Texbook Flashcards
Why were pea plants ideal for Mendel’s experiments?
They have distinct traits, a short generation time, self-pollinate naturally, and can be easily cross-pollinated.
What are the three key principles Mendel discovered?
The Law of Segregation, the Law of Independent Assortment, and the Principle of Dominance.
What is the Law of Segregation?
During gamete formation, the two alleles for each gene separate, so each gamete gets only one allele.
How does meiosis relate to Mendel’s Law of Segregation?
Homologous chromosomes separate during anaphase I of meiosis, ensuring each gamete receives one allele.
What is the Law of Independent Assortment?
Genes for different traits assort independently of one another during gamete formation.
How does genetic linkage affect independent assortment?
Linked genes, located close together on the same chromosome, are inherited together and do not assort independently.
What is a dihybrid cross?
A genetic cross between two individuals heterozygous for two traits.
What phenotypic ratio results from a dihybrid cross of two heterozygous individuals (AaBb × AaBb)?
9:3:3:1.
What is the purpose of a Punnett square?
To predict the genotypic and phenotypic outcomes of a genetic cross.
What is the product rule in genetics?
The probability of two independent events occurring together is the product of their individual probabilities.
What is the sum rule in genetics?
The probability of either of two mutually exclusive events occurring is the sum of their probabilities.
How does a branching diagram simplify multihybrid cross predictions?
It breaks each gene’s inheritance into individual probabilities and combines them at the end.
Why do Punnett squares become impractical for multihybrid crosses?
The number of boxes increases exponentially with more traits, making it cumbersome to analyze.
What inheritance pattern does Huntington’s disease follow?
Dominant inheritance.
What inheritance pattern does cystic fibrosis follow?
Recessive inheritance.
How can a pedigree help determine if a trait is dominant or recessive?
Dominant traits appear in every generation, while recessive traits can skip generations.
Why are recessive alleles often associated with nonfunctional proteins?
They usually result from mutations that cause a loss of function in the encoded protein.
What is epistasis?
When one gene’s expression masks or modifies the effect of another gene.
Provide an example of epistasis in animals.
Coat color in Labrador Retrievers, where one gene determines pigment and another gene determines pigment deposition.
What is the biochemical role of the Sbe1 gene in Mendel’s peas?
It encodes an enzyme that converts unbranched starch to branched starch, affecting seed shape.
What does the Sgr gene control in Mendel’s pea experiments?
It controls the breakdown of chlorophyll, affecting seed color.
How did Mendel use statistical methods to validate his hypotheses?
He analyzed large sample sizes to observe consistent patterns that matched predicted ratios.
Why was Mendel’s approach revolutionary?
He applied quantitative analysis and statistics to biological inheritance, which was novel at the time.
What was the main goal of the Human Genome Project?
To sequence the entire human genome and identify all its genes.