biology case study 6 objectives:
Describe the pattern of ABO blood type inheritance.
ABO blood type inheritance is an example of codominance where IA and IB are dominant alleles and i is a recessive allele. Blood type A: IA IA, IA i (only A antigens) Blood type B: IB IB, IB i (only B antigens) Blood type AB: IA IB (both B and A antigens) Blood type O: ii (no antigens)
Explain the relationship between dominant and recessive alleles of a gene.
Alleles are different versions of the same gene. The dominant allele is expressed in the phenotype, while the recessive allele is only expressed in the phenotype in the absence of the dominant allele.
Describe the pattern of autosomal dominant inheritance.
Autosomal dominant inheritance is a way a genetic trait or condition can be passed down from parent to child. One copy of a dominant mutated gene from one parent can cause the genetic condition. A child who has a parent with the mutated gene has a 50% chance of inheriting that mutated gene.
Compare and contrast genotype and phenotype.
Genotype is the total set of all alleles in an individual's diploid genome, while phenotype is the physical expression of the gene.
Compare and contrast homozygous and heterozygous.
Homozygous is to have 2 identical alleles of a gene, either homozygous recessive (rr) or homozygous dominant (RR). Heterozygous is to have 2 different alleles of the a gene (Rr).
Describe the pattern of autosomal recessive inheritance.
In autosomal recessive inheritance, a genetic condition occurs when the child inherits one recessive mutated copy of a gene from each parent. The parents usually do not have the condition. The parents are called carriers because they each carry one copy of the recessive mutated gene and can pass it to their children.
Describe the pattern of ABO blood type inheritance when accounting for Rhesus factor (Rh + / -).
Rhesus factor (Rh + / -) antigens are encoded independently of ABO and their inheritance pattern is an example of complete dominance where if the Rh gene is present the blood type will be positive, and if the Rh gene is not present, the blood type will be negative.
Incomplete dominance
Situation in which one allele is not completely dominant over another allele, resulting in a blending of the two dominant alleles. (red and white make pink)
Describe the pattern of ABO blood type inheritance when accounting for rare mutations that may occur at the "connector molecule" (H) locus, aka "Bombay phenotype".
The inheritance pattern of the connector molecule encoded by H is an example of epistasis, because this gene effects the expression of another gene. The Bombay phenotype results where the genotype (hh) does not encode for the connector molecule to the antigens on the red blood cells and blocks the expression of any inherited blood type.
Codominance
The simultaneous complete expression of two dominant alleles.
epistasis
a gene at one locus alters the phenotypic expression of a gene at a second locus
Complete dominance
a relationship in which one allele is completely dominant over another; mendelian inheritance
pleiotropic inheritance
mutation or defect in one gene leads to multiple phenotypic defects
polygenic inheritance
occurs when multiple genes determine the phenotype of a trait
