GENETICS VOCABULARY SBI 3

IMPORTANT TERMS: Genetics: – The study of the relationship between genes and heredity Mitosis – Division of nucleus into two genetically identical nuclei Meiosis – Cell division process that involves two divisions with only one duplication of chromosomes Parent cell – Cell that divides by mitosis into two genetically identical cells Daughter cells – Genetically identical cells produced from parent cell

IMPORTANT TERMS: Chromatin – Thread-like structure of DNA and proteins in nucleus Chromatid – Each of the two identical chromosome strands in a replicated chromosome attached by their shared centromere Chromosome – Carries genes, formed when chromatin condenses Chromatid (when together and chromosome when separated)

IMPORTANT TERMS:  Gene  Segment of DNA that carries the code for a specific protein  Allele  One form of a gene for specific trait (ex. If gene was eye colour, allele would be blue/brown/green)  Diploid  (2n) number of chromosomes in a body cell of an organism, having two chromosomes of each type per cell  Haploid  (n) number of chromosomes in a cell that contains a single set of chromosomes, present in gametes  Somatic cells  General body cells, have the diploid number of chromosomes  Sex cells  Haploid reproductive cells, sperm and egg, whose union is necessary in sexual reproduction to initiate the development of a new individual (also called gametes)  Gametes  Egg and sperm cells that unite during sexual reproduction

CELL CYCLE AND MITOSIS SBI 3

THE CELL CYCLE: Interphase: in between stages of dividing G1—beginning cell growth S—DNA duplicates (makes a copy) DNA is in the form of chromatin G2—cell undergoes it’s function Purpose:  to replace dead or dying cells  to allow an organism to grow and develop interphase

MITOSIS: What is it? – DNA copies (chromosomes) are separated & sorted into two sides of the cell – the cell then splits in two and part of each parent is carried to the two new cells. – each ‘daughter’ cell is identical to the parent cell – results in cells such as internal organs, skin, bones, blood, etc.

PHASES OF MITOSIS: Interphase Prophase Metaphase Anaphase Telophase Cytokinesis IPMATC

Interphase occurs just before Mitosis begins: DNA is replicated along with organelles and other cellular components and the cell prepares for division.

Mitosis Interphase Animal cellPlant cell

STEP 1:Prophase (preparation phase) the DNA recoils, and the chromosomes condense the nuclear membrane disappears mitotic spindles begin to form Nuclear membrane

Mitosis Prophase Photographs from: Animal cell Plant cell

STEP 2: Metaphase (organizational phase) spindle fibres attach to the chromosomes at the centromere chromosomes line up the middle of the cell

Mitosis Metaphase Animal cellPlant cell Photographs from:

STEP 3: Anaphase (separation phase) the chromosomes split at the centromere the ‘sister’ chromatids are pulled by the spindle fibers to opposite poles of the cell.

Mitosis Anaphase Animal Cell Plant cell Photographs from:

STEP 4: Telophase the chromosomes, the cytoplasm and organelles divide into 2 portions. this diagram shows the end of telophase

Mitosis Telophase Animal cellPlant cell Photographs from:

After Mitosis: Cytokinesis  the actual splitting of the cytoplasm into two separate cells is called cytokinesis  occurs differently in both plant and animal cells  Animal cells: cleavage furrow pinches cell  Plant cells: cell plate forms in between Beginning of cytokinesis in a plant: Beginning of cytokinesis in an animal: