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93 Cards in this Set
- Front
- Back
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• Cell cycle
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life of a cell from the time it is first formed until its own division into two cells
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• Daughter cells
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the two cells that come from the splitting of one cell
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• Genome
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a cell’s DNA
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• Somatic cells
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all human body cells except reproductive cells
o Somatic cells have 46 chromosomes (two sets of 23- one set inherited from each parent) |
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• Gametes
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reproductive cells
o Sperm and egg o Have 23 chromosomes (half of a somatic cell) |
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• Chromatin
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complex of DNA and associated protein molecules
o Proteins maintain structure of chromosome and control activity of genes |
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• Sister chromatids
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→ after DNA replication, each chromosome is composed of two identical sister chromatids
one is an original chromosome and one is a replicate |
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o Centromere
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attaches two sister chromatids
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• Mitosis
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division of the nucleus
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• Cytokinesis
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division of the cytoplasm
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• Zygote
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a fertilized egg (sperm+egg)
the union of two gametes |
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• Meiosis
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replication of reproductive cells (sperm and eggs)
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• Gonads
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reproductive organs- testes and ovaries
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• Interphase
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accounts for 90% of cell cycle- Cell grows and copies its DNA in preparation for mitosis
o G1 phase- growing o S phase- DNA replication o G2 phase- growing • Centrosome replicates into two centrosomes • Chromosomes cannot be seen |
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• Mitotic (M) phase
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mitosis and cytokinesis- the shortest part of the cell cycle
PPMAT |
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o Prophase
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• Sister chromatids become visible
• Nucleoli disappear • Mitotic spindle forms • Centrosomes move away from each other |
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o Prometaphase
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• Nuclear envelope fragments
• Microtubules of the mitotic spindle attach to kinetochore of each sister chromatid |
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o Metaphase
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• Longest stage of mitosis
• Centrosomes are now at opposite ends of the cell • Chromosomes line up on the “metaphase plate” (imaginary line down the middle of the cell) • Chromosomes’ centromeres lie on the metaphase plate |
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o Anaphase
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• Shortest stage of mitosis
• Sister chromatids separate • Sister chromatids move towards opposite ends of the cell • Nonkinetochore microtubules lengthen to lengthen the cell • Kinetochore microtubules shorten to pull chromatids apart |
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o Telophase
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• Two daughter nuclei form on opposite ends of the cell
• Nuclear envelopes start to form • Chromosomes are no longer visible • Mitosis is complete |
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• Cytokinesis
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cytoplasm splits
o Formation of cleavage furrow pinches the cell in two (or cell wall) |
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• Mitotic spindle
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structure consisting of fibers made of microtubules and other proteins
o Mitosis depends on the formation of the mitotic spindle o Microtubules of the cytoskeleton disassemble while the mitotic spindle assembles (to provide material to construct the mitotic spindle) • Spindle includes the centrosomes, spindle microtubules, and asters (see picture on page 222) |
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• Centrosome
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non membranous organelle→ assembly of spindle microtubules starts here
o Centrioles are located in the centrosome but they don’t do anything to contribute to the formation of microtubules o Centrosome replicates during interphase to make 2 centrosomes o The two centrosomes surround the nucleus during mitosis to form the spindle fibers |
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• Aster
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• Aster→ radial array of short microtubules- asters come out of the centrosomes during mitosis
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• Kinetochore
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structure of proteins associated with specific sections of chromosomal DNA at the centromere- each of the sister chromatids has a kinetochore
o Spindle microtubules attach to the kinetochores (called kinetochore microtubules) |
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• Cleavage
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→ cytokinesis process in animal cells
• Cleavage furrow→ first sign of cleavage o Shallow groove in the cell surface near the old metaphase plate o Furrow is composed of a contractile ring of actin microfilaments (made of the protein myosin) • Actin and myosin are proteins associated with cell movement • Actin filaments interact with myosin molecules and cause the ring to contract • As the ring gets smaller the cell pinches in two |
