Podcast
Questions and Answers
What are the three primary components of chromatin?
What are the three primary components of chromatin?
Which step occurs during the S phase of the cell cycle?
Which step occurs during the S phase of the cell cycle?
What is the main function of helicase during DNA replication?
What is the main function of helicase during DNA replication?
What occurs at the G1 checkpoint in the cell cycle?
What occurs at the G1 checkpoint in the cell cycle?
Signup and view all the answers
During which phase do chromatids condense to become visible chromosomes?
During which phase do chromatids condense to become visible chromosomes?
Signup and view all the answers
What is the total number of chromosomes in a human cell?
What is the total number of chromosomes in a human cell?
Signup and view all the answers
What is the role of DNA ligase in DNA replication?
What is the role of DNA ligase in DNA replication?
Signup and view all the answers
What happens during the late phase of prophase?
What happens during the late phase of prophase?
Signup and view all the answers
What is the primary role of separase during cell division?
What is the primary role of separase during cell division?
Signup and view all the answers
Which of the following statements correctly describes telophase?
Which of the following statements correctly describes telophase?
Signup and view all the answers
What is a function of mRNA?
What is a function of mRNA?
Signup and view all the answers
Which process occurs first during transcription?
Which process occurs first during transcription?
Signup and view all the answers
What is the role of transcription factors in gene expression?
What is the role of transcription factors in gene expression?
Signup and view all the answers
During translation elongation, where do new tRNA molecules bind?
During translation elongation, where do new tRNA molecules bind?
Signup and view all the answers
What modifications are made to pre-mRNA during processing?
What modifications are made to pre-mRNA during processing?
Signup and view all the answers
Which region of DNA is NOT typically involved in transcription initiation?
Which region of DNA is NOT typically involved in transcription initiation?
Signup and view all the answers
What is a polyribosome and its function?
What is a polyribosome and its function?
Signup and view all the answers
Which type of RNA serves as a structural component of ribosomes?
Which type of RNA serves as a structural component of ribosomes?
Signup and view all the answers
Flashcards
What is chromatin?
What is chromatin?
Thread-like structures composed of DNA, histone proteins, and RNA. It's the form DNA takes in the nucleus of eukaryotic cells, except during cell division.
How is chromatin formed?
How is chromatin formed?
DNA winds around histone proteins to form nucleosomes. Multiple nucleosomes interact in a 'beads on a string' arrangement.
Explain the transition from chromatin to chromosomes
Explain the transition from chromatin to chromosomes
Chromatin condenses and intertwines, forming structures called chromosomes. This tightly packaged form is essential for cell division, as it ensures equal distribution of genetic material to daughter cells.
What are metaphase chromosomes?
What are metaphase chromosomes?
Signup and view all the flashcards
What is the cell cycle?
What is the cell cycle?
Signup and view all the flashcards
What is interphase?
What is interphase?
Signup and view all the flashcards
What happens in the G1 phase of interphase?
What happens in the G1 phase of interphase?
Signup and view all the flashcards
What happens in the S phase of interphase?
What happens in the S phase of interphase?
Signup and view all the flashcards
Anaphase
Anaphase
Signup and view all the flashcards
Cytokinesis
Cytokinesis
Signup and view all the flashcards
G2 Checkpoint
G2 Checkpoint
Signup and view all the flashcards
Cyclins
Cyclins
Signup and view all the flashcards
Kinase
Kinase
Signup and view all the flashcards
Replication Fork
Replication Fork
Signup and view all the flashcards
Centromere
Centromere
Signup and view all the flashcards
Transcription Factor
Transcription Factor
Signup and view all the flashcards
tRNA (Transfer RNA)
tRNA (Transfer RNA)
Signup and view all the flashcards
RNA Polymerase
RNA Polymerase
Signup and view all the flashcards
Study Notes
Chromatin Structure and Chromosome Formation
- Chromatin is a thread-like structure composed of DNA (30%), histone proteins (60%), and RNA (10%).
- Chromatin is found in nucleosomes.
- During cell division, chromatin condenses into bar-like chromosomes.
- DNA winds around histone molecules, forming nucleosomes.
- Nucleosomes interact to form chromatin, similar to "beads on a string".
- Chromatin condenses and intertwines to become a chromosome.
- A metaphase chromosome is highly condensed, making transcription impossible due to the tight structure.
Chromosome Number and Genes
- Humans have 23 pairs (46 total) of chromosomes.
- The 23rd pair determines sex (XX or XY).
- Chromosomes are not equal in gene content. Some, like chromosome 1, carry more genes than others.
- Approximately 32,000 genes code for a large number of different proteins.
Cell Cycle Overview
- The cell cycle includes interphase and mitosis/cytokinesis.
- Interphase is divided into G1, S, and G2 phases.
