Question

eukaryotic chromosome structure: questions

1. where is the dna normally found in the cell?
2. most of the time, what form does dna take in the cell?
3. on the chromosome on the right, label the chromatid, chromosome arms, and centromere region.
4. during what phase is dna replicated and two chromatids form per chromosome?
5. what is the term used for the phase when the cell divides?
6. what is the purpose of the centromere region?
7. nucleosomes and histones can have \tags\ that affect whether the dna wound around them is \turned on\ or \turned off\. look up information on one of those tags and describe how it affects dna gene expression.

Explanation:

• Question 4: In the cell cycle, DNA replication occurs during the S - phase (Synthesis phase). During this phase, each chromosome is replicated, and sister chromatids are formed.
• Question 5: The phase when the cell divides is called mitosis (for somatic cells) or meiosis (for gamete - forming cells). The general term for cell division (when referring to the division of the nucleus and cytoplasm in a non - specific context) is mitosis.
• Question 6: The centromere region is crucial for chromosome segregation during cell division. It is the site where spindle fibers attach. Spindle fibers are microtubules that pull chromosomes apart during mitosis or meiosis.
• Question 7: For example, histone acetylation. Histones are proteins around which DNA is wrapped. When histones are acetylated (a small acetyl group is added), the chromatin structure becomes more relaxed. This relaxed structure allows transcription factors and RNA polymerase to access the DNA more easily, so genes are more likely to be "turned on" (transcribed).

Answer:

1. S - phase
2. Mitosis
3. It is the site of spindle - fiber attachment for chromosome segregation during cell division.
4. Histone acetylation: Acetylation of histones relaxes chromatin structure, facilitating access of transcription machinery to DNA and "turning on" genes.