Unit 4: Reproduction Chapter 4 The nucleus controls the functions of life.

Traits Traits: are physical features of an organism. They can vary in size or form from one individual to another. Examples include eye color, height and tongue rolling ability.

Heredity Heredity: is the process through which trait patterns are passed from parents to their offspring. Heredity explains why offspring share features with other family members.

Nucleus: The Control Center Nucleus: is the cell organelle that is responsible for heredity and controlling cell activities such as cell division. The nucleus contains the organism’s DNA. The nucleus contains the master set of instructions. These instructions determine what each cell will become, how it will function, when it will grow and divide, and when it will die.

DNA – deoxyribonucleic acid

Characteristics of DNA DNA is located within the nucleus of cells. DNA carries instructions for cell activities and processes. DNA is double stranded. The two strands wrap around each other in a spiral shape called the Double Helix. The sides of the Double Helix are made of sugar and phosphate. The sides of the Double Helix are connected by chemical bonds between the nitrogenous bases.

DNA – Base Pairing The DNA molecule contains 4 nitrogenous bases: 1.Adenine (A) 2.Cytosine (C) 3.Guanine (G) 4.Thymine (T) The pairing of bases is specific. A always joins with T. C always joins with G.

Chromosomes When a cell is ready to undergo cellular division, loosely coiled DNA folds up and becomes compacted. These compacted forms of DNA are called Chromosomes. Chromosomes are X-shaped structures.

Chromosomes

Genes Genes: segments (sections) of DNA. They code for producing proteins in cells. Proteins determine what body cells will become and how they will function.

Differences & Similarities: DNA, Chromosomes and Genes

Mutation Gene Mutation: is a specific, and permanent change in the chemical make up of a gene. A gene mutation is a change in the sequence of A, C, G and T bases. For example, a change from ACCTTGGA to ACTTGGA may result in a malfunctioning protein. Gene mutations can, or may not be, harmful to an organism. Some mutations are beneficial. A gene mutation may result in a malfunctioning protein.

Mutagens Mutagens: are substances or factors that can cause mutations. These factors result in changes to Gene Sequences. There are 2 sources of mutagens. (1)Mutagens that occur naturally. Examples include X-rays, UV rays and viruses. (2) Mutagens that are created by human activities. Examples include cigarette smoke, pollutants and radiation.

Unit 4: Reproduction Chapter 5 Mitosis is the basis of asexual reproduction

Cell Cycle & Development It is necessary for cells to divide, producing more cells, as an organism develops. Cells die and need to be replaced. Cells that take a lot of wear and tear, including skin cells, stomach cells and intestinal cells need to be replaced. The Cell Cycle ensures that body cells are replaced and the overall health of the organism is maintained.

Cell Cycle Stages Cell Cycle: is a series of three stages in the life of a cell. The cycle involves cellular division to produce more identical cells. The 3 stages of the Cell Cycle are: 1.Interphase 2.Mitosis 3.Cytokinesis

Stage 1: Interphase Interphase: is the first and longest stage of the cell cycle. During this stage the cell carries out its various functions and prepares for division. During Interphase the cell doubles all of its material, including its DNA in preparing for division. The process of doubling the amount of DNA in interphase is called Replication.

Stage 2: Mitosis Mitosis: the second, and usually the shortest stage of the cell cycle, involves the division of a cell’s nucleus producing two identical daughter cells.

Stages of Mitosis Mitosis involves 4 distinct stages or steps. The 4 stages of Mitosis, in order, are: 1.Prophase 2.Metaphase 3.Anaphase 4.Telophase

Prophase During prophase the double stranded chromosomes shorten and thicken. The nuclear membrane that surrounded the nucleus breaks down and disappears.

Metaphase During metaphase chromosomes line up across the middle (or equator) of the cell.

Anaphase During anaphase chromosomes are pulled to opposite ends (poles) of the cell. The chromosomes are pulled at their centers.

Telophase At telophase, the sets of chromosomes that reached opposite poles form nuclei. They cell is now ready to divide into two identical daughter cells.

Stage 3: Cytokinesis Cytokinesis: is the final stage of the cell cycle. Once mitosis is complete, the cell membrane pinches together and the cell divides into two identical daughter cells.

The products of Mitosis Mitosis results in one parent cell dividing to produce two identical daughter cells which have the same number of chromosomes as the parent cell. Think about it … How many brain cells originally underwent cell division to produce 24 brain cells? A cell divides by mitosis once every two hours. How many of these cells will be produced after an 8 hour period?

Checkpoints in the Cell Cycle Special proteins at checkpoints monitor cell activities and send this information along to the nucleus. At each checkpoint, the nucleus instructs the cell whether or not to divide. A cell will stop undergoing division if: Not enough nutrients for cell growth Not enough nutrients for cell growth Replication of DNA did not occur Replication of DNA did not occur DNA is damaged DNA is damaged

Asexual Reproduction Asexual Reproduction: a method of reproduction involving only ONE parent, producing identical offspring to the parent. Cloned organisms are produced through asexual reproduction.