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• Cytokinesis in plant cells
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o No cleavage furrow
o Vesicles from Golgi move along microtubules to the middle of the cell o Vesicles form a cell plate o Cell plate enlarges until its surrounding membrane fuses with the cell’s plasma membrane o Two daughter cells result- their cell walls come from the cell plate |
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Binary fission
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• Prokaryotes divide using binary fission
o Origin of replication→ place on the bacterial chromosome where replication starts o Bacteria replicates its origin of replication (producing two origins) o One origin moves rapidly towards the opposite end of the cell as the rest of the DNA replicates o Cell starts to elongate o When all the DNA is replicated the plasma membrane grows inward and divides the cell in half • Bacteria don’t have visible mitotic spindles or microtubules • Prokaryotes have one long chromosome instead of multiple chromosomes |
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• Dinoflagellates
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o Has a nuclear envelope
o Nuclear envelope remains intact during cell division o Chromosomes attach to nuclear envelope o Microtubules pass through the nucleus inside cytoplasmic tunnels which then divides in a fission process |
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• Diatoms
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o Microtubules form a spindle within the nucleus
o Microtubules separate the chromosomes and the nucleus splits |
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evolution of mitosis
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prokaryotes
dinoflagellates diatoms eukaryotes |
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• Cell cycle control system
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o Controls the sequential events of the cell cycle
o Cyclically operating set of molecules in the cell • Nerve and muscle cells don’t divide • Skin cells divide all the time • Liver cells sometimes divide |
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• Checkpoints
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regulate the cell cycle
o Critical control point where stop and go signals can regulate the cycle o Animal cells have built in stop signals that halt the cell cycle at checkpoints until overridden by go signals o There are 3 checkpoints-→ at G1 G2 and M |
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• G1 checkpoint
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(restriction point)
o if a cell receives a go signal at the G1 checkpoint the cell will go ahead and complete S G2 and M phases o if a cell receives a stop signal at the G1 checkpoint the cell will enter the G0 phase (a nondividing state) o nerve and muscle cells are in the G0 phase |
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• Kinases and cyclins
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two proteins that regulate the cell cycle
• Protein kinases o enzymes that activate or inactivate other proteins by phosphorylating them o Give the go signals at the G1 and G2 checkpoints o Cells usually have a constant concentration of kinases • Cyclin o kinases must attach to cyclins to be active o Cyclins exist in varying concentrations |
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• CDK
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o Cyclin dependent kinases
• Name for kinases that must be attached to a cyclin to be active o CDK activity fluctuates according to changes in cyclin concentrations |
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• MPF
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o Type of CDK complex
o MPF activity corresponds with cyclin concentration o “Maturation promoting factor” o “M phase promoting factor” o Triggers the cell’s passage past the G2 checkpoint into M phase o MPF initiates mitosis o MPF initiates a process that leads to the destruction of its own cyclin during anaphase→ CDK part of MPF exists in the inactive form until it associates with another cyclin during the S and G2 phases of the next round of the cell cycle |
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• Growth factor
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protein released by certain cells that stimulate other cells to divide
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• Mitogen
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protein that promotes mitosis
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• Platelet derived growth factor (PDGF)→
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made by platelets (type of blood cell)
o Required for the division of fibroblasts (type of connective tissue) in culture o Fibroblasts have PDGF receptors on their plasma membranes o When PDGF binds to the receptors it triggers a signal transduction pathway that allows the cell to pass through the G1 checkpoint and divide o When an injury occurs platelets release PDGF which results in the proliferation of fibroblasts (which help heal the wound) |
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• Density dependent inhibition
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o When crowded cells stop dividing
o When a cell population reaches a certain density the availability of nutrients becomes insufficient to allow continued growth • Density dependent inhibition and anchorage dependence ensure that cells grow at an optimal density and location |
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• Anchorage dependence
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o In order for the animal cell to divide it must be attached to something
• Density dependent inhibition and anchorage dependence ensure that cells grow at an optimal density and location |
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The problems with cancer cells
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• Cancer cells divide excessively and invade other tissues
• Cancer cells do not heed the normal signals that regulate the cell cycle • Do not exhibit density dependent inhibition or anchorage dependence • Don’t stop dividing when growth factors are depleted • Cancer cells stop dividing at random points in the cycle- not at the checkpoints • Cancer cells will divide forever in culture o Normal mammalian cells divide only 20-50 times before they die o Cancer cells divide forever |
