Biology Chapters 9 And 12
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Questions and Answers
- 1.
Mendel obtained plants that were true- breeding for particular traits by
- A.
Growing plants from the seeds of others plants that showed that trait
- B.
Discarding plants that showed others traits
- C.
Allowing plants to self- pollinate for several generations
- D.
Allowing plants to cross- pollinate for one generation
Correct Answer
C. Allowing plants to self- pollinate for several generationsExplanation
Mendel obtained plants that were true-breeding for particular traits by allowing plants to self-pollinate for several generations. This means that he allowed the plants to fertilize themselves, ensuring that the offspring inherited the same traits as the parent plants. By doing this for multiple generations, Mendel was able to establish a population of plants that consistently exhibited the desired traits. This process of self-pollination helped him in his experiments to study the principles of inheritance.Rate this question:
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- 2.
When Mendel crossed a strain of tall pea plants with a strain of short pea plants, he observed that all of the plants in the F1 generation were tall. This suggests that
- A.
The tall trait was controlled by a dominant factor
- B.
The short trait was controlled by a dominant factor
- C.
Both traits were controlled by a recessive factor
- D.
The strain of short plants was not capable of pollinating the strain of tall plants
Correct Answer
A. The tall trait was controlled by a dominant factorExplanation
When Mendel crossed a strain of tall pea plants with a strain of short pea plants and observed that all of the plants in the F1 generation were tall, it suggests that the tall trait was controlled by a dominant factor. This is because if the short trait was dominant, some of the plants in the F1 generation would have been short. Since all the plants were tall, it indicates that the tall trait is dominant over the short trait.Rate this question:
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- 3.
A cross between true- breeding green- podded pea plants and true- breeding yellow- podded pea plants produces only green- podded plants. When the F1 generation is allowed to self pollinate, the F2 generation consists of
- A.
Only green- podded plants
- B.
Only yellow- podded plants
- C.
About three quarters yellow- podded plants and one quarter green podded plants
- D.
About three quarters green- podded plants and one quarter yellow- podded plants
Correct Answer
D. About three quarters green- podded plants and one quarter yellow- podded plantsExplanation
When true-breeding green-podded pea plants are crossed with true-breeding yellow-podded pea plants, the resulting F1 generation will all have green pods. This is because the green pod trait is dominant over the yellow pod trait. When the F1 generation self-pollinates, the alleles for green pods and yellow pods will segregate randomly during meiosis, resulting in a 3:1 ratio of green-podded plants to yellow-podded plants in the F2 generation. This is because the green pod trait is determined by a dominant allele (G) and the yellow pod trait is determined by a recessive allele (g).Rate this question:
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- 4.
When alleles for different characteristics are one separate chromosomes, they are distributed to gametes independently. This obersvation is summarized by the law of
- A.
Cross- pollination
- B.
Independent assortment
- C.
Segregation
- D.
Molecular genetics
Correct Answer
B. Independent assortmentExplanation
The correct answer is independent assortment. This is because independent assortment refers to the random distribution of alleles for different characteristics on separate chromosomes to gametes during meiosis. This process occurs independently of each other, meaning that the inheritance of one characteristic does not affect the inheritance of another. This principle was proposed by Gregor Mendel and is one of the fundamental laws of genetics.Rate this question:
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- 5.
The appearance of an organism is its
- A.
Genotype
- B.
Phenotype
- C.
Genotypic ratio
- D.
Phenotypic ratio
Correct Answer
B. PhenotypeExplanation
The appearance of an organism refers to its phenotype. Phenotype is the observable physical characteristics of an organism, such as its color, size, shape, and behavior. It is determined by the interaction between an organism's genotype (genetic makeup) and its environment. Genotype refers to the genetic information or alleles present in an organism, while genotypic ratio and phenotypic ratio are terms used to describe the proportion of different genotypes or phenotypes in a population. Therefore, the correct answer is phenotype, as it specifically refers to the outward appearance of an organism.Rate this question:
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- 6.
A genetic crossed performed many times produces 798 long- stemmed plants amd 266 short- stemmed plants. The probability of obtaining a short- stemmed plant in a similar cross is
- A.
266/ 1, 064.
- B.
266/ 798
- C.
798/ 266
- D.
798/ 1, 064.
