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Genetics of Inheritance

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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.

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