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REPRODUCTION CHAPTER 3 TRAITS • Heredity is the passing of traits from parents to offspring. • What are traits? ASEXUAL REPRODUCTION • Asexual Reproduction – A new organism or cell is produced from one organism or cell – Because there is only one parent, the offspring will be genetically identical to the parent – The offspring will have all the same traits as the parent TYPES OF ASEXUAL REPRODUCTION Fission • Parent cell splits in two • Very fast, can take as little as 20 minutes TYPES OF ASEXUAL REPRODUCTION Forming Spores • Spores can develop into new organism with the same DNA TYPES OF ASEXUAL REPRODUCTION Budding During budding, the organism grows a “bud” on a part of it by mitosis. When the bud grows large enough, it breaks off and lives on its own. TYPES OF ASEXUAL REPRODUCTION Regeneration Regeneration is the process that uses mitosis to regrow body parts. Some organisms will only regrow the body part that was severed. In some organisms, the severed part will become its own separate organism HOW ARE TRAITS PASSED ON? CHAPTER 3, LESSON 2 DNA • The instructions for an organism’s traits can be found in it’s DNA • The structure of DNA makes it possible for organisms to pass traits to their offspring GENES • A gene is a series of base pairs • The number of base pairs varies from gene to gene DNA NITROGENOUS BASES PAIRING • Nitrogenous bases in DNA always pair up in a specific pattern • Adenine (A) always pairs up with Thymine (T) • Cytosine (C) always pairs up with Guanine (G) A->T C-> G SEXUAL REPRODUCTION CHAPTER 3, LESSON 3 MITOSIS VS. MEIOSIS • Meiosis is the formation of sex cells – Mitosis is asexual reproduction • Sex cells have half the number of chromosomes of the parent cell – Parent cells have chromosome pairs, sex cells have single chromosomes • Meiosis results in 4 new cells – Mitosis results in 2 new cells • Meiosis has 2 cycles – Mitosis has 1 cycle FERTILIZATION IN FLOWERING PLANTS • The stamen is the male reproductive organ of flowers • Produces pollen • The pistil is the female reproductive organ • The ovary is the base of the pistil • Ovules are formed in the ovary FERTILIZATION IN ANIMALS • Sperm cells contain unpaired chromosomes • Egg cells contain unpaired chromosomes • During fertilization, the sperm cell and egg cell unite, and the DNA of the two cells combines • The fertilized egg cell is called a zygote INDIVIDUALS DIFFER • Offspring produced by sexual reproduction get half of their chromosomes from their mother and half from their father, resulting in shared characteristics from both parents – Offspring from asexual reproduction have an exact copy of the chromosomes from the one parent cell COMPARING SEXUAL AND ASEXUAL REPRODUCTION ASEXUAL REPRODUCTION • • • • Can happen quickly Requires less energy Needs just one parent cell Produces offspring with DNA identical to parent SEXUAL REPRODUCTION • • • • Is a slow process Requires more energy Must have two parent cells Produces offspring with unique DNA HOW DO GENES DETERMINE TRAITS? CHAPTER 3, LESSON 4 DOMINANT AND RECESSIVE • Genes work together to determine individual traits. • Dominant Trait – A trait that will appear in the offspring if one of the parents contributes it. – In humans, dark hair is a dominant trait; if one parent contributes a gene for dark hair and the other contrib utes a gene for light hair, the child will have dark hair. DOMINANT AND RECESSIVE • Recessive Trait – A trait that must be contributed by both parents in order to appear in the offspring. • Recessive traits can be carried in a person's genes without appearing in that person. – A dark-haired person may have one gene for dark hair, which is a dominant trait, and one gene for light hair, which is recessive. – Because of this, it is possible for two dark-haired parents to have a light-haired child – Both parents would have had to pass on their recessive gene to the child SHARING DOMINANCE • Not all genes follow the dominant-recessive pattern • Some traits show both versions of a gene at work – Erminette Chicken – Four O’Clock Plants SELECTIVE BREEDING • Selective Breeding – Selecting a few organisms with desired traits to serve as parents of offspring – Selective breeding has been used for thousands of years – Used in plants and animals to get desired traits such as better fruits and vegetables, better/stronger animals, colors of flowers, etc.