Transcription, Translation, & Mitosis Flashcards
Explain the process of transcription
In the nucleus, RNA polymerase reads bases from one strand of DNA, and then makes corresponding mRNA.
Describe the process of translation
1) Initiation Initiator tRNA (bearing methionine) pairs with start codon. Ribosome pulls mRNA molecule through it like a ribbon. When start codon (AUG) is reached, protein synthesis begins 2) Elongation Next, tRNA (with its amino acid) binds to the ribosome while its anticodon pairs with the next codon of mRNA. A peptide bond forms between methionine and the second amino acid. The ribosome slides to read the next codon. Next, tRNA with the appropriate anticodon brings its amino acid to the ribosome. Another peptide bond forms (between the 2nd and 3rd amino acids). Process continually repeats, extending the peptide into a protein 3) Termination Ribosome reaches stop codon, finished protein breaks away from ribosome, ribosome dissociates into two subunit
Explain what happens to a protein after its amino acid sequence has been synthesized.
1) Protein is formed by ribosomes on rough ER.
2) Protein is packaged into transport vesicle, which buds from ER.
3) Transport vesicles fuse into clusters that unload the protein into the Golgi complex.
4) The golgi complex modifies the protein structure.
5) The golgi vesicle containing the finished protein is formed.
6) Lastly, secretory vesicles release the protein by exocytosis.
Describe the process of DNA replication.
DNA unwinds from histones
An enzyme unzips a segment of the double helix exposing its nitrogenous bases
DNA polymerase builds new DNA strands
Newly made DNA wraps around histones
Discuss the three phases of interphase and what occurs in each phase.
1) G1: first gap phase
The interval between cell birth (from division) and DNA replication. The cell carries out normal tasks and accumulates materials for next phase
2) S: synthesis phase
The cell replicates all nuclear DNA and duplicates centrioles
3) G2: second gap phase
The second gap phase; the interval between DNA replication and cell division. The cell repairs DNA replication errors, grows and synthesizes enzymes that control cell division
Distinguish between the process of mitosis and cytokinesis.
Mitosis does not include the cell membrane splitting into two.
Describe the four phases of mitosis and explain what occurs in each of the phases.
1) Prophase
Genetic material condenses into compact chromosomes
46 chromosomes are made of two sister chromatids
Nuclear envelope disintegrates
Centrioles sprout spindle fibers (long microtubules)
Spindle fibers push centriole pairs apart
Some spindle fibers attach to kinetochores of centromeres of chromosomes
2) Metaphase
Chromosomes are aligned on cell equator
Shorter microtubules from centrioles complete an aster which anchors itself to inside of cell membrane
3) Anaphase
Enzyme cleaves two sister chromatids apart at centromere
Single-stranded daughter chromosomes migrate to each pole of the cell as motor proteins in kinetochores crawl along spindle fibers
4) Telophase
Chromosomes cluster on each side of the cell
Rough ER makes new nuclear envelope around each cluster
Chromosomes uncoil to chromatin
Mitotic spindle disintegrates
Each nucleus forms nucleoli
Describe the prophase phase of mitosis
Genetic material condenses into compact chromosomes
46 chromosomes are made of two sister chromatids
Nuclear envelope disintegrates
Centrioles sprout spindle fibers (long microtubules)
Spindle fibers push centriole pairs apart
Some spindle fibers attach to kinetochores of centromeres of chromosomes
Describe the metaphase phase of mitosis
Chromosomes are aligned on cell equator
Shorter microtubules from centrioles complete an aster which anchors itself to inside of cell membrane
Describe the anaphase phase of mitosis
Enzyme cleaves two sister chromatids apart at centromere
Single-stranded daughter chromosomes migrate to each pole of the cell as motor proteins in kinetochores crawl along spindle fibers
Describe the telophase phase of mitosis
Chromosomes cluster on each side of the cell
Rough ER makes new nuclear envelope around each cluster
Chromosomes uncoil to chromatin
Mitotic spindle disintegrates
Each nucleus forms nucleoli
List the 4 stages of mitosis in order
Prophase, metaphase, anaphase, telophase (PMAT)
Discuss factors that would inhibit cell division
- They snugly contact neighboring cells
- Nutrients or growth factors are withdrawn
- They undergo contact inhibition—the cessation of cell division in response to contact with other cells
Discuss factors that would promote cell division
- They have enough cytoplasm for two daughter cells
- They have replicated their DNA
- They have adequate supply of nutrients
- They are stimulated by growth factors (chemical signals)
- Neighboring cells die, opening up space