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• Transformation
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process that converts a normal cell to a cancer cell
• Usually the immune system kills the mutated cell- but sometimes it doesn’t • When the immune system doesn’t kill the cancer cell the cell proliferates and creates a tumor |
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• Benign tumor→
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when the cancer cells remain at the original site
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• Malignant tumor
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when cancer cells spread away from original site
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• Abnormalities in cancer cells
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o Excessive proliferation
o Uncontrolled cell cycle o Abnormal amount of chromosomes o Disabled metabolism o Non functioning o Not attached to neighboring cells through ECM- so they can spread to other tissues |
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• Metastasis
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• Metastasis→ when cancer cells spread to other parts of the body
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• HeLa
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• HeLa cells→ type of cancer cell line that has existed since 1951- oldest cell line available
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• Kinetochore microtubules shorten at the ____ during anaphase
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kinetochore end
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• Kinetochore microtubules
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• Kinetochore microtubules→ shorten during anaphase to pull apart the chromosomes
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Non Kinetochore Microtubules
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• Non Kinetochore microtubules→ lengthen during anaphase to stretch the cell out
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Homologues
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two chromosomes that belong together
are paired together in a karyotype one chromosmoe is maternal and one chromosome is paternal |
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• Heredity
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• Heredity→ transmission of traits from one generation to the next
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• Variation
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• Variation→ offspring differ somewhat in appearance from parents and siblings
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• Genetics
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• Genetics→ study of heredity and hereditary variation
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• Gametes
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reproductive cells
o Transmit genes from one generation to the next o Sperm and egg o When two gametes unite the zygote has both the sperm’s chromosomes and the egg’s chromosomes (becomes diploid) |
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Humans have ___ chromosomes
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46
(23 are maternal and 23 are paternal) |
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• Locus
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gene’s specific location along the length of the chromosome
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• Asexual reproduction
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one parent reproduces to form offspring that are exact copies of it
o Parent passes all of its genes to the offspring o Offspring have same genes as parents o Asexual reproducers give rise to a clone (genetically identical to the parent) o Mutations cause genetic variation |
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• Sexual reproduction
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two parents give rise to offspring that have unique combinations of genes inherited from the two parents
o Offspring are not identical to their parents or siblings o Allows for genetic variation |
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• Life cycle
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generation to generation sequence of stages in the reproductive history of an organism from conception to production of its own offspring
• Somatic cells have 46 chromosomes |
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• Karyotype
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ordered display of chromosomes according to size
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• Homologous chromosomes
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two chromosomes composing a pair
o Have the same length, centromere position, and staining pattern o One from your dad and one from your mom o They are homologues o Both chromosomes of each pair carry genes controlling the same inherited characteristics o Not attached to each other- they are just two chromosomes that resemble each other |
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• Sex chromosomes
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• XY chromosomes are the exception to the homologue rule
o Females have XX and males have XY o X and Y chromosomes are not complete homologues o X and Y chromosomes determine an individual’s sex |
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• Autosomes
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• Autosomes→ all chromosomes except X and Y
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• N
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number of chromosomes in a single set
In humans N=23 |
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• Diploid
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cells with two chromosome sets (diploid number is 2N)
o Human diploid number is 46 (two sets, one from dad and one from mom) o Number of chromosomes in somatic cells |
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• After synthesis_____
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humans have 46 original chromosomes and 46 replicates (totaling 92 chromosomes)
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• Sister chromatids