Correct Answer
A. 266/ 1, 064.Explanation
In this genetic cross, there were a total of 798 long-stemmed plants and 266 short-stemmed plants. The probability of obtaining a short-stemmed plant in a similar cross can be calculated by dividing the number of short-stemmed plants (266) by the total number of plants in the cross (798 + 266 = 1,064). Therefore, the correct answer is 266/1,064.Rate this question:
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- 7.
A monohybrid cross of two individuals that are heterozygous for a trait exhibiting complete dominance would probably result in a phenotypic ratio of
- A.
4 dominant: 0 recessive
- B.
1 dominant: 3 recessive
- C.
3 dominant: 1 recessive
- D.
1 dominant: 1 recessive
Correct Answer
C. 3 dominant: 1 recessiveExplanation
In a monohybrid cross, two individuals that are heterozygous for a trait exhibiting complete dominance would result in a phenotypic ratio of 3 dominant: 1 recessive. This is because in complete dominance, the dominant allele masks the expression of the recessive allele. Therefore, out of the four possible offspring genotypes (DD, Dd, Dd, dd), three will have the dominant phenotype and one will have the recessive phenotype.Rate this question:
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- 8.
To determine the genotype of an individual that shows the dominant phenotype, you would cross that individual with one that is
- A.
Heterozygous dominant
- B.
Heterozygous recessive
- C.
Homozygous dominant
- D.
Homozygous recessive
Correct Answer
D. Homozygous recessiveExplanation
When trying to determine the genotype of an individual that displays a dominant phenotype, it is necessary to cross that individual with one that is homozygous recessive. This is because the individual displaying the dominant phenotype could either be homozygous dominant (DD) or heterozygous dominant (Dd). By crossing with a homozygous recessive individual (dd), if any of the offspring display the recessive phenotype, it means that the dominant individual must be heterozygous (Dd). If all the offspring display the dominant phenotype, it means that the dominant individual must be homozygous dominant (DD).Rate this question:
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- 9.
In a dihybrid cross between an individual with the genotype RRYY and an individual with the genotype rryy, all of the offspring will have the genotype
- A.
RRYY
- B.
RrYY
- C.
RrYy
- D.
Rryy
Correct Answer
C. RrYyExplanation
In a dihybrid cross, the genotype of the offspring is determined by combining the alleles from both parents. In this case, the individual with the genotype RRYY has two dominant alleles for both traits, while the individual with the genotype rryy has two recessive alleles for both traits. When these individuals are crossed, all of the offspring will inherit one dominant allele for each trait from the RRYY parent and one recessive allele for each trait from the rryy parent. Therefore, the correct answer is RrYy.Rate this question:
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- 10.
Genes that belong to the same linkage group tend to be
- A.
Located on different chromosomes
- B.
Inherited together
- C.
Found only in males
- D.
Found only in somatic cells
Correct Answer
B. Inherited togetherExplanation
Genes that belong to the same linkage group tend to be inherited together. This is because genes located close to each other on the same chromosome are less likely to undergo recombination during meiosis, which is the process of genetic exchange between homologous chromosomes. As a result, these genes are more likely to be transmitted as a unit to the next generation, maintaining their linkage. This phenomenon is known as genetic linkage and is the basis for understanding patterns of inheritance and mapping genes on chromosomes.Rate this question:
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- 11.
Two genes that are one map unit apart are separated by crossing- over
- A.
1% of the time
- B.
20% of the time
- C.
50% of the time
- D.
100% of the time
Correct Answer
A. 1% of the timeExplanation
When two genes are one map unit apart, they are said to be located on different chromosomes. The percentage given in the answer options represents the frequency at which these genes are separated by crossing-over during meiosis. Crossing-over occurs during the process of genetic recombination, where homologous chromosomes exchange genetic material. Since the genes are only one map unit apart, they have a low chance of crossing-over, hence the low percentage of 1% of the time.Rate this question:
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- 12.
Mutations that can be inherited arise in
- A.
Somatic cells
- B.
Body cells
- C.
Germ cells
- D.
