Lecutre 9 - Review for Exam #1

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Esteban Parra

Review for Midterm #1 The Main Topics Reviewed So Far - Topic 1: A review of the molecular basis of life: o DNA, RNA, proteins, and how the information stored in DNA is transmitted: Replication (and mitosis), transcription, translation - Topic 2: How the genetic information is transmitted from generation to generation o Meiosis in the sex cells, and Menellian inheritance - Topic 3 o Population genetics: mutation, gene flow Topic 1: The Molecular Basis of Life Topic 2: How the Genetic Information is Transmitted from Generation to Generation - In organisms with sexual reproduction, a new individual is formed by the union of two gametes - This means that gametes Meiosis - The process of reduction of the number of chromosomes happens only in the sex cells (cells producing gametes), during a process known as meiosis - You should know the details of meiosis, and the differences between meiosis and mitosis - Meiosis is fundamental to understand inheritance and evolution - Differences and similarities Main Differences of Mitosis and Meiosis - Mitosis occurs in somatic cells; meiosis in germ cells - Mitosis has one round of division; meiosis two - Homologous chromosomes do not pair and recombine during mitosis; they do in meiosis Evolutionary Importance of Meiosis - Meiosis is important to understand inheritance and evolution because: o After meiosis, every individual has a different combination of paternal and maternal chromosomes (This explains Mendel’s laws!!!) o Recombination during the first meiotic division further increases variability - Linkage***  know this, this is very important Problems During Meiosis - You should know that some times the process of meiosis is not perfect, and problems during disjunction can alter the final number of chromosomes an individual carries - In most cases, these problems cause spontaneous abortion, but in some cases the zygote is viable. Normally, individuals with trisomies (three copies of one chromosome), or monosomies (one copy of one chromosome), have developmental and health problems - Some examples are down syndrome, turner’s syndrome and Klinefelter’s syndrome If you understand meiosis, you will understand Mendelian Inheritance - If you have no doubt about the process and consequences of meisosi, you will have no problem in understand how simple Mendelian traits are inherited - Some terms that you should know before we revied Mendelian inheritance are: o Locus o Allele o Genotype:  Homozygotes  Heterozygote o Phenotype Using Punnet Squares To Estimate Possible Combinations of Parental and Maternal Gametes - Punnett squares are used to estimate all the possible genotypes resulting from the combination of parental and maternal gametes - When you know if the alleles are dominant, codominant, or if there is incomplete dominance you can also known the resulting phenotypes - The procedure is straightforward, and will help you understand Mendelian inheritance, and the different possibilities of transmission of simple Mendelian inheritance Remember that.. - The genotype outcomes of fertilization depends only on the genotype of the parents, but the phenotype outcome depends on the genotype of the parents and the pattern of dominance/codominance of the alleles - Example: Outcome of a Yy X Yy cross o Dominance  Genotypes 25= YY, 50= Yy, 25=yy  Phenotype: 25 Y, 50 Yy, 25 yy o Codominance  Genotypes: 25= YY, 50  Phenotype: 25 Y, 50 Yy, 25 yy Mendelian Inheritance and Simple Mendelian Diseases - If you know how Punnett squares work, it will be easy for you to understand the transmission of simple Mendelian diseases, or the basic concepts of population genetics - You have to know the different typ
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