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15 Flashcards in this deck.
Inherited traits are features or characteristics that individuals acquire from their parents through genetic information. These traits are encoded in genes, which are segments of DNA located on chromosomes. Humans have 23 pairs of chromosomes, with one set inherited from each parent, making the study of heredity crucial in genetics.
Traits are often categorized as dominant or recessive based on their expression. A dominant trait is one that is expressed in the phenotype even if only one copy of the gene is present. In contrast, a recessive trait requires two copies of the gene to be expressed.
Co-dominant traits occur when both alleles in a gene pair are fully expressed, resulting in a phenotype that shows both traits simultaneously. A classic example is the ABO blood group system, where individuals can exhibit both A and B antigens, resulting in the AB blood type.
Gregor Mendel's work laid the foundation for understanding inheritance patterns. His experiments with pea plants revealed the principles of segregation and independent assortment, explaining how traits are passed from one generation to the next.
Unlike single-gene traits, polygenic traits are influenced by multiple genes, often resulting in a spectrum of phenotypes. Human skin color, height, and eye color are examples of polygenic traits, where the combination of multiple genes contributes to the final phenotype.
While genetics play a significant role in determining traits, environmental factors can also influence their expression. For instance, nutrition can affect height, and exposure to sunlight can influence skin pigmentation.
Genetic variations arise from mutations, which are changes in the DNA sequence. While some mutations can lead to genetic disorders, others contribute to the diversity of traits within a population.
Mosaicism occurs when an individual has cells with different genetic makeup, typically due to mutations after fertilization. Chimerism involves the presence of two distinct sets of DNA in one individual, resulting from the fusion of two embryos.
Sex-linked traits are associated with genes located on sex chromosomes. In humans, most sex-linked traits are found on the X chromosome, making them more prevalent in males due to their single X chromosome.
Incomplete dominance occurs when neither allele is completely dominant, resulting in a blended phenotype. An example is the flower color in certain plants where red and white alleles produce pink flowers.
Multiple alleles refer to the presence of more than two alleles for a particular gene within a population, such as the ABO blood group system, which includes A, B, and O alleles.
Pedigree charts are tools used to trace the inheritance of traits through generations within a family. They help in predicting the probability of an individual inheriting a particular trait based on genetic patterns.
Genetic counseling involves advising individuals and families about the risks of inherited disorders. By understanding inheritance patterns, genetic counselors can provide information on the likelihood of passing on certain traits or conditions.
Type of Trait | Definition | Example |
Dominant | Expressed in the phenotype when at least one allele is present. | Brown eyes |
Recessive | Expressed only when two copies of the allele are present. | Blue eyes |
Co-Dominant | Both alleles are fully expressed in the phenotype. | AB blood type |
Incomplete Dominance | Blended expression of both alleles. | Pink flower color |
Polygenic | Influenced by multiple genes, leading to a range of phenotypes. | Human height |
To remember the difference between dominant and recessive traits, think of "Dominant" starting with "D" as in "Displayed." Use the mnemonic "DARK" for Dominant Alleles are Rarely Kept as recessive. For Mendelian inheritance, visualize the Punnett square to predict trait probabilities effectively.
Did you know that the ability to taste certain bitter compounds is a co-dominant trait? This means some people can taste both forms of the compound, leading to a unique flavor perception. Additionally, the gene responsible for freckles is influenced by both genetic and environmental factors, such as sun exposure, showcasing the intricate interplay between heredity and environment.
Students often confuse dominant and recessive traits, assuming that dominant traits are always more common. For example, having brown eyes is dominant, but this doesn't mean everyone has brown eyes. Another common mistake is misinterpreting co-dominance as incomplete dominance, leading to confusion in scenarios like the AB blood type versus pink flowers.