number of chromatids per chromosome during cell cycle?

Question

I need to know how many chromatids per chromosome there are for the stages G1, S, G2, prophase, metaphase, anaphase, and telophase.

I think its
G1=1,
S=2,
G2=2,
prophase=2,
metaphase=2,
anaphase=1
telophase=2

Am I correct in my thinking or do I have the whole thing messed up or just some of it?

Answer 1

In G1, there are 46 chromosomes, EACH CONSISTING OF A SINGLE CHROMATID. You will have two copies of chromosome one (one from mom, the other from dad), two copies of chromosome two, etc. These pairs are called homologues. Consequently there are 23 homologous chromosomes in G1 and, again, there is one chromatid per chromosome in this phase. This gives a total of 46 chromosomes. You should know that each chromosome is decondensed (not coiled up) at this time.

S phase is the synthesis or replication phase of the cell cycle. After S phase is complete, the definition of a chromosome changes. It is now a "replicated chromosome" that consists of 2 chromatids (some texts describe these as "sister chromatids"). Again, the total number of chromosomes is 46; however, because of the definition change of the S-phase chromosome, each chromosome how includes twice as much DNA due to replication. After S phase there are two chromatids per chromosome. These chromosomes are decondensed.

In G2, there are 46 chromosomes: 2 chromatids per chromosome, decondensed, with the chromosomes existing in homologous pairs.

In prophase of mitosis, the chromosomes condense to facilitate easy separation into the daughter cells. Here there are still 2 chromatids per chromosome.

In metaphase, there are STILL 2 chromatids per chromosome, all smartly arranged at the "equator" of the cell, the metaphase plate.

In anaphase, the replicated chromosomes (i.e., the "sister chromatids") are pulled apart. At the point that they are separated, the definition of a chromosome changes AGAIN, BACK to a single chromatid. Each daughter cell will receive 46 of these single chromatids and, therefore, will have 46 chromosomes in 23 homologous pairs. The chromosomes are still condensed at this point.

In telophase, the chromosome situation is exactly the same. 23 homologous PAIRS of chromosomes (46 single chromatids). The difference here is that the chromosomes are now decondensing.

Summary: the number of chromatids per chromosome

G1-1
after S- 2
G2-2
prophase-2
metaphase-2
late anaphase-1
telophase-1

Answer 2

Chromosomes uncoil and them replicate them selves, genetic material will double. They then re-coil into chromosomes with double the number and line up at the cell centre to be split during the division stage of cell cycle. So that each daughter cell get the identical genetic material (chromosomes).

Answer 3

Well I am not exactly sure off hand, but I do know that in part of mitosis (anaphase), they are not referred to as chromatids at all, but daughter cells, I believe this to be true as far as cytokinesis is concerned as well. They are only considered chromatids when the centromeres are intact. I know this doesn't fully answer your question, but I hope it helped.

Answer 4

Chromosomes In Cell Cycle