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composed of one original chromosome and its replicate
o Attached to each other with a centromere |
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• Nonsister chromatids
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any two chromatids in a pair of homologous chromosomes that are not sister chromatids (the two original chromosomes)
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• Chromosome set
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→ the number of chromosomes inherited from one parent (in humans a set equals 23 chromosomes)
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• Haploid cells
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cells that contain one chromosome set
o Gametes are haploid o Have a chromosome number N o Haploid number in humans is 23 o 2 Haploid cells= 1 diploid cell o sperms have X or Y and eggs have X |
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• fertilization
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→ the union of two gametes- a sperm and an egg- to create a diploid zygote
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• zygote
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the diploid cell resulting from the union of a sperm and an egg
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• Three types of life cycles
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• Human and animal life cycle
• Alternation of generations→ plants and algae • Fungi and protist life cycle |
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• Human and animal life cycle
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o Gametes are the only haploid cells
o Meiosis occurs during the production of gametes o Diploid zygote produces a multicellular organism that is diploid • The three sexual life cycles differ in the timing of meiosis and mitosis and haploid and diploid |
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• Alternation of generations→ plants and algae
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o Includes both diploid and haploid multicellular stages
o Sporophyte→ multicellular diploid stage o Spores→ haploid cells created by meiosis in the sporophyte • Unlike gametes, spores give rise to multicellular organisms without fusing with another cell o Gametophyte→ spores reproduce mitotically to make a gametophyte (haploid) • Gametophytes make gametes through mitosis • Fertilization between haploid gametes make a diploid zygote • Diploid zygote develops into the next sporophyte generation |
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• Fungi and protist life cycle
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o Gametes fuse to form a diploid zygote
o Meiosis occurs without a diploid offspring developing o Meiosis produces haploid cells that divide by mitosis and give rise to multicellular haploid adult organisms o Haploid adult organisms carry out mitosis and make gametes o The only diploid stage is the single celled zygote |
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Stages of Meiosis
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• Memorize them from the book
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• Crossing over happens in
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Prophase I of meiosis I
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• Tetrad
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group of four chromosomes
(two homologues and their replicates) |
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• Chiasmata
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• Chiasmata→ criss crossed regions where crossing over has occurred
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• Meiosis I
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separates homologous chromosomes
(In mitosis ONLY the sister chromatids are separated- the homologues aren’t) |
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• Meiosis II
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separates sister chromatids
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Comparison of mitosis and meiosis
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• Meiosis
o 2N→ N o daughter cells are distinct from parents o crossing over o paired tetrads line up on the metaphase plate • Mitosis o 2N→2N o daughter cells are genetically identical o sister chromatids line up on the metaphase plate |
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• Synaptonemal complex
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connect duplicated homologous chromosomes to form a tetrad
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• Synapsis
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the joining of two replicated homologues to form a tetrad
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• Crossing over
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occurs between nonsister chromatids→ occurs in Prophase I
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Three things that contribute to genetic variability
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• Independent assortment of chromosomes
• Crossing over • Random fertilization |
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• Independent assortment of chromosomes
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o Random orientation of homologous pairs of chromosomes in metaphase of meiosis I creates genetic variation
o 50% chance that a daughter cell of meiosis I will get the maternal chromosome (and vis versa) o Independent assortment→ first meiotic division results in each pair sorting its maternal and paternal homologues into daughter cells independently of every other pair • each daughter cell doesn’t have to have ALL paternal or maternal chromosomes • it’s completely random o in humans, number of possible combinations of maternal and paternal chromosomes in resulting gametes is about 8 million |
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• Crossing over
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o Crossing over produces recombinant chromosomes- individual chromosomes that carry genes derived from two different parents
o Creates even more genetic variation o Happens in prophase I of meiosis I o Happens between two nonsister chromatids |
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• Random fertilization
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o Random nature of fertilization adds to genetic variation
there's a gajillion possible combinations of sperm and egg |
