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Questions and Answers
What key event occurs during zygotene in meiosis?
What key event occurs during zygotene in meiosis?
- Chromosomes condense into distinct structures.
- Sister chromatids are separated.
- DNA is synthesized.
- Homologous chromosomes are paired closely together. (correct)
What is the result of synapsis during meiosis?
What is the result of synapsis during meiosis?
- Formation of sister chromatids.
- Matching up of homologous pairs to form tetrads. (correct)
- Increasing the number of chromosomes in the cell.
- Separation of chromosomes into new cells.
During which stage of meiosis does crossing over primarily occur?
During which stage of meiosis does crossing over primarily occur?
- Metaphase
- Zygotene
- Pachytene (correct)
- Anaphase
What do chiasmata represent in the context of crossing over?
What do chiasmata represent in the context of crossing over?
How many sister chromatids are present in a single tetrad?
How many sister chromatids are present in a single tetrad?
What is the role of chromosomes according to the Chromosome Theory of Inheritance?
What is the role of chromosomes according to the Chromosome Theory of Inheritance?
How many chromosomes does a typical human body cell contain?
How many chromosomes does a typical human body cell contain?
What is the result of the complex reacting with tRNA?
What is the result of the complex reacting with tRNA?
Which codon is always the initiating codon?
Which codon is always the initiating codon?
What structure is DNA described as?
What structure is DNA described as?
What type of RNA is produced by RNA Polymerase II?
What type of RNA is produced by RNA Polymerase II?
What is a gene responsible for?
What is a gene responsible for?
During elongation, which site does the second tRNA bind to after the P site?
During elongation, which site does the second tRNA bind to after the P site?
What occurs to homologous chromosome pairs during meiosis?
What occurs to homologous chromosome pairs during meiosis?
What happens when a stop codon appears during translation?
What happens when a stop codon appears during translation?
What is the significance of the random sorting of chromosomes during meiosis?
What is the significance of the random sorting of chromosomes during meiosis?
What is the role of post-translational modification?
What is the role of post-translational modification?
Which statement accurately reflects the composition of gametes produced by each parent?
Which statement accurately reflects the composition of gametes produced by each parent?
Which of these statements about the structure of tRNA is true?
Which of these statements about the structure of tRNA is true?
What is true about the relationship between Mendel's laws and the Chromosomal Theory of Inheritance?
What is true about the relationship between Mendel's laws and the Chromosomal Theory of Inheritance?
What does the term 'activated tRNA' refer to?
What does the term 'activated tRNA' refer to?
Which characteristic is unique to Chromosome 15?
Which characteristic is unique to Chromosome 15?
What defines aneuploidy?
What defines aneuploidy?
Which chromosome is the largest in Group G?
Which chromosome is the largest in Group G?
What type of chromosome is Chromosome 16?
What type of chromosome is Chromosome 16?
Which chromosome has the least number of base pairs?
Which chromosome has the least number of base pairs?
What is the primary cause of aneuploidy?
What is the primary cause of aneuploidy?
Chromosomes 17 and 18 are categorized as which type of chromosome?
Chromosomes 17 and 18 are categorized as which type of chromosome?
Which chromosome is known to have a stalk and is categorized as acrocentric?
Which chromosome is known to have a stalk and is categorized as acrocentric?
Which of the following describes polyploidy?
Which of the following describes polyploidy?
What is the main purpose of chromosomal banding techniques?
What is the main purpose of chromosomal banding techniques?
Which staining technique produces reverse patterns of G-bands?
Which staining technique produces reverse patterns of G-bands?
Euchromatin is characterized by which of the following features?
Euchromatin is characterized by which of the following features?
What does G-banding reveal about chromosomes when stained with Giemsa stain?
What does G-banding reveal about chromosomes when stained with Giemsa stain?
Which type of chromatin is associated with transcriptional repression?
Which type of chromatin is associated with transcriptional repression?
Which statement about R-banding is accurate?
Which statement about R-banding is accurate?
What staining method is used in Q-banding?
What staining method is used in Q-banding?
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Study Notes
Chromosome Theory of Inheritance
- Identifies chromosomes as genetic material responsible for Mendelian inheritance.
- Proposes that during meiosis, homologous chromosome pairs segregate independently.
- Each parent generates gametes with half of their chromosomal complement.
Chromosomes
- Structures in cells containing organized strands of DNA with multiple genes.
- Humans typically have 23 pairs (46 total) of chromosomes.
DNA
- Deoxyribonucleic acid, a double helix molecule.
- Stores genetic information essential for building and maintaining organisms.
Gene
- A segment of DNA located on chromosomes.
- Codes for specific proteins that determine traits.
RNA Polymerase
- Enzymes that synthesize different types of RNA:
- RNA Polymerase I: synthesizes rRNA.
- RNA Polymerase II: synthesizes mRNA.
- RNA Polymerase III: synthesizes tRNA.
Translation Process
- Initiation: mRNA attaches to the ribosomal subunit, with the initiating codon AUG (methionine) at the P site.
- Elongation: A second tRNA binds at the A site, and amino acids transfer between sites.
- Termination: Polypeptide elongation stops upon encountering a stop codon (UAA, UAG, UGA), resulting in protein release.
Meiosis
- Consists of two stages: Meiosis I and Meiosis II, with one chromosome replication.
- Homologous chromosomes undergo synapsis, forming bivalents (tetrads).
Synapsis
- Pairing of homologous chromosomes during meiosis.
- Promotes crossover and genetic variation.
Crossing Over
- Exchange of genetic segments between non-sister chromatids at chiasmata during pachytene phase.
Chromosome Structures
- Chromosome 15: Medium acrocentric, 100 million base pairs.
- Chromosome 22: Small acrocentric, 49 million base pairs.
- Group E: Includes chromosomes 16-18, primarily small acrocentric and submetacentric.
- Y chromosome: Largest in Group G, 50 million base pairs.
Euploidy vs. Aneuploidy
- Euploidy: Normal number of chromosomes (e.g., diploid).
- Aneuploidy: Abnormal chromosome number due to nondisjunction.
- Trisomy: Extra chromosome.
- Monosomy: Missing a chromosome.
Polyploidy
- Higher than normal chromosome counts, exact multiples of the haploid number.
- Triploidy (3n): 69 chromosomes.
- Tetraploidy (4n): 92 chromosomes.
Chromosome Banding
- G-Banding: Staining technique that reveals alternating dark (A-T rich) and light (G-C rich) bands.
- R-Banding: Reverse pattern of G-banding.
- Q-Banding: Quinacrine stain produces a fluorescent pattern.
Heterochromatin vs. Euchromatin
- Heterochromatin: Tightly packed, low gene density, inactive transcription.
- Euchromatin: Lightly packed, enriched in genes, active transcription.
Chromosomal Banding Techniques
- Types include G-banding, R-banding, Q-banding, C-banding, T-banding, and NOR banding.
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