CHROMOSOMES

• Chromosome-before a cell divides it copies all the DNA (replication) and then coils it into Chromosomes

CHROMATIDS

• CHROATIDS- One side of the chromosome. Each side is the same.

• (One of the copies of the DNA)

CENTROMERE

• CENTROMERE- Point where the two chromatids are attached to each other.

HUMANS HAVE 23 PAIRS OF CHROMOSOMES

KARYOTYPE- A PICTURE OF A HUMANS CHROMOSOMES ARANGED BY SIZE. These are used to test for Chromosomal

Disorders in Unborn Babies.

TWO TYPES OF CHROMOSOMES

• THE FIRST 22 ARE CALLED AUTOSOMES WHICH ARE THE SAME FOR BOTH MALES AND FEMALES

• THE LAST PAIR ARE CALLED SEX CHROMOSOMES AND THEY DETERMINE GENDER

• XY= MALE XX= FEMALE

Down syndrome (extra 21st)

Trisome X

(Extra X Chromosome)

Cri du chat (Missing piece of 5th Chromosome)

Digeorge Syndrome (Missing piece of 22ndchromosome)

DNA REPLICATION

- TAKES PLACE DURING “S” PHASE OF THE CELL CYCLE

3 STEPS1. ENZYMES “DNA HELICASE” BREAKS HYDROGEN BONDS TO “UNZIP” THE DNA.

STEP 2-ENZYME “DNA POLYMERASE” MOVES ALONG

THE REPLICATION FORKS ADDING NITROGEN BASES(A,C,T,G)

STEP 3TWO COMPLETE DNA STRANDS ARE

FORMED. EACH STRAND IS IDENTICAL

The replication process usually takes place on many segments of the DNA at the same

time. This speeds up the process.

http://www.youtube.com/watch?v=teV62zrm2P0

http://www.youtube.com/watch?v=cDlKrLJjRlY&feature=related

INTERPHASEG1=Growth Phase 1,

Normal cell function

S=Synthesis Phase, Copy the DNA

G2=Growth Phase 2, Compress DNA into Chromosomes, prepare for cell division.

MITOSIS• P= Prophase,

Chromosomes become visible and nuclear envelope breaks down

• M=Metaphase, Chromosomes line up in the middle

• A= Anaphase, Chromosomes get pulled apart

• cells

Mitosis Continued

• T= Telophase, Chromosomes bunch at the poles of the cell and it begins to split

• Cytokinesis- Two new daughter cells are formed and new cytoplasm is formed to make two adult

Interphase

• Can be broken into G1, S and G2

Prophase

• Chromosomes are formed

• The nuclear envelope breaks down

Metaphase

• Chromosomes line up along the “equator” of the cell

Anaphase

• Chromatids are pulled apart by the spindle fibers and move toward the poles of the cell.

Telophase

• Chromosomes reach the poles and the cell builds a cell membrane/wall down the middle of the cell

Cytokinesis

New daughter cells replace organelles and grow into new adult cells which return to Interphase