GED Practice

GED Science Review: Genetics

Questions:
Questions 1 through 3 refer to the following passage and diagram.

            In 1903 American geneticist Walter Sutton, who was studying the egg and sperm cells of grasshoppers, discovered that Mendel's units of heredity—genes—were located on the chromosomes. Chromosomes are composed of a chemical called DNA. The structure of the DNA molecule was not known until 1953, when an American biologist James D. Watson, and a British biophysicist Francis Crick, worked it out. They described DNA as a double helix, or spiral, made up of two strands wound around each other and connected by crosspieces. The DNA molecule looks like a twisted ladder.

The sidepieces of DNA are made of sugar and phosphate. The rungs of the DNA ladder are composed of pairs of four nitrogen bases: adenine, cytosine, guanine, and thymine. On the rungs, adenine always pairs with thymine, and guanine always pairs with cytosine. The sequence of bases along the ladder varies in different organisms ( but each cell in a given organism has the same sequence in its copy of DNA). These variations form a genetic code that controls the production of proteins in the organism's cells. The proteins help determine the characteristic and functions of an organism.

Directions: Choose the answer to each question.


  1. Which of the following is a function of DNA?
    • breaking down proteins in the cell
    • controlling the production of proteins in the cell
    • producing energy from food molecules inside the cell
    • joining adenine with guanine and cytosine with thymine
  2. Which of the following statements is supported by the information shown in the diagram?
    • The base thymine is always attached to a guanine base.
    • Only the base adenine can attach to the sidepieces of DNA molecules.
    • Different nitrogenous bases form the sidepieces of DNA molecules.
    • The sidepieces of DNA are formed of alternating units of sugar and phosphate.
  3. suppose the sequence of bases along one side of a particular section of DNA is ATGTCAGC. The correct sequence of bases with which this sequence would be paired is
    ______________________________________
  4. In sexual reproducing organisms, offspring receive one allele for each gene from each parent. If a set of parents have the genotype Bb, what is the probability that their offspring will have the genotype BB?
    ______________________________________

    Questions 5 and 6 refer to the following passage and diagram.

    The pedigree chart shows a how a trait determined by a single gene is inherited by several generations. Circle indicate females and squares indicate males. The first generation in the chart is represented by the top row. The circles and squares on the next row  represent their children and their children's spouses. The third row represents the third generation. A black circle or square is an individual expressing the trait being studied.



    Directions: choose the one best answer to the question.
  5. What conclusion about the trait is supported by the information in the pedigree chart?
    • The trait is present in each generation shown.
    • The trait has only affected males in this family.
    • only a parent with the trait can pass it on to a child.
    • Females are more likely than males to display this trait.
  6. Let A represent the dominant allele for the gene, and let a represent the recessive allele. Using this information and the information in the pedigree chart, the genotype of the individuals expressing the trait is
    ___________.
  7. Traits are not always dominant or recessive. Sometimes the inheritance of traits occurs in a pattern called incomplete dominance. For example, the four o'clock plant has three genotypes for flower color. The genotype A results in a red flower; aa results in a white flower; and Aa results in a pink flower.

    If you cross a white-flowered four o'clock plant with a red-flowered four o'clock plant, what is the probability of producing a plant with pink flowers?
    • 1 out of 4
    • 2 out of 4
    • 3 out of 4
    • 4 out of 4
  8. In 1950, Erwin Chargaff found that the percentages of adenine and thymine bases in a DNA molecule are equal, and the percentage of cytosine and guanine bases in a DNA molecule are also equal. If 30% of the bases in a DNA sample are adenine, what percentage of its bases are cytosine?
    • 20%
    • 30%
    • 40%
    • 60% 
Answer:

  1. controlling the production of proteins in the cell
  2. The sidepieces of DNA are formed of alternating units of sugar and phosphate.
  3. TACAGTCG
  4. 25%
  5. The trait has only affected males in this family.
  6. aa
  7. 4 out of 4
  8. 20%









Reference:


Complete Test Preparation for the GED Test 2014 by Steck-Vaughn