Chat with AIExam 5: The Inheritance of Complex Traits
Illustrate how the five basic human eye colors can be explained by a model using two genes (A and B),each of which has two alleles (A and a,B and b).
(29) 
VerifiedIn this model,human eye color is determined by different combinations of alleles of two genes interacting to synthesize and deposit melanin in the iris.If two genes control a trait and each has a dominant and a recessive allele,there are five phenotypic classes in the F2,each of which is controlled by four,three,two,one,or zero dominant alleles.The F2 ratio of 1 : 4 : 6 : 4 : 1 results from the genotypic combinations that produce each phenotype.At one extreme is the homozygous dominant (AABB)genotype with four dominant alleles; at the other extreme is the homozygous recessive (aabb)genotype with no dominant alleles.The largest phenotypic class (6/16)has six genotypic combinations.Combinations of alleles result in small differences in eye color.
Describe the approach using genomics to identify genes that contribute to the variations in cognitive ability observed in humans.
(39) VerifiedThis approach uses SNPs and other DNA markers to identify chromosome regions that contain genes related to specific traits.Identifying the number of these regions associated with variation in a specific phenotype is an indirect way of determining whether that phenotype is controlled by many genes,each having a small effect,or by a small number of genes,each with a major effect on the phenotype.One study has provided strong evidence that a large proportion of individual differences in intelligence is due to genetic variation,and that many genes,each with a small additive effect,are involved in these differences.
For threshold traits,the liability for a genetic disorder is distributed among individuals in a bell-shaped curve.
(26) VerifiedTrue
IQ is calculated by dividing the individual's ____________________ age by his or her ____________________ age and multiplying the quotient by 100.
(39) Dizygotic twins originate from two separate fertilization events.
(40) Dizygotic twins are no more or less genetically similar than are other pairs of ____________________.
(29) Summarize the results of one of the first investigations of the genetics of skin color.
(36) Spina bifida is one of the most common and most complex birth defects involving the ____ system.
(35) In obesity studies in mice,the binding of leptin activates the leptin receptor and initiates changes in ____ in the hypothalamus.
(41) An expanded definition of intelligence that goes beyond IQ is called ____________________ and includes verbal and spatial abilities,memory,speed of perception,and reasoning.
(40) Genomic technology allows researchers to use ____ to survey the genome to detect associations between common variations and a specific phenotype.
(32) The ____ model of genetic analysis of complex traits assumes that each gene involved has an equal effect on the phenotype.
(37) A trait with a heritability value of 0.75 indicates that 75% of the phenotypic variability seen in the population is caused by ____ of the population.
(28) Phenotypic variation among individuals with the same genotype is known as genetic variance.
(37) If only one twin has a trait,the twins are ____________________ for that trait.
(33) In twin studies,geneticists look for situations in which genetic and environmental influences are clearly ____________________.
(38) ____________________ traits are controlled by two or more genes and significant environmental interactions
(43) Heritability studies cannot provide information about the number,location,or identity of genes involved in specific complex traits.
(35) 
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