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27 Cards in this Set
- Front
- Back
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What causes Hemophilia A?
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The absence of a protein called factor VIII that is vital in the formation of blood clots.
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How can Hemophilia A be treated?
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Injection of factor VIII into the bloodstream.
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How is hemophilia inherited through the mother, and why is it more frequent in males?
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It is entirely possible that hemophilia is an x-chromosome linked disease, and males would experience it more frequently because, due to their possession of only one x-chromosome, any gene present in that x-chromosome would be expressed more dramatically.
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In the mid-nineteenth century, what were the two theories that had emerged to explain the results of breeding experiments?
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The theory of blending inheritance, which proposed that gametes contained hereditary determinants (what we now call genes) that blended when the gametes fused during fertilization. The theory or particulate inheritance, which proposed that each determinant had a physically distinct nature; when gametes fused in fertilization, the determinants remained intact. (according to this theory, if a plant that made spherical seeds was crossed with a plant that made wrinkled seeds, the offspring would still contain the determinants for the two characteristics.
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Why did Gregor Mendel use the garden pea for his experiments on inheritance?
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He chose to study the common garden pea because of its ease of cultivation and the feasibility of making controlled crosses.
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What are the male and female sex organs of flowers?
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The stamen is the male organ, as it contains pollen, while the pistil and ovule are the female organs, as the ovule contains the eggs.
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What is the difference between a character and a trait?
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A character is an observable physical feature, such as seed shape. A trait is a particular form of a character, such as spherical or wrinkled seeds.
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What were some examples of the traits that Mendel tested for?
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Seed shape, seed color, flower color.
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What does "true-breeding" mean?
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Crossing individuals of the same variety to produce pheno- and genotypically identical offspring. For example, crossing a plant that produced wrinkled seeds with another of the same variety, and this union producing offspring that produced wrinkled seeds.
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How did Mendel conduct his experiments?
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He removed the stamens from flowers of one parental variety so that it couldn't self-fertilize. Then he collected pollen from another parental variety and placed it on the pistils of the emasculated flowers. The plants providing and receiving the pollen were the parental generation (designated P). In some experiments, the resulting F1 plants were allowed to self-pollinate in order to produce a second fillial generation (F2).
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What does hybrid mean?
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It refers to the offspring of crosses between organisms differing in one or more characters.
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What is a monohybrid?
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A generation wherein only one trait is tested for. For instance, crossing "GG" with "gg" and getting 4 individuals with "Gg". Then allowing one "Gg" to self-pollinate, producing an F2 generation with varying traits; "GG", "Gg", and "gg".
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What was the result of Mendel's monohybrid cross?
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It led to the rejection of the blending theory of inheritance and strongly supported the particulate theory.
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What is the nature of hereditary determinants? (i.e. are they particulate?)
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They are not particulate, but they are physically distinct entities; sequences of DNA carried on chromosomes.
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How did Mendel expand on the particulate theory?
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He proposed that "genes" (hereditary determinants) occur in pairs and segregate from one another during the formation of gametes. He concluded that each pea plant has two genes for each character (such as seed shape), one inherited from each parent. We now use the term diploid to describe the state of having two copies of each gene; haploids have just a single copy.
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What is Mendel's first law?
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The law of segregation, which states that when any individual produces gametes, the two copies of a gene separate, so that each gamete receives only one copy.
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How many base pairs long are genes?
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They are usually one to two thousand base pairs in length.
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How long are chromosomes?
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Usually millions of base pairs long.
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How do genes determine phenotypes?
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Mostly by producing proteins with particular functions, e.g. enzymes.
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What does it mean for a gene to be expressed?
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For it to be transcribed and translated. Transcription is the process by which DNA is scripted into RNA, and translation is how that script is made into a functional protein.
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How are recessive genes "expressed"?
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They are not expressed, or they encode a mutant protein that is not functional. For example, the molecular nature of the wrinkled pea seed phenotype is the absence of the enzyme SBE1, which is essential for starch synthesis. With less starch, the developing seed has more sucrose and this causes an inflow of water by osmosis. When the seed matures and dries out, this water is lost, leaving a shrunken seed.
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What is mutation?
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Rare, stable, and inherited changes in the genetic material.
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What is wild-type?
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It is the allele that is present in most individuals in nature. All other alleles are called mutant alleles, and produce different phenotypes. A gene with a wild-type allele that is present less than 99% of the time is said to be polymorphic.
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What may occur if a gene has multiple alleles?
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The alleles may show a hierarchy of dominance when present in heterozygous individuals (coat color in rabbits).
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What is incomplete dominance?
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When a gene has alleles that are neither dominant nor recessive to one another, and instead have an intermediate phenotype that a combination of each of the alleles.
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What is codominance?
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When two alleles of the same gene both produce their phenotypes when present in a heterozigote,
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What is a dihybrid cross?
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A cross between individuals that are identical double heterozygotes (heterozygous for two different traits). For instance, P generation SSYY x ssyy produces the individual SsYy, whose gametes are SY, Sy, sY, and sy. This individual is the F1 generation, and is allowed to self-pollinate, causing sperm cells SY, Sy, sY, and sy to fertilize egg cells SY, Sy, sY, and sy. This self pollination creates the F2 generation, which is composed of 16 individuals. There are nine genotypes in this generation, resulting in 4 phenotypes in a ratio of 9:3:3:1, meaning that (in the case of peas) 9 individuals are smooth and yellow, three individuals are smooth and green, three individuals are wrinkled and yellow, and one individual is wrinkled and green.
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