The Cellular Basis of

Reproduction and Inheritance

Cell Division: The Cell Cycle and Mitosis

The Production of Identical Cells

Meiosis

The Production of Sperm and Eggs

Homologous Chromosomes

Homologue inherited

from dad

Homologue inherited

from mom

This karyotype shows the 23 pairs of

homologous chromosomes In humans

In an nondividing cell theDNA in the nucleus is called?

These “worms” in the nucleus are called?

What is this?

Chromosomes and Chromatin

DNA exists

as chromatin

during interphase Chromosomes are

seen during mitosis

Interphase

Mitosis

Cytokinesis

occurs during

telophase

The Cell Cycle (Cell Division)

1. Interphase: Growth and DNA replication

(The chromosome number doubles).

2. Mitosis: The division of the nucleus

3. Cytokinesis: The division of the cytoplasm

The Purpose of Cell Division

1. Growth

2. Replacement of damaged cells

3. Asexual reproduction

DNA replication

occurs during

interphase

DNA Replication

Interphase

Phases of the Cell Cycle

• Interphase

– Growth and DNA replication

– Chromosomes have duplicated but they are still

in the form chromatin fibers

Phases of the Cell Cycle

• Prophase

– Chromosomes become visible

– Nucleolus disappears

– Nuclear membrane disappears

Phases of the Cell Cycle

• Metaphase

– Mitotic spindle fully formed

– Centromeres of chromosomes at “cell equator”

Metaphase Anaphase

How many

chromosomes

are in this

cell?_____

How many

chromosomes

are in this

cell?_____

Metaphase Anaphase

How many

chromosomes

are in this

cell?_____

How many

chromosomes

are in this

cell?_____

Pair of centrioles Spindle fibers

Phases of the Cell Cycle

• Anaphase

– Sister chromatids of each replicated

chromosome separate creating identical

daughter chromosomes

Metaphase Anaphase

Phases of the Cell Cycle

• Telophase

– Daughter chromosomes at opposite poles

– Cytokinesis begins

Animal Cell Cytokinesis Plant Cell Cytokinesis

The Cell Cycle

Interphase and Mitosis

Cytokinesis: The division of cytoplasm

Interphase

Mitosis

The Human Life Cycle

+

Sperm Egg

Zygote

N = ___ N = ___

Haploid Haploid Diploid: N = ___

2 2

4

B b

B

b

B = Brown Eyes b = Blue Eyes

Fertilization Creates Diploid Cells

Meiosis: The Production of Eggs and Sperm

• Somatic Cells: Typical body cells

– _____ Chromosomes

– _____ Pair of homologous chromosomes

– Diploid

• Gametes or Sex Cells: Eggs and sperm

– _____ Chromosomes

– Haploid

Meiosis Reduces the

Chromosome Number in Half

Meiosis Is a Source of

Genetic Variation Homologue

inherited from

dad

Homologue

inherited

from mom

Homologous

chromosomes

exchanged pieces

Crossing Over

Crossing Over

Meiosis is a Source of Genetic Variation

Independent Assortment of Chromosomes

Apoptosis:

Programmed Cell Death

What might damage DNA? G0 is an

extended

resting

period.

(The cell is committed to divide if it

passes this checkpoint)

(The cell performs

its functions but

does not divide.)

Interphase

Interphase Interphase

Mitosis

Cancer: Uncontrolled Cell Division

• Benign Tumors

– Encapsulated

• Malignant Tumors

– Invasive

– Cells may leave the tumor and spread throughout the body

• Metastases

– Cells that leave a tumor and spread throughout the body

forming new tumors at distant sites

Angiogenesis:

The formation

of new blood

vessels that

bring oxygen

And nutrients to

a cancerous

tumor.

Prevention of Cancer

• Lung Cancer

• Skin Cancer

• Colon Cancer

p53: A gene that plays a key role in the G1 Checkpoint of Cell Division

(Apoptosis)