Ch. 5 - Beyond Mendel's Laws Flashcards
In the parental generation, a male fruit fly with a gray body (BB) and straight wings (CC) was crossed with a female fruit fly with a black body (bb) and curved wings (cc). The F1 flies all had gray bodies and straight wings. A female F1 fly was crossed with a male fly that was homozygous recessive for both traits. The female fly had the B and C alleles on one chromosome and the b and c alleles on the other chromosome. Because the genes are linked, the expected ratio in the F2 generation would be 50% with gray bodies and straight wings and 50% with black bodies and curved wings. But four different phenotype combinations appear in the offspring, with two expected, but there were also offspring with gray bodies and curved wings and offspring with black bodies and straight wings. Which of the following best explains what happened?
A recombination occurred during the formation of the F1 female’s egg cells
I^AI^A
Blood type A
I^BI^B
Blood type B
I^AI^B
Blood type AB
ii
Bloody type O
When a genotype is _____ , some individuals with the genotype do not have the associated phenotype.
Incompletely penetrant
The severity or extent to which a phenotype is expressed is its _____.
Expressivity
The same phenotype may result from different genotypes due to _____.
Genetic heterogeneity
An environmentally caused condition whose symptoms are similar to those of a known inherited disorder is called a(n) _____.
Phenocopy
A(n) _____ allele may result in a phenotypic class that does not survive long enough to reproduce.
Lethal
Which of the following statements describe mitochondrial DNA?
Fewer types of DNA repair than nuclear DNA
Inherited from the mother only
No crossing over
High exposure to oxygen free radicals
Carries 37 genes
In epistasis, the blocked gene is expressed normally, but the product of the modifier gene inactivates it.
True
An allele combination that produces a phenotype in everyone who inherits it is not penetrant.
False
A phenotype is variably expressive if symptoms vary in intensity among different people.
True
On a molecular level, genetic heterogeneity occurs when a single protein affects different body parts, participates in more than one biochemical reaction.
False
Phenocopies are genetically caused traits that appear to be inherited.
False
What is the best explanation for the inheritance pattern shown in the pedigree below?
Mitochondrial inheritance
An investigator determines that gene c and gene f are linked on chromosome 5 of the honeybee genome. Bees that are homozygous for the dominant wild type alleles have long stingers (c+c+) and bi-lobed wings (f+f+). Bees that are homozygous for the recessive mutant alleles have short stingers (cc) and tri-lobed wings (ff). The parent generation was composed of homozygous dominant male bees (c+c+f+f+), and homozygous recessive females (ccff), which produced a heterozygous F1 generation. Male bees from the F1 generation (c+cf+f) were mated in a testcross with homozygous recessive females (ccff). The testcross produced the F2 generation. The resulting phenotypic ratios in the F2 generation were as follows: Long stingers and bi-lobed wings (362); short stingers and tri-lobed wings (348); long stingers and tri-lobed wings (151); and short stingers and bi-lobed wings (139). Based on the recombination frequency of this cross, what is the map distance between the c and f genes?
29 map units
When the cystic fibrosis gene was discovered in 1989, only one mutation was described, and a diagnostic test was developed to detect it. Over the years, as more mutations were discovered, they were added to the test panel. Today, most pregnant women are offered a CF test that detects 100 or so alleles, although more than 1600 mutations have been discovered. Which of these is reflected by the given facts?
The presence of multiple alleles
In humans, the melanocortin 1 receptor (MC1R) is a key protein involved in human skin and hair color. Several versions of the MC1R gene with changes in single nucleotides have been reported. One of these has the amino acid histidine where the amino acid aspartate normally is found at a certain location in the MC1R protein. Another version has a tryptophan where an arginine should be. Both of these versions of the gene are associated with red hair, whereas the wild type version of this gene is associated with dark hair. What phenomenon is occurring with these genes?
Multiple alleles
You are working in the lab, studying what you suspect to be a mitochondrial disease. You isolate mitochondria from a child with this disease, and sequence the mitochondrial genome. You also sequence the mitochondrial genomes of the parents. You are surprised to find that the child has a mutation in a very important mitochondrial gene, but that neither of her parents have this mutation. Further, both parents are healthy. What most likely explains this finding?
Because mitochondrial DNA mutates much more quickly than nuclear DNA, the girl likely incurred a new mutation in her mitochondrial DNA
Imagine that the genes for eyelash length and hair texture are on the same chromosome. A man with long eyelashes and straight hair has one chromosome with the E gene and the S gene, and a second chromosome with the recessive genes, e and s. Assuming crossing over does not occur in meiosis, what combinations of genes should you see in his gametes?
ES and es
A pair of college sweethearts do a DNA test to find out their respective ancestries. They are shocked to find that they share nearly 1% of their genome. What is their likely relationship?
Third cousins
You identify a rare purple plumed parrot. When you cross the parrot to a true breeding white parrot, you get 1/2 white and 1/2 purple parrots. When you cross two purple parrots you get 1/3 white parrots and 2/3 purple parrots. Which of the following best explains this result?
The purple allele is lethal in the homozygous state
