5.2- Chromosomes and Mitosis

5.2: Chromosomes ● DNA stores genetic information

● DNA is packaged into chromatin● Chromatin = long and thin strands of DNA and protein

● Chromatin is packaged into chromosomes● Chromosomes = tightly coiled strands of DNA and

protein

DNA

Chromatin

Chromosomes

Condensed

Condensed

Chromosome Structure:● Chromatids (sister

chromatids) = identical halves of chromosome

● Centromere = connects chromatids of chromosome

Types of Chromosomes:1. Sex chromosomes = determine gender

a. For humans, the sex chromosomes are X or Y

b. Female = XX = c. Male = XY = d. Normal number of sex chromosomes

for humans is 2

Types of Chromosomes:2. Autosomes = Non-sex chromosomes

(Ex: Chromosomes that determine height, eye color, etc.)

● Humans have 44 autosomal chromosomes

Karyotype● Humans have 2 sex

chromosomes and 44 autosomal chromosomes … Can you find them?

● Is this person a male or female?

Karyotype

● A karyotype is a picture of an organism’s chromosomes● Can be used to diagnose genetic disorders

Karyotype● Notice anything about

the karyotype?

● There are TWO chromosomes for each number…● These are called

homologous chromosomes

Homologous Chromosomes● Homologous chromosomes are matched pairs of

chromosomes that contain information that codes for the same traits (or the same genes)

Mitosis

Mitosis● Cell division which leads to 2 cells with identical genetic

material (nuclear division)

● Mitosis has 4 phases:1. Prophase2. Metaphase3. Anaphase4. Telophase

Mitosis: Prophase● Chromatin condenses to form visible chromosomes

● The nuclear membrane and nucleolus disappear● Why is it important that these structures disappear?

Mitosis: ProphaseANIMAL CELLS

ANIMAL CELLS:

● A spindle forms between centrioles

● Centrioles and spindle move toward poles

Mitosis: ProphaseANIMAL CELLS

Mitosis: ProphasePLANT CELLS

PLANT CELLS

● Only the spindle forms

Prophase

Spindle

Mitosis: Metaphase● Meta = middle

● Spindle fibers move the chromosomes to the equator (center) of the cell● Spindle fibers are attached to

chromosomes at the centromere

Centriole at pole of cell

Centromere

Mitosis: Metaphase

Mitosis: Anaphase● Moving apart

● The spindle (which is attached to the centromere) pulls chromatids to opposite poles

Spindle

Mitosis: Anaphase

Mitosis: Telophase1. Chromatids uncoil to form chromatin

2. The nuclear membrane and nucleolus reappear

3. Spindle fibers disappear

● The cell resets

Chromatin

Mitosis: Telophase

Cytokinesis● Cytoplasm and organelles are divided into the two new

cells● These cells are called daughter cells

CytokinesisANIMAL CELLS

ANIMAL CELLS

● A cleavage furrow is formed as the cell pinches off into two identical daughter cells

Daughter Cells

CytokinesisPLANT CELLS

PLANT CELLS

● A cell plate forms as cell membranes gather and connect between the two nuclei, forming two identical daughter cells

ReviewPhases of the Cell Cycle1. Interphase: Prepares the cell for cell division

● G1● S● G2

2. Mitosis: Cell division● Prophase● Metaphase● Anaphase● Telophase

3. Cytokinesis: Cytoplasm dividesMitosis: The Amazing Cell Process that uses Division to Multiply!

ReviewAnimal Cells

● Have centrioles● Spindle and centrioles move

towards the poles during prophase

● During cytokinesis, a cleavage furrow is formed as the cells pinch off and two daughter cells form

Plant Cells● Do not have centrioles

● Only the spindle forms

● A cell plate forms between the two nuclei, forming two daughter cells