Chapter 10.2 Notes NAME Honors Biology Organisms have tens of thousands of genes that determine individual traits Genes don t exist free in the nucleus but lined up on a Diploid and Haploid Cells In the body cells of animals and most plants, chromosomes occur in One comes from parent, one from parent A cell with of each kind of is called a cell Contains a diploid, or, number of chromosomes This supports idea that we have 2 for every A cell containing of each kind of chromosome is called cell Contains a haploid, or, number of chromosomes Homologous chromosomes chromosomes are chromosomes of each in a diploid cell On homologous chromosomes, are arranged in the order but because there are different possible alleles for the same gene, the 2 chromosomes in a homologous pair are not always to each other. Every pea plant has copies of chromosome 4 (just an example) One came from each
Since the chromosomes in the picture are the for each allele, the plant is for each trait Why meiosis? Remember cell division results in cells with exactly the same and kind of But if mitosis were the form of cell division, each pea plant parent ( chromosomes) would produce with a set of 14 chromosomes That means that each formed by fertilization would have the number of as its parents F 1 would have chromosomes; F 2 would have chromosomes.. That s a! To solve it------! Meiosis cell division that produces containing the number of as a parent s body cell Meiosis is broken down into and Meiosis I = cell creates 2n cells Meiosis II = cell creates two cells Sexual reproduction is the uniting of sperm and egg to form a The sex cells are (male is sperm, female is egg)
Phases of Meiosis
Interphase Prophase I Metaphase I Anaphase I Telophase I Meiosis II The cell its chromosomes Now each chromosome consist of 2 sister chromatids held together by a coils up, forms chromosomes line up with each other and form a part structure called a = 2 homologous, each made up of 2 chromatids They pair so that -sister chromatids from chromosomes can actually break and genetic material = Estimated that during in humans an average of crossovers occurs for each pair of homologous chromosomes Centromere becomes attached to fiber Spindle fibers pull into Homologous chromosomes Each new cell will receive only chromosome from each homologous Spindle breaks down, chromosomes, and cytoplasm into 2 new cells Each cell has of the information of original cell The division is simply a division of products of meiosis I Has prophase II, metaphase II, anaphase II, telophase II
Prophase II Metaphase II Anaphase II Telophase II Spindle forms, spindle fibers attach to chromosome Chromosomes (sister chromatids) pulled to the center of cell Each chromosome splits to opposite poles Nuclei re-form, spindles break down, and cytoplasm divides All of is identical to, except the chromosomes don t before dividing At the end of meiosis II, cells are formed They become, ready to give genetic information to Genetic Variation Mitosis results in genetically cells during meiosis provides a way to allele combinations This means there is an genetic in every generation Genetic Recombination How many sperm can a pea plant produce? Each cell has pairs of chromosomes The 7 pairs can line up in 2 different ways, 128 different kinds of sperm are possible (2 n = 2 7 = 128) Factor in the same number for eggs Now multiply number of possible x number of possible to get the number of different possible offspring 128x128 = 16,384 possible offspring!!
The genetic combinations very depending on the way chromosomes line up during (randomly) For humans, n = So possible sperm = 2 23 = over 8 million Possible eggs = 2 23 = over 8 million Multiplied together gives you over trillion different zygotes that are possible! major source of genetic variation among organisms caused by re-assortment or during meiosis Nondisjunction Polyploidy Sometimes chromosomes fail to correctly This is called Both chromosomes of a homologous pair move to the pole Results in one with an chromosome, and one with a chromosome If fertilization of the one with the chromosome takes place, it results in In humans, trisomy occurs if chromosome is the one with an extra, and results in a baby with Syndrome. If a chromosome it is called Offspring usually don t Syndrome is monosomy. Only found in ; it is when they lack one of their chromosomes organisms with than the usual number of chromosome sets Rare in, usually results in death of zygote Frequently occurs in The flowers and fruits are and plants are An example: plant