If the white-flowered parental variety in Figure 1-3 were crossed to the first-generation hybrid plant in that figure, what types of progeny would you expect to see and in what proportions?

In Mendel’s 1866 publication as shown in Figure 1-4, he reports 705 purple-flowered (violet) offspring and 224 white-flowered offspring. The ratio he obtained is 3.15:1 for purple : white. How do you think he explained the fact that the ratio is not exactly 3:1?

In Figure 1-6, the students have 1 of 15 different heights, plus there are two height classes (4’11” and 5’ 0”) for which there are no observed students. That is a total of 17 height classes. If a single Mendelian gene can account for only two classes of a trait (such as purple or white flowers), how many Mendelian genes would be minimally required to explain the observation of 17 height classes?

Figure 1-7 shows a simplified pathway for arginine synthesis in Neurospora. Suppose you have a special strain of Neurospora that makes citrulline but not arginine. Which gene(s) are likely mutant or missing in your special strain? You have a second strain of Neurospora that makes neither citrulline nor arginine but does make ornithine. Which gene(s) are mutant or missing in this strain?

Consider Figure 1-8a.

In Figure 1-8b, can you tell if the number of hydrogen bonds between adenine and thymine is the same as that between cytosine and guanine? Do you think that a DNA molecule with a high content of A + T would be more stable than one with high content of G + C?

Which of three major groups (domains) of life in Figure 1-11 is not represented by a model organism?

Figure 1-13b shows the human chromosomes in a single cell. The green dots show the location of a gene called BAPX1. Is the cell in this figure a sex cell (gamete)? Explain your answer.

Figure 1-15 shows the family tree, or pedigree, for Louise Benge (Individual VI-1) who suffers from the disease ACDC because she has two mutant copies of the CD73 gene. She has four siblings (VI-2, VI-3, VI-4, and VI-5) who have this disease for the same reason. Do all of the 10 children of Louise and her siblings have the same number of mutant copies of the CD73 gene, or might this number be different for some of the 10 children?

Below is the sequence of a single strand of a short DNA molecule. On a piece of paper, rewrite this sequence and then write the sequence of the complementary strand below it.

GTTCGCGGCCGCGAAC

Comparing the top and bottom strands, what do you notice about the relationship between them?

Mendel studied a tall variety of pea plants with stems that are 20 cm long and a dwarf variety with stems that are only 12 cm long.

If a DNA double helix that is 100 base pairs in length has 32 adenines, how many cytosines, guanines, and thymines must it have?

The complementary strands of DNA in the double helix are held together by hydrogen bonds: G ≡ C or A = T. These bonds can be broken (denatured) in aqueous solutions by heating to yield two single strands of DNA (see Figure 1-13a). How would you expect the relative amounts of GC versus AT base pairs in a DNA double helix to affect the amount of heat required to denature it? How would you expect the length of a DNA double helix in base pairs to affect the amount of heat required to denature it?

The figure below shows the DNA sequence of a portion of one of the chromosomes from a trio (mother, father, and child). Can you spot any new point mutations in the child that are not in either parent? In which parent did the mutation arise?

Fathers contribute more new point mutations to their children than mothers. You may know from general biology that people have sex chromosomes—two X chromosomes in females and an X plus a Y chromosome in males. Both sexes have the autosomes (A’s).

For young men of age 20, there have been 150 rounds of DNA replication during sperm production as compared to only 23 rounds for a woman of age 20. That is a 6.5-fold greater number of cell divisions and proportionately greater opportunity for new point mutations. Yet, on average, 20-year-old men contribute only about twice as many new point mutations to their offspring as do women. How can you explain this discrepancy?

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In computer science, a bit stores one of two states, 0 or 1. A byte is a group of 8 bits that has 2⁸ = 256 possible states. Modern computer files are often megabytes (10⁶ bytes) or even gigabytes (10⁹ bytes) in size. The human genome is approximately 3 billion base pairs in size. How many nucleotides are needed to encode a single byte? How large of a computer file would it take to store the same amount of information as a single human genome?

The human genome is approximately 3 billion base pairs in size.