Introduction to Cell Division

Notes

Cell Division

Where do new cells come from?

Other cells… skin cells make skin cells, muscle cells make muscle cells and so on.

A skin cell can not make a muscle cell, only another skin cell.

The process of one cell making another cell is called cell division.

Cell Division What is cell

division? how a cell

reproduces, makes a copy of itself.

how living things grow (Mitosis) and make sex cells (Meiosis).

Why do we need new cells? Need new cells to:

Grow Repair scratches and

tears (scars)

Prokaryotic vs. Eukaryotic??

• What is the difference?• Do both have a cell membrane?• YES!!!!

• Eukaryotic cells have a nucleus and organelles with membranes and Prokaryotic cells do NOT have a nucleus!!

Cell Division

Cell Divison for: 1. Prokaryotes (like

bacteria cells) Binary Fission (unicellular

organisms) DNA copied, cell grows, cell splits in two.

Unicellular organisms- this is how they reproduce.

Cell Division 2. Eukaryotes –

(plant/animal cells) Mitosis (multicellular

organisms) DNA copied, cell grows, cell splits in two.

new cells have identical genetic material; produces clones.

Mitosis is about the division of the nucleus.

Nucleus

Nucleus is important for: 1. Stores hereditary

information in its DNA. 2. DNA makes RNA 3. Contains the nucleolus

(where DNA is in nucleus, dark circle)

Nucleic Acids

Function of DNA – Store and transmit hereditary information DNA – stands for Deoxyribose Nucleic Acid

Cell Division: Mitosis

Before a cell can divide it must organize its DNA and form chromosomes, so it copies and divides DNA accurately.

Making Chromosomes

How DNA condenses to form chromosomes: 1.Strands of DNA wrap around proteins called

Histones. 2. This then forms a

molecule called chromatin. Chromatin is found in the

nucleus and is how DNA spends the majority of its life.

Chromosomes Chromatin continues to condense and

eventually it forms chromosomes. Chromosomes – tightly coiled packages of

DNA held together by proteins.

Chromosomes Chromatid – half of a

chromosome; forms as DNA copies itself before cell division

Centromere – holds the chromatids together until they separate

Chromosomes Each species has a unique number of chromosomes

How many chromosomes do humans have?

46 chromosomes or 23 pairs.

Chromosomes 2 Types of Chromosomes: 1. Sex Chromosomes – are the chromosomes

that determine the sex of an organism.

Female: XX

Male: XY

2. Autosomes – all other chromosomes Humans: 44 autosomal chromosomes

Chromosomes Karyotype – is a picture

of the chromosomes in a dividing cell.

22 homologous pairs of autosomes.

2 sex chromosomes

Chromosomes

Homologous chromosomes – two copies of each autosome (maternal and paternal)

Homologous chromosomes are the same size, shape, and carry genes for the same trait.

Chromosomes

Diploid Cells (2n)– are cells that have 46 chromosomes.

All cells in your body are diploid except sex cells

Haploid Cells (n)– cells that only have 23 chromosomes

Ex. Gametes (sex cells)

Chromosomes Examples of haploid

cells?

Gametes - sperm and egg cells; they have 23 chromosomes

Fertilization 23 in sperm + 23 in egg = 46