Methods of Asexual Reproduction Methods of asexual reproduction include: 1.Binary fission 2.Budding 3.Fragmentation 4.Vegetative reproduction 5.Spore formation

Binary fission Binary fission: a single one-celled parent replicates its genetic material and divides into two equal parts. This method is the only method of reproduction for some types of bacteria. Amoebas reproduce by binary fission. Algae and protozoa also reproduce by binary fission.

Budding Budding: part of a cell pushes outward to form an outgrowth or bud that may detach from the parent cell. Unicellular yeasts, and multicellular organisms such as the hydra and sponges reproduce by budding.

Fragmentation Fragmentation: a fragment, a piece of an organism broken off as a result of injury, develops into a clone of its parent. Some species of sea stars reproduce asexually by Fragmentation. Some plant also reproduce this way.

Vegetative Reproduction Vegetative Reproduction: special cells, usually in plant stems and roots, dived repeatedly to eventually form a plant that is identical to the parent. Tulips, Daffodils, Potato Sprouts (“eyes”), and Strawberry stem runners produce plants this way.

Spore Formation Spore Formation: reproducing asexually by forming single celled spores. Spores: a reproductive cell that grows into a new individual by mitosis. Spores can be carried easily by the actions of wind and water. Some plants, including ferns and mosses reproduce by spore formation. Mold also can reproduce this way.

Unit 4: Reproduction Chapter 6 Meiosis is the basis of sexual reproduction.

Sexual Reproduction Sexual Reproduction: a method of reproduction involving two parents, producing offspring that are genetically different from each other, either parent, and from other members of their species.

The Process of Sexual Reproduction Sexual reproduction involves uniting specialized cells called Gametes. In animals, male gametes are called sperm and female gametes are called eggs. Fertilization occurs when the gametes unite, with the sperm penetrating an egg cell. The process of fertilization results in a cell called a Zygote. The Zygote undergoes cell division and mitosis and develops into an Embryo. The embryo grows continuously to form a new organism.

Chromosome Numbers Diploid number (2n): body cells (all cells excluding sperm and egg) have two sets of chromosomes. The diploid number for humans is 46 (2 x 23). Humans inherit one set of 23 from their male parent and one set of 23 from their female parent. Haploid number (n): gametes (sperm and egg cells) have only one set of chromosomes and are termed haploid. Human gametes have one set of 23 chromosomes. So, the haploid number for humans is 23. During fertilization, a haploid (n) sperm cell unites with a haploid (n) egg cell to form a diploid (2n) zygote. n + n = 2n

Meiosis Meiosis: process of producing gametes (sperm and egg cells) with the haploid (n) number of chromosomes. Meiosis occurs in the male and female sex organs (respectively the testes and ovaries).

Meiosis Meiosis involves two rounds of cellular division: 1.Meiosis I 2.Meiosis II

Homologous Chromosomes Homologous Chromosomes: are pairs of chromosomes that are the same size, shape and have genes that are in the same locations.

Meiosis I: Stages Meiosis I involves: 1.Prophase I 2.Metaphase I 3.Anaphase I 4.Telophase I

Prophase I Homologous chromosomes pair up.

Metaphase I Homologous chromosomes pair up at the equator.

Anaphase I Homologous chromosomes separate and are pulled towards opposite poles (ends) of the cell.

Telophase I Homologous pairs have moved to opposite ends of the cell and the cell begins to divide.

Interkenesis Interkenesis: is the stage between cell divisions. The cells grow and make various proteins.

End Products of Meiosis I The end products of Meiosis I are two diploid (2n) daughter cells. These cells now go on to enter Meiosis II.

Meiosis II Meiosis II involves: 1.Prophase II 2.Metaphase II 3.Anaphase II 4.Telophase II

Prophase II There is one chromosome of the homologous pair in each cell.

Metaphase II Chromosomes line up at the equator (middle of the cell).

Anaphase II Half of each X-shaped chromosome is pulled apart towards opposite poles (ends) of the cell.

Telophase II A nucleus forms around each set of chromosomes and the cell begins to divide to produce 4 gametes.

Comparing/Contrasting Mitosis verses Meiosis MitosisMeiosis Types of CellsBody CellsSex Cells (sperm and eggs) Number of Daughter Cells produced 24 Amount of Genetic Material in each daughter cell Same number of chromosomes (2n) in each cell. Each daughter cell is diploid. Half the number of chromosomes (n) in each cell. Each gamete (sex cell) is haploid.

Sexual Reproduction Sexual reproduction involves two parents. Sexual Reproduction does not necessarily require sexual intercourse.

Method of Fertilization Fertilization may be: 1.Internal Fertilization – sperm cells are deposited inside the female’s body where they meet an egg cell. Requires sexual intercourse. 2.External Fertilization- sperm and egg cell unite outside the bodies of parents. This is common in animals that live in water.

