IB Cell Cycle, DNA, and DNA Replication
Diploid
-2n -2 copies of each chromosome -somatic/body cells
Cyclins
-Bind to cyclin dependent kinases to activate them -Cyclin complexes bind to target proteins activate them to start the next phase of the cell cycle -Different cyclins produced at different times bind to specific cyclin dependent kinases to ensure the cell cycle in proper sequence at the proper rate
What occurs during prophase?
-Chromatin (DNA and chromosomes) condenses and chromosomes become visible -Nucleolus disappears -Nuclear membrane breaks down -Mitotic spindle forms -Centrosomes move away from each other to opposite ends of the cell
What occurs during metaphase?
-Chromosomes align on the metaphase plate -Spindle fibers attach to the centromere of each chromosome
What occurs during telophase?
-Chromosomes gather at the poles of the cell -Mitotic spindle disappears -Two nuclear membranes form -Chromosomes decondense
Cell cycle controls
-Cyclins -Genes
Eukaryotic Cells
-DNA associated with proteins -DNA is linear -DNA in nucleus -DNA contains introns -Membrane bound organelles -80s ribosomes -larger BOTH HAVE - DNA, Cell Membrane, Cytoplasm, Ribosomes
Mutagens
-Radiation: UV Radiation, X-rays -Chemicals: Smoke, BBQ, Nitrate preservatives, Benzoyl Peroxide -Infectious Agents: Viruses, Bacteria
What takes place in animal cells during cell division?
-Re-formation of nuclear membranes -DNA replication -Cleavage furrow
Benign Tumor
-Remain at the original site -Contained within a membrane
What occurs during anaphase?
-Sister chromatids separate at the centromere -Centromeres divide -Spindle fibers contract pulling one copy of each chromosome to each opposite ends of the cell
Nitrogenous Bases
-Thymine (T) -Adenine (A) -Cytosine (C) -Guanine (G) (T->A and G-> C)
Genes
-Tumor suppressor genes (makes proteins to inhibit cell growth/division when activated) -Oncogenes (make proteins that promote cell growth/division when activated)
Endodymbiotic Theory
-a prokaryotic cell engulfed (through endocytosis) a heterotrophic cell -symbiotic relationship formed EVIDENCE -have two membranes -have their own ribosomes -have their own DNA -about the same size as prokaryotic cells
What occurs during interphase?
-about 90% of the cell cycle -produces porteins (transcription/translation) -carries out metabolic reactions -increases number of mitochondria/chloroplasts/other organelles -G1 (first growth) -S-Phase (DNA replication) -G2 (second growth)
Plant Cells
-cell walls -chloroplasts -carbs stored as starch -no centrioles -no cholesterol in cell membrane -large, central vacuoles
Antiparallel
-double helix -left side starts with 5' end -right side starts with 3' end
Nucleosome
-fundamental unit of DNA packaging in eukaryotic cells -8 histone proteins (+ charged) make the core -A DNA stand (- charged) wraps around the core twice -9th histone protein (H1) attaches to hold the DNA in place around core -form along a single molecule of DNA -"beads on a string"
Cell Theory Exceptions
-groups of cells -viruses -some tissues are not just made out of cells -first cells
Complementary base pairing
-hydrogen bonds with A->T and C->G -proper base incorporation into DNA strand -ensures that there are identical copies of the DNA strand
Surface Area to Volume Ratio
-more surface area equals more nutrients, oxygen, etc. -volume determines the rate of heat and waste production and consumption -cells with a smaller ratio, are able to move more waste and head of of the cell and more resources into the cell
Haploid
-n -1 copy of each chromosome -gametes/sex cells (eggs/sperm)
Prokaryotic Cells
-naked DNA (no proteins) -circular DNA -DNA in nucleoid -70s ribosomes -smaller BOTH HAVE - DNA, Cell Membrane, Cytoplasm, Ribosomes
Animal Cells
-no cell walls -no chloroplasts -centrioles -small, if any vacuoles -carbs stored as glycogen -cholesterol in cell membrane
Structural sequences
-no protein-coding function -highly coiled sequences -occur at the centromere and telomeres of chromosomes -aid in maintaining the structure of DNA -pseudogenes appear to be structural sequences providing support in DNA molecules
Mitotic Index
-number of cells in mitosis/total number of cells -cells are dividing at a higher rate (cancer)
Highly repetitive sequences of DNA
-occurs multiple times in genome -no protein-coding functions -introns -not genes -larger differences -short sequences
Protein-coding sequences
-occurs once in genome -protein-coding functions -exons -genes -small differences -long sequences
Water
-polar -hydrogen bonds -cohesive properties (water to water) -adhesive properties (water to something else) -thermal properties (high specific heat) -solvent properties ("like" dissolves "like")
Number of sister chromatids after anaphase
0
Cell Theory
1. All organisms are composed of one or more cell 2. Cells are the smallest units of life 3. All cells come from pre-existing cells
How does replication happen?
