Chapter 5 Study Guide Flashcards
Huntington’s disease (HD) is an autosomal dominant condition that is often not obviously expressed until middle age. However, children receiving the mutant allele from their father often express the condition earlier in life than he did. What term describes this situation?
reduced penetrance
genomic imprinting
anticipation
variable expressivity
complementation
anticipation
____ genes suppress the effect of other genes at a different locus.
Maternal
Hypostatic
Lethal
Dominant
Epistatic
the effect of another gene at a different locus, a phenomenon known as epistasis.
Sex- _____ characteristics are encoded by autosomal genes that are expressed differently in males and females.
dominant
linked
limited
determined
influenced
influenced
Characteristics that have a few easily distinguished phenotypes are called _____ characteristics.
polygenic
continuous
dominant
discontinuous
pleiotropic
discontinuous
Which type of dominance occurs when the heterozygote has the same phenotype as one of the homozygotes?
overdominance
complete dominance
incomplete dominance
partial dominance
codominance
complete dominance
Type of dominance in which the same phenotype is expressed in homozygotes (AA) and in heterozygotes (Aa); only the dominant allele is expressed in a heterozygote.
Sex-influenced characteristics are determined by what type of genes?
X-linked and Y-linked
autosomal
homologous
Y-linked
X-linked
autosomal
True or False? Anticipation can be explained by Mendel’s principles.
True
False
False
Another genetic phenomenon that is not explained by Mendel’s principles is anticipation, in which a genetic trait becomes more strongly expressed, or is expressed at an earlier age, as it is passed from generation to generation.
Which type of dominance occurs when the heterozygote has a phenotype that is intermediate to the phenotypes of the two homozygotes?
incomplete dominance
Type of dominance in which the phenotype of the heterozygote is intermediate between the phenotypes of the two homozygotes.
Assume that ptosis (droopy eyelid) is inherited as an autosomal dominant human trait. Among 100 people who are known to be heterozygous for the ptosis allele, 80 have ptosis and 20 have normal eyelids. What is the penetrance for ptosis?
80%
50%
40%
20%
10%
80%
Disorders that arise from mutations in mitochondrial DNA exhibit which type of inheritance?
autosomal
X-linked
cytoplasmic
sex-limited
sex-linked
cytoplasmic
True or False? Anticipation can be explained by Mendel’s principles.
False
A middle-aged acquaintance discloses to you that he has begun experiencing involuntary muscle movements. Other members in his family history, such as a grandmother, had experienced these symptoms, but their symptoms developed after the age of 60. What concept in genetics might best explain his early onset of symptoms?
Anticipation
complementation
codominance
sex-limited traits
discontinuous characteristics
Anticipation
A gene at one locus affecting the expression of a gene at a different locus is termed
multiple alleles.
gene interaction.
dominance.
variable expressivity.
independent assortment.
gene interaction
