AP Biology- Unit 5 GENETICS REVIEW

Pt 2 The probability that individual III-5III-5 will develop Friedreich's ataxia is closest to which of the following?

25%

Pt 2 The probability that Matthew and Jane's first child will be an achondroplastic dwarf is

50%

A scientist is investigating the possibility that two traits in a particular plant are determined by genes that are on the same chromosome. The scientist crossed a plant that is homozygous dominant for both traits with a plant that is homozygous recessive for both traits. The heterozygous offspring in the F1F1 generation were then crossed with a plant that is homozygous recessive for both traits. The results expected if the genes independently assort and the observed results are presented in the table.

7.81

Pt 1 Friedreich's ataxia is an inherited disorder. Friedreich's ataxia is caused by an insertion mutation in a noncoding portion of the FXNFXN gene where a GAAGAA triplet is repeated hundreds of times. The FXNFXN gene encodes the protein frataxin. A pedigree of a family with members affected by this disorder is shown in Figure 1. Based on the data in Figure 1, which of the following best describes the inheritance pattern of Friedreich's ataxia?

Autosomal recessive

Pt 2 Which of the following is probably the genotype of the dark, short-haired parent in cross I?

CCBB

Pt 2 In Table I, the ratio of phenotypes in the offspring from the testcross with F1 plants that had purple flowers and inflated pods suggests that the genes for flower color and pod shape are located

on different chromosomes

The diploid number of chromosomes in the cell of a domesticated dog is 7878. Which of the following options includes the correct number of chromosomes in a cell after each cellular process (G2G2 checkpoint, meiosis, and fertilization, respectively)?

After G2 Checkpoint 78 After Meiosis 39 After Fertilization 78

Pt 1 In dogs, one pair of alleles determines coat color (dark and albino). Another pair of alleles determines hair length (short and long). Thus, each gamete will contain one of the coat-color alleles, C or c and one of the hair-length alleles, B or b. In repeated crosses of a specific dark, short-haired dog with an albino, long-haired dog, all the offspring were dark with short hair, as shown in cross I. However, in subsequent crosses of another dark, short-haired dog with a dark, long-haired dog, the ratios shown in cross II below were obtained.

CcBb

Within a forest ecosystem, there is a large amount of diversity among members of a warbler species. Of the following stages of meiosis illustrated for a typical cell, which contributes most to diversity among the warblers?

Chromosomes are in the middle of the nucleus; still have not detached

Pt 1 Table I shows the results of breeding experiments to examine the inheritance of flower color (purple versus white) and pod shape (inflated versus constricted). For the crosses recorded in Table I, true-breeding parents were crossed to produce F1 offspring, which were then testcrossed to homozygous recessive individuals. Table II shows the results of computer-simulated crosses to model the inheritance of leaf shape (broad versus narrow) and flower color (purple versus white). Based on the data in Table I, which of the following best explains why there are no individuals with constricted pods in the F1 generation?

Inflated pod shape is dominant to constricted pod shape.

Pt 1 Achondroplastic dwarfism is a dominant genetic trait that causes severe malformation of the skeleton. Homozygotes for this condition are spontaneously aborted (hence, the homozygous condition is lethal) but heterozygotes will develop to be dwarfed. Matthew has a family history of the condition, although he does not express the trait. Jane is an achondroplastic dwarf. Matthew and Jane are planning a family of several children and want to know the chances of producing a child with achondroplastic dwarfism. The genotypes of Matthew and Jane are best represented as

Matthew- aa and Jane- Aa

The data above represent the results of three different crosses involving the inheritance of a gene that determines whether a certain organism is blue or white. Which of the following best explains the mechanism of inheritance of the gene?

The allele for blue is an X-linked dominant allele because there are no blue male offspring in cross 2.

In pea plants, flower color and the length of the flower's pollen grains are genetically determined. Researchers studying pea plants crossed homozygous dominant pea plants with homozygous recessive pea plants. The F1F1 plants were then crossed, and the number of offspring with each phenotype was recorded. The researchers' observed data, however, differed from the expected data. The researchers did a chi-square analysis and calculated the chi-square value to be 5.55.5.

The differences between observed data and expected data are due to chance.

A researcher observes that when two heterozygous plants with red flowers are crossed, the resulting offspring include plants with red, white, or pink flowers. The researcher proposes the null hypothesis that flower color is the result of independent assortment and incomplete dominance. The researcher calculates a chi-square value of 7.37.3. Assuming two degrees of freedom, which of the following is the correct interpretation of the chi-square analysis, using a pp-value of 0.050.05 ?

The null hypothesis should be rejected because the critical value is less than the calculat

Pt 3 Which of the following provides the best justification for an assumption that might have been used in the computer simulation (Table II)?

The purple allele is dominant to the white allele because all the offspring from the cross of purple-flowered and white-flowered plants had purple flowers.