Meiosis and Sexual Reproduction Study Guide PDF

Meiosis and Sexual Reproduction Chapter 10 Study Guide Reading and Resources Mader and Windelspecht, Chapter 10 (pp. 166 - 185). Most emphasis on sections 10.1 - 10.4. Khan Academy Videos: https://www.khanacademy.org/science/biology/cellular-molecular-biology/intro-t...

Meiosis and Sexual Reproduction Chapter 10 Study Guide Reading and Resources Mader and Windelspecht, Chapter 10 (pp. 166 - 185). Most emphasis on sections 10.1 - 10.4. Khan Academy Videos: https://www.khanacademy.org/science/biology/cellular-molecular-biology/intro-to-cell-division/v/f ertilization-haploid-diploid-gamete-zygote-homologous https://www.khanacademy.org/science/biology/cellular-molecular-biology/meiosis/v/comparing-m itosis-and-meiosis Vocabulary Meiosis: -​ A type of cell division that reduces the chromosome number by half, producing four unique haploid cells, which are essential for sexual reproduction and genetic variety. Diploid (2n): -​ Refers to the total number of chromosomes, which exist in two sets. Haploid (n) -​ Refers to half the total amount of chromosomes, which is a single set of chromosomes. Chromosome -​ A threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes. Chromatid: -​ one of the two identical halves of a chromosome that has been replicated in preparation for cell division Homologous chromosomes (homologues) -​ \ Gamete -​ A gamete is a reproductive cell (sperm or egg) that carries half of the genetic material needed to create a new organism. Zygote: -​ fertilized egg cell that results from the union of a female gamete (egg, or ovum) with a male gamete (sperm) Gene: -​ The basic unit of heredity, consisting of a sequence of DNA, located in the chromosomes. Allele: -​ one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome. Synapsis: -​ the fusion of chromosome pairs at the start of meiosis. Crossing over: -​ The exchange of genetic material between homologous chromosomes during meiosis. This increases the genetic diversity by mixing up the alleles. Nondisjunction: -​ Failure of two chromosomes to separate during gamete formation Independent assortment: -​ The random distribution of chromosomes into gametes. It ensures that each gamete gets a unique combination of genes contributing to genetic variation/diversity. Fertilization: -​ the action or process of fertilizing an egg, female animal, or plant, involving the fusion of male and female gametes to form a zygote. Aneuploidy (monosomy or trisomy) -​ The correct number of chromosomes in a species is known as “euploidy,” so “aneuploidy” means that the number of chromosomes has changed because of nondisjunction during meiosis. Monosomy means that an individual only has one of a particular type of chromosome, and trisomy means that the individual has three of a particular type of chromosome. Karyotype: -​ a visual display of the chromosomes arranged by size, shape, and banding pattern, may be performed to identify babies with Down syndrome and other aneuploid conditions. Or a complete set of chromosomes.  Meiosis and Sexual Reproduction Collaborative Exercise 1.​ What are the main differences between asexual reproduction and sexual reproduction? -​ Asexual means that the offspring is genetically identical to a single parent. One parent is involved. -​ Sexual means that two parents contribute to create unique offspring. It involves gametes merging into a zygote. 2.​ In what ways does sexual reproduction increase the amount of genetic variation within a species? Why is genetic variation important? (Note: we will repeatedly return to the importance of variation throughout this semester!) Sexual reproduction increases the amount of genetic variation because it takes half of the genes from one parent and half from the other. These genes cross over during meiosis. Independent assortment of chromosomes during meiosis I. Which homologue goes to which cell is random - the gametes will all be different from one another. It makes variation in a species, which is important for evolution 3.​ Why must the cellular division process be different for somatic cells versus gametes? The cellular division process has to be different because gametes have to undergo meiosis while somatic cells only go through mitosis. 4.​ Consider meiosis I. a.​ In one sentence, summarize what happens during meiosis I. -During meiosis, homologous chromosomes are separated into two different cells, reducing the chromosome number by half. b.​ In what ways are mitosis and meiosis I similar? A picture might help! -Mitosis and meiosis are similar because they all involve alignment, separation and chromosome condensation. c.​ In what ways are mitosis and meiosis I different? A picture might help! -Meiosis reduces chromosomes by half, while mitosis maintains it.  5.​ Consider meiosis II. a.​ In one sentence, summarize what happens during meiosis II. -During meiosis two, the sister chromatids of each chromosome are separated into two different cells, resulting in four haploid cells, each with half the original chromosome number. b.​ In what ways are mitosis and meiosis II similar? A picture might help! In what ways are mitosis and meiosis II different? A picture might help! Mitosis produces two genetically identical “daughter” cells from a single “parent” cell, whereas meiosis produces cells that are genetically unique from the parent and contain only half as much DNA.  6.​ At what point during meiosis does: a.​ Crossing over happen? Crossing over happens in meiosis 1 b.​ A cell become haploid? Meiosis 2 7.​ Last semester, we looked at mutations that affected one or a few nucleotides. Consider the effects of chromosome-level mutations. a.​ What causes aneuploidy? At what stage(s) of meiosis does this occur? A change in the chromosome number resulting from nondisjunction during meiosis is aneuploidy. It can happen in meiosis 1, but it usually happens in meiosis 2 b.​ What are deletions, duplications, inversions, and translocations? At what stage(s) of meiosis do these occur? A deletion is when an end of a chromosome breaks off or when two simultaneous breaks lead to the loss of an internal segment. A duplication is the presence of a chromosomal segment more than once in the same chromosome. This may or may not cause visible abnormalities depending on the size of the duplicated chromosome. An Inversion is when a segment of a chromosome has been turned around 180 degrees. A translocation is the movement of a chromosome segment from one chromosome to another, nonhomologous chromosome. These can occur during crossing over Notes from T Leslie: Asexual reproduction - offspring are genetically identical to a parent organism ​ Many single-celled organisms (bacteria, protists) ​ Yeast (fungus) ​ Some species can reproduce by either asexual or sexual means - echinoderms can break off a body part and reproduce asexually or release sperm/eggs Sexual reproduction - Offspring have contributions from two individuals, not genetically identical to either ​ Half genes come from one parent, half from other ​ Two copies of each chromosome. These are called homologous chromosomes (homologues) ​ When a cell has two copies of each chromosome, it is diploid. In contrast, gametes are haploid. ​ Genes are certain regions of the chromosomes. Different versions of a gene are alleles. ​ Because we combine two gametes to form a diploid zygote during fertilization, gametes must be haploid, and thus need a different way of dividing. They do this through the process of meiosis. Why sexual reproduction? This seems like a lot of work. ​ ​ Increases genetic variation ○​ Important for making a species resilient - if a disease, other environmental factor wipes out a large portion of the population, greater chance that someone will survive. ○​ Variation is also the raw material for evolution - if everyone is identical, few opportunities for adaptation ​ 3 ways sexual reproduction increases genetic variation ○​ Crossing over during meiosis I ○​ Independent assortment of chromosomes during meiosis I  ​ Which homologue goes to which cell is random - the gametes will all be different from one another ○​ Fertilization - combines genetic info of two individuals