• How are chromosomes put together?

• How do new cells get their chromosomes?

• How do new organisms get their chromosomes?

• Compare and contrast these two processes.

How are chromosomes put together?

The packaging of CHROMOSOMES! (protein and DNA)

HUMAN DNA AND ITS PACKAGING IN HOMOLOGOUS CHROMOSOMES

MOM

DAD

HUMAN DNA AND ITS PACKAGING IN HOMOLOGOUS CHROMOSOMES

MOM

DAD

How do new cells get their chromosomes?

MITOSIS

INTERPHASE

EARLY PROPHASE: condensation

PROPHASE: Mitosis begins

METAPHASE: Alignment of the chromosomes

ANAPHASE: Separation of the chromatids

TELOPHASE: Re-formation of the nuclei and CYTOKINESIS

RESULT: TWO NEW DAUGHTER CELLS WITH IDENTICAL SET OF CHROMOSOMES OF PARENT CELL

MITOSIS

6

6 6

34

78

94

646

18

Very accurate copies of chromosomes!

How do new organisms get their chromosomes?

INTERPHASE (future egg or sperm)

MIEOSIS

FIRST PROPHASE

Exchange of segments

FIRST METAPHASE

FIRST ANAPHASE

FIRST TELOPHASE AND FIRST DIVISION

SECOND INTERPHASE

SECOND PROPHASE

SECOND METAPHASE: perpendicular axis

SECOND ANAPHASE

SECOND TELOPHASE

RESULT: FOUR NEW UNIQUE DAUGHTER CELLS EACH WITH HALF THE CHROMOSOMES OF THE ORIGINAL CELL

NOTE THAT WHICH COPY OF EACH CHROMOSOME GOES TO WHICH CELL IS COMPLETELY RANDOM

6

66

6

33 3 3

Comparing Mitosis and Meiosis

• Number of divisions

PROPHASE

METAPHASE

mitosis meiosis

6

66

6

33 3 3

Comparing Mitosis and Meiosis • Number of divisions • Number of chromosomes in daughter cells• Genetic identity of daughter cells• Where they occur

• miTosis = each daughter cells get TWO complete sets of chromosomes

• meiOsis = each daughter cells get ONE complete set of chromosomes