Grade 11 Bio

LESSON #9 22a) There would be 3 chromosomes present in each of the cells that make up the stomach of mosquito. 22b) Interphase | b | Prophase | C | Metaphase | D | Anaphase | A | Telophase | E | 22c) There would be 3 chromosomes present in the sperm cells of a mosquito. 22d) Interphase | C | Prophase 1 | A | Metaphase 1 | I | Anaphase 1 | E | Telophase 1 | F | Prophase ii | H | Metaphase ii | B | Anaphase ii | G | Telophase ii | d | Prophase 1 is where the homologous chromosomes pair up and recombination occurs. 23) Non – Disjunction is the failure of chromosomes to separate properly. Non disjunction may occur during anaphase 1 or anaphase ii. If the tetrads do not separate normally during anaphase 1, an entire tetrad can end up on one side, therefore during the stages of meiosis ii gamates can be produced that either have extra chromosomes or are missing chromosomes. In the case of Down Syndrome the non disjunction has produced a gamete with an extra chromosome 21. 24a) Interphase 1 – there are three double stranded chromosomes, it is not a diploid because it does not contain 2 sets of DNA. The DNA in the nucleus has replicated the extra double stranded chromosome. b) Anaphase 1 – The double stranded tetrads are pulled apart so that the chromosomes are separated to each pole, however one pole has an extra pair because of the extra set. c) The nuclear membranes have reappeared and the spindle fibers have disappeared. One of the daughter cells is a haploid and one is not because of the extra chromosome. D) Telophase II the daughter cells have split into 4, daughter cells contain the correct number of chromosomes and 2 others have an extra chromosome each. 25) There are a number important factors to consider in this answer. The first being is whether or not the non down syndrome parent is a carrier of the recessive down syndrome gene. If so it increases the