Organisms that reproduce sexually Mosses External fertilization occurs in mosses. External fertilization occurs in mosses. Water is needed to transport gametes, allowing sperm cells and egg cells to unite. Water is needed to transport gametes, allowing sperm cells and egg cells to unite. Male and female sex organs develop on the end of stems or branches. Male and female sex organs develop on the end of stems or branches. Asexual reproduction may also occur by spore production. Asexual reproduction may also occur by spore production.

Organisms that reproduce sexually Flowering Plants Internal fertilization occurs in flowering plants. Internal fertilization occurs in flowering plants. The process of Pollination occurs. Male gametes are formed in special cases called Pollen. Pollination is the transfer of pollen to the female part of the flower. The process of Pollination occurs. Male gametes are formed in special cases called Pollen. Pollination is the transfer of pollen to the female part of the flower. The male reproductive organ in a flower is called the Stamen. The female reproductive organ in a flower is called the Pistil. The male reproductive organ in a flower is called the Stamen. The female reproductive organ in a flower is called the Pistil. Pollination and fertilization occurs at the female reproductive organ, at the pistil. The pollen lands on the pistil and sperm are delivered to the egg cells. The fertilized egg becomes a seed. The seed protects the developing embryo. Pollination and fertilization occurs at the female reproductive organ, at the pistil. The pollen lands on the pistil and sperm are delivered to the egg cells. The fertilized egg becomes a seed. The seed protects the developing embryo.

Organisms that reproduce sexually Insects The life cycle of insects involves metamorphosis. Metamorphosis is the change in an individual's form as it develops.

Incomplete Metamorphosis Incomplete Metamorphosis: involves subtle (minor) changes through 3 life cycle stages: 1.Egg 2.Nymph (smaller immature version of adult) 3.Adult Grasshoppers go through Incomplete Metamorphosis.

Complete Metamorphosis Complete Metamorphosis: a change in the form of an insect as it matures, where the adult is completely different than the larval stage. The four common stages of complete metamorphosis, as seen in the butterfly are: 1.Egg 2.Larva (caterpillar) 3.Pupa 4.Adult

Asexual verses Sexual Reproduction AsexualSexual # of parent cells12 Gametes (eggs or sperm) None (cell divides)2 (egg cell and a sperm cell unite to form a zygote) Variation (difference) in offspring Lesser (all offspring identical) Greater (genetic diversity) Amount of Energy required LesserGreater Parental careLesserGreater Mitosis or Meiosis?MitosisMeiosis

Genetic Conditions Genetic conditions that cannot be solved using current scientific & technological knowledge include: 1.Down Syndrome 2.Cystic Fibrosis 3.Allderdice Syndrome

Shifts in the Field of Genetics Our understanding of genetics has changed over time as new technologies have become available. New technologies have made it possible to get a better look at genes and their influence on traits.

Mendel’s Experiments In the mid 1800’s, Gregor Mendel experimented with inherited traits in pea plants, including color and shape. Mendel’s studies of pea plants demonstrated that traits were inherited from one generation to the next. Mendel’s studies suggested the involvement of “dominant” and “recessive” factors in the transmission of traits from parents to offspring. Dominant traits are always expressed, however recessive traits are not always expressed.

Watson and Crick: The double helix model of DNA A more clear understanding of genes came about when Francis Crick and James Watson, described the structure of DNA in Crick and Watson showed that DNA is an organization of genes in a double helix shape, like a twisted ladder. Specific base pairing on this ladder helped to explain how DNA could replicate (copy itself). This development also helped to explain how and why mutations occur.

Human Genome Project In the Human Genome Project, scientists around the world collaborated for about 20 years to identify every gene in human DNA, mapping the human genome. The Human Genome Project made a sort of map that can be used to search for and identify particular genes. The Human Genome Project has provided information into how and why various genetic diseases come about.

Genetic Engineering Genetic Engineering: is biotechnology that deals with the manipulation of the genome. Scientists have figured out how to cut a gene out of one DNA strand and place it into another. The ability to recombine DNA (recombinant DNA) has made significant contributions to food and medicine.

Genetic Engineering & Food Production Plants and animals have improved through recombinant DNA technology. Such organisms are labeled as Genetically Modified Organisms (GMOs). This plays an important role in the agricultural industry, specifically crop production. Genes have been altered to produce plants that are resistant to colder temperatures, chemicals and disease. Genetic engineering has been used to produce organisms with desired traits.

Genetic Engineering & Medicine Scientists use recombinant DNA technology to produce drugs and provide human gene therapy. Recombinant DNA technology is being used to help Diabetes patients, in which the correct human gene for insulin production, is placed within the genome of a bacterium. The bacterium then produces insulin which can be used as medicine. Humans who lack a specific gene or who have a defective gene can have a healthy, functioning gene inserted into their DNA. This is human gene therapy.