm
Arcocentric - centromere near the end(telomere)
Telocentric - centromere right at the end of chromatids
What are telomeres and what are they made of
Ends of chromosomes
Made of repeated motifs (TTAGGG)
What is the 2 functions of telomeres
1- allow cell to find end of chromosome instead of the artificial end(of a chromosome is broken)
2- solve the end replication problem
What is the end replication problem
During replication, the 3’ end is cut short and not replicated which shortens the chromosomes
What is it called if genes are not replicated in the end replication problem
Telomere crisis or senescence
How does the enzyme telomerase solve senescence
The uncopied end region of the chromosome is recognised by telomerase which then adds repeated motifs (TTAGGG)
The replication machinery then still allows the synthesis of the other strand
Fun fact about telomeres / telomerase
Born with active telomerase which means our telomeres are full length
In somatic cells the telomerase is turned off and eventually the telomeres shorten
Eventually senescence does occur and chromosomes end up not functioning
How is chromatin arranged within nucleus
2 loops of dna wrapped around an octamer of histone proteins (8 subunits)
