Biology: Probability Of Inheritance Quiz!

The Punnett square is a tool used to predict the probability of offspring inheriting certain traits from their parents. In this case, the question states that short needles (S) are dominant to long needles (s). This means that if an offspring inherits at least one short needle allele (Ss or SS), it will have short needles. However, if it inherits two long needle alleles (ss), it will have long needles. Therefore, since the Punnett square shows that there is a 50% chance of an offspring inheriting the long needle allele (s), the probability of an offspring having long needles is 50%.

When a heterozygous tall plant (Tt) is crossed with a short plant (tt), the offspring have a 50% chance of being tall. This is because the tall plant is heterozygous, meaning it carries one dominant allele for tallness (T) and one recessive allele for shortness (t). The short plant is homozygous recessive, carrying two recessive alleles for shortness (tt). During the process of genetic inheritance, there is a 50% chance that each offspring will inherit the dominant allele from the tall parent and thus be tall.

If Tracey's parents have another child, there is a 25% chance that the child will have sickle-cell anemia. This is because sickle-cell anemia is caused by a recessive allele, which means that both parents must carry the recessive allele in order for the child to have the disease. Since one of Tracey's brothers has sickle-cell anemia, we can infer that both of Tracey's parents carry the recessive allele. Therefore, there is a 25% chance that the child will inherit the recessive allele from both parents and have sickle-cell anemia.

To fill out a Punnett square for a cross between a homozygous recessive parent (aa) and a heterozygous parent (Aa), we'll denote the alleles for the homozygous recessive parent as "a" and for the heterozygous parent as "Aa". 

The Punnett square would look like this:

| a | a |

--------------

A | Aa | Aa |

--------------

a | aa | aa |



So, the lower right box contains the genotype "aa", indicating homozygous recessive offspring.

When the allele for hot flavor (H) is dominant to the allele for mild flavor (h), crossing a homozygous dominant plant (HH) with a recessive plant (hh) will result in all the offspring having the dominant hot flavor allele (H). Therefore, the percentage of offspring with hot flavor is 100%.

SS represents offspring with homozygous long-haired traits.

Ss represents offspring with heterozygous long-haired traits.

ss represents offspring with homozygous short-haired traits.

Out of the four possible combinations, 2 out of 4 (or 50%) have the genotype for long hair (SS or Ss).

A heterozygous genotype refers to an individual having two different alleles for a particular gene. In this case, the genotype Tt represents a heterozygous genotype because it contains both the dominant allele (T) and the recessive allele (t) for the gene. The presence of both alleles makes the individual heterozygous for that gene.