Mapping Genes Practice Problems

Consider the following recombination frequencies of three genes on chromosome 5 of a mouse:
A-D: 11 cM
A-G: 15 cM
D-G: 4 cM
Which of the following gives the correct gene sequence?

In a study of a pea plant, researchers have identified two genes, A and B, located on the same chromosome. A dihybrid plant that is heterozygous for both genes (AaBb) is crossed with a homozygous recessive plant (aabb). The following offspring were obtained:

150 AaBb
150 Aabb
25 aaBb
25 aabb
Which of the following are the genotypes of the recombinants?

In a study of a certain plant species, researchers have identified two genes, G and H, located on the same chromosome. A dihybrid plant that is heterozygous for both genes (GgHh) is crossed with a homozygous recessive plant (gghh). The following offspring were obtained:

250 GgHh
50 ggHh
50 Gghh
250 gghh
Using this information, which of the following gives the correct genetic map?

In a study of pea plants, an RFLP marker was identified and found to be linked to the gene for purple flowers, which is dominant over the gene for white flowers. The RFLP marker has two alleles: A and B. A genetic cross between two heterozygous purple-flowered plants produced the following offspring:

Genotype        Number of Offspring
AA                          23
AB                          46
BB                          23
Total     .                 92

Assuming the recombination frequency between the RFLP marker and the purple flower gene is 15%, which of the following shows the correct gene map?

Consider the following DNA sequences for four individuals:

Person 1:  ATCGTTAGGACGTAC
Person 2: ATCGCTAGGACCTAC
Person 3: ATCGGTAGGACCTAC
Person 4: ATCGATAGGACGTAC

You want to identify the haplotype sequence for the region between nucleotides 5 and 10 (inclusive). Which of the following is the most likely haplotype sequence for this region?

The DNA sequences for five individuals at a particular genomic region are given below.

Individual 1: AGGCTACCGT
Individual 2: AGGCTACCGG
Individual 3: AGGCTACCGC
Individual 4: AGGCTACCGT
Individual 5: AGGCTACCGA

Which of the following gives the correct haplotype sequence for this region?

A genetic study of a certain disease identified three SNPs located on the same chromosome in a group of patients. Based on the genotype data of these patients, the following haplotypes were found:

Haplotype 1: TCG
Haplotype 2: CCG
Haplotype 3: TCA
Haplotype 4: TTA

Which of the following statements is most likely true about these haplotypes?

Consider the following DNA sequences:

Nucleotide position
                   1       5       10
Person 1 ...GCCTGCCTGA...
Person 2 ...GCCAGCCTTA...
Person 3 ...GCCGGCCTCA...
Person 4 ...GCCCGCCTAA...

What is the nucleotide position of all the SNPs in the given sequences?

A genetic study of a rare autoimmune disease identified 20 affected individuals from 10 unrelated families. The disease shows autosomal recessive inheritance pattern, but no mutation has been found in the known genes responsible for the disease. Whole genome sequencing was conducted in 5 affected individuals and 10 unaffected individuals from the same population. A bioinformatics analysis showed a novel variant in a gene on chromosome 6 to be present in all affected individuals but not in unaffected individuals. The variant is predicted to be deleterious and affect the function of the encoded protein. The genetic linkage analysis for the variant showed a LOD score of 3.1. 

What is the most appropriate next step for this genetic analysis?

In a genetic study of an early onset form of heart disease, a marker on chromosome 8 was found to be associated with the disease in six out of ten families. Analysis of the marker produced a lod score of 1.9.

What do these findings suggest about the marker?

A geneticist is studying a family with an autosomal dominant disease that has been mapped to chromosome 7. Two DNA markers, A and B, are located on chromosome 7 near the disease locus. The following LOD scores were obtained:

 θ = recombination frequency
                        LOD score
       Marker A       θ = 0.10     2.1
       Marker A       θ = 0.20     0.1
       Marker B       θ = 0.05     1.8
       Marker B       θ = 0.10     0.4

Based on the LOD scores, which marker is most closely linked to the disease locus?

