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- Genes control characteristics and each trait is associated with specific genes.
- The mechanism of heredity involves the contribution of genetic material from both parents.
- Germ cells have one set of genes, ensuring diversity in offspring during sexual reproduction.
- Chromosomes, present as separate pieces, are inherited from each parent, contributing to trait inheritance.
- Mendelian experiments: Tested with pea plants showing two different characteristics. It illustrated the concept of dominance and recessiveness with examples.
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Genetic Determination of Sexual Phenotype: The X and Y Chromosomal Dynamics in Human Sex Determination
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- Genetic determination largely influences the sex of newborn individuals in humans.
- Instructions for determining a baby’s sex are within the fertilized egg or zygote.
- Chromosomes carry these instructions and reside in the cell nucleus.
- Humans have 23 pairs of chromosomes, with two being sex chromosomes: X and Y.
- Females have two X chromosomes, while males have one X and one Y chromosome.
- Gametes (egg and sperm) carry only one set of chromosomes.
Sex determination in human beings
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Role of Sex Chromosomes in Determining Sex
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- Unfertilized eggs always have one X chromosome.
- While sperms carry either X- chromosome or Y-chromosome.
- Fertilisation: Fertilization by X-carrying sperm results in a female child, while Y-carrying sperm leads to a male child.
- Identity: Sex chromosomes from the father determine the unborn baby’s sex.
- Mythical Belief: The notion that the mother determines the baby’s sex is inaccurate and unjustified.
- Role of Environment: For species other than humans, environmental cues and different strategies are used for sex determination as environmental factors play a role in the selection of variants and evolutionary processes.
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Genetic Harmony: The Crucial Role of Heredity in Species Stability and Evolutionary Success
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- The mechanism of heredity ensures the stability of the DNA of the species.
- Sexually reproducing organisms follow similar rules of inheritance, ensuring variation and adaptation.
- Hence, variations are important for the survival and evolution of species.
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