1. Genetics of Inheritance
CST Review
Genetics of Inheritance
Part II

2. CHROMOSOMES… -complexes of DNA and protein.
-Chromosomes are the package for DNA and genes.
-duplicated before the cell divides.
-chromosome number is specific for each species. A human cell has 46 [or 23 pairs] while a fruit fly has 8 [or 4 pairs].
centromere
sister chromatids

3. Cells in the body of sexually producing organisms can be…
SOMATIC CELLS
-body cells
GAMETES
-sex cells
-contain the DIPLOID [2n] chromosome number.
-produced through MITOSIS.
-examples: muscle cell, nerve cell, stomach cell.
-contain the HAPLOID [n] chromosome number.
-produced through MEIOSIS.
-examples: sperm cell and egg cell

4. Fertilization restores the diploid number.
Egg is “n” = haploid +
Sperm is “n” = haploid
ZYGOTE is 2n.
Repeated mitosis ultimately leads to the development of multi-cellular organism.

5. A picture of all the chromosomes in a somatic cell is a karyotype.
A human karyotype reveals 23 pairs of chromosomes. Each pair is called a homologous pair.
The 23rd pair is easy to spot [unequal in size]. They are the sex chromosomes, called X and Y.

6. Table of Chromosome Number
Organism
Chromosome #
Human 46
Corn 20
Yeast 32
Onion 16
Cow 60
Lily 24
Dog 78
Donkey 62
Chicken
Earthworm 36
Toad
Pig 38

7. CELL CYLE
A cell goes through a cell cycle, going through stages of growth and division.

8. Stages of the Cell Cycle
Interphase: sometimes called the “resting phase.” This refers to the stage in the life of a cell when it is not dividing.
-made up of these sub-stages-
a. G1- cells grow in size, cells get ready for DNA synthesis.
b. S-phase- DNA replication occurs at this stage.
c. G2- cell continues to grow and make proteins.

9. 2. Mitosis: cell divides to produce two daughter cells with the same chromosome number as the parent cell. This stage takes only from 1-2 hours.

10. Important points to remember:
Chromosomes condense for easy separation [no tangling].
Spindle fibers attach to the centromeres, controlling chromosome movement.
Sister chromatids separate during anaphase.
Cytokinesis [division of cytoplasm and other cell contents] happen during telophase.