The Cell Cycle and Protein Synthesis Chapter 5

5A Genes & Cell Division Respiration & Photosynthesis are just two of many jobs cells perform Different types of cells in the same organism have different functions Genes & Chromosomes Genes are the cell’s blueprints. They contain information needed to build cells and cell products Genes contain information for an organisms visible traits, and thousands of traits that cannot be seen Genes are stored in chromosomes in the nucleus Chromosomes consist of DNA and special proteins that protect the DNA Genes , located on chromosomes, are specific sections of DNA that code for a specific protein Not all chromosomes have the same number of genes, some are short and have a few genes, some are long and have many genes Each cell usually contains a complete set of all the organism chromosomes Chromosome number of different organisms can vary greatly Humans have 46 chromosomes, a housefly has 12, an onion has 16, a horse 64, a cat38, a mouse 40, a tomato 24 Chromosomes occur in pairs One of the pair comes from the mother and one from the father (in humans) Humans have 23 pair of chromosomes Each member of a pair has the same type of genes A cell that has pairs of chromosomes is a diploid cell (most organisms are diploid, most humans cells are diploid)

5A Genes & Cell Division Cell Division Occurs when one cell (parent) divides to form two new cells (daughter) Cells go through several stages as they prepare and then divide into new cells Cell cycle has 3 stages: interphase, mitosis and cytokinesis Interphase First stage of cell cycle Genes are copied When all genes have been copied, the two identical chromosome strands are called sister chromatids Mitosis Equal distribution of the parent’s cell’s duplicated genes between the two new cells Begins after the sister chromatids are formed Mitosis has 4 phases: prophase, metaphase, anaphase, telophase Prophase: Membrane around nucleus disappears, chromosomes coil up Chromosomes are visible as individual Each chromosome composed of identical sister chromatids attached in the middle, appear X-shaped A spindle of fibers forms across the cell, these fibers move the chromosomes during the next phases

5A Genes & Cell Division Cytokinesis Metaphase All sister chromatids lined up in center of spindle Anaphase Each pair of sister chromatids separates into two chromosomes Daughter chromosomes move along spindle fibers to opposite ends of cell Telophase Daughter chromosomes reach the end of the spindle and uncoil As they uncoil the spindle disappears and a new nuclear membrane forms around each group of chromosomes This results in two new nuclei each with a complete copy of the cell’s chromosomes Cytokinesis Final stage of the cell cycle Each daughter cell gets some cytoplasm and organelles Parent cell pinches between the two nuclei until two new cells are formed Purpose of mitosis (mitotic cell division) is each new daughter cells has identical genes to those in parent cell Worn out or dead cells are replaced by mitotic cell division Also needed for growth

5A Genes & Cell Division Asexual Reproduction Some unicellular organisms use mitotic cell division Eukaryotic organisms – asexual reproduction Budding- another method of asexual reproduction Yeast reproduce by budding, yeast are tiny, unicellular fungi Inside the cell nucleus undergoes mitosis, when it is complete, the new nuclei goes into a bulge off the side of the yeast, called a bud The bud grows and received cytoplasm, it may break off or stay attached to the parent yeast cell Regeneration Process of regrowing missing body parts The process takes place by mitotic cell division A method of repair or replacement Some organisms use regeneration as a form of asexual reproduction Spores Cell surrounded by a protective covering The protective covering helps them survive in unfavorable conditions

5A Genes & Cell Division Sexual Reproduction Two organisms give each other one complete copy of their genes to from a new organism Most cases the two organisms are male and female Genetic information used during sexual preproduction are divided by meiosis Genetic material doubles before meiosis, however, another step is added, new daughter cells separate chromosomes into a single copy, cytoplasm divides a second time, two more daughter cells are formed Meiosis involves two cell divisions, not just one, when meiosis is complete there are 4 cells not two Each cell has one copy of genes Reproductive cells are called gametes Only have one of each chromosome, haploid cell Only have 23 chromosomes One of two types of gametes Eggs are female Larger than male, not mobile Sperm are male Smaller than female, mobile Contribute one half of chromosomes needed 23 from egg, 23 from sperm Combining gametes is called fertilization The diploid cell that results is called a zygote

5A Genes & Cell Division Major difference between asexual and sexual reproduction seen in offspring asexual offspring is identical to parent Sexual reproduction produces offspring different from parents

5B HOW GENES FUNCTION NUCLEOTIDE CODON GENE PROTEINS ARE INVOLVED IN NEARLY EVERYTHING IN YOUR BODY NUCLEOTIDES - the basic structural unit of nucleic acids such as DNA CODONS - a sequence of three nucleotides that together form a unit of genetic code in a DNA or RNA molecule GENES -  distinct sequence of nucleotides forming part of a chromosome INSTRUCTIONS FOR MAKING PROTEINS, NECESSARY FOR LIFE REPRODUCTION- COMPLETE COPY OF GENES GIVEN TO EACH NEW ORGANISM JAMES WATSON & FRANCES CRICK WORKED MODEL OF DNA – DEOXYRIBONUCLEIC ACID DOUBLE HELIX SUGAR, PHOSPHATE, BASE BASES: ADENINE, THYMINE, CYTOSINE, GUANINE DNA REPLICATION DNA MAKES COPIES OF GENES TO REPLACE/REPAIR CELL PARTS OR PRODUCE SUBSTANCES ONLY GENES NEEDED FOR THAT CELL ARE USED IN THAT CELL

5B HOW GENES FUNCTION RNA mRNA tRNA WHEN CELLS NEED PROTEIN, THE GENE FOR THAT PROTEINMAKES RNA SINGLE CHAIN OF NUCLEOTIDES URACIL INSTEAD OF THYMINE SUGAR BASE IN RNA DIFFERENT THAN DNA mRNA TRANSCRIPTION – MAKING MESSENGER RNA PROTEIN SYNTHESIS RIBOSOME MAKES THE PROTEIN DESIGNATED IN THE CODE CODON – GROUP OF 3 BASES EACH CODON CODES FOR ONE AMINO ACID tRNA 20 types, attaches to different amino acids, carries amino acids to ribosomes PROTEIN – CONTAINS AT LEAST ONE CHAIN OF AMINO ACIDS IRREDUCIBLE COMPLEXITY AMINO ACIDS IN PROTEINS ARE VERY SPECIFIC THRU DNA’S PROPERTIES THAT GENETIC TRAITS PASS ON