Unit IV:Can You Divide?

Cell Reproduction

• All organisms REPRODUCE.

• Why?– This allows for growth, development and

the survival of the species

There are 2 types of reproduction

1. Asexual Reproduction

– Requires A single parent!!! (sorry, just ONE).

Asexual Reproduction (cont)…

• Results in the offspring having the same hereditary material (DNA)

• In other words, the new cells are an exact copy of its parent (allow for little variation among species)

Asexual Reproduction (cont)…

Types of Asexual Reproduction

• Fission – cell splits in half (ex: Amoeba)

Types of Asexual Reproduction (cont)…

• Budding – a new organism grows off from the side of an adult (ex: Hydra)

Types of Asexual Reproduction (cont)…

• Regeneration – a new organism grows from a severed body part (ex: starfish)

What is a chromosome?

• Structure found in the nucleus of a eukaryotic cell that contains hereditary material

The structure of a chromosome

ChromosomeCentromere

Chromatid arm

Gene

How do we replace old skin cells?• Mitosis

– The process in which the newly duplicated chromosome pairs are separated from each other

What happens to a cell before Mitosis starts?

• Interphase– Cell grows and develops– Chromosomes duplicate themselves– Centrioles appear

Steps of Mitosis• Prophase

– Nuclear membrane disappears– Centrioles move to opposite ends of the cell– Spindle fibers appear in the cell

Steps of Mitosis Continued• Metaphase

– Chromosomes line up in the center of the cell– Centromeres attach to the spindle fibers

Steps of Mitosis Continued• Anaphase

– Centromeres separate– The two strands of chromosomes are pulled

apart by centrioles towards opposite ends of the cell

Steps of Mitosis Continued• Telophase

– Centrioles and spindle fibers disappear– Nuclear membrane begins to reappear

What happens to a cell after Mitosis is complete?

• Cytokinesis– Cell splits into two identical daughter cells

with complete set of organelles

How did you get here?• Sexual Reproduction

– Reproduction in which two (2) parents are involved

– Sex cells are called gametes (egg and sperm cells are gametes)

What is sexual reproduction?

• Sexual reproduction– starts with the formation of gametes and

ends when one gamete joins another gamete. The joining of egg and sperm is called fertilization, resulting in the production of a zygote

zygote

How are gametes produced?

• Meiosis – A process whose purpose is to reduce the

chromosome number in the cells – Produces 4 new cells with half the number of

chromosomes as the parent

Parent Cell

1st Division

Meiosis – two divisions of the nucleus

2nd Division – 4 new daughter cells with ½ the # of chromosomes

Meiosis continued• Diploid Cells: have two of every

chromosome (body cells)

• Haploid Cells: have just one chromosome from each pair (gametes)