A group of researchers conduct a study to investigate the linkage between a particular DNA marker 'X' and a rare genetic disorder gene. The maximum logarithm of the odds (LOD) score value obtained is 13.01. Which of the following statement is correct regarding this score?

A genetic study is carried out to determine the genetic linkage between an autosomal dominant neuromuscular disorder-producing gene and DNA markers on a specific chromosome. The maximum LOD score value obtained is 0.07. What does this mean?

________is a genetic approach that looks across families for chromosomal segments that cosegregate with the disease phenotype.

_________ is a type of physical mapping in which high-molecular-weight DNA is digested using a restriction enzyme with a few restriction sites.

A genetic study is carried out to determine the genetic linkage between an autosomal dominant neuromuscular disorder producing gene and DNA markers on a specific chromosome. Which of the following LOD score values is considered statistically significant evidence of genetic linkage?

The distance between two genes on the same chromosome is calculated by applying a:  

What is the highest recombination frequency that may be seen in a genetic cross if the two genes are on the same chromosome?

Which of the following is a drawback of using a high number of genetic markers in linkage mapping?

There are 600 total combinations in the offspring of a dihybrid cross. What is the number of recombinant type offspring if this cross has a 40% recombination frequency?

Marfan Syndrome is a rare autosomal dominant condition affecting 1 in 5000 individuals, caused by a mutation in a gene called FBN1. Mapping the FBN1 gene on chromosome 15 requires genetic linkage studies to test the segregation of FBN1 gene and DNA genetic markers on different chromosomes. A DNA marker comprising of two alleles denoted as 1 and 2, is linked to FBN1. The pedigree diagram given below gives the genotype of each family member.

Which of the following options gives the correct estimate of the recombination frequency of DNA markers among offspring?

What is the recombination frequency between two genes that are 20 map units apart?

Based on the given recombination frequencies, PR - 30%; PQ - 8%; PS - 27%; RQ - 22%; QS - 35%, which of the following is the correct order sequence in which genes are located on a chromosome?

In a three-point mapping experiment, gene A is 15 map units away from gene B and 25 map units away from gene C. How far apart are genes B and C on the map?

The formula 2ⁿ is used to determine the types of gametes, where "n" is the number of heterozygous gene loci. The number of gametes that can be produced by a diploid organism that is heterozygous for 6 loci is:

Recombination is the generation of non-parental gene combinations, whereas linkage is the phenomenon of the physical association of genes on a chromosome. In terms of linkage and recombination, which of the following statements is true?

The values of the recombinant frequencies of different gene pairs are given as follows: 

AC= 50% 

BC= 30% 

BD= 12% 

Which of the following statements about the linked gene is true, based on the data presented above? 

A heterozygous person for two gene pairs AaBb, who is the offspring of AABB and aabb parents is mated with a double-recessive individual aabb. Individual genotypes and resultant numbers of offspring are as follows:

AaBb= 300 

Aabb= 200 

aaBb= 150 

aabb= 100 

What is the recombinant frequency of two gene pairs? 

The frequency of recombination between genes A and B is 24% and the following cross was done: A B/a b X a b/a b. If 1000 progeny are produced from this cross, determine the number of progeny with  A B/a b genotype.

The frequency of recombination between genes A and B is 24% and the following cross was done: A b/a B X a b/a b. If 2000 progeny are produced from this cross, determine the number of recombinant progeny.

The frequency of recombination between genes A and B is 17%, and between genes B and C is 5%. Determine the sequence of the three genes.

__________ is a mechanism in evolutionary genetics that occurs when irreversible harmful mutations accumulate in an asexual population in the absence of recombination.

A person is homozygous for two gene pairs, A and B, which are linked on a chromosome. What is true about the gametes produced by the person if there is no gene crossing between the linked genes?

