Meiosis and Sexual Reproduction PDF

Lesson 3.2 Meiosis and Sexual Reproduction Objectives https://edpuzzle.com/media/677c296ca05c77140999 5566 1.3.2.1 Identify the similarities and differences within homologous chromosomes (Length, centromere position, gene carried) Homologous Chromosomes Human body cells have 46 chromosome...

Lesson 3.2 Meiosis and Sexual Reproduction Objectives https://edpuzzle.com/media/677c296ca05c77140999 5566 1.3.2.1 Identify the similarities and differences within homologous chromosomes (Length, centromere position, gene carried) Homologous Chromosomes Human body cells have 46 chromosomes. Each parent contributes 23, resulting in 23 pairs of chromosomes. Chromosomes that make up a pair, one from each parent, are called homologous chromosomes. Homologous chromosomes have the same length and centromere position. They carry genes that control the same traits.  Chromosome Numbers All cells contain genetic information in the form of DNA molecules. The instructions for traits (for example, hair color) are located on chromosomes. The DNA on chromosomes is arranged in regions called genes that code for the formation of proteins, which carry out most of the work of cells. Each chromosome consists of hundreds of genes, each playing a role in determining characteristics and functions of the cell. Sexual reproduction 3.2.2 Differentiate between haploid and diploid cells and give examples of each  3.2.12 Define karyotype and explain how it is prepared 2.2.12 Define “karyotype” and explain how it is prepared. Karyotypes The study of genetic material does not involve the study of genes alone. Scientists also study whole chromosomes by using images of chromosomes stained during metaphase. The staining bands identify or mark identical places on homologous chromosomes. During metaphase of mitosis, each chromosome has condensed greatly and consists of two sister chromatids. The pairs of homologous chromosomes are arranged in decreasing size to produce a micrograph called a karyotype. I can explain the transmission of genetic material to offspring is through egg and sperm. 12345 3.2.12 Define karyotype and explain how it is prepared 3.2.4 Explain how the individual’s sex is determined 3.2.10 Compare and contrast sexual and asexual reproduction 3.2.5 Describe the specific events that occur within each stage of meiosis I and meiosis II 3.2.6 Identify each phase of meiosis in a diagram and put them in the correct order 3.2.7 Describe the processes of crossing over and independent assortment and explain how they contribute to genetic variations https://edpuzzle.com/media/63fd058724cd6a416ca39be5  Meiosis I Gametes ( which are eggs and sperms) form during meiosis, a type of cell division that reduces the number of chromosomes. Meiosis occurs in the reproductive structures of organisms that reproduce sexually, forming haploid gametes or spores. It reduces the chromosome number by half through the separation of homologous chromosomes.  Meiosis I Interphase Chromosomes replicate. Chromatin condenses. Prophase I Homologous chromosomes pair. Each chromosome consists of two chromatids. Crossing over produces the exchange of genetic information. The next slide illustrates the process. The nuclear envelope breaks down. Spindles form.  Meiosis I Crossing over is a process during which chromosomal segments are exchanged between a pair of homologous chromosomes.  Meiosis I Metaphase I Chromosome centromeres attach to spindles. Homologous chromosomes line up at equator. Anaphase I Homologous chromosomes separate and move to opposite poles of the cell. Telophase I Spindles break down. Chromosomes uncoil to form two nuclei. The cell divides.  Meiosis II Prophase II Chromosomes condense. Spindles form in each new cell. Spindle fibers attach to chromosomes. Metaphase II Centromeres of chromosomes line up randomly at the equator of each cell. Anaphase II Centromeres split. Sister chromatids separate and move to opposite poles.  Meiosis II Telophase II Four nuclei form around chromosomes. Spindles break down. Cells divide. Products Four cells have formed. Each nucleus contains a haploid number of chromosomes. 3.2.7 Analyze diagrams to compare and contrast mitosis and meiosis  The Importance of Meiosis Meiosis Provides Variation Depending on how chromosomes line up at the equator, four gametes with four different combinations of chromosomes can result. This independent assortment of alleles during gamete formation is a source of genetic variation. 3.2.7 Describe the processes of crossing over and independent assortment and explain how they contribute to genetic variations 3.2.13 use diagrams to explain how nondisjunction is related to errors in mitosis and meiosis Karyotypes and Nondisjunction Nondisjunction Cell division during which sister chromatids fail to separate properly (which happens occasionally) is called nondisjunction. Nondisjunction can result in extra copies of certain chromosomes or only one copy of a particular chromosome in offspring. In humans, alterations of chromosome numbers are associated with serious disorders, which are often fatal. Nondisjunction  Karyotypes and Nondisjunction Autosomes Autosomes are chromosomes that are not sex chromosomes. Humans typically have 22 pairs of autosomes. Down syndrome is the result of an extra chromosome 21 and is often called trisomy 21.  Genetic Material The cell in this graph is undergoing normal meiosis. Meiosis produces daughter cells with half as many chromosomes as the parent cell (2nà n) and this graph shows this pattern. Meiosis I: Homologous pairs separate. Each daughter cell has half the initial number of chromosomes, but each chromosome has two S phase chromatids. Meiosis II: Chromatids separate. Each daughter cell has half the initial number of chromosomes, wach with only one chromatid. I can explain how the quantity of genetic material changes during meiosis.  Quiz 2. Which is not a characteristic of homologous chromosomes? A Homologous chromosomes have the same length. B Homologous chromosomes have the same centromere position. C Homologous chromosomes have the exact same type of allele at the same CORRECT D Homologous chromosomes pair up during meiosis I.  Quiz 3. Which does not occur during telophase II? A Chromosomes C Spindles break down. condense. CORRECT B Four nuclei form D Cells divide. around chromosomes.  Quiz 4. What could explain a human karyotype showing 47 chromosomes? A monosomy C codominance B dominant traits D trisomy CORRECT  Quiz 5. Why does nondisjunction occur? A The sister chromatids do C Cytokinesis does not not separate. CORRECT occur properly. B The chromosomes do D The nucleoli do not not condense disappear. properly.