Mendelian Inheritance Notes Pt. 2 Flashcards
What is the ratio of genotypes in the F2 progeny from a Yy × Yy cross?
1:2:1 (1/4 YY, 1/2 Yy, 1/4 yy)
This ratio indicates the genetic combinations possible from the cross.
What is the phenotype ratio in the F2 progeny from a Yy × Yy cross?
3:1 (3/4 yellow, 1/4 green)
This ratio reflects the observable traits resulting from the genotype combinations.
What does the Law of Segregation state?
Allele pairs separate randomly during gamete formation
This law explains the predictable ratios of offspring in Mendelian inheritance.
What is a testcross?
A cross involving an individual with a dominant phenotype and a homozygous recessive organism to determine the genotype
This method helps identify whether the dominant phenotype is homozygous or heterozygous.
What are the possible outcomes of a testcross for a dominant phenotype?
- All yellow offspring → Parent was YY (homozygous dominant)
- 1:1 yellow to green offspring → Parent was Yy (heterozygous)
These outcomes provide insight into the parent’s genotype based on offspring phenotypes.
What traits did Mendel examine in a dihybrid cross?
- Seed color (Yellow, Y, dominant over Green, y)
- Seed shape (Round, R, dominant over Wrinkled, r)
This cross allows the study of inheritance patterns for two traits simultaneously.
What is the result of a dihybrid cross in terms of parental and recombinant types?
Produces both parental types and recombinant types
Parental types are the same as the original generation, while recombinant types are new combinations.
What is the phenotype ratio produced by a dihybrid cross of F1 dihybrids?
9:3:3:1
This ratio reflects the independent assortment of two traits during gamete formation.
What does Mendel’s Law of Independent Assortment state?
Different pairs of alleles segregate independently of each other during gamete formation
This law explains how the inheritance of one trait does not affect the inheritance of another.
What occurs during Meiosis I?
Separates homologous chromosomes, reducing chromosome number from diploid (2n) to haploid (n)
This is crucial for the formation of gametes.
What is the outcome of Meiosis II?
Separates sister chromatids, resulting in four genetically unique haploid cells
This process ensures genetic diversity in the resulting gametes.
What types of gametes can a dihybrid F1 plant (Yy Rr) produce?
- YR (dominant yellow, dominant round)
- Yr (dominant yellow, recessive wrinkled)
- yR (recessive green, dominant round)
- yr (recessive green, recessive wrinkled)
These gametes combine randomly during fertilization to produce the F2 generation.
What genetic variation occurs during Prophase I of meiosis?
Crossing over occurs, exchanging segments between homologous chromosomes
This process increases genetic diversity beyond what is explained by Mendelian ratios.
What is the molecular explanation for the shape of Mendel’s peas?
The R allele encodes Starch branching enzyme (Sbe1), while the r allele does not, leading to wrinkled peas
This genetic basis explains the phenotype observed in the peas.
What are the two general molecular principles in genetics?
- A specific gene determines a specific protein, affecting the phenotype
- A dominant allele usually determines a normally functioning protein, while a recessive allele usually does not encode a functional protein
These principles help explain the relationship between genotype and phenotype.
Fill in the blank: The genotype YY leads to _______ production.
Sgr produced
This enzyme is responsible for breaking down chlorophyll, resulting in yellow peas.