Two genes, M and N, that are on the same chromosome have a 40% recombinant frequency. A test cross between parents who are heterozygous for genes M and N produced 280 offspring. Calculate the number of parental genotypes for the genes M and N.

A wild-type fruit fly (heterozygous for its brown body color and red eyes) is mated with a black-bodied fly with brown eyes. The offspring have the following phenotypic distribution: 

Brown body with red eyes=770

Brown body with brown eyes=780 

Black body with red eyes =156 

Black body with brown eyes=160 

Calculate the recombination frequency between the genes for the body color and eye color. 

The following diagram shows the genetic map of four linked genes on a chromosome. 

What will be the distance between D and B? 

The laboratory approach utilized to locate the position of a specific disease that is associated with a gene on a chromosome is called:

If the distance between the non-allelic genes is 24 map units after the F1 individual was test crossed from the parent cross SSyy X ssYY,  the percentage of ssYy in the F2 generation is as follows:

If a test cross yields the following results:

Parental: 1104
Parental: 1037
Recombinant 1: 134
Recombinant 2: 155

What is their recombination frequency?

The genetic distances between the three genes (genes AB, CD, and EF) were identified using a two-point mapping cross. Given the following distances, what is the sequence of the three genes in the chromosome?

 AB-EF: 39 mu
 AB-CD: 5 mu
 CD-EF: 34 mu

850 out of 1000 individuals in a cross between individuals homozygous for (x, y) and the wild type (+ +) were of the parental type. The distance that separates x from y is then?

What might be the order of the genes in a linkage map if the Recombination frequency between genes A and B is 6%, between A and C is 14%, and between B and C is 20%?

Which of the following is true when genes are located close to each other on chromosomes and cannot be separated even by crossing over?

In the pea plant's chromosomal linkage map, two genes A and B are very close together. When AABB and aabb genotypes are hybridized, the result will show

Which of the following statements is true concerning gene crossing over?

Bloom syndrome is characterized by prenatal and postnatal retardation of growth, great sensitivity of the facial skin to the sun, immune deficiency, and abnormal behavior patterns. It is caused by a mutation in the BLM gene located on chromosome 15. Which of the following is elevated in Bloom syndrome?

If genes are located on the same chromosome, they are said to be:

The purple gene in Drosophila specifies the normal and red eyes (for the dominant pr+ allele) and purple eyes ( for the recessive pr allele). Another gene called the vestigial gene specifies normal, long wings (for dominant vg+ allele) and short wings (for recessive vg allele). A double heterozygous female mates with a tester (homozygous recessive for both genes) and yields the following offspring:

     pr+ vg+ and pr vg: 1422
     pr vg and pr vg: 1032
     pr+ vg and pr vg: 134
     pr vg+ and pr vg: 139

What is the recombination frequency between the purple and vestigial genes?

Four genes are all located on the same chromosome. The genes have the following recombination frequencies:

G-I: 3%
F-H: 9%
I-F: 15%
I-H: 24%
G-H: 27%
G-F: 18%

Considering the mentioned data, which of the following images illustrates the correct gene sequence in the chromosome?

A student conducted a sequence of two-point crosses for four genes, specifically, genes a, b, c, and d. These genes have the following recombination frequencies:

a and b = 50%
a and c = 50%
a and d = 50%
b and c = 20%
b and d = 9%
a and d = 29%

Considering the given data, which of the following statements is true?

Recombination frequencies are helpful in figuring out the order of genes on a specific chromosome. Suppose we have the following recombination frequencies:

  Recombination frequency of E-F = 12.1%
  Recombination frequency of F-G = 7.3%
  Recombination frequency of E-G = 19.4%

Which of the following gives the correct order of genes E, F, and G in the chromosome?

The following image shows the location of genes X, Y, and Z in a chromosome. If the distance between genes Y and Z is 10 mu and the distance between genes X and Y is 30 mu, what is the distance between genes X and Z?