Abnormal Meiosis

Introduction

• Welcome back to Miss Angie's Biology Class
• Focus on abnormal meiosis
• Recap on normal meiosis
• Learn about results and explanations for exams
• Recommendations: study guide and membership for extra resources

Normal Meiosis

• Purpose: To halve chromosomes from one cell into two, then four non-identical cells
• Starting with 8 chromosomes, end with 4 chromosomes in each of the four cells
• Videos available for clarification on meiosis stages

Non-Disjunction

• Occurs when chromosomes fail to separate, often during anaphase
• Two types: in Meiosis 1 (homologous pairs fail to separate) and Meiosis 2 (chromatids fail to separate)
• Resultant cells have too many or too few chromosomes, marked as +1 or -1

What and When?

• Definition: Failure of chromosomes to separate
• Happens during anaphase
• Important phases: Prophase, Metaphase, Anaphase, and Telophase (PMAT)
• Critical point between Metaphase and Anaphase

Results of Non-Disjunction

• Monosomy: missing a chromosome
• Trisomy: extra chromosome
• Focus on Trisomy for exams

Explanation for Tests

• Spindle fibers pull chromosomes to the same pole
• Results in uneven chromosome distribution: Trisomy (+1) and Monosomy (-1)
• Non-disjunction occurs in anaphase 1 or 2

Real-World Applications

• Aneuploidy: Incorrect chromosome number, a chromosomal mutation
• Examples of Trisomy: Down syndrome (extra chromosome 21)

Explaining Down Syndrome

• Due to non-disjunction: 24 chromosomes in sperm/ovum instead of 23
• Fertilization with normal gamete results in 47 chromosomes (trisomy 21)

Terminology Recap

• Chromosomal Mutation: Too many or too few chromosomes
• Non-Disjunction: Failure to separate during anaphase
• Aneuploidy: Incorrect number of singular chromosomes
• Trisomy and Monosomy: Extra or missing chromosomes

Conclusion

• Reminder to like the video and subscribe for notifications
• Videos released every Tuesday and Thursday
• Encouragement to use additional resources for studying

These notes summarize the lecture on abnormal meiosis, its phases, implications, and real-world examples such as Down syndrome. These insights are crucial for understanding and explaining meiosis-related anomalies in academic assessments.