Jeans to Genes and Asexual vs. Sexual Reproduction

Vocabulary Chromosomes- condensed chromatin, contains DNA that carries genetic information Genes- a segment of DNA that codes for a specific trait (which are instructions for making a specific protein) Alleles- alternate forms of a gene that code for a single trait at the same location on a homologous chromosome

Genes control…. the production of proteins (or other materials) made by the cell. Where are proteins made in the cell…… ribosomes

History of Chromosome Research Walter Sutton- an American geneticist (1903) who studied grasshoppers. He was trying to figure out how sex cells were formed (the movement of chromosomes from parents to offspring) He observed that the egg and sperm have half the number of chromosomes as the body cells

Theory of Inheritance Genes are carried from parents to their offspring on chromosomes. Previous thought…… Father contribute all of the information for the child, mother only contributed nutrition.

Mitosis vs. Meiosis What happens to the number of chromosomes in a cell before mitosis begins? When does this happen? The number of chromosomes double (each is copied) during the S-phase of the cell cycle.

Mitosis Part of the cell cycle in which the doubled chromosomes separate into two sets, in order to produce daughter cells that are exact copies of the parent cell.

Meiosis The doubled chromosomes divide twice to produce four daughter cells that have half the number of chromosomes as the parent cell.

Comparing the two processes… # of chromosomes in each cell at the end of the process # of cells at the end of the process haploid/diploid Mitosis Full set2diploid Meiosis Half of the set4haploid Haploid: contain half of the complete set of chromosomes (sex cells- gametes) Diploid: contain a complete set of chromosomes (body cells- somatic cells)

Gametes different than somatic Gametes (sex cells) have half the number of chromosomes as body cells, so during fertilization two gametes combine to form one offspring with a full set of chromosomes.

Reproduction Asexual vs. Sexual

What is reproduction? Reproduction is the process by which organisms produce more of their own kind. Think about it – Without reproduction, all life on earth would no longer exist.

Reproduction: The Continuity of Life Reproduction Sexual Reproduction Asexual Reproduction

What is Asexual Reproduction? Only one parent is involved. Offspring are genetically identical to their parents. All cells that come from a single cell are genetically identical to it and to each other; they are all clones.

Types of Asexual Reproduction 1.Binary Fission - occurs in one-celled organisms such as the ameoba and paramecium. The nucleus divides by mitosis and the cytoplasm divides, forming 2 new daughter cells of equal size.

Types of Asexual Reproduction 2.Conjugation- occurs in one-celled organisms such as the paramecium. Here the organisms exchange genetic material prior to reproducing by binary fission.

Types of Asexual Reproduction 3.Budding - Occurs in Hydra and yeast. Buds (daughter cells) form on the side of parent. The daughter cells can separate or remain attached.

More examples of budding include: Sponges, Corals and Jellyfish…

Types of Asexual Reproduction 4.Fragmentation – occurs in flatworms (Planaria) Refers to the replacement or regrowth of lost or damaged body parts

Some of these animals can also grow new organisms from the severed pieces (Segmented Worms and Sea Stars)

Types of Asexual Reproduction 5. Parthenogenesis Occurs in some Fish, Reptiles, Amphibians and Aphids. Offspring can arise from unfertilized eggs. Most of these species can switch between sexual and asexual reproduction. (depending on conditions)

Example: Bees – unfertilized eggs become male drones - fertilized eggs – female workers or queens

Types of Asexual Reproduction 6. Vegetative Propagation- offspring are produced from plant parts. Advantages: clones of parents (helpful when trying to produce more of a desirable plant) plants bypass immature seedling stage

OrganismDescription of Sexual Form of Reproduction Description of Asexual Form of Reproduction ParameciumBinary Fission- splits in half to form two Conjugation- exchange of genetic material between two, before binary fission HydrasOne forms testes, the other forms ovaries. Budding- offspring forms on body of parent, separates eventually PlanariaHermaphrodites- each animal possesses complete male and female organs. Fragmentation- organism splits in the middle, and grows new halves. Komodo DragonMale and female KDs.Parthenogenesis- eggs becomes embryos without male fertilization. Potato Strawberry Vegetative Propagation- offspring produced from plant parts

Sexual Reproduction

What are the differences between the two types of reproduction? # parentsOffspring produced compared to the parent Asexual Reproduction 1 parentexact copies (except parthenogenesis) Sexual Reproduction 2 parentsunique combination of genes- produce variation in the species

Compare the result of mitosis and meiosis in dog cells that have 78 chromosomes. HINT: How many daughter cells are produced? How many chromosomes are in each daughter cell? MitosisMeiosis