Chromosomes Flashcards
What is chromatin?
Chromatin is a DNA/protein complex in which
chromosomes exist.
What is the key feature of chromatin organization?
condensation or compaction
How long is the DNA molecule in the average
human chromosome when stretched out to its full
length?
5 cm long
What is the difference between metaphase and interphase?
Metaphase is highly condensed for transmission to daughter cells, while interphase is the real
functional chromosome undergoing replication and transcription.
What is a nucleosome?
DNA wrapped around a histone
octamer.
__________ are folded loops of chromatin separated by _______.
Topological domains
Boundary element
What is the mechanism of giant interphase chromosomes formation?
Cellular giantism” is driven by “DNA” and involves approximately 10 cycles of DNA replication without cell division, resulting in all approximately 1024 daughter chromatids being in perfect alignment to create a giant chromosome with “dark bands” (topological domains) and “light bands” (boundary elements).
What are dark bands and light bands in giant interphase chromosomes?
Dark bands are condensed chromatin (topological domains), and light bands are boundary elements.
What are polytene chromosomes?
Polytene chromosomes are giant chromosomes with many parallel identical chromatids formed by repeated replication without separation (10 cycles -> 1024 copies).
What do polytene chromosome puffs show?
chromatin decondensation with transcriptional activation.
What are puffs associated with?
They are associated with the active form of RNA polymerase II, which means active transcription.
What are metaphase sister chromatids?
They are the identical products of the previous semiconservative replication of a single chromosomal DNA molecule.
What does the karyotype of metaphase chromosomes show?
It shows the chromosomal complement of the species.
What is chromosome painting?
It is a technique that reveals the karyotype by fluorescence in situ hybridization (FISH) with a panel of probes representing sequences differentially distributed among the chromosomes.
Can chromosomes break and rejoin?
Yes, they can.
What are translocations?
Chromosomes can break and rejoin giving translocations.
What can cause disease in an organism during a somatic cell division cycle?
Mutations caused by chromosome rearrangements can cause disease, such as cancer.
What is the effect of germ-line chromosome rearrangements on offspring?
reduced fertility.
Why is the karyotype so consistent across a species?
Germ-line chromosome rearrangements are usually a dead end, so the karyotype is consistent across a species.
What are the elements required for replication and stable inheritance of linear chromosomes?
1) Origin of replication
2) Centromere
3) 2 telomeres (ends)
Why does the introduction of a circular bacterial plasmid with the wild-type yeast LEU gene into leu- yeast cells matter in the experiment?
The introduction of the circular bacterial plasmid containing the wild-type yeast LEU gene into leu- yeast cells is significant because it allows researchers to assess whether the plasmid can “rescue” leucine-independent growth in these cells, which would indicate that the LEU gene in the plasmid can function in yeast cells.
In a yeast experiment, what is the significance of having the LEU gene inactivated by mutation in leu- yeast cells?
In leu- yeast cells, inactivating the LEU gene by mutation means that these cells require external (exogenous) leucine for growth because they can’t produce it themselves.
Why can’t the LEU plasmid replicate in yeast cells, even though it replicates well in bacteria?
The LEU plasmid cannot replicate in yeast cells because bacterial origins of DNA replication do not function in eukaryotes like yeast. Yeast and bacteria have different replication mechanisms.
How does the introduction of a random piece of yeast DNA containing a yeast origin of replication into the plasmid change its ability to support leu- yeast growth in the absence of leucine?
When a random piece of yeast DNA containing a yeast origin of replication is inserted into the plasmid, it enables the plasmid to support leu- yeast growth in the absence of leucine. This is because the yeast origin of replication allows the plasmid to replicate within yeast cells, thus providing the necessary LEU gene function for growth.
