1. The Cell Cycle and Protein Synthesis
Chapter 5

2. 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)

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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