- reduction of diploid cells into haploid gametes in the reproductive organs
- organisms that are have two copies of each chromosome (homologous chromosomes) need to reduce it to only one copy so that the fertilisation of two haploid cells will create one diploid zygote. Homologous chromosomes have the same strucural features and all the genes are located on the same loci position.
- Meiosis is divided into two divisions. Meiosis I reduces a diploid nucleus into a haploid nucleus. Meiosis II separates sister chromatids before they are replicated in interphase
Process of Meiosis: See 10.1
Non-Disjunction: failure of chromosomes to properly separate can result in gametes with extra or missing chromosomes. this can occur during anaphase I (leading to four affected cells) or anaphate II (leading to two affected cells).
Down Syndrome: three copies of chromosome 21. A parent had two copies of chromosome 21, as a result of non-disjunction, in addition to the one copy from the other parent.
Karyotype: Visual profile of the chromosomes within a cell. Chromosomes are arranged in their homologous pairs and arranged according to their structural characteristics.
Karyotyping is done by harvesting cells usually from the fetus or white blood cells of adults. Cell division is induced chemically and stopped when the chromosomes are condensed in mitosis. Chromosomes are stained, photographed then arranged according to its structure. Disorders can be found by looking at the chromosome number with disjunction or at the number of chromosomes that are present
Pre-Natal Karyotyping can be used to determine the gender of the child and to test for any chromosomal abnormalities such as down syndrome. This is done by amniocentesis or chorionic villus sampling. Amniocentesis can be done at week 16 of pregnancy with a 0.5% chance of miscarriage. A needle is inserted into the amniotic cavity in the uterus through the abdominal wall. A sample of the amniotic fluid with the fetal cells is taken. Choronic villus sampling can be done at the 11th week of pregnancy. A sample of chorionic villi, which also contains fetal cells, is collected with a tube that is inserted through the cervix
Non-Disjunction: failure of chromosomes to properly separate can result in gametes with extra or missing chromosomes. this can occur during anaphase I (leading to four affected cells) or anaphate II (leading to two affected cells).
Down Syndrome: three copies of chromosome 21. A parent had two copies of chromosome 21, as a result of non-disjunction, in addition to the one copy from the other parent.
Karyotype: Visual profile of the chromosomes within a cell. Chromosomes are arranged in their homologous pairs and arranged according to their structural characteristics.
Karyotyping is done by harvesting cells usually from the fetus or white blood cells of adults. Cell division is induced chemically and stopped when the chromosomes are condensed in mitosis. Chromosomes are stained, photographed then arranged according to its structure. Disorders can be found by looking at the chromosome number with disjunction or at the number of chromosomes that are present
Pre-Natal Karyotyping can be used to determine the gender of the child and to test for any chromosomal abnormalities such as down syndrome. This is done by amniocentesis or chorionic villus sampling. Amniocentesis can be done at week 16 of pregnancy with a 0.5% chance of miscarriage. A needle is inserted into the amniotic cavity in the uterus through the abdominal wall. A sample of the amniotic fluid with the fetal cells is taken. Choronic villus sampling can be done at the 11th week of pregnancy. A sample of chorionic villi, which also contains fetal cells, is collected with a tube that is inserted through the cervix
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