Biology 103 Chapter 10 – Flashcards
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A portion (location) of DNA that encodes a specific protein is a
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gene.
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Alternate forms (the DNA sequences indicated by alphabetic abbreviations) of the same gene are called
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alleles.
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In humans, alleles for each gene are inherited from
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males and females (one allele from each parent).
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Gametes may carry different combinations of alleles because of
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crossing over and random alignment of chromosomes.
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Mendel kept detailed records of the genetic traits of parent plants and their offspring plants. Among observations, he found that some traits would be expressed, whenever one particular allele was present, and called this allele
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dominant.
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If you, like Mendel, grow plants in the lab, and cross short (tt) pea plants with short pea plants, the offspring will be
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all short.
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When Mendel crossed tall (Tt) plants with tall plants of the same genotype, the offspring
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were a variable mix of tall and short.
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If the two alleles for a particular gene are identical the gene pair is
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homozygous.
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If an individual is heterozygous for a particular trait,
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each parent contributed a different allele for that trait.
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Genotype means
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the combination of alleles in an individual.
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Phenotype means
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the observable expression of the genes in an individual.
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The "P" in P generation refers to
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parental.
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In the study of genetics, the offspring of the parental generation is referred to as the
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F1 generation.
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Mendel's monohybrid cross of Tt parents resulted in a tall to short ratio of
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3:1.
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A testcross is a mating of an individual with an unknown genotype and an individual that
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is homozygous recessive.
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In a testcross, if all the offspring show the dominant phenotype, then the individual with the unknown genotype was
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homozygous dominant.
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The fact that the two alleles of each gene are packaged into separate gametes because they move apart from each other during gamete formation is Mendel's law of
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segregation.
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The fact that during gamete formation, the segregation of alleles for a gene on one chromosome does not influence the segregation of alleles for a gene on another chromosome is Mendel's law of
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independent assortment.
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In the ABO blood type system the alleles IA, IB, and i produce
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four phenotypes.
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In the biology lab, you observed that your lab partner's blood type is AB. The placement of the A and B molecules on each cell is controlled by proteins, coded by different versions of the same gene. Having both is an example of
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codominant inheritance.
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If the heterozygous phenotype is intermediate between those of the two different homozygotes, this is called
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incomplete dominance.
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A gene that produces a protein that is important in more than one biochemical pathway, or other trait, is a ___ gene.
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pleiotropic
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Linked genes, by definition, are genes that
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are found on the same chromosome.
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If any of the traits that Mendel worked with had been due to linked genes, his dihybrid crosses would have
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had different results.
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Crossing over is more likely to separate genes on a chromatid if they are
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far apart.
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If a person has a recessive allele for a disorder and that allele is masked by presence of a normal dominant allele, this person
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is termed a carrier.
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In pedigree charts, autosomal dominant disorders typically
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appear in every generation.
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In pedigree charts, autosomal recessive disorders typically
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seem to disappear in one generation, only to reappear in the next generation.
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At a given position, homologous chromosomes have
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the same genes but can have different alleles.
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If you cross two pea plants, one with green peas and the other with yellow peas, you find all of the offspring have yellow peas. You conclude the yellow parent was
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homozygous for the dominant allele.
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If a pea plant is heterozygous for yellow seeds (Gg), which gametes could it produce?
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G or g
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If you conduct a monohybrid cross of two heterozygous Yy pea plants, what percentage of the offspring will be heterozygous?
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50%
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In pea plants, Y confers yellow peas, and y confers green peas. If you cross two heterozygous Yy pea plants, what fraction of the offspring will be yellow?
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75%
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If you cross RrYy and RRyy pea plants, what fraction of the offspring will have yellow peas? R = round, r = wrinkled, Y = yellow, y = green.
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50%
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If you cross RrYy and RRyy pea plants, what percentage of the offspring will have round yellow peas? R = round, r = wrinkled, Y = yellow, y = green.
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50%
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Which gametes can a RrYy plant produce?
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RY, Ry, rY, or ry
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In an inherited form of high cholesterol, rr individuals have a blood cholesterol level greater than 500 mg/dL, Rr individuals are near 300 mg/dL, while normal (RR) cholesterol levels should be less than 200 mg/dL. The R allele is ___ to the r allele.
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incompletely dominant
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A man with type A blood and a woman with type B blood have a child with type O blood. What are the genotypes of the man and woman?
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IA i , and IB i
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In cystic fibrosis, two unaffected carriers can have a child with the disease. It is as common in boys as in girls. This disease is
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autosomal recessive.
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Hemophilia A is an X-linked recessive disorder. If a normal man marries a woman who is a carrier, what fraction of their sons will have hemophilia?
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50%
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Hemophilia A is an X-linked recessive disorder. If a normal man marries a woman who is a carrier, what fraction of their daughters will have hemophilia?
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0%
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In order for a girl to inherit hemophilia A, her parents would have which genotypes?
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XHXh, and XhY
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The wide variation in skin color in humans is best explained by
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skin color is a polygenic trait.
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When a farmer grows cotton containing the gene for Bt toxin, insects that are resistant (rr) survive and reproduce. This is an example of
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natural selection.
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When a farmer grows cotton containing the gene for Bt toxin, they often leave a strip of non-Bt cotton around the outside of the field for what reason?
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to allow some RR bollworm caterpillars to survive and limit selection pressure for resistance
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Bollworms raised for decades in a lab without exposure to Bt were ___ while those fed Bt were ___
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RR; rr.
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In this figure, the genotype of the resistant parental bollworms is ___ while the susceptible parental bollworms have a ___ genotype
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rr; RR
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Mendel's monohybrid cross of Tt parents resulted in a tall to short ratio of
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3:1.
