For the following list identify if each statement applies to autosomal recessive traits autosomal dominant traits or both

Question

For the following list identify if each statement applies to autosomal recessive traits autosomal dominant traits or both

 males and females affected

 successive Generations affected

 affected individuals may be heterozygous

traits skips Generations

 both male females transmit the trait

 affected individuals are always homozygous 

Answer 1

Hi Anya- great question!

First, let's breakdown the terms. Autosomal refers to the chromosomes that are NOT sex chromosomes. Meaning we all have 22 pairs of autosomes and one pair of sex chromosomes. When deciding between the two, I find it helpful to see who is affected. For example: if only males are affected, the likelihood that the trait is sex-linked is higher.

Now let's talk about recessive vs dominant traits. Recessive traits are traits that are expressed only when both recessive alleles are present (also called homozygous recessive), meaning that they can be 'overruled' by a dominant allele. Dominant traits are traits that only require a single allele to express. Dominance can be presented in two ways- homozygous dominant meaning that the affected has two dominant alleles or heterozygous where the affected carries both the dominant allele and recessive, but only the dominant phenotype is shown.

So looking at your question:

 males and females affected-

As I said in the first paragraph, sex-linked traits tend to affect one sex over the other. So if both males and females are affected it is likely an autosomal trait. Now what about recessive vs dominant? Well, in my family my dad, brother, and sister can all roll our tongues in the shape of a taco. My mother and my husband cannot. We know from research that tongue rolling is a dominant trait so those of us that can roll our tongues carry at least one dominant allele whereas people like my mom and husband only have two recessive alleles. In this example you can see that both males and females can be either recessive or dominant. So if males and females are affected- they can have either autosomal recessive or autosomal dominant traits.

 Successive Generations affected- This means that at least one person per generation is affected. Is it more likely that it is a dominant or recessive trait if a lot of generations are affected?

 affected individuals may be heterozygous- In my explanation above, I explained that in order to be affected by a recessive trait you needed to have two recessive alleles making you homozygous. If you only need one, that means it's a ______ trait.

traits skips Generations- If the trait isn't around much, is it more likely recessive or dominant?

 both male females transmit the trait- See answer to first question

 affected individuals are always homozygous- In my explanation above, I explained that in order to be affected by a recessive trait you needed to have two recessive alleles making you homozygous. If affected individuals are ALWAYS homozygous, that means it must be a recessive trait.