2026 - Term - human genetic diversity

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Marion Longoni, lycée Marguerite de Flandre, Gondecourt.

Chapter I: reproduction and genetic diversity

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II- Meiosis and the production of sex cells

I- Recall: basic genetics

III- Meiosis and genetic disorders

BACK TO INDEX

I-Recall: basic genetics

BACK TO INDEX

Visit the different pages linked below and build a diagram which will show the link between these 6 themes: DNA, genes, proteins, traits, mutation, inheritance.

BACK TO INDEX

II- Meiosis and the production of sex cells

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II- Meiosis and the production of sex cells

Index

* Comprehension orale

* Diagram of the meiosis process

* Meiosis and ploidy

* Summary

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Oral comprehension

Use the video to answer the questions. Try not to use the script.

Questions

Script

Direct link to the video

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Build a diagram of meiosis process. Each step has to be described by a short sentence. (group work => 3 to 4)

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We understood that when gametes are formed, they eventually possess one chromatid of one chromosome of the original pair of chromosome.

Before meiosis

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gametes

gametocyte = mother cell

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As a result, the quantity of DNA in the cells produced is different from the one of the mother cell. Ploidy is the number of sets of chromosomes in a cell or an organism. So, we can say the ploidy varies during the meiosis process. diploid organisms => 2n = two sets of chromosomes in the nucleus of the cell haploid organisms => 1n = 1 set of chromosomes in the nucleus of the cell

Before meiosis

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Complete your diagram, add 2n or 1n to the captions

gametes

gametocyte = mother cell

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Exercise

Explain the evolution of the DNA content shown on this diagram.

S = Interphase M1 = meiosis first division M2 = meiosis second division

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PROBLEM: We are diploid organisms. How is it possible? Because... the gametes that form our egg cells are haploids... aren't they? How can they produce diploid organisms? Do you have the answer?

Complete your diagram with the answer.

Before meiosis

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How is the diploidy of the egg cell restored?

gametes

gametocyte = mother cell

HAPLOID CELLS

DIPLOID CELL

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Note this

SUMMARY Meiosis is the process which leads to the creation of four haploid cells, also called gametes, through a series of two divisions of a diploid mother cell. Fertilization is the fusion of two haploid gametes. It restores the diploid states necessary for the zygote to survive. Thus, the zygote is the reunion of two genotypes of different origin, each one bringing a set of alleles. As a result, each gene possesses two different copies (or alleles). If the copies are identical, the individual is homozygous, otherwise, he's heterozygous. When people are heterozygous, their gametes are more diverse. The study of the genetics of a population can help us understand its evolution. In the human population, it can help the prediction of genetic diseases in newborns.

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Pick one topic out of the following: - Down's syndrome or trisomy 21 - Edward's syndrome or trisomy 18 - Patau syndrome or trisomy 13 - Cri du chat syndrome or 5p minus syndrome (partial deletion of short arm of chromosome 5) - Wolf-Hirschhorn syndrome or deletion 4p syndrome - Jacobsen syndrome or 11q deletion disorder - Klinefelter's syndrome or presence of additional X chromosome in males - Turner syndrome or presence of only a single X chromosome in females - XYY syndrome and XXX syndrome Build an illustrated oral presentation in order to present this chromosomal abnormality to your classmates. You have to explain the origin of the abnormality, its symptoms and consequences on the everyday life of people affected. (work by pair or triplet)