What's the difference between a chromosome and a chromatid?

Question

You know, in meiosis and mitosis and such?

Please answer only if you are certain...

Answer 1

A chromatid forms one part of a chromosome after it has coalesced for the process of mitosis or meiosis. During either process, the word "chromosome" indicates a pair of two exactly identical ("sister") chromatids joined at the central point of each chromatid, called the centromere.

A chromosome, by definition, has exactly one centromere. Thus when sister chromatids are pulled apart by the mitotic spindle during anaphase -- that is, when the centromere joining two sister chromatids splits into two centromeres -- then each sister chromatid becomes an independent chromosome.

In non-gametic, non-dividing human cells, there are 23 pairs of chromosomes, thus 46 chromatids. When it is ready for mitotic cell division, each chromosome will replicate itself during the synthesis phase within its life cycle, making a total of 92 chromatids before dividing, producing two cells each with 46 (remember, since the term "chromosome" is redefined,but still the number of chromosomes remains 46 despite the replication).

In gametic cell division (meiosis),the cell replicates once but divides twice so that 23 chromosomes are left in each of four egg or sperm cells. (23 chromosomes are each needed from the male and female to combine and make 46 chromosomes for the zygote.)

A common mistake among students is that they think that chromatids always exist; chromatids ONLY exist when a chromosome replicates itself.

Answer 2

Chromosome; A chromosome (in Greek chroma = colour and soma = body) is, minimally, a very long, continuous piece of DNA, which contains many genes, regulatory elements and other intervening nucleotide sequences. In the chromosomes of eukaryotes, the uncondensed DNA exists in a quasi-ordered structure inside the nucleus, where it wraps around histones (structural proteins, Fig. 1), and where this composite material is called chromatin.

Chromatid: A chromatid forms one part of a chromosome after it has coalesced for the process of mitosis or meiosis. Each chromosome consists of two exactly identical ("sister") chromatids. After they have been pulled apart by the mitotic spindle, chromatids are called "chromosomes". Sister chromatids are joined at a point called the centromere. In non-gametic, non-dividing human cells, there are 23 pairs of chromosomes, thus 46 chromosomes.

Answer 3

A chromatid is part of a chromosome during Mitosis/ Meiosis. When you look at the "X" during Mitosis, it is a whole chromosome, and each side (they are identical to one another) is the sister chromatid. When the two sides split during anaphase (or anaphase II of meiosis), the chromatids are separating, and the moment that they do, they become full chromosomes. So, chromatids when theyre together in 1 chromosome (X- 2 chromatids in the chromosome), and they become chromosomes the instant they split (you go from 1 chromosome to 2)

Answer 4

Chromosomes are the X shaped strands of shortened, coiled, thickened (stainable), VISIBLE genetic material in eucaryotic cells. They are visible under the microscope during the processes of prophase, metaphase and telophase of the dividing cells of mitosis or meiosis. Mitosis is asexual reproduction of cells, meiosis for sexual reproduction) Chromosomes are capable of moving during cell division with the help of its centromere.

Chromatids are the 2 side by side "arms" of a dyad (identical chromatids) that are not able to move individually on their own yet as a chromosome because they do not have their own centromere yet. They can move as a dyad, and are a chromosome when they are dbl. Once a dyad has centromere replication and becomes 2 monads and each monad has its own centromere, both strands can move independently and be called chromosomes. (This process happens in meiosis 2)

(Meiosis has prophase 1, metaphase 1, anaphase 1, telophase 1, prophase 2, metaphase 2, anaphase 2, telophase 2) Chromosomes can be found in monad (n) form, dyad (2n) form or tetrad (4n) form in meiosis. Mitosis has dyads (2n) A monad chromosome has one centromere that helps the single chromosome plus single centromere move on spindle fibers across the cell. A dyad also has only one centromere, but there are two identical homologous chromatids held together by the single centromere. (identical chomosomes are homologous, but not all homologous chromosomes are identical) The tetrad is a very temporary moment when two homologous pairs (each dyad with its own centromere) pair up in metaphase of meiosis 1 to crossover and exchange genetic material between homologous maternal-paternal chromosomes..

So, "movement by a centromere" is the key defining factor to identify a chromosome from a chromatid.

Also, the Y chromosme obviously is not shaped like an X.

BTW, chromatin is uncoiled, unshortened, elongated, non-thickened, non moving genetic material found in the nucleus of the non-dividing cell of interphase of meiosis or mitosis.

Answer 5

A chromosome is a collection of chromatids after mitosis/meiosis is completed

Answer 6

Chromosome: Components in a cell that contain genetic information. Each chromosome contains numerous genes. Chromosomes occur in pairs: one obtained from the mother; the other from the father. Chromosomes of different pairs are often visibly different from each other (see also DNA).

Chromatoid: Each of the two daughter strands of a duplicated chromosome joined at the centromere during mitosis and meiosis or one half of a replicated chromosome.

Answer 7

Chromatid