L8 Structure of Eukaryotic Genomes Flashcards
The C-Value Paradox… 🤔
The number of genes does not increase linearly with genome size
Protein coding DNA makes up about ? % of the human genome
2
What is the reason for the existence of the C-Value Paradox
Lower gene density, but more introns per gene. More repeated sequences.
The majority of the human genome does not code for proteins. What is one likely function of these regions?
Regulatory sequences
Eukaryotic chromosomes are ( always / sometimes / never ) linear
Always
One way of visualising a karyotype (set of chromosomes) is with a…
Karyogram
During mitosis, chromosomes become highly condensed, forming…
Chromatids
During interphase, chromosomes are decondensed, however…
They still occupy a distinct territory within the nucleus
Centromeres hold together…
Sister chromatids
Centromeres are the assembly site for…
The kinetochore
The shape of sister chromatids can be classified in four ways…
- Metacentric (equal)
- Sub-metacentric (shorter arms (p) / longer arms (q))
- Acrocentric (much shorter arms (p) / much longer arms (q))
- Telocentric (centromere at one end, only one pair of arms)
Telomeres are repeated motifs at the end of chromosomes. They have two main functions…
1) Allowing the cell to differentiate between real ends and unnatural breaks, which must be repaired
2) As a solution to the End Cell Replication Problem (end sequence where primer attaches cannot be replicated, so degrades over time. Telomerase adds TTAGGG sequences to the end)
If a chromosome shortens so far that it reaches an important gene, this leads too…
a Telomere Crisis and replicative senescence
In most somatic cells, telomerase is turned ( on / off ) to prevent…
OFF, to prevent uncontrolled cell growth ⛔️
In the nucleus, DNA is bound to…
Histone proteins
