MSH AP Biology | Non-Mendelian Genetics

Question 11 point

In snapdragons, red-flowered plants crossed with white-flowered plants produce pink F1 offspring. When two pink F1 plants are crossed, which F2 phenotypic ratio is expected?

A 3 red : 1 white B 1 red : 2 pink : 1 white C 9 red : 3 pink : 4 white D 1 red : 1 pink

Incomplete dominance produces a 1:2:1 phenotypic ratio in a heterozygote × heterozygote cross.

Question 21 point

A person with blood type AB has children with a person with blood type O. Which statement best describes the possible phenotypes of their children?

A Only type AB B Only type O C Type A or type B D Type A, B, AB, or O

IᴬIᴮ × ii produces Iᴬi (type A) or Iᴮi (type B). The ABO locus demonstrates multiple alleles and codominance.

Question 31 point

A single mutation causes abnormal hemoglobin, altered red blood cell shape, anemia, and multiple organ effects. This is best described as

A polygenic inheritance B pleiotropy C codominance D independent assortment

Pleiotropy occurs when one gene influences multiple phenotypic traits.

Question 41 point

Human skin pigmentation is influenced by several genes, each contributing to the phenotype. This inheritance pattern is best described as

A polygenic inheritance B complete dominance C Y-linked inheritance D genomic imprinting

Polygenic traits are influenced by two or more genes and commonly show continuous variation.

Question 51 point

Two genes are located on the same chromosome and are 8 map units apart. What percentage of recombinant offspring is expected from a testcross involving a heterozygote for both genes?

A 4% B 8% C 16% D 92%

One map unit corresponds approximately to a 1% recombination frequency, so 8 map units predicts about 8% recombinants.

Question 61 point

In a testcross, offspring occur in the following numbers: AB/ab = 412, ab/ab = 398, Ab/ab = 96, aB/ab = 94. What is the estimated map distance between genes A and B?

A 9.5 map units B 19 map units C 38 map units D 81 map units

Recombinants = 96 + 94 = 190 of 1000 total offspring. The recombination frequency is 19%, so the genes are about 19 map units apart.

Question 71 point

Which meiotic event most directly produces recombinant chromosomes between two linked genes?

A Independent assortment at metaphase II B Crossing over between homologous chromosomes in prophase I C Separation of sister chromatids in anaphase II D DNA replication in interphase

Crossing over between nonsister chromatids of homologous chromosomes during prophase I can separate linked alleles.

Question 81 point

A recessive allele causing red-green color blindness is X-linked. A carrier female and a male with normal vision have a son. What is the probability that this son is color-blind?

A 0% B 25% C 50% D 100%

A son receives his X chromosome from his mother. A carrier mother transmits the recessive allele to half of her sons.

Question 91 point

A male expresses an X-linked recessive trait. He reproduces with a female who is homozygous for the normal allele. Which outcome is expected?

A All sons express the trait B All daughters are carriers C Half the sons are carriers D Half the daughters express the trait

All daughters receive the father's affected X chromosome and a normal X from the mother, making all daughters heterozygous carriers.

Question 101 point

A trait appears in every generation, affects males and females similarly, and affected individuals usually have an affected parent. Which pattern is most consistent with these observations?

A Autosomal dominant B X-linked recessive C Y-linked D Mitochondrial

A vertical pedigree pattern affecting both sexes similarly is most consistent with autosomal dominant inheritance.

Question 111 point

A woman with a mitochondrial disorder has children with an unaffected man. Which prediction is most consistent with mitochondrial inheritance?

A Only sons inherit the disorder B Only daughters inherit the disorder C All children may inherit the mutant mitochondrial DNA D No children inherit the disorder

Mitochondria are typically maternally inherited, so a mother can transmit mitochondrial variants to sons and daughters.

Question 121 point

In a species, allele C produces red pigment and allele c produces no pigment. At a second gene, individuals with genotype ee fail to deposit pigment regardless of the C locus. The ee genotype is an example of

A epistasis B codominance C linkage equilibrium D incomplete penetrance

Epistasis occurs when one gene masks or modifies the phenotypic effect of another gene.

Question 131 point

Two heterozygous organisms are crossed for a trait showing incomplete dominance. Among 200 offspring, 56 show phenotype 1, 96 show the intermediate phenotype, and 48 show phenotype 2. The expected 1:2:1 ratio predicts 50, 100, and 50 offspring. What is the chi-square value?

A 0.24 B 0.96 C 2.00 D 6.00

χ² = (56−50)²/50 + (96−100)²/100 + (48−50)²/50 = 0.72 + 0.16 + 0.08 = 0.96.

Question 141 point

For a chi-square test of a 1:2:1 phenotypic ratio with three categories, how many degrees of freedom are used?

A 1 B 2 C 3 D 4

Degrees of freedom = number of categories − 1 = 3 − 1 = 2.

Question 151 point

Researchers obtain χ² = 1.2 with 2 degrees of freedom. The critical value at p = 0.05 is 5.99. Which conclusion is most appropriate?

A Reject the null hypothesis because 1.2 < 5.99 B Fail to reject the null hypothesis because 1.2 < 5.99 C Reject the null hypothesis because the observed values equal the expected values D The inheritance pattern must be Mendelian

Because χ² is below the critical value, the deviation is not statistically significant at p = 0.05, so the null hypothesis is not rejected.

Question 161 point

A heterozygous individual has linked alleles arranged AB/ab. If no crossing over occurs between the two loci, which gametes will be produced?

A AB and ab only B Ab and aB only C AB, Ab, aB, and ab equally D Only AB

Without crossing over, only the parental haplotypes AB and ab are transmitted.

Question 171 point

A heterozygous individual has alleles arranged Ab/aB. Which offspring classes should be most frequent in a testcross if the genes are tightly linked?

A AB and ab B Ab and aB C All four classes equally D Only double-recessive offspring

The most frequent classes reflect the parental chromosome arrangements, here Ab and aB.

Question 181 point

Why can two genes on the same chromosome sometimes appear to assort independently?

A They always undergo mutation together B They may be far enough apart that crossing over produces approximately 50% recombination C Linked genes cannot be expressed simultaneously D Homologous chromosomes do not pair in meiosis

Genes far apart on the same chromosome can have recombination frequencies approaching 50%, making them appear unlinked.

Question 191 point

A heterozygous organism shows both allele products simultaneously rather than an intermediate phenotype. This pattern is

A incomplete dominance B codominance C recessive epistasis D polygenic inheritance

In codominance, both alleles contribute detectably to the heterozygous phenotype.

Question 201 point

A genetically identical strain of plants develops different heights when grown under different nutrient conditions. Which conclusion is best supported?

A Height must be controlled only by a single dominant allele B Environmental conditions can influence phenotypic expression C The plants have different genotypes D Meiosis created the height differences

Phenotype reflects genotype plus environmental effects; identical genotypes can differ phenotypically under different environments.