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level: Level 1

Questions and Answers List

level questions: Level 1

Question	Answer
What is phenotype?	Observable expression of alleles resulting from an interaction with the environment.
What is epistasis?	Where an allele present on one chromosome interacts and affects the expression of an allele on another chromosome.
What is epigenetics?	Heritable changes in the DNA that do not affect the genetic code.
What is a dihybrid cross?	The effect of the inheritance of two different traits that are expressed by separate genes on two chromosomes.
What is a monohybrid cross?	The effect of the inheritance of one gene comprising of dominant and recessive alleles.
What is an allele?	A different version of the same gene that may have a dominant, recessive, or codominant effect on the trait expressed in the phenotype.
What is meant by dominant allele?	An allele for a trait that is expressed in the phenotype when only one of the two alleles is required.
What is meant by recessive allele?	An allele for a trait where both are required to be expressed in the phenotype.
What is meant by codominant?	Where both alleles within a genotype are expressed in the phenotype
What is the expected Mendelian Ratio for a monohybrid heterozygous cross?	3:1
What is the expected Mendelian Ratio for a dihybrid heterozygous cross?	9:3:3:1
What are they described as when an individual's genotype provides a heterozygous situation whereby a "problem" recessive allele is present masked by a "normal" dominant allele	Carrier
What statistical test is appropriate to assess the significance of an expected Mendelian ratio on the outcomes of a breeding programme?	Chi-squared
What is the probability of a homozygous recessive phenotype (e.g. nnaa) in a dihybrid heterozygous cross e.g. NnAa x NnAa?	0.0625 (6.25% or 1 in 16 or 1/16th)
What is the situation where alleles are carried on an X or Y chromosome e.g. colour blindness ?	Sex Linked
What is an autosome?	Any chromosome that is not a sex chromosome e.g. not X or Y in humans
What is the situation when alleles are found on the same chromosome?	Autosomal Linkage
What process in meiotic cell division can compromise Autosomal linkage?	Crossing over/chiasmata