Chromosomes and Cell Cycle
Cell Basics There are trillions of cells in your body Cells are microscopic Cells have DNA inside a structure called the nucleus The nucleus is enclosed by a structure called the nuclear membrane Cells are filled with a jelly like substance called the cytoplasm
cytoplasm nuclear envelope nucleus DNA
When a cell divides, each new cell must have a complete copy of DNA. Why? The information stored in DNA directs a cell s activities and determines its characteristics.
When a cell is ready to divide, its DNA is coiled up into structures called chromosomes http://www.youtube.com/watch?v=9kqpydcnu14&safety_mode=true&persist_safety_mode=1
Chromosome Structure Chromosomes are coiled up DNA Chromatids are 2 exact copies of DNA that make up each chromosome The center of chromosome where 2 chromatids attached is the centromere A gene is a segment of DNA that codes for a certain protein or inherited trait gene centromere chromatids
Chromosomes Homologous chromosomes- are chromosomes that are similar in shape, size and genetic content
Types of chromosomes An autosome is any chromosome other than a sex chromosome Determines every trait in an organism other than gender Examples: eye color, height A sex chromosome determines the gender of an organism XX = female XY = male
Karyotypes A karyotype is an image that shows chromosomes arranged by size Karyotypes can reveal chromosomal abnormalities
Somatic Cells Somatic cells make up your body (soma = body ) any cell other than a sperm or egg (reproductive) cell Cheek, blood, brain, bone, liver, kidney Somatic cells are diploid contain 2 sets of chromosomes (2n) One set comes from the mother, the other from the father Human somatic cells contain 46 chromosomes (23 pairs of homologous chromosomes)
Somatic Cells Mitosis results in 2 somatic cells Asexual: daughter cells are genetically identical to parent cell
Reproductive cells A gamete cell is a reproductive cell (sperm or egg) Gametes are haploid Contain only one set of chromosomes (n) A human gamete contains 23 chromsomes Meiosis results in 4 gamete cells Sexual: daughter cells are genetically unique
Types of cells Fertilization- fusion of two gametes (fusion of sperm and egg) Zygote- fertilized egg cell The first cell of a new individual
Haploid (n) Diploid (2n) Types of cells n = number of chromosomes (23 in humans) Sperm 23 chromosomes n Egg + 23 chromosomes + n Total 46 chromosomes 2n (diploid)
Cell Division: Mitosis Cell division is the splitting of a single cell into two daughter cells Daughter cells are two new cells that are identical to each other and the parent cell Mitosis is dividing the nucleus (genetic material) of a cell Cytokinesis is dividing the cytoplasm of a cell
Components of Cell Division Microtubules are hollow rods that help structurally support the cell Centrioles are groups of microtubules only found in animal cells Spindle fibers move chromosomes during mitosis Attach centrioles to chromosomes at the kinetichores
Spinde fibers Centrioles
Why do cells divide? Growth- when an organism grows, its cells don t get bigger in size, they get bigger in number Repair- cells get worn out or injured your skin cells are replaced every 28 days your stomach every 7 Reproduction: Asexual (mitosis: produces somatic cells) one parent offspring identical to parent Sexual (meiosis: produces gamete cells) combination of genetic material from two parents
The Cell Cycle Mitosis occurs in somatic cells Review: What are somatic cells? One (parent) cell divides into two new (daughter) cells. Each new cell repeats the process again Interphase G1 S G2 Prophase Metaphase Anaphase Telophase Cytokinesis Growth and Preparation- 90% of the life of the cell Mitosis- division of the nucleus Division of the cytoplasm
Interphase The Cell Cycle The cell spends 90% of its life in this phase Growth Performs operations unique to the type of cell (liver, eye, lung, muscle, etc ) Three stages within Interphase: - G1 (gap stage 1) - S (synthesis) - G2 (gap stage 2)
The Cell Cycle G 0 : Growth zero stage A resting stage for cells after mitotic division A cell leaves the cycle of division and performs its specific function A pancreas cell will produce and secrete insulin Salivary gland will produce and secrete enzymes in the mouth to aid in digestion Cancer cells cannot enter G 0 and will continue to divide indefinitely, resulting in tumors
G 1 : Growth 1 Stage The Cell Cycle The cell becomes larger and prepares to divide The cell produces structural proteins and enzymes necessary for DNA replication
The Cell Cycle S: Synthesis (DNA Replication) Each chromosome is copied Human cells contain 23 pair of chromosomes = 46
The Cell Cycle G 2 : Growth 2 Phase DNA replication is checked by DNA repair enzymes Cell prepares for mitosis Proteins organize themselves to form a series of fibers called the spindles
INTERPHASE IN AN ANIMAL CELL INTERPHASE IN A PLANT CELL
Mitosis Division of the nucleus (genetic material) 4 main phases Prophase Metaphase Anaphase Telophase
PROPHASE ANAPHASE METAPHASE TELOPHASE
MITOSIS PROPHASE DNA coils up into chromosomes Becomes visible Centrioles replicate and begin to move to opposite sides of the cell Nuclear membrane disappears
MITOSIS METAPHASE Spindle fibers extend from centrioles and attach to chromosomes at the kinetichore Chromosomes are moved to the middle of the cell This organization helps to ensure that in the next phase, when the chromosomes are separated, each new nucleus will receive one copy of each chromosome
MITOSIS ANAPHASE Spindle fibers move chromosomes apart to opposite ends of the cell Results in equal separation and distribution of chromosomes
MITOSIS TELOPHASE Nuclear envelope reappears around the newly separated chromatids, forming two new nuclei The chromosomes uncoil and are no longer visible Cytokinesis begins
Tissue sample of cells in multiple phases of mitosis
CYTOKINESIS Division of the cytoplasm Creating two independent cells (daughter cells) Cleavage furrow forms in animals, Cell plate forms in plants
Animal cell cleavage Plant cell plate