Genotype and Phenotype
Distinction Between Genotype and Phenotype
Definitions:
Genotype: The set of genes that an individual inherits.
Phenotype: The observable properties of the body, including physical and behavioral traits.
Environmental Impact on Phenotype:
The same genotype can produce different phenotypes depending on environmental factors and interaction with other genes.
Example:
Genetically identical rats may exhibit different behaviors toward infant rats if one has been previously exposed to them and the other has not.
Genetically identical human twins can differ in size due to varying exposure to growth-promoting factors in their environments.
Differences in behavior may arise from different learning experiences subjected to the twins.
Visual Reference:
See Figure 3.2 in the original material for an illustration of these concepts.
How Genes Are Passed Along in Sexual Reproduction
Function of Genes:
Genes serve as the codes for building proteins and act as biological units of heredity.
They are replicated and transmitted from parents to offspring.
Arrangement of Genes in Cells:
The genetic material is contained within structures called chromosomes, which are housed within the cell nucleus.
During cell division, chromosomes condense into compact forms that can be visually examined and photographed.
Human Chromosome Count:
A normal human cell contains 23 pairs of chromosomes.
22 pairs of these chromosomes are ordinary somatic chromosomes (autosomes) that appear similar in both males and females.
The 23rd pair constitutes the sex chromosomes:
In normal human males:
Comprises one large chromosome labeled X and one small chromosome labeled Y.
In normal human females:
Comprises two X chromosomes (XX), forming a true pair of sex chromosomes.
Visual Reference:
See Figure 3.3 in the original material for an illustration of sex chromosomes.