Interphase Details
- G1 (Gap 1): Metabolic activity and growth. Organelles, centrosomes, and DNA are duplicated. A G1 checkpoint assesses if the cell can proceed. Failure results in G0 (permanent cell cycle exit).
- S (Synthesis): DNA replication occurs via the replisome, an enzyme complex.
- DNA's double helix unwinds using helicase.
- Topoisomerases relieve tension in the DNA.
- DNA polymerase III adds complementary nucleotides to the separated strands in a 5' to 3' direction, creating a copy of the DNA.
- RNA primase makes RNA primers that allow the start of DNA replication by DNA polymerase III.
- DNA polymerase I replaces RNA primers w DNA.
- DNA ligase connects the DNA fragments.
- G2 (Gap 2): Final preparations for division; another checkpoint.
Mitotic Phase
- Prophase (early): Chromatin condenses into visible chromosomes. Centrosomes divide and move to opposite poles. Mitotic spindles and asters form.
- Prophase (late): Nuclear envelope fragments. Kinetochore microtubules attach to the centromeres of chromosomes, and chromosomes begin to move to the cell center.
- Metaphase: Chromosomes align at the metaphase plate (center of the cell). Centrosomes are positioned at opposite poles.
- Anaphase: Sister chromatids separate and move to opposite poles.
- Telophase + Cytokinesis: Nuclear envelopes reform. Chromosomes decondense. Nucleoli reform. Cytokinesis (division of cytoplasm) occurs, forming two daughter cells.
Cell Cycle Regulators
- Internal regulators: Surface/volume ratio, proteins like cyclins and CDKs (cyclin-dependent kinases), G1 and G2 checkpoints.
- External regulators: Growth factors (GFs), hormones, contact inhibition (cells stop dividing when they touch).
DNA to Protein
- DNA undergoes transcription to produce mRNA.
- mRNA undergoes processing to become mature mRNA.
- mRNA is translated by ribosomes to synthesize proteins.
- Proteins are further processed and modified.
- This process occurs in the nucleus (transcription) and cytoplasm (translation).
Types of RNA
- mRNA (messenger RNA): Carries the genetic code from the DNA to the ribosomes.
- tRNA (transfer RNA): Carries amino acids to the ribosomes, aligning with mRNA codons.
- rRNA (ribosomal RNA): Structural component of ribosomes.
Transcription Factors
- Transcription factors bind to the promoter region of DNA to facilitate unwinding of histones, allowing RNA polymerase to access the promoter.
RNA Polymerase II
- RNA polymerase II uses ribonucleoside triphosphates (NTPs) as substrates to synthesize pre-mRNA.
Transcription Steps
- Initiation: Requires factors that promote unwinding like HAT (histone acetyltransferase) and chromatin remodeling complexes.
- Elongation: RNA polymerase synthesizes a pre-mRNA copy of the DNA.
- Termination: Transcription process ends.
Important DNA Regions
- Enhancer: A region of DNA, upstream or downstream of the gene, that can influence transcription when bound by transcription factors (it can bend).
- Promoter: A region of DNA close to the gene, crucial for transcription initiation.
- Coding Strand: The DNA strand whose sequence is similar to the mRNA (except for T = U).
- Template Strand: The DNA strand that is transcribed into mRNA.
Sigma Factor
- Sigma factor promotes specificity, increasing the accuracy of RNA polymerase binding & selection for the appropriate gene/region.
Transcription Modification
- mRNA undergoes modifications like a 5' cap, a 3' poly-A tail, and splicing (removing introns) to become mature mRNA.
Translation
- Initiation: Small ribosomal subunit finds the START codon (AUG) on mRNA. Methionine (fMet) tRNA binds. Large ribosomal subunit joins.
- Elongation: New tRNA brings amino acids to the A site of the ribosome. Peptide bonds form. Ribosome moves along mRNA.
- Termination: STOP codons (UAA, UAG, UGA) signal the end of the protein.
Protein Synthesis in RER (Endoplasmic Reticulum)
- mRNA-ribosome complex goes to ER via signal sequence and SRP (signal recognition particle).
- SRP detaches. Polypeptide chain enters ER membrane pore.
- Signal sequence is removed, and sugars are added.
- Completed protein folds.
- Protein is transported in a vesicle to the Golgi for further processing.
Genetic Code
- The genetic code dictates how mRNA sequences translate to amino acid sequences to form a protein.
- START codon (AUG) and STOP codons (UAA, UAG, UGA) specify protein synthesis initiation and termination.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
This quiz delves into the structure of chromatin and the formation of chromosomes, including their composition and organization during cell division. Additionally, it covers the fundamental aspects of the cell cycle, highlighting the phases of interphase. Test your knowledge on these essential biological concepts!
