40 Questions
What was Gregor Mendel's primary goal when conducting his experiment?
To create hybrid pea plants and observe the outcome
What is the term that encompasses the inherited genes, traits, and DNA coding passed from the parental generation to the offspring?
Genotype
What is the term for the offspring of the parental generation in Mendel's experiment?
F1 generation
What is the ratio of the phenotypic expression in the F2 generation of Mendel's monohybrid cross?
3:1
What is the principle that explains that in a cross between two parents that are pure for a particular trait, one allele will dominate over the other?
Law of Dominance
What is the purpose of allowing the F1 generation to self-fertilize?
To produce the F2 generation
What is the purpose of a pedigree in genetics?
To chart the history of traits passed on among several generations of a family
What is the characteristic of the F1 generation in Mendel's experiment?
It shows only one of the two contrasting traits
What is the advantage of using pea plants in Mendel's experiment?
They are highly versatile
What is the term that refers to the observable physical traits inherited by the offspring?
Phenotype
What is the term for the study of the passing of traits from parents to offspring?
Genetics
What is the ratio of the genotypic expression in the F2 generation of Mendel's monohybrid cross?
1:2:1
What is the principle that explains that the alleles of particular genes are inherited independently from one another?
Law of Independent Assortment
What is the result of crossing one purebred yellow seed and one purebred green seed in Mendel's experiment?
An F1 generation that shows only the dominant trait
What is the characteristic of the Y chromosome?
It carries very few genes.
What is the purpose of crossing the F1 generation to obtain the genotypic and phenotypic ratios of the F2 generation?
To obtain the genotypic and phenotypic ratios of the F2 generation
What is the significance of Mendel's experimental method?
It was based on many repeated trials to find the likely outcome
Why do recessive genes attached to the X chromosome of a male individual express themselves in the phenotype?
Because they are unpaired and cannot be either recessive or dominant.
Who will inherit the X chromosome from the father?
Only daughters.
What is required for a daughter to inherit hemophilia?
A double recessive allele of an individual.
What is the genotype of a female carrier of hemophilia?
XHXh
Why do recessive male traits pass only to daughters?
Because daughters inherit the X chromosome from the father.
What is the condition necessary for a daughter to inherit hemophilia?
The father is hemophiliac and the mother is either affected or a carrier.
What is the result of crossing a male parent carrying a recessive X-linked gene with a female parent that is homozygous dominant for the same X-linked trait?
Heterozygous daughters that carry the recessive X-linked gene.
What types of seeds did Mendel use in his experiment?
Yellow or green and round or wrinkled
What is the result of crossing two F1 generation seeds with each other?
A phenotypic ratio of 9:3:3:1 and a genotypic ratio of 1:2:1:2:4:2:1:2:1
What is represented by the symbols in a pedigree?
The relationships between individuals and the likelihood of expressing a particular trait
What did Josef Kolreuter discover in 1760?
The mixing of colors in carnations
What is the characteristic of traits in Mendel's study?
They are simple and independently segregating
What is the result of crossing a yellow round seed with a green wrinkled seed?
Only yellow round seeds in the F1 generation
What is the purpose of a pedigree?
To analyze the inheritance of traits in a family
What is the significance of the F2 generation?
It exhibits a characteristic ratio of traits due to Mendel's laws
What is the genotype of a female who is a carrier of the hemophilia gene?
XhXh
What is the chance that a son inherits the hemophilia gene from the female parent?
50%
What type of genes are responsible for the inheritance of hemophilia?
Sex-linked genes
What is the result of the lack of Factor VII in hemophilia?
Blood clots improperly
What is an example of a Holandric gene?
Hypertrichosis of pinnae
What is the main difference between sex-linked traits and sex-limited traits?
Sex-limited traits are influenced by sex hormones
What is the genotype of an unaffected male?
XHY
Why do sex-linked traits tend to affect the male population more often?
Because males have only one X chromosome
Study Notes
Mendel's Experiment and Laws of Heredity
- Mendel's experiment aimed to create hybrid pea plants and observe the outcome, leading to the discovery of the laws of heredity.
- He used self-fertilization for several generations to ensure pure breeds and crossed contrasting P generation plants to produce the F1 generation.
- The F1 generation always showed only one of the two contrasting traits, known as the dominant trait.
- The F2 generation was produced by allowing the F1 generation to self-fertilize, resulting in a genotypic ratio of 1:2:1 and a phenotypic ratio of 3:1.
- Mendel's laws of heredity include the Law of Dominance and the Law of Independent Assortment.
Genotypes and Phenotypes
- A genotype refers to the complete combination of alleles for a particular gene, encompassing the inherited genes, traits, and DNA coding passed from the parental generation to the offspring.
- A phenotype refers to the observable physical traits inherited by the offspring, such as the yellow or green seed color in Mendel's experiment.
Pedigree Analysis
- A pedigree is a family tree that charts the history of traits passed on among several generations of a family.
- Pedigrees are used to trace the passing of an allele from parents to offspring and to detect which members of the family are afflicted with a genetic disorder.
- The pedigree contains symbols that identify sex, relationships between individuals, and the likelihood of an individual to express a particular trait or carry the allele as part of a heterozygous genotype.
Non-Mendelian Genetics and Sex Linkage
- Sex linkage occurs when alleles are attached to the X or Y chromosome, expressing X-linked or Y-linked traits.
- Recessive genes attached to the X chromosome of a male individual will express themselves in the phenotype, since this gene or allele is unpaired and thus, cannot be either recessive nor dominant.
- Sex-linked traits tend to affect the male population more often, with examples including red-green color blindness and hemophilia.
- Hemophilia is caused by a recessive X-linked allele or gene that codes for Factor VII, a protein important in blood clotting.
Sex-Limited Traits
- Sex-limited traits are caused by sex-limited genes that are expressed only in the presence of sex hormones and are observed in one sex of a species.
- Unlike sex-linked traits, sex-limited traits are controlled by autosomal genes that occur only or dominantly in either male or female species.
- Examples of sex-limited traits include hypertrichosis of pinnae, or the growth of tiny hairs in the ear.
Learn about Gregor Mendel's experiment on heredity, including self-fertilization and cross-fertilization of pea plants, and how it laid the foundation for modern genetics.
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