Let's suppose that a normal chromosome carries genes labeled A through /. The centromere is located between genes B and C. As shown below, a chromosome with an inversion has a region where the order of certain genes is reversed. Note: The genes on the inverted chromosome carry recessive alleles that are designated with lowercase letters. Normal chromosome: A B Centromere C D E F G H I Chromosome with an inversion: a b Centromere c d h g fei A. If you ignore possible fertility issues, do you think this individual will otherwise be phenotypically normal or abnormal? Explain why. B. Let's suppose a single crossover during meiosis occurs between these two homologs in the region between genes F and G (and between g and f). Following the crossover, what is the order of genes (designated with upper and lower case letters) on the two resulting chromosomes. Include centromeres in your answer. Hint: Both of the resulting chromosomes will carry gene deletions and gene duplications.

The following corn loci are on one arm of chromosome9 in the order indicated (the distances between themare shown in map units):c-bz-wx-sh-d-centromere12 8 10 20 10C gives colored aleurone; c, white aleurone.Bz gives green leaves; bz, bronze leaves.Wx gives starchy seeds; wx, waxy seeds.Sh gives smooth seeds; sh, shrunken seeds.D gives tall plants; d, dwarf.A plant from a standard stock that is homozygous for allfive recessive alleles is crossed with a wild-type plantfrom Mexico that is homozygous for all five dominantalleles. The F1 plants express all the dominant allelesand, when backcrossed to the recessive parent, give thefollowing progeny phenotypes:colored, green, starchy, smooth, tall 360white, bronze, waxy, shrunk, dwarf 355colored, bronze, waxy, shrunk, dwarf 40white, green, starchy, smooth, tall 46colored, green, starchy, smooth, dwarf 85white, bronze, waxy, shrunk, tall 84colored, bronze, waxy, shrunk, tall 8white, green, starchy, smooth, dwarf 9colored, green, waxy, smooth,…

three recessive genes a, b, and c in the model plant Arabidopsis are found to be linked on chromosome 4. A three point test cross is done with a homozygous recessive plant with a heterozygous for all three genes. Following is the number of progenies a  b  C     65 A  B  c     56 A   B   C   1267 a    b    c   1310 A   b   C    550 a   B    c     515 a   B    C    470 A   b     c   489 Total   =   4,722 Determine the middle locus by your choice of method and after that calculate the map distance between the genes in map unit (m.u.).

In tomato plants, the genes for fruit colour (C), fruit fructose content (F), fruit length (L), and plant height (H) are all found on chromosome 4. Map distances between the four genes are shown below.    Genes Distance in Map Units H and F  40 F and L  12 C and F 75 L and C  87 L and H  52   Sketch and label a gene map to identify the order of the four genes on chromosome 1 in tomato plants.

Consider the following "pericentric" ("around the center") inversion. In one an individual, a simplified 8-gene sequence along one chromosome is 1234 5678 while a pericentric inversion occurred on their other homologous chromosome, resulting in the sequence 1265 4378 (the dot represents the centromere). Draw these homologous chromosomes lined up (as during crossing over, in Prophase l). If a crossover event occurred between gene locus 3 and 4 (slicing between them) on the original chromosome, what would the crossover products look like? What would be the "problem" with each of the chromosomes that result?

An initial crossover event will occur between A and B, as indicated in the corresponding image. After this initial event occurs, a second cross over event occurs (not illustrated) involving the products of the first crossover event.  Given the chromosome organization below, which two chromatids of the bivalent were involved and between which genes did the second crossover event occur to produce the indicated chromosomes?          a. A B c, A b c, a B C, and a b C           b. A B C, A B C, a b c, and a b c (return to the original crossover depicted in the image, and then determine how the second crossover event produced this arrangement

In the fruit fly, recessive mutations in either of two independently assorting genes, brown and purple, prevent the synthesis of red pigment in the eyes. Thus, homozygotes for either of these mutations have brownish-purple eyes. However, heterozygotes for both of these mutations have dark red, that is, wild-type eyes. If such double heterozygotes are intercrossed, what kinds of progeny will be produced, and in what proportions?

Which of the following disorders in humans has an X-linked recessive inheritance pattern?   a.Hutchinson-Gilford progeria b.Tay-Sachs disease c.Marfan syndrome d.Red-green color blindness   Which of the following is described as a structural rearrangement of a chromosome in which a broken piece has become reattached in the wrong location?   a.Duplication b.Translocation c.Inversion d.Deletion   Which of the following disorders arises from translocation events?   a.Huntington’s disease b.Infertility c.Burkitt lymphoma d.Duchenne muscular dystrophy

A geneticist discovers that a girl with Down syndrome has a Robertsonian translocation involving chromosomes 14 and 21. If she has an older brother who is phenotypically normal, what are the chances that he is a translocation carrier?

Variations in Chromosome NumberAneuploidy Describe the process of nondisjunction and explain when it takes place during cell division.