Heredity- The science of passing traits from parents to offspring

-the traits are passed in genes found on chromosomes -Genes are small segments of DNA on chromosomes.

-DNA is the genetic information found in the nucleus of a cell. -DNA controls all the cell’s activities

2 ways of passing on traits 1. Asexually- one parent makes an exact copy that is genetically identical, meaning the same DNA 2. Sexually- two parents combine genes to make a new genetic variety

Sexual Reproduction -created from the union of two sex cells -Sex cells are created from meiosis which reduces chromosome number by half.

Fertilization- When two sex cells combine and each contribute one half of the chromosomes

Meiosis-creation of sex cells Fertilization-union of sex cells

Human example: During meiosis sex cells are created that have 23 chromosomes each. Sperm cell- 23 chromosomes (½ of 46) Egg cell- 23 chromosomes (½ of 46) During fertilization the egg and sperm combine and create a unique cell that again has 46 chromosomes and all the DNA to create a human.

Chromosome number varies from species to species. In plants a pollen cell(male sex cell) combines with an egg cell (female sex cell) to create a new seed(organism).

1. What is sexual reproduction? 2. Pea plants have 14 chromosomes. How many chromosomes would be in a new pea plant? How many chromosomes would be in a sex cell of a pea plant? 3. Draw a brief sketch showing fertilization at the cellular level in pea plants

Asexual reproduction one parent makes an exact copy NO sex cells NO union of cells

Types of asexual reproduction Budding- a new individual grows out of the body of the parent Ex: Hydra Fragmentation- Parent breaks into pieces that can each form an individual Ex: Flat worms Regeneration- Part of the parent is detached and can form a new individual Ex: Star fish

Vegetative reproduction A type of asexual reproduction employed by plants wherein new independent individuals emerge from the vegetative parts of plants, such as specialized stems, leaves, roots, and not from seeds or spores. Supplement Examples include the formation of plantlets on specialized leaves (e.g. kalanchoe), the growth of new plants out of rhizomes or stolons (e.g. strawberry), or the formation of new bulbs (e.g. tulips). Spore Formation A dormant, reproductive cell formed by certain organisms. It is thick-walled and highly resistant to survive under unfavorable conditions so that when conditions revert to being suitable it gives rise to a new individual. Some of the spore-producing organisms are bacteria, fungi, algae and plants. In plants, a spore is similar to a seed by being a dispersal unit. The difference is that the spore has very little stored food resources compared with seeds. Some bacteria that can form spores are health hazards as they can survive pasteurization and sterilization.

Passing on Traits -Parents pass genes to their offspring. -Gregor Mendel experimented with pea plants to discover how traits are passed on. - He found out some genes are dominant and some are recessive

Dominant- gene that masks another gene - represented with capital letter Recessive- genes that are hidden -represented with a lowercase letter Example: dominant tall gene = T recessive= t

Each individual has two genes for each trait Each parent passes on one gene for each trait. Example: Tall plant crosses with a short plant Parents: T T x tt Offspring: Tt -Because of the dominant trait this offspring would be tall

Punnett Squares

Genotype: Actual genetic makeup or genes (letters) EX: TT or Tt Phenotype: The trait the organism portrays (looks) Ex: Tall or short

Homozygous (Pure or purebred): Having 2 genes that are the same Ex: TT or tt Heterozygous: Having 2 genes that are different Ex: Tt