Chromosome Structure and the Eukaryotic Cell Cycle Flashcards
What do chromosomes contain?
Chromosomes contain the genetic material of an organism
Where are genes located within chromosomes?
Genes are physically located within the chromosomes
What are chromosomes composed of?
Chromosomes are composed of DNA and proteins
What does the DNA-protein complex make in chromosomes?
Chromatin
What is the primary function of genetic material?
The primary function of genetic material is to store needed information
What is chromosome compaction?
Chromosome compaction is the process by which DNA is tightly packed into the nucleus of a cell
What is a nucleosome?
A nucleosome is a repeating unit of DNA wrapped around an octamer of histone proteins
How does DNA wrap around histone proteins in a nucleosome?
DNA wraps itself around histone proteins in a nucleosome through the attraction between the negative charges of DNA and the positive charges of histones
How much does the length of DNA shorten when it wraps around histone proteins?
The length of DNA shortens about sevenfold when it wraps around histone proteins
What is the structure of the nucleosome units when they are further compacted?
The nucleosome units are organized into a more compact structure that is 30 nm in diameter
What is the effect of further nucleosome compaction on DNA length?
Further nucleosome compaction shortens the nucleosome structure another sevenfold
Why is the structure of the more compact nucleosome units difficult to determine?
Because the conformation of the DNA may be substantially altered when extracted from living cells
What are radial loop domains?
Loops of DNA that extend outwards from a central protein scaffold, forming a hierarchical structure of chromatin
What is the interaction between 30-nm fibers and nuclear matrix proteins?
The 30-nm fibers of chromatin are thought to interact with nuclear matrix proteins, providing additional stability and organisation to chromosomes.
How are chromosomes separated?
Each chromosome is located in a discrete, non-overlapping chromosome territory within the nucleus
Do different chromosomes become intertwined when they are not compacted?
No, different chromosomes are not substantially intertwined even when they are not compacted
Why is the level of compaction of chromosomes not uniform?
Different regions of chromosomes have different functions and therefore require different levels of compaction
What are the 2 forms of chromatin that exist?
- heterochromatin
- euchromatin
What is heterochromatin?
- a highly compacted form of chromatin
- transcriptionally inactive, meaning that genes are not read to produce RNA
What is euchromatin?
- a less condensed form of chromatin
- capable of gene transcription
Where is most chromosomal regions found in non-dividing cells?
Most chromosomal regions are found in non-dividing cells in a partially compacted form
When do chromosomes compact further?
Chromosomes compact further when the cell is preparing to divide (cell division)
What happens to all euchromatin during cell division?
All euchromatin is converted to heterochromatin during cell division
What happens to most transcriptional activities during cell division?
Most transcriptional activities cease during cell division