genetics Flashcards
chapter 11 content
What do chromosomes contain
chromosomes contain very long DNA molecules that are tightly packed
What does supercoiling result from
Supercoiling results from strain produces when rotations are added to a relaxed DNA molecule or removed from it
What produces positive supercoiling
Overrotation
What produces negative supercoiling
underrotation
What is supercoiling controlled by
Supercoiling is contolled by topoisomerase enzymes
What does a bacterial chromosome consist of
A bacterial chromosome consists of a single circular DNA molecule that is bound to proteins and exists as a series of large loops, it usually appears in the cell as a distinct clump, also known as the nucleiod.
What does each eukaryotic chromosome contain
Each eukaryotic chromosome contains a single, long linear DNA molecule that is bound to a histone and nonhistone chromosomal protein
What does Euchromatin undergo?
Euchromatin undergoes the normal cycle of decondensation and condensation in the cell cycle.
What remains highly condensed throughout the cell cycle
Heterochromatin
What is the nucleosome?
The nucleosome is a core particle of 8 histone proteins and the DNA wraps around them.
What happens if you neutralize the positive charge on a histone protein?
It causes them to bind less tightly to the DNA.
how are nucleosomes folded?
into a 30nm fiber that forms a series of 300 nm long loops; these loops are condensed to form a fiber that is itseld tightly coiled to produce a chromatid
What is sensitive to digestion by DNase 1?
Active transcripton, indicating that DNA is more exposed during transcription.
What are epigenetic changes?
Stable alterations of gene expression that do not require changes in DNA sequences. Epigenetic changes can take place through alterations of chromatin structure.
What are centromeres?
They are chromosomal regions where spindle microtubule attack; chromosomes without centromeres are usually lost in the course of cell division. Most centromeres are definied by epigenetic changes to chromatin structure. Telomeres stabilize the end of chromosomes.
