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What are the 3 components of the cell theory?
all living things are composed of cells, cells are the basic units of life, all cells come from pre-existing cells
What are organelles?
A specialized part of a cell that carries out specific functions necessary for its survival
Prokaryotic Cells
Prokaryotic cells: pro = before; karyon = nucleus, lacks a nucleus and membrane-bound organelles, all prokaryotic cells are unicellular
Eukaryotic Cells
Eukaryotic cells: eu = true; karyon = nucleus, contains a nucleus and membrane-bound organelles, plant and animal cells have the same basic structure and function in similar ways
The nucleus (structure & function)
Structure: Nuclear membrane, nuclear pores, nucleolus.
Function: Stores genetic information (DNA), controls cell activities.
Nucleolus: a membrane-free organelle that floats in the nucleus and makes ribosomes (make protein)
What is DNA?
located in the nucleus and contains the instructions for the cell
What is the structure of DNA?
double helix (twisted ladder)
Sugar-phosphate backbone: (sides of ladder)
Paired nitrogenous bases (steps of ladder)
Base pair rule
Adenine(A) pairs with Thymine (T)
Guanine(G) pairs with Cytosine (C)
What is a nucleotide?
Building block of DNA (sugar + phosphate + nitrogenous base)
What are the different forms of DNA?
Uncoiled double helix: loose form
Chromatin: DNA wrapped around proteins
Chromosomes: Tightly packed DNA for cell division
What is a karyotype?
A picture of an organism's chromosomes arranged in pairs
How many chromosomes are in human cells?
46 chromosomes (23 pairs of homologous chromosomes)
Somatic Cells
Body cells (46 chromosomes, diploid)
Sex Cells (Gametes)
Sperm & egg (23 chromosomes, haploid)
Autosomes
22 pairs (non-sex chromosomes)
Sex Chromosomes
1 pair (XX for female, XY for male)
Genes
Segments of DNA that code for proteins
Proteins
molecules that perform functions in the body (enzymes, hormones, transport proteins)
Cell division purpose
grow, repair, and reproduce
3 steps of DNA replication
Unwinding: strands are separated, each strand acts as a template for a new strand
Complementary Base Pairing: Bases along each template are matched with free nucleotides
Stitch Together: Nucleotides are stitched together to form the sugar-phosphate backbone, completes the new strand of DNA
Interphase
cell grows and duplicates DNA before division
Mitosis (PMAT)
Prophase: spindle fibers extend, X-shaped chromosomes, nucleus disappears
Metaphase: chromosomes line up at the equator
Anaphase: sister chromatids separate
Telophase: two nuclei in one cell
Cytokinesis
Cell membrane splits, forming two identical daughter cells.
Animal: Cleavage furrow pinches cell
Plant: Cell plate forms
Cancer
A disease that results from uncontrolled cell division, cancer cells don't respond to instructions and continue to grow → forms tumours
Chromatin
Unwound DNA
Chromatid
One-half of a duplicated chromosome
Chromosome
Condensed DNA
Centromere
Region where sister chromatids are joined
Centrioles
Help organize spindle fibers
Spindle Fibers
Move chromosomes during mitosis
Binary fission
Prokaryotes/bacteria
Budding
Yeast
Fragmentation
Starfish
Vegetative reproduction
Potatoes and strawberries
Somatic cell nuclear transfer
Dolly the sheep
Diploid (2n)
Cells with both sets of homologous chromosomes (somatic cells)
Haploid (n)
Cells that contain only one set of chromosomes, no homologous pairs (human sex cells/gametes)
Fertilization counterbalance
Diploid (2n) → Meiosis → Haploid (n) → Fertilization → Diploid (2n)
Meiosis 1
Homologous Chromosomes Separate
Prophase I: chromosomes condense and attach to spindle fibres, Tetrads (4 chromatids) cross over and exchange genetic information
Metaphase I: Tetrads (homologous chromosomes) line up and go through independent assortment (random)
Anaphase I: Homologous chromosomes separate and move to opposite poles of the cell
Telophase I & Cytokinesis: chromosomes decondense, cleavage furrow forms and cytoplasm divides
Meiosis II
Sister Chromatids Separate
Interphase II: does not occur to ensure DNA doesn't replicate
Prophase Il: Chromosomes condense and attach to spindle fibres
Metaphase II: Chromosomes line up at the equatorial plate in a single row
Anaphase Il: Sister chromatids separate
Telophase Il & Cytokinesis: Four unique gametes form
Gamete Formation in Humans
Spermatogenesis (males): Produces 4 sperm cells
Oogenesis (females): Produces 1 egg cell and 3 polar bodies
Genetic Variation in Meiosis
Crossing Over (Prophase I): Exchange of DNA between homologous chromosomes, Independent Assortment (Metaphase I): Random alignment of chromosome pairs, Random Fertilization: Any sperm can fertilize any egg.
First trimester
Zygote → Embryo → Fetus, Major organs and systems begin forming
Second trimester
Time of growth, bone formation occurs
Third trimester
Weight of fetus more than doubles, most major nerve tracks are formed in brain