Chromosomes

[sayonara]

I should be studying evolution but anyway...

1. Do chromosomes normally exist as a single strand before replication?
2. The typical four-armed chromosome we're familiar with; are the two chromatids that make it up identical?
3. In somatic cells, are there 2 chromosomes for each number (1-22) in the nucleus?

Just need to confirm this information before moving on. Our class went through meiosis/mitosis way too fast, :S

[ed_saifa]

1. They exist as chromatin and remains as chromatin after duplication; in prophase the chromatin starts to condense into discrete chromosomes

2. The sister chromatids are identical

3. Yes from the sperm and egg; 46 total including the sex chromosomes

[sayonara]

Thanks for the response, but what do you mean by "from the sperm and egg"?

[ed_saifa]

Sperm and egg are both haploid(23 chromosomes) and together they form a diploid(46).

[sayonara]

Thanks!

[TrueLight]

yeah chromosomes are highly supercoiled around proteins (double stranded DNA still) and need to unwind before they can replicate.

humans have 23 pairs of chromosomes in somatic cells