1. helicases unzips the double helix, breaking the hydrogen bonds between the bases 2. gyrase and single-strandbinding proteins stabilize the unzipped DNA 3. primase adds a sequence of RNA bases to each parental DNA molecule at the replication origin (primer) 4. DNA polymerase III adds new nucleotides to the RNA primer to create a new complementary strand (leading strand is continuous, while lagging strand through Okazaki fragments) 5. In the lagging strand, DNA ligase fills the gaps between fragments 6. DNA polymerase I removes RNA primers and replaces them with DNA nucleotides (except at the tip of the 5' end)
Number of chromosomes at the beginning of interphase
2n
Number of chromosomes in each daughter cell after mitosis
2n
Number of sister chromatids after the S-phase of interphase
4n
Which direction is DNA assembled?
5' to 3' direction
What is a difference between a cell in the G1 phase and a cell in the G2 phase of the cell cycle?
A cell in the G2 phase would have more mitochondria than a cell in the G1 phase
What is the composition of the backbone of DNA?
Alternating sugar and phosphate molecules
What are the four most common elements in living systems
C - carbon H - hydrogen O - oxygen N - nitrogen
How do plants complete the cell cycle?
Cell Plate formed by vesicles
What type of bonds connect the phosphate and deoxyribose?
Covalent bonds: Phosphodiester bonds
What occurs during cytokinesis?
Cytoplasm divides forming two genetically identical daughter cells
Pyrimidine Bases
Cytosine (C) and Thymine (T) -single-ring structures
What does a nucleosome consist of?
DNA and histones
In the structure of DNA what binds with cytosine?
Deoxyribose
What are the components of a DNA nucleotide?
Deoxyribose, a phosphate, one of the bases
Passive Transport
Diffusion, Osmosis, Facilitated Diffusion -does not require ATP -goes down in concentration gradient -substances move from areas of high concentration to low concentration
Active Transport
Endocytosis, Exocytosis, Pinocytosis, Phagocytosis -require ATP -goes up in concentration gradient -substances move from areas of low concentration to high concentration
What type of bonds connect nucleotides?
Hydrogen bonds -T->A (2 bonds) -G-> C (3 bonds)
What are homologous chromosomes
Non-identical chromosomes with the same genes in the same sequence but not necessarily the same alleles
In the Hershey and Chase experiment what observation led to the conclusion that DNA was the genetic material?
Radioactive phosphorus was found in the pellet
What happens during the G2 phase of interphase?
Synthesis of proteins
How can cells in a multicellular organism differentiate?
They express some of their genes but not others
Semiconservative
When DNA is replicated, the two new DNA molecules both consist of an original, parent strand, and a newly built daughter strand -one of the original parent strands is maintained in each of the new DNA molecules -Meselson and Stahl experiments -5' to 3' direction
What are Hydrolysis reactions?
When one subunit of a macromolecule is hydrolysed from another, a molecule of water is split to break the covalent bond between the subunits -water is always a reactant
What are condensation reactions?
When one subunit of a macromolecule is joined to another, a molecule of water is removed, and the subunits are joined by covalent bonds -water is always a product
Metastasize Tumor
if they reach blood vessels, they can move to other parts of the body where they can form secondary tumors
Malignant Tumor
invade surrounding tissues
Cancer
uncontrolled cell division
Organic
compounds containing carbon and found in living organisms
Purine Bases
Adenine (A) and Guanine (G) -double-ring structures
Magnification
Mag=M/A
