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T2 - BIO - Preview 22 - 1N - Ploidy and recombination
Jan 6, 2025
Useful Genetics Lecture 1n: Ploidy and Recombination
Key Concepts
Ploidy Changes in Sexual Reproduction
Alternation between haploid and diploid cells
Introduction of new genome versions through recombination
Key processes: reassortment and crossing over
Essential Terms
Haploid Cell
Contains one complete set of chromosomes
Example: haploid set of N=5 chromosomes
Diploid Cell
Contains two homologous complete sets of chromosomes
Example: diploid set of 2N=10 chromosomes
Humans: N=23, hence diploid chromosome count is 2N=46
Ploidy
Not used to differentiate DNA amounts before and after replication
Identifies genetic constitution based on chromosome sets
Genetic Consequences of Sexual Reproduction
Alternation between haploid gametes and diploid organisms
Generation of new genetic combinations
Reassortment (Shuffling)
Inheritance of mixed chromosome sets from parents
New gametes contain mixed sets from maternal and paternal grandparents
Crossing Over
Creates genetic variation within each chromosome
Chromosome segments mix from maternal and paternal sources
Result in gametes with new combinations of segments
Process Descriptions
Reassortment
Chromosome shuffling like a deck of cards
New combinations in each generation
Crossing Over
Segments of chromosomes break and rejoin in new combinations
Increases genetic diversity significantly
Conclusion
Sexual reproduction involves changing ploidy levels
Gametes have one set; somatic cells have two sets
Generates genetic variation through reassortment and crossing over
Upcoming Topics
Genetic variation in populations
Connection to human evolution and interaction with Neanderthals
Further exploration in subsequent lectures
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