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[start]
[q] How do cells communicate?
[a] by generating, transmitting, receiving, and responding to chemical signals
[q] How does a cell communicate with another cell that it’s touching
[a]
1. Juxtracrine signaling
2. In animals, this is done by gap junction (little holes connecting membranes)
3. In plants, this is done by plasmodesmata (little holes connecting cell wall)
4. this can also be done via proteins
[q] How do cells a short distance away communicate? (close but not touching)
[a] Paracrine signaling: cell secretes a signaling molecule that will signal close by cells that have a receptor for it.
[q] How do cells communicate with cells that are far away?
[a] Endocrine signaling: cells secrete a signaling molecule, usually into the bloodstream, that will travel to a far away cell. The molecules are usually hormones traveling through the blood stream.
[q] How does a cell signal itself?
[a] Autocrine: a cell secretes a signaling molecule that binds to its own receptors.
[q] what are signaling molecules called? what do they do?
[a] Ligands: bind to a receptor protein in or on another cell to make it do something
[q] What are the three stages of cell signaling?
[a]
1. Reception: the signal is received
2. Transduction: a series of reactions happen in the signal transduction pathway, which amplifies the signal
3. Response: what the cell actually does
[q] How can cell signaling be messed up?
[a]
mutations can cause cells to not be able to send or receive signals
For example, the SRY gene controls testosterone production, but mutations can mess this gene up and someone with an XY chromosome will develop into a female because they can’t make the signaling molecule testosterone. This is called Swyer Syndrome.
[q] What are the two types of feedback?
[a]
1. Negative feedback: Tries to maintain a constant level of something (homeostasis)
Ex: If blood glucose is too high, insulin will be made to decrease it, if blood glucose is to low, glucason will be made to increase it.
2. Positive feedback: tries to create more of the same response
Ex: childbirth.
The baby pushes in the cervix, stretching the uterus, which sends a signal to the brain to release oxytocin. Oxytocin causes the uterus to contract and the baby to push on the cervix more, creating a positive feedback loop.
[q] What are the phases of the cell cycle?
[a]
1. Interphase: 90% of the cells life. Normal functions.
2. Gap 1 (G1): cell grows
3. Synthesis (S phase): DNA replicated
4. Gap 2 (G2): cell grows some more
5. Mitosis: cell duplicates
6. Cytokinesis: after mitosis, the cytoplasm is divided, separating the two cells made from mitosis.
[q] What are the four phases of mitosis?
[a] prophase, metaphase, anaphase, telophase (PMAT)
[q] parts of a chromosome
[a] chromosomes are counted by the amount of centromeres. A chromosome with two sister chromatids is still one chromosome, just with double DNA.
[q] Describe prophase
[a] 1. spindle fibers form
2. nuclear envelope breaks down
3. chromatin (long strings of DNA) turns to chromosomes (nicely packed structures of DNA)
[q] Describe metaphase
[a] 1. Chromosomes align in the center
2. centrioles go to the poles
3. spindle fibers attach to the chromosomes and centrioles
[q] Describe anaphase
[a] spindle fibers rip sister chromatids apart, doubling the amount of chromosomes.
[q] Describe telophase
[a]
1. Cleavage happens as the cell begins to split
2. Two nuclei begin to form, one for each new set of chromosomes
[q] What is the final product of mitosis (after cytokinesis)
[a] Two identical daughter cells
[q] What regulates the cell cycle?
[a]
Cyclin dependent kinase (Cdks)
Cdks activate target enzymes based on what type of cyclin binds to their active site.
For example, if S-phase cyclin binds to Cdks, dna will be replicated
[q] At what points in the cell cycle is each type of cyclin present?
[a]
[q] Signal Transduction Pathway
[a] A series of steps linking a mechanical or chemical stimulus to a specific cellular response.
[q] Hormone
[a] signal molecule released into the bloodstream that triggers particular responses
[q] Ligand
[a] A signal molecule that binds specifically to a receptor site of another molecule
[q] Protein Kinases
[a] Enzymes that activate or inactivate other proteins by adding a phosphate group to them
[q] Protein Phosphatases
[a] An enzyme that removes phosphate groups from proteins, often functioning to reverse the effect of a protein kinase.
[q] Second Messengers
[a] A small, nonprotein, water-soluble molecule or ion, such as calcium ion or cyclic AMP, that relays a signal to a cell’s interior in response to a signal received by a signal receptor protein.
[q] Cyclic AMP
[a] Second messenger made from ATP by adenylyl cyclase, inactivated by phosphodiesterase which converts it to AMP
[q] Apoptosis
[a] Programmed cell death involving a cascade of specific cellular events (starting with a chemical signal) leading to death and destruction of the cell.
[q] Genome
[a] the complete genetic material contained in an individual that makes the individual unique
[q] Chromosome
[a] condensed threads of genetic material formed from chromatin as a cell prepares to divide
[q] Chromatin
[a] granular material visible within the nucleus; consists of DNA tightly coiled around proteins
[q] Gamete
[a] egg or sperm sex cell that contains a single set of chromosomes, one from each homologous pair (haploid)
[q] Somatic Cell
[a] Any cell in a multicellular organism except a sperm or egg cell.
[q] Sister Chromatid
[a] one of a pair of identical chromosomes created before a cell divides
[q] Centromere
[a] The region of the chromosome that holds the two sister chromatids together during mitosis
[q] Mitosis
[a] in eukaryotic cells, a process of cell division that forms two new daughter cells, each of which has the same number of chromosomes
[q] Citokinesis
[a] near the end of telophase, the cytoplasm divides into two daughter cells, each with a complete nucleus and its own set of organelles
[q] Mitotic Spindle
[a] An assemblage of microtubules and associated proteins that is involved in the movements of chromosomes during mitosis.