Skin cells
Correct Answer
C. Germ cellsExplanation
Mutations that can be inherited arise in germ cells. Germ cells are the cells that give rise to eggs and sperm, and they are responsible for passing genetic information from one generation to the next. Mutations that occur in somatic cells, body cells, or skin cells may affect the individual in which they occur, but they are not passed on to offspring. Therefore, only mutations that occur in germ cells can be inherited.Rate this question:
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- 13.
Which of the following sequences could result from an inversion of the sequence GAGACATT?
- A.
GAGCATT
- B.
GTGACATT
- C.
CTCTGATT
- D.
GATACAGT
Correct Answer
D. GATACAGTExplanation
The given sequence GAGACATT is inverted by reversing the order of the nucleotides. In the correct answer, GATACAGT, the sequence is reversed, resulting in the inversion.Rate this question:
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- 14.
Which of the following is a point mutation that does not produce a frameshift?
- A.
Substitution
- B.
Insertion
- C.
Deletion
- D.
Inversion
Correct Answer
A. SubstitutionExplanation
A substitution is a type of point mutation where one nucleotide is replaced by another in the DNA sequence. This mutation does not produce a frameshift because it only affects a single nucleotide, rather than causing an insertion or deletion of nucleotides. In a frameshift mutation, the reading frame of the DNA sequence is altered, resulting in a completely different amino acid sequence during protein synthesis. However, in a substitution mutation, only one amino acid in the protein may be changed, but the overall reading frame remains intact.Rate this question:
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- 15.
Which individual (s) in the pedigree shown below must be a carrier?
- A.
1 only
- B.
4 only
- C.
3 only
- D.
Both 1 and 4
Correct Answer
D. Both 1 and 4Explanation
In the given pedigree, individuals 1 and 4 must be carriers because they have unaffected parents (2 and 3) and affected offspring (5 and 6). This pattern suggests that individuals 1 and 4 have one copy of the recessive allele for the trait, which they can pass on to their children. Therefore, they are carriers of the trait.Rate this question:
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- 16.
Since the ABO blood group alleles are codominant, an individual with the genotype IAIB will have blood type
- A.
A
- B.
B
- C.
AB
- D.
O
Correct Answer
C. ABExplanation
In the ABO blood group system, there are three alleles: A, B, and O. The A and B alleles are codominant, meaning that if an individual has both alleles (IAIB genotype), they will express both A and B antigens on their red blood cells. This results in blood type AB, which is characterized by the presence of both A and B antigens. Therefore, the correct answer is AB.Rate this question:
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- 17.
Which of the following human traits is not a polygenic trait?
- A.
Skin color
- B.
Eye color
- C.
Height
- D.
ABO blood type
Correct Answer
D. ABO blood typeExplanation
ABO blood type is not a polygenic trait because it is determined by a single gene with multiple alleles. Polygenic traits, such as skin color, eye color, and height, are influenced by multiple genes, each with multiple alleles, and are therefore more complex in their inheritance patterns.Rate this question:
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- 18.
A trait whose expression is affected by the presence of sex hormones is said to be
- A.
Sex- influenced
- B.
Sex- linked
- C.
X- linked
- D.
Y- linked
Correct Answer
A. Sex- influencedExplanation
Sex-influenced traits are those that are influenced by the presence of sex hormones. These traits are not exclusive to one sex, but their expression is influenced by the presence of specific sex hormones. For example, male pattern baldness is a sex-influenced trait, where the presence of testosterone can lead to hair loss in individuals who are genetically predisposed. Similarly, female pattern baldness can also occur, but it is influenced by different hormones. Therefore, sex-influenced traits can be expressed differently in males and females due to the influence of sex hormones.Rate this question:
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- 19.
In humans, PKU can be treated by
- A.
Insulin injections
- B.
Diet
- C.
Gene therapy
- D.
Surgery
Correct Answer
B. DietExplanation
PKU (Phenylketonuria) is a genetic disorder that affects the body's ability to process an amino acid called phenylalanine. The correct answer, "diet," is an effective treatment for PKU. Individuals with PKU need to follow a strict diet that limits their intake of phenylalanine. By avoiding foods high in phenylalanine, such as certain proteins, the levels of this amino acid in the body can be controlled. This helps prevent the buildup of toxic byproducts and reduces the risk of neurological damage associated with PKU. Insulin injections, gene therapy, and surgery are not relevant or effective treatments for PKU.Rate this question:
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