1. Karyotypes IB1 Biology Song Hee Bae

2. Karyotypes Karyotype: the number and appearance of the chromosomes in an organism. Karyotype is always found in a photograph of the chromosomes found in a cell arranged according to a standard format. Organisms that are same species usually have the same karyotype. Can detect: oGender oChromosome abnormalities

3. Karyotyping 1.Fetal cells obtained 2.Cells are stimulated to divide by mitosis. 3.Stops mitosis in stage of metaphase, because chromosomes are mostly visible in metaphase. 4.Chromosomes in the photograph are cut out and arranged into pairs according to their size and structure. Two Methods of Karyotyping oAmniocentesis: a sample of amniotic fluid is removed from the amniotic sac around the fetus. oChorionic villus sampling: obtaining a tissue sample from the placentas finger-like projections into the uterus wall.

4. Examining Karyotypes Gender Sex chromosomes. oXX – female oXY - male Women - X chromosomes Men - either X or Y chromosomes Chromosome disabilities sometimes, chromosomes do not split during meiosis - non- disjunction. Gametes are produced with either specific chromosome too many or too few. Gametes with one chromosome too few usually quickly die. Gametes with one chromosome too many sometimes survive. = down syndrome

5. Down Syndrome 47 Chromosomes in total Three chromosomes of type 21, rather than two. Can be due either to non-disjunction during the formation of the sperm or egg. Cant deduce the extent of affect. The chance of down syndrome increases with the age of the parents.

6. Vocabulary Karyotype: the number and appearance of the chromosomes in an organism. Karyotyping: the process of cutting the chromosomes in the photograph and arranging into pairs. Amniocentesis: a method of extracting fetus cell by removing a sample of amniotic fluid from the amniotic sac around the fetus, using a hypodermic needle. Chorionic villus sampling: a method of extracting fetus cell by obtaining a tissue sample from the placentas finger-like projections into the uterus wall. Non-disjunction: non-separation of chromosomes.

7. Reference IB Biology Study Guides (page 25) Pearson Biology (page 97) Human Karyotype image linked Mitotic metaphase image linked Sex chromosome image linked Down Syndrome Karyotype image linked