Chapter 5: Part 1

Question 1

Name four factors that alter single-gene phenotypic ratios

Answer 1

• Multiple alleles
• Codominance
• Epistasis
• Pleiotropy

Question 2

Multiple Alleles

Answer 2

• many variants or degrees of a phenotype occur
• Two or more alleles of the same gene existing within a population
• example: cystic fibrosis

Question 3

Codominance

Answer 3

• a heterozygous phenotype is intermediated between those of two homozygotes
• A pattern of inheritance in which two alleles are both expressed in the heterozygous condition
• For example, aperson with the genotype IAIB has the bloodtype AB and expresses both surface antigensA and B

Question 4

Epistasis

Answer 4

• one gene masks or otherwise affects another’s phenotype
• Allelic variation of two or more separate genomic loci influence the same trait
• The effect of a mutation in an allele of one genomic locus is dependent upon the
  presence or absence of mutations at a second (or more) genomic locus.
• An inheritance pattern in which one gene can mask the phenotypic effects of a different gene
• example: Bombay phenotype

Question 5

Pleiotropy

Answer 5

• the phenotype includes many symptoms, with different subsets in different individuals
• happens on one single genomic locus
• single gene creates multiple affects of phenotype
• Alleles of a single genomic locus (often called a master regulator) influence several different phenotypic traits
• It is embryonic lethal to have full LOF of pleiotropic master regulator
• Cancers are often caused by a GOF allele of a pleiotropic master regulator

Question 6

2n+1 Equation

Answer 6

• If n=number of diallelic additive loci, (2n+1)= the number of expected phenotypic classes

Question 7

Epsistasis beneficial mutation

Answer 7

• positive epistasis is synergistic
• negative epistasis is antagonistic

Question 8

Epistasis harmful mutation

Answer 8

• negative epistasis is synergistic
• positive epistasis is antagonistic

Question 9

Syngergistic

Answer 9

• 2 “substances” coming together to create a much greater affect when combined, over their separate effects

Question 10

Antagonistic

Answer 10

• one gene masks or interferes with the expression of another

Question 11

Gene interaction

Answer 11

• The phenomenon in which two or more different genes influence the outcome of a single trait

Question 12

Recessive Epistasis

Answer 12

• A form of epistasis in which an individual must be homozygous for a recessive allele for a particular phenotype to be masked

Question 13

Complementation

Answer 13

• The phenomenon in which the presence of two different mutant alleles in the same organism produces a wild-type phenotype
• It usually happens because the two mutations are in different genes, so the organism carries one copy of each mutant allele and one copy of each wild-type allele

Question 14

Gene modification

Answer 14

• The phenomenon in which an allele of one gene modifies the phenotypic outcome of the alleles of a different gene

Question 15

Gene redundancy

Answer 15

• The phenomenon in which an inactive gene is compensated for by another gene with the same or a similar function

Question 16

paralogs

Answer 16

• Homologous genes within a single species