Complete and Incomplete Linkage

Q.

What is the recombination frequency?

Q.

Define complete linkage. Give an example of a cross, showing complete linkage.

Q. The classification of linkage into complete and incomplete linkage is based on their

1. size of the linkage group
2. genome size
3. both a and b
4. linkage strength

Q. Have you ever wondered why siblings sometimes look so similar to each other? Or sometimes even so different?

Q. The frequency of crossing over would be higher if:

1. Two genes are located closely.
2. Two genes are far apart on a chromosome.
3. Two genes are not located in the same chromosome.
4. None of the above

Q. Suppose if the recombination frequency between two gene present on same chromosome q and r is 13%, p and r is 2%, q and s is 4%, q and p 15%, and r and s is 17%. Based on these frequencies, identify the correct sequence of genes on the chromosome. A/ p, q, r, s B/ p, r, q, s C/ r, P, q, s D/ s, q, P, r.

Q. From which of the following observations did Morgan conclude that the gene for eye colour in Drosophila was located on the X chromosome?

1. Presence of only males with red eyes in the $F_2$ generation
2. Presence of only females with red eyes in the $F_2$ generation
3. Presence of only males with white eyes in the $F_2$ generation
4. Presence of only females with white eyes in the $F_2$ generation

Q. Crossing over occurs at

1. two-stranded stage of chromosomes
2. eight-stranded stage of chromosomes
3. six-stranded stage of chromosomes
4. four-stranded stage of chromosomes

Q. Simplest unit of chromosomes that undergoes crossing over is

1. Cistron
2. Muton
3. Recon
4. Both a and b

Q. When the phenotypic and genotypic ratio resemble each other in the $F_2$ generation, it is an example of

1. dihybrid cross
2. independent assortment
3. incomplete dominance
4. segregation of factors

Q. The percentage of crossing over between two linked genes determine their relative on a chromosome.

1. concentration
2. position
3. expression
4. mutation

Q. What type of chromosomal mutation is given in the image below?

1. Duplication
2. Inversion
3. Deletion
4. Reciprocal translocation

Q. What proportion of the offsprings obtained from cross $AABBCC\times AaBbCc$ will be completely heterozygous for all the genes segregated independently?

1. $1/8$
2. $1/4$
3. $1/16$
4. $1/2$

Q. The percentage of crossing over between two linked genes determine their relative on a chromosome.

1. concentration
2. position
3. expression
4. mutation

Q. A woman with O blood group marries a man with AB blood group

Q. Complete and incomplete linkage is classified based on their

1. Size of the linkage group
2. genome size
3. both a and b
4. linkage strength

Q. Assertion : When yellow bodied, white eyed Drosophila females were hybridised with brown-bodied, red eyed males; and F${}_1$ progeny were intercrossed, F${}_2$ ratio deviated from 9:3:3:1.
Reason : When two genes in a dihybrid are on the same chromosome, the proportion of parental gene combinations in the offsprings are much higher than the non-parental type.

1. Both assertion and reason are true and reason is the correct explanation of the assertion
2. Both assertion and reason are true but reason is not the correct explanation of the assertion
3. Assertion is true but the reason is false
4. Assertion and reason both are false

Q. A test cross of $F_1$ flies +a/ +b produced the following offspring
++ / ab = 9
ab / ab = 9
+b / ab = 41
a+ / ab = 41
What will be distance between linked gene:-

1. 18 cM (trans)
2. 82 cM
3. 18 cM (cis)
4. 20 cM

Q. Alleles for some contrasting traits in a species located on the chromosomes are as follows:


In which of the given cross, recombinants will not be observed in the resultant offspring?
[0.7 mark]

1. A – Because dihybrid condition is not present
2. B – Because two genes are not far a part
3. C – Because both the wild type genes are present on the same chromosome
4. Both B and C – Because mutated genes are present on the same chromosome

Q. In a cross, 80% parental and 20 % recombinant type progenies occured. Its recombination frequency is :

1. 10%
2. 20%
3. 80%
4. 40%

Q. One of the following shows complete linkage.

1. Male Culex
2. Male Drosophila
3. Female Drosophila
4. Neurospora

Q. Two heterozygous parents are crossed. If the two loci are linked what would be the distribution of phenotypic features in $F_1$ generation for a dibybrid cross?

Q. Determination of percentage of crossing over between two linked genes is important in __________.

1. Maintaining heterozygosity in population
2. Indicating relative position of genes in chromosomes
3. Fixation of heterosis in organisms
4. Explaining the phenomenon of coupling and repulsion

Q. Individual homozygous for cd genes were crossed with wild type ++. The $F_1$ dihybrid, thus produced was test crossed. It produced progeny in the following ratio ++ 900; +d115; cd 880; c + 105. What is the distance between c and d genes?

1. 47 units
2. 88 units
3. 11 units
4. 5.75 units

Q. The unit of linkage map is

1. Centimetre
2. Morgan
3. Centimorgan
4. All of the above

Q. Crossing over in diploid organism is responsible for:

1. Segregation of alleles
2. Recombination of linked alleles
3. Dominance of genes
4. Linkage between genes

Q. Explain polygenic inheritance and multiple alleism with the help of suitable examples.

Q. The percentage of crossing over between two linked genes determine their relative on a chromosome.

1. concentration
2. position
3. expression
4. mutation

Q. In recombination frequency between AB genes is $20\%$ and BC gene is $40\%$ and interference is $30\%$ in the case of a double crossover then what will be coincidence under this condition?

1. 2.4
2. 8
3. 5.6
4. 0.7

Q. What fraction of offsprings of the cross $AaBbDdEEFf\times AaBBDdEeFf$ are homozygous for all the genes, assuming that they are on different chromosomes?

1. $1/8$
2. $1/4$
3. $1/32$
4. $1/64$