![]() There are 23 pairs of chromosomes in a diploid human body cell. Only two pairs of chromosomes are shown in the diagrams below. The stages of mitosis are: prophase, metaphase, anaphase and telophase. The cell membrane pinches in and eventually divides into two daughter cells. New membranes form around the chromosomes at each end of the cell. The membrane around the nucleus disappears.Ĭhromosomes and their copies line up in the middle of the cell.Ĭhromosomes and their copies are pulled to different ends of the cell. The DNA in chromosomes and their copies condenses to become more visible. The DNA in chromosomes copies itself ready for mitosis. The cell spends most of its life in this phase. Every base pair of their DNA is identical. The daughter cells are clones of each other. Microtubules from one centrosome attach to the kinetochore (protein structures at the centromeres) of one chromosome from each of the homologous pairs, while the other centrosome connects to the kinetochore of the other chromosome in each homologous pair, and each homologous pair moves towards the metaphase plate (where they line up before anaphase).Mitosis is a type of cell division in which a diploid body cell copies itself and finally divides into two identical diploid daughter cells. Centrosomes move to opposite ends of the cell, and the nuclear envelope dissolves.ħ. This formation occurs because of sister chromatid cohesion, where a gene that has been given to the homologous pair in synapsis is still bonded to the corresponding part on the sister chromatid of its former chromatid.Ħ. Some of these homologs have one or more chiasmata, an X shaped region where a genetic rearrangement has occurred. Synapsis ends, and the homologs move slightly apart, no longer bonded along their lengths like in the synaptonemal complex.ĥ. This forms a synaptonemal complex.ģ.The random rearrangement of corresponding genes occurs between the non sister chromatids (because at this stage each chromosome consists of two sister chromatids).Ĥ. Ans: The \(6\) stages of the cell cycle are interphase, prophase, metaphase, anaphase, telophase, and cytokinesis. The paired homologs become physically connected along their lengths through a process called synapsis. Chromosomes condense and homologs loosely pair along their lengths, aligned by gene.Ģ. The above is also how a 46 chromosome (double strand) cell in mitosis can result in 2 daughter cells each with 46 chromosomes (single strand).Įven Sal admits how confusing this is, but he explains all this visually in a separate video differentiating the terms chromatid, chromosome, and chromatin.ġ. So a haploid parent cell of 23 chromosomes (double strand) just created two haploid daughter cells of 23 chromosomes (now single strand). When the chromatids are separated they are now called chromosomes Anaphase II splits the sister chromatids which now separate (23 chromatids go to one pole and 23 chromatids go to other pole). The parent cell starts with 23 chromosomes (EACH double stranded=two sister chromatids, so there are 46 chromatids. This means that in meoisis II when we split the sister chromatids: It is only when the sister chromatids separate are they each considered separate chromosomes. The single strand chromosome (1 chromosome) became two stranded yet attached identical sister chromatids (still 1 chromosome) Likewise chromosome 5 of dad is similar to chromosome 5 of mom)Īfter replication how many chromosomes do we have? In interphase before S (replication phase) we have 46 single stranded chromosomes: 23 are from mom and 23 are from dad (they code for the same things meaning chromosome 1 of mom codes for the same thing as chromosome 1 of dad. ![]() Remember that when replicating in interphase, the chromosome number DOES NOT CHANGE
0 Comments
Leave a Reply. |