Problem 2 - Biological Psychology

Question

Suppose you have high sensitivity to tasting PTC. If your mother can also taste it easily, what (if anything) can you predict about your father's ability to taste it?

Step-by-Step Solution

Answer

Your father's ability to taste PTC cannot be directly predicted; he may be a taster or non-taster.

Step 1: Understanding PTC Sensitivity

PTC (phenylthiocarbamide) tasting sensitivity is determined by a dominant gene, often represented as T for the taster allele and t for the non-taster allele. To taste PTC, one must have at least one T allele (either TT or Tt genotypes). Non-tasters typically have the genotype tt.

Step 2: Inheritance Pattern of PTC Sensitivity

Since you can taste PTC and this sensitivity is determined by a dominant gene, you must have at least one T allele. If both you and your mother can taste it easily, she must also have at least one T allele.

Step 3: Predicting Father's Genotype

Given your mother's ability to taste PTC, her genotype could be either TT or Tt. Since your father is not mentioned to be a taster and a direct prediction is unclear, the possibility that he is a non-taster (tt) exists, especially considering that you only need one T allele from your mother to taste PTC. Alternatively, if he has a taster allele, it would be Tt.

Step 4: Analyzing Possible Scenarios

Two scenarios can be considered: if your father's genotype is tt, you inherit the T allele from your mother; if he is Tt, you could inherit the T allele from either parent. Without clear evidence of his tasting ability, the presence of a non-taster genotype (tt) remains unconfirmed without further information.

Key Concepts

PTC Sensitivity

PTC Sensitivity refers to the ability to taste the chemical phenylthiocarbamide (PTC). PTC tasting is a classic example used to understand genetic inheritance because of its clear dominant-recessive gene pattern. Most people are either sensitive tasters or non-tasters when it comes to PTC, based on their genetic makeup. The taste is perceived as bitter to those who can detect it. This sensitivity is influenced mainly by genetic factors, particularly by a single gene that follows Mendelian inheritance patterns. You'll be using this fascinating aspect of biology to predict genetic traits in a family setting.

Dominant Gene

A dominant gene is one that expresses its trait even when there is only one copy of it in a pair of alleles. In the context of PTC sensitivity, the dominant gene is represented by the allele T. If you have even one T allele, you will be a PTC taster. This dominance explains why PTC tasters are more common in populations, as the presence of just one T allele overpowers a non-tasting allele, represented as t. It's important to grasp how dominant genes work because they dictate how certain traits are inherited and expressed in offspring. While dominant traits aren't always the most common in all contexts, they certainly command what we observe in straightforward dominant-recessive gene scenarios.

Genotype

Genotype refers to the genetic make-up of an individual regarding a particular trait. For PTC sensitivity, genotypes include:

• TT - Homozygous dominant, where both alleles are for the taster trait.
• Tt - Heterozygous, where one allele is for taster and the other is non-taster.
• tt - Homozygous recessive, where both alleles are for non-taster.

Understanding your genotype helps you predict traits in yourself and potential offspring. For example, if you are a PTC taster, your genotype could be either TT or Tt. This genotype means you have at least one dominant T allele. In genetic discussions about inheritance, identifying the genotype allows individuals to draw family trait conclusions and predict future genetic outcomes.