Questions and Answers
What did Gregor Mendel use to study the inheritance of traits?
pea plants
What are offspring that result from crosses between true breeding parents with different traits called?
hybrids
What are the chemical factors that determine traits called?
genes
How are traits inherited according to Gregor Mendel?
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When Gregor Mendel crossed a tall plant with a short plant, what did the F1 plants inherit?
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What does the principle of dominance state?
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Why were all offspring tall when true-breeding tall plants were crossed with true-breeding short plants?
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What happens if the tall F1 pea plants are allowed to self-pollinate?
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How can the principle of probability be used in genetics?
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In the P generation, what is the probability that an F2 plant will be tall when a tall plant is crossed with a short plant?
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What do you call organisms that have two identical alleles for a particular trait?
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What does a Punnett square show?
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What is shown by a Punnett square showing Gregor Mendel's cross between true-breeding tall plants and true-breeding short plants?
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What principle states that during gamete formation, genes for different traits separate without influencing each other's inheritance?
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How many different allele combinations would be found in the gametes produced by a pea plant whose genotype was RrYY?
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If a pea plant that is heterozygous for round, yellow peas is crossed with a homozygous round but heterozygous yellow pea plant, how many different phenotypes are their offspring expected to show?
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What do you call a situation in which one allele for a gene is not completely dominant over another allele for that gene?
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What type of inheritance is illustrated by a cross of a red cow with a white bull producing all roan offspring?
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What is the number of chromosomes in a gamete represented by?
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If an organism's diploid number is 12, what is its haploid number?
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What do gametes have for each gene?
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By which process are gametes produced?
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What is the diagram of chromosomes created during crossing over?
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During which phase do chromosomes form tetrads?
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What happens between meiosis I and meiosis II that reduces the number of chromosomes?
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Unlike mitosis, what does meiosis result in?
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In a two-factor cross where both parents are heterozygous for both traits, what would the expected phenotypic ratio be?
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The wide range of skin colors in humans is an example of what?
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What is it called when human blood type alleles of A and B are equally dominant to each other and both are expressed?
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When the heterozygous phenotype is a combination or an intermediate of the two homozygous phenotypes, what is it called?
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If the sex cell of an organism has 20 chromosomes, how many chromosomes will the body cells have?
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A trait is a specific characteristic that varies from one individual to another.
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An organism with a dominant allele for a particular form of a trait will sometimes show that trait.
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When alleles segregate from each other, they join.
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The probability that a gamete produced by a pea plant heterozygous for stem height will contain the recessive allele is 100%.
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Mitosis results in two cells, whereas meiosis results in one cell.
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What are the different forms of a gene called?
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The principle of independent assortment states that ________ for different traits can segregate independently during the formation of gametes.
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Red, white, and pink phenotypes in flowers called four o'clocks are an example of what?
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An organism's ____ have half the number of chromosomes found in the organism's body cells.
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What is genetics?
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How many recessive alleles for a trait must an organism inherit in order to show that trait?
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What is the difference between incomplete dominance and codominance?
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What cross should you perform to determine whether a tall pea plant is homozygous or heterozygous for tallness?
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When would Mendel allow the tall F1 pea plants to self-pollinate?
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Linked genes are always located where?
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What does a Punnett square show?
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Study Notes
Mendelian Genetics
- Gregor Mendel conducted experiments using pea plants, exploring the inheritance of traits.
- Offspring from true breeding parents with different traits are termed hybrids.
- Genes are the fundamental chemical factors determining traits.
Principles of Inheritance
- Traits are inherited through factors passed from parents to offspring.
- Dominant alleles overshadow recessive alleles, as seen when tall plants crossed with short plants resulted in all tall offspring.
- The probability of F2 plants being tall after self-pollination of tall F1 plants is 75%.
Genetic Terminology
- Organisms with identical alleles for a particular trait are homozygous.
- A Punnett square visually represents potential offspring genotypes but does not show actual results.
- The Principle of Independent Assortment states that genes for different traits segregate independently during gamete formation.
Genetic Combinations
- Gametes from a pea plant with genotype RrYY will have 2 different allele combinations.
- Crossing heterozygous round, yellow peas (RrYy) with homozygous round peas (RRYy) yields 2 different phenotypes.
Patterns of Inheritance
- Incomplete dominance occurs when one allele isn't completely dominant over another, resulting in a mix in heterozygous phenotypes.
- Codominance occurs when both alleles are equally dominant and expressed, as seen in roan offspring from a red cow and a white bull.
- Polygenic traits, such as human skin color, arise from the interaction of multiple genes.
Chromosomes and Meiosis
- Gametes contain one allele for each gene; they are produced through meiosis, which results in four genetically distinct cells.
- Diploid organisms have double the number of chromosomes compared to their haploid gametes.
Genetic Probability and Ratios
- In a two-factor cross of heterozygous parents (TtYy x TtYy), the expected phenotypic ratio is 9:3:3:1.
- The probability that a gamete from a heterozygous plant will carry a recessive allele is 50%.
Traits and Alleles
- Traits are specific characteristics, and different gene forms are called alleles.
- An organism must inherit two recessive alleles to express a recessive trait.
- Additional traits can range from red, white, to pink in four o'clock flowers, serving as examples of incomplete dominance.
Key Concepts in Genetics
- Gametes have half the chromosome number of body cells, essential for sexual reproduction.
- Mitosis produces two identical cells, while meiosis produces four varied cells.
- Linked genes are located on the same chromosome, influencing inherited traits.
Mendel's Experimentation
- To determine whether a tall pea plant is homozygous or heterozygous, cross it with a short plant; offspring patterns reveal the plant's genotype.
- If Mendel allowed tall F1 plants to self-pollinate, it was to observe whether any short plants appeared.
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Test your knowledge on Chapter 11 of Biology with flashcards that cover key concepts such as inheritance of traits, hybrids, and genes. Perfect for reinforcing your understanding of Mendelian genetics.