Anaphase
Non-disjunction is the failure of a pair of chromosomes or chromatids to separate. Since this happens in both metaphase I and II, non-disjunction can occur in either stage.In metaphase I it is the failure of the two homologous chromosomes in the pair to separate. In this case all of the gametes will be affected.In metaphase II it is the failure of the two sister chromatids to separate. In this case only half of the gametes are affected.Non-disjunction is the cause of a number of genetic conditions eg Down syndrome, Triple-X syndrome.See http://en.wikipedia.org/wiki/Nondisjunction
Crossing-over occurs between non-sister chromatids, since (prior to crossing-over) sister chromatids are genetically identical (i.e. one is a duplication of the other). Therefore, if sister chromatids underwent a cross-over, no genetic variation would occur.
Yes. It leads to exchange of genetic information between the chromosomes. Which in anaphase II would split in to separate single chromosomes that would be different than if crossing over didnt occur.
Nondisjunction is the failure of homologous chromosomes or chromatids to segregate during mitosis or meisos with the result that one daughter cell has both of a pair of parental chromosomes or chromatids and the other has none. An example is Trisomy 21, which is also called Down's Syndrome. This person has 3 chromosome #21.Nondisjunction of genes occur during meiosis I when homologous chromosomes fail to separate or during meiosis II when there is unequal distribution of chromosomes. This leads to aneuploidy.
Sister chromatids are two copies of a replicated chromosome. Chromosomes occur in pairs. These will be separated in anaphase of mitosis and one chromatid pair will be left for each daughter cell.
In general, nondisjunction can occur in any form of cell division that involves ordered distribution of chromosomal material.There are three forms of nondisjunction: failure of a pair of homologous chromosomes to separate in meiosis I, failure of sister chromatids to separate during meiosis II, and failure of sister chromatids to separate during metaphase going into anaphase of mitosis.mitosis
Non-disjunction is the failure of a pair of chromosomes or chromatids to separate. Since this happens in both metaphase I and II, non-disjunction can occur in either stage.In metaphase I it is the failure of the two homologous chromosomes in the pair to separate. In this case all of the gametes will be affected.In metaphase II it is the failure of the two sister chromatids to separate. In this case only half of the gametes are affected.Non-disjunction is the cause of a number of genetic conditions eg Down syndrome, Triple-X syndrome.See http://en.wikipedia.org/wiki/Nondisjunction
when two of homologous chromosomes form a tetrad sister chromatids and crossover
Crossing-over occurs between non-sister chromatids, since (prior to crossing-over) sister chromatids are genetically identical (i.e. one is a duplication of the other). Therefore, if sister chromatids underwent a cross-over, no genetic variation would occur.
Yes. It leads to exchange of genetic information between the chromosomes. Which in anaphase II would split in to separate single chromosomes that would be different than if crossing over didnt occur.
Separation of transition metals is difficult. They have similar size, occur together and difficult to separate.
Nondisjunction is the failure of homologous chromosomes or chromatids to segregate during mitosis or meisos with the result that one daughter cell has both of a pair of parental chromosomes or chromatids and the other has none. An example is Trisomy 21, which is also called Down's Syndrome. This person has 3 chromosome #21.Nondisjunction of genes occur during meiosis I when homologous chromosomes fail to separate or during meiosis II when there is unequal distribution of chromosomes. This leads to aneuploidy.
The problem that occur in the brain is the Mental Problem.
The chromatin condenses into thick thread-like structures that later become chromatids.
They are separate processes. So it can be occured
Crossing over occurs between homologous chromosomes, which are not identical, as one member of each pair of homologous chromosomes comes from the mother, and one member comes from the father. Sister chromatids are identical and crossing over would have no effect.
Sister chromatids are two copies of a replicated chromosome. Chromosomes occur in pairs. These will be separated in anaphase of mitosis and one chromatid pair will be left for each daughter cell.