Chapter 20:1 NotesPages 590-597

•Continuing Life

Reproduction

•How offspring are produced

•Species could not go on without •reproduction

•Parents pass on heredity •material

•DNA controls how offspring will look because the DNA controls what proteins each cell will produce

Life’s Code - DNALife’s Code - DNA• DNA is found inside chromosomes

• DNA is your individual blueprint

• DNA determines your hair color, ear shape, blood type, and EVERYTHING else about you!

• The basic shape is like a twisted ladder or zipper

• The ladder rungs contain pairs of bases

• There are 4 bases that pair up in different orders on the ladder

Cell Division• Mitosis creates new cells due to aging,

missing, or injured cells

• Interphase- Chromosomes are duplicated

• Prophase- The chromosomes are now visible

through a microscope

• Metaphase- Chromosome pairs line up in the

middle of a cell

• Anaphase- The pairs separate (apart) to

opposite ends

• Telephase – the cell divides into 2 (two) daughter cells

Interphase

Mitosis

• Mitosis is what occurs after meiosis has taken place. Once you have your full set of chromosomes, mitosis can begin.

• Some cells do not do much division to replace themselves (such as neurons, or nerve cells)

• However, many others have a high turnover, such as epidermal cells. If they did not, eventually your skin would wear out.

Asexual Reproduction (3 types) 1. Budding• When a new individual grows on a another

one.

• It will eventually break away.

• It has the exact DNA copy of the original

• EX- hydra, potato

2. Regeneration

• Replace a body part (regenerate) due to an injury

• EX- starfish, chameleon

3. Cloning

• Exact copy

• Initially, plants were cloned

• First successful cloned mammal was Dolly the Sheep in 1997

Sexual Reproduction

• An organism is produced from the DNA of 2 cells

• Sex cells join together

• The sex cells are the male sperm and the female egg

Human Reproduction- fertilization• A female sex cell, egg, has 23

chromosomes

• A male sex cell, sperm, has 23 chromosomes

• They unite and create a new cell with 46 chromosomes

• This cell forms into a fully formed baby

Chromosomes• There are 23 pairs of chromosomes

in the human body.

• 23+23=46

• 46 TOTAL

chromosomes

Meiosis• Sex cells are created through meiosis• Interphase- Chromosomes are duplicated• Prophase- The chromosomes are now visible through a microscope• Metaphase- Chromosome pairs line up in the middle of a cell• Anaphase- The pairs separate (apart) to opposite ends• Telephase – the cell divides into 2(two) daughter cells

• The process then REPEATS with the two daughter cells to form a total of 4 daughter cells

3 Key Differences Between Meiosis and Mitosis

• A. Mitosis divides one nucleus into two; Meiosis divides one nucleus into four.

• B. Mitosis conserves chromosome number; Meiosis reduces it in half (usually from diploid [46 in humans] to haploid [23] ).

• C. Mitosis produces genetically identical daughter nuclei;

Meiosis produces genetically different daughter nuclei.

Interphase

Sex Cells in Plants• Male flower parts produce pollen,

which contain sperm cells

• Female flower parts produce eggs

• When the sperm and egg join they create a cell which isprotected in a SEED

Homework

• Page 597