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Hi All,
I was going over Ari's answer to the 2007 DAT bio section and I was confused by one of the answers and I was hoping someone could clarify.
Here is his answer-
Organisms that are diploid have two copies of each chromosome. For example, human body cells are diploid containing 23 pairs of chromosomes, with one chromosome being inherited from each parent. For a given locus or location on a gene, there are at most two types of alleles, which could either be recessive and dominant. One chromosome often carries two alleles, either two recessive alleles (homozygous recessive), two dominant alleles (homozygous dominant), or one dominant and one recessive allele (heterozygous). This is “usually” true as some traits may involve multiple alleles, more than just a dominant and a recessive, as is the case with blood groups. Likewise, the alleles that code for the same gene are located in identical areas on homologous (related chromosomes). A single chromatid only contains one copy of an allele.
I understand everything except the line I bolded and underlined. I thought that one chromosome carried 1 allele? And that two homologous chromosomes would carry 2 alleles? So for example, chromosome from mom could carry either recessive or dom but not both?
I was going over Ari's answer to the 2007 DAT bio section and I was confused by one of the answers and I was hoping someone could clarify.
Here is his answer-
Organisms that are diploid have two copies of each chromosome. For example, human body cells are diploid containing 23 pairs of chromosomes, with one chromosome being inherited from each parent. For a given locus or location on a gene, there are at most two types of alleles, which could either be recessive and dominant. One chromosome often carries two alleles, either two recessive alleles (homozygous recessive), two dominant alleles (homozygous dominant), or one dominant and one recessive allele (heterozygous). This is “usually” true as some traits may involve multiple alleles, more than just a dominant and a recessive, as is the case with blood groups. Likewise, the alleles that code for the same gene are located in identical areas on homologous (related chromosomes). A single chromatid only contains one copy of an allele.
I understand everything except the line I bolded and underlined. I thought that one chromosome carried 1 allele? And that two homologous chromosomes would carry 2 alleles? So for example, chromosome from mom could carry either recessive or dom but not both?
