Cellular Communication
Explain the concept of "amplification" in a signal transduction pathway.
Amplification in signal transduction means that a small signal triggers a chain reaction inside the cell, where each step creates more active molecules. This process ensures a large cellular response from a tiny initial signal.
What are the four features of DNA?
2) Antiparallel
3) Right-handed
4) Presence of major and minor grooves
The origin of replication is the site where:
A) DNA replication begins.
B) The two parent DNA strands are separated to form the replication fork.
C) DNA helicase binds and begins unwinding the DNA.
D) All of the above
D
What is the main purpose of mitosis in eukaryotic cells?
The main purpose of mitosis is to produce two genetically identical daughter cells for growth, repair, and asexual reproduction.
Humans are diploid organisms. What does this mean?
A) Humans have one set of chromosomes, inherited from both parents.
B) Humans have two sets of chromosomes, one inherited from each parent.
C) Humans have two copies of every chromosome, but only one set of chromosomes.
D) Humans have three sets of chromosomes, one inherited from each grandparent.
B
What do protein kinases do? When do we find them working? What are phosphatases?
Protein kinases are enzymes that add phosphate groups to other molecules, a process called phosphorylation. This is important during the transduction stage of signal transduction pathways, where it triggers a phosphorylation cascade.
Phosphatases, on the other hand, remove phosphate groups from molecules, helping to turn off the signal.
If a cell contains 25% thymine nucleotides, what is the percentage of guanine nucleotides?
25% guanine
25% cytosine
25% adenine
25% thymine
Define the following look-alike words:
1) Chromosome
2) Chromatid
3) Chromatin
4) Centrosome
5) Centromere
1) Condensed DNA
2)
3) Uncondensed DNA
4) Organelle that sprouts microtubule spindles
5) Region where sister chromatids are attach together
What is the role of kinetochores in mitosis?
Kinetochores are protein structures on the centromere of each chromatid. They serve as attachment sites for spindle fibers, which help to align and pull the chromosomes apart during mitosis.
What are the differences between somatic cells and gametes?
Somatic cells are the cells NOT utilized for reproduction (the creation of a zygote). For example: skin cells, muscle cells, hair cells, etc.
Gametes are the cells directly utilized for reproduction (the creation of a zygote). This includes a sperm cell that comes together with an oocyte to create a zygote.
What are the two key features of the transduction stage?
1) The creation of second messengers (cAMP/Ca+)
2) The phosphorylation cascade conducted by protein kinases
Define the "semiconservative model" of DNA.
This means that after DNA replication, each daughter DNA molecules will have one new strand and one parental strand.
What is the function of telomerase in DNA replication?
Telomerase adds repetitive (useless) nucleotide sequences to the ends of chromosomes, called telomeres, to prevent the loss of important genetic information during DNA replication.
This is done to protect the DNA.
1) During which phase of mitosis do the chromosomes line up at the cell's equator?
2) During which phase of mitosis do we see the first appearance of daughter chromosomes?
3) During which phase of mitosis do we see a checkpoint?
1) Metaphase
2) Anaphase
3) Metaphase: this checkpoint ensures that all of the sister chromatids are attached to microtubule spindles correctly
What are the three main sources of genetic variation in organisms?
1) Independent Assortment: Homologous chromosomes line up in a random order during Metaphase I in Meiosis.
2) Recombination of nonsister chromatids: During meiosis I, nonsister chromatids exchange pieces of DNA, creating new gene combinations.
3) Fertilization: one RANDOM sperm cell and one RANDOM oocyte come together
Define the following types of cell signaling methods:
1) Endocrine signaling
2) Synaptic signaling
3) Paracrine signaling
1) Method of signaling where ligands, referred to as hormones, are secreted into the bloodstream and travel to distant target cells
2) Method of signaling where ligands, referred to as neurotransmitters, are secreted by neuron cells
3) Method of signaling where ligands are secreted and travel to neighboring cells nearby (short distance)
DNA is organized by histones (proteins); units of DNA + histones are called nucleosomes
How does the cell ensure that there is the least amount of errors made in our DNA???
DNA polymerase proofreads during DNA replication.
Mismatch repair is done after DNA replication.
Nucleotide excision repair is done if thymine-dimers are caused by UV rays.
How does cytokinesis differ between animal and plant cells during mitosis?
In animal cells, cytokinesis occurs through cleavage furrow formation, where the cell membrane pinches in two. In plant cells, cytokinesis involves the formation of a cell plate, which eventually fuses with the cell membrane to divide the cell into two
1) What is the difference between Prophase I of Meiosis and Prophase of Mitosis?
2) What is the difference between Anaphase I of Meiosis and Anaphase of Mitosis?
1) Prophase I of Meiosis is where synapsis, crossing over, and recombination of nonsister chromatids occurs (they exchange genes *for diversity purposes*)
2) Anaphase I of Meiosis separates homologous chromosomes; while Anaphase of Mitosis separates sister chromatids.
Explain when a ligand might use an intracellular receptor instead of an extracellular receptor when delivering a signal.
a) When are extracellular receptors necessary?
A ligand that can easily cross the cell membrane will diffuse through the cytoplasm and bind to an intracellular receptor, directly initiating a cellular response. In this case, the typical "transduction" phase is bypassed, as this type interaction is sufficient to trigger the response without the need for other relay molecules.
a) Extracellular receptors are required when a ligand is too large or polar to cross the cell membrane. In this case, the receptor binds the ligand on the cell surface, and the signal is transmitted into the cell through a series of relay molecules, allowing the cell to produce a response.
DNA is found in two forms, what are they? When do we find these?
1) Chromatin; uncondensed DNA; ideal for protein synthesis and DNA replication (INTERPHASE)
2) Chromosomes; condensed DNA; ideal for cell division (MITOSIS/MEIOSIS)
How does the leading strand differ from the lagging strand in DNA replication?
The leading strand is synthesized continuously in the 5' to 3' direction towards Helicase, while the lagging strand is synthesized discontinuously in short segments (Okazaki fragments) in the opposite direction, away from Helicase.
Indicate how DNA differs throughout the stages of mitosis.
In prophase, DNA exists as sister chromatids; condensed duplicated chromosomes attached at centromere
In metaphase, DNA is still existing at sister chromatids; condensed duplicated chromosomes attached at centromere
In anaphase, DNA is no longer considered sister chromatids because they have been fully separated; first appearance of daughter chromosomes
In telophase; DNA is beginning to decondense back into chromatin
What are the key differences between Meiosis and Mitosis????????
1) Meiosis produces four non-identical, haploid (1n) daughter cells, while mitosis produces two identical, diploid (2n) daughter cells.
2)Meiosis involves two rounds of PMAT (Prophase, Metaphase, Anaphase, Telophase), whereas mitosis only involves one round of PMAT
3) Meiosis occurs only in reproductive cells (gametes), while mitosis is responsible for the division of somatic (non-reproductive) cells.