2. Lactase persistence in adulthood (i.e., the continued production of high amou
ID: 50524 • Letter: 2
Question
2. Lactase persistence in adulthood (i.e., the continued production of high amounts of lactase, the enzyme that breaks down lactose, the sugar found in fresh milk) is a genetically inherited trait that is dominant to lactose intolerance (cannot digest lactose sugar).
a. If your mom is heterozygous for lactase persistence but your dad is lactose tolerant, what is the probability (as a percentage) that you are lactose tolerant as an adult?
b. Serena and Jacob are both lactose intolerant. Is it possible for them to produce a child that has lactase persistence? Explain.
3. Peaches, known by the scientific name Prunus persica, come from a tree domesticated in northwestern China about 4000 years ago. Peaches can have yellow flesh (w) or white flesh (W). The fruit may also be covered in fuzz (F) or be smooth skinned (f).
a. A peach tree homozygous recessive for flesh color was crossed with a peach tree homozygous dominant for flesh color. What color fruit is possible from the offspring of this cross?
b. A breeder pollinates a WwFF peach tree with pollen from a wwFf tree. What percentage of the offspring will be yellow-fleshed and smooth-skinned?
c. Growers have named smooth-skinned peaches nectarines. Based on the information given here, are nectarines a different species of fruit than peaches? Explain.
d. A grower placed square forms around the developing peach fruits on several trees. As a result, the peaches have a square shape instead of a round shape. If the seed (i.e., the offspring) of one of the square peaches is planted, will the fruit of that offspring also be square shaped? In other words, is the square shape heritable? Explain.
3. A new mutation occurs in an adult. The new mutation occurs in a gene that causes the cell to become cancerous. In order for this cancer to become heritable (passed on to the person’s offspring), the mutation has to occur in which cells of the adult (i.e., where in the adult’s body)?
4. What is the relationship between genes and chromosomes?
Explanation / Answer
3)
Based on the given data,
S.no
Genotype
Phenotype
Condition
Recessive/dominant
1
WW
flesh
Homozygous
Dominant
2
Ww
flesh
Heterozygous
Dominant
3
ww
yellow
Homozygous
Recessive
4
FF
fuzz
Homozygous
Dominant
5
Ff
fuzz
Heterozygous
Dominant
6
ff
smooth skinned
Homozygous
Recessive
Thus,
a.
Homozygous recessive for flesh (ww) × homozygous dominant for flesh color (WW): For example, consider same genotypes for fruit also, and then cross between the genotypes is as possible.
Thus, the color fruit is possible from the offspring of this cross is heterozygous dominant “fuzz.”
b.
The cross between the WwFF× wwFf is as follows:
Thus, percentage of the offspring will be yellow-fleshed and smooth-skinned is 0%.
c.
Both Peach and Nectarines are of the same species, although they are considered commercially as different fruits. Peaches have characteristic fuzz on the skin, while nectarines do not. Going into the genetics, it is found that nectarines are produced due to recessive allele, while peaches are produced from dominant allele for fuzzy skin.
d.
No, the fruit of that offspring will not be square shape. Shaping the fruit with some mould while it is growing will not show any effect on it's seed. Therefore, their offspring will be in round shape.
3.
Mutations are nothing but alterations to DNA, the heriditary material that passes from one generation to the next. They can result in the formation of new characteristics and are heritable. Germinal mutations are those that occur in the sperm cell or egg cell; they are passed onto the organism's offspring for sure.
4.
A gene is a segment of DNA that provides information to construct a protein. Chromosome is a thread like structure located inside the nucleus and contain genes.
S.no
Genotype
Phenotype
Condition
Recessive/dominant
1
WW
flesh
Homozygous
Dominant
2
Ww
flesh
Heterozygous
Dominant
3
ww
yellow
Homozygous
Recessive
4
FF
fuzz
Homozygous
Dominant
5
Ff
fuzz
Heterozygous
Dominant
6
ff
smooth skinned
Homozygous
Recessive
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