[q] Centrosome
[a] A structure present in the cytoplasm of animal cells that functions as a microtubule-organizing center and is important during cell division. A centrosome has two centrioles
[q] Cleavage [Furrow]
[a] the area of the cell membrane that pinches in and eventually separates the dividing cell
[q] Binary Fission
[a] type of asexual reproduction in which an organism replicates its DNA and divides in half, producing two identical daughter cells
[q] Cell Cycle Control System
[a] A cyclically operating set of molecules in the cell that triggers and coordinates key events in the cell cycle.
[q] Cyclin dependent kinases
[a] A protein kinase (enzyme) that is active only when attached to a particular cyclin. Cyclin binds to the kinase during interphase and mitosis, triggering and controlling activities during the cell cycle.
[q] Density Dependent Inhibition
[a] cells stop dividing when they come into contact with one another (crowded cells stop dividing)
[q] Anchorage dependence
[a] the requirement that to divide, a cell must be attached to a solid surface
[q] Malignant Tumor
[a] mass of abnormal cells resulting from uncontrolled cancer cell division (can spread throughout the body)
[q] Metastasis
[a] spread of cancer cells beyond their original site in the body
[q] Gene
[a] A segment of DNA on a chromosome that codes for a specific trait; for each trait, there is one gene from mom and one from dad
[q] Locus
[a] the specific site of a particular gene on its chromosome
[q] Asexual Reproduction
[a] reproduction that does not involve the union of gametes and in which a single parent produces offspring that are genetically identical to the parent
[q] Sexual Reproduction
[a] reproduction involving the union or fusion of genetic material from a male and a female gamete
[q] Karyotype
[a] A picture of all the chromosomes in a cell arranged in pairs
[q] Autosome
[a] Any chromosome that is not a sex chromosome.
[q] Sex Chromosome
[a] one of the pair of chromosomes that determine the sex of an individual
[q] Cell Cycle
[a] sequence of events from the production of a eukaryotic cell to the time the cell itself reproduces
[q] Meiosis
[a] cell division that produces reproductive cells in sexually reproducing organisms
[q] Fertilization
[a] process in sexual reproduction in which male and female reproductive cells join to form a new cell
[q] Zygote
[a] fertilized egg
[q] Recombinant Chromosomes
[a] a chromosome created when crossing over combines the DNA from two parents into a single chromosome
[q] Law Segregation
[a] Mendel’s law that states that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair (each parent) is present in each gamete.
[q] Alleles
[a] The different forms of one gene.
[q] Monohybrid
[a] genetic crosses that involve one trait
[q] Heterozygote
[a] when an organism’s genotype has dominent and recessive genes for a trait (ex. Bb)
[q] Dominant Allele
[a] An allele whose trait always shows up in the organism when the allele is present. This allele produces more proteins for its trait than its counterpart does
[q] Recessive Allele
[a] an allele that is masked when a dominant allele is present
[q] Homozygote
[a] when an organism’s genotype has either both dominant genes for a trait or both recessive genes (ex. BB or bb)
[q] True Breeding
[a] describes organisms or genotypes that are homozygous for a specific trait and thus always produce offspring that have the same phenotype for that trait (purebreds)
[q] Law of Independent assortment
[a] Mendelian principle stating that genes for different traits are inherited independently of each other (genes of one trait don’t interfere with genes of another trait)
[q] Dihybrid
[a] Crosses between individuals that differ in two traits (tracking two traits in a cross)
[q] Multiplication Rule
[a] A rule of probability stating that the probability of two or more independent events occurring together/simultaneously can be determined by multiplying their individual probabilities. (“AND”)
[q] Addition Rule
[a] the probability that any one of two or more mutually exclusive events will occur is calculated by adding together their individual probabilities. (“OR”)
[q] Sex-linked gene
[a] a gene located on a sex chromosome
[q] Linked Genes
[a] genes located on the same chromosome that tend to be inherited together in genetic crosses
[q] Crossing Over
[a] process in which homologous chromosomes exchange portions of their chromatids during meiosis
[q] Linkage Map
[a] A genetic map based on the frequencies of recombination between markers during crossing over of homologous chromosomes.
[q] Aneuploidy
[a] an abnormality involving a chromosome number that is not an exact multiple of the haploid number (one chromosome set is incomplete); there are extra or missing chromosomes
[q] Nondisjunction
[a] meiosis in which there is a failure of paired homologous chromosomes to separate
[q] Trisomy
[a] A genetic condition of having three chromosomes instead of two (an extra chromosome).
[q] Monosomy
[a] a condition in a diploid cell in which one chromosome of one pair is missing as a result of nondisjunction during meiosis
[q] Polyploidy
[a] condition in which an organism has a full extra set of chromosomes
[q] Genetic Deletion
[a] Deleting of some genes on a chromosome
[q] Genetic Duplication
[a] the doubling of a gene allowing the modification and mutation of one of the genes without being deleterious to the organism
[q] Genetic Inversion
[a] a segment of chromosome is reversed end-to-end
[q] Genetic Translocation
[a] chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes
[q] Down Syndrome
[a] a congenital disorder caused by having an extra 21st chromosome (Trisomy 21); results in a flat face and short stature and mental retardation
[q] Genomic Imprinting
[a] a phenomenon in which expression of an allele in offspring depends on whether the allele is inherited from the male or female parent.
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