Genetics Warm Up Exercise: -Using your previous knowledge of genetics, determine what maternal genotype would most likely yield offspring with such characteristics. -Use the genotype that you came up with for the mother, to complete a punnett square.
Defining Key Terms Heredity- the transmission of traits from one generation to the next. Variation- differences between members of the same species. Genetics- the scientific study of heredity and hereditary variation. Meiosis- a modified type of cell division in sexually reproducing organism consisting of two rounds of cell division but only one round of DNA replication. It results in cells with half the number of chromosome sets as the original cell.
Gene- a unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA in some viruses). A gene s specific location along the chromosome is called the gene s locus. Gametes- reproductive cells that transmit genes from one generation to the next.
Sexual vs. Asexual Reproduction Asexual Reproduction- a single individual is the sole parent and passes copies of all its genes to its offspring. As a result, the offspring are an exact copy of themselves (a clone). Sexual Reproduction- two parents give rise to offspring that have unique combinations of genes inherited from two parents. Offspring of sexual reproduction vary genetically to their siblings and both parents.
Karyotypes Karyotype- a display of the chromosome pairs of a cell arranged by size and shape. 22 pairs of autosomes 1 pair of sex chromosomes Sister chromatids Centromere Pair of Homologous Replicated Chromosomes
Fig. Key 2n = 6 Maternal set of chromosomes (n = 3) Paternal set of chromosomes (n = 3) Two sister chromatids of one replicated chromosome Centromere Two nonsister chromatids in a homologous pair Pair of homologous chromosomes (one from each set)
Exit Slip Provide the following information on a note card. List two authentic examples of offspring that reproduce sexually and two that reproduce asexually. How are homologs similar, and how are they different? The fruit fly, Drosophila melanogaster has a chromosome number of 4. Draw a picture of this cell. Homework: Finish reading chapter 13 and complete reading guide- due Friday! Work on genetics disease project.
The Human Life Cycle Fertilization- the union of haploid gametes to produce a zygote. Meiosis- gametes (sex cells) reproduce by meiosis
Fig. 13-7-3 Interphase Homologous pair of chromosomes in diploid parent cell Chromosomes replicate Homologous pair of replicated chromosomes Sister chromatids Diploid cell with replicated chromosomes Meiosis I Meiosis II 1 Homologous chromosomes separate Haploid cells with replicated chromosomes 2 Sister chromatids separate Haploid cells with unreplicated chromosomes
Fig. 13-8a Prophase I Metaphase I Anaphase I Telophase I and Cytokinesis Sister chromatids Centrosome (with centriole pair) Chiasmata Spindle Centromere (with kinetochore) Metaphase plate Sister chromatids remain attached Homologous chromosomes Fragments of nuclear envelope Microtubule attached to kinetochore Homologous chromosomes separate Cleavage furrow
Fig. 13-8d Prophase II Metaphase II Anaphase II Telophase II and Cytokinesis Sister chromatids separate Haploid daughter cells forming
SUMMARY
Genetic Variation Independent Assortment of Chromosomesallele pairs separate independently during the formation of gametes.
Fig. 13-11-3 Possibility 1 Possibility 2 Two equally probable arrangements of chromosomes at metaphase I Metaphase II Daughter cells Combination 1 Combination 2 Combination 3 Combination 4
Genetic Variation Crossing Over- the exchange of genetic material between nonsister chromatids during prophase I of meiosis.
Fig. 13-12-5 Prophase I of meiosis Pair of homologs Chiasma Nonsister chromatids held together during synapsis TEM Anaphase I Centromere Anaphase II Daughter cells Recombinant chromosomes
Genetic Variation Random Fertilization- there are over 70 trillion possible diploid combinations of a zygote during fertilization. This makes each individual truly unique. Mutations
Exit Slip Meiosis II is similar to mitosis in that: a) Sister chromatids separate during anaphase. b) DNA replicates before the division. c) The daughter cells are diploid. d) Homologous chromosomes synapse. e) The chromosome number is reduced. Homework: Finish lab questions. Read chp. 14, section 1. Complete reading guide. Study for quiz (tomorrow). Genetics presentation research due next class.