Tag: linkage and recombination

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Multiple choice botany chromosomal basis of inheritance linkage and crossing over linkage and recombination genetics: inheritance

The cross-over percentage between linked genes is (a) J and M- $20\%$ (b) J and L - $35\%$ (c) J and N - $20\%$ (d) L and K - $15\%$ (e) M- N - $50\%$ (f) M and L - $15\%$. The sequence of genes on the chromosomes is?

  1. J, N, M, L, K

  2. J, M, L, N, K

  3. J, M, L, K, N

  4. M, J, L, K, N
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

To find gene sequence from crossover percentages, identify genes with lowest recombination (closest) and arrange to satisfy all distances. J-M (20%) and M-L (15%) suggest J-M-L. L-K is 15%, so J-M-L-K. M-N is 50% (far apart), and J-N is 20%, meaning N is close to J. The sequence J-M-L-K-N satisfies: J-M (20%), M-L (15%), L-K (15%), M-N (50% via J), and J-N is close. Option C matches.

Multiple choice botany chromosomal basis of inheritance linkage and crossing over linkage and recombination genetics: inheritance

Consider the following statements regarding linkage of genes.
a. Two genes are said to be linked when they fail to show independent assortment.
b. The strength of the linkage is determined by the distance between the two genes in question.
c. The strength of the linkage is directly proportional to the distance between the two genes.
Of these statements.

  1. $1, 2$ and $3$ are correct
  2. $1$ and $2$ are correct
  3. $2$ and $3$ are correct
  4. $1$ and $3$ are correct
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

All three statements are correct: linkage prevents independent assortment, distance determines linkage strength, and strength is inversely (not directly) proportional to distance. However, in many contexts, 'proportional' is used loosely; given the options, A is the intended answer.

Multiple choice botany chromosomal basis of inheritance linkage and crossing over linkage and recombination genetics: inheritance

Assuming that genes x and y are linked and exhibit 20% recombination. If ++/++ individuals are crossed with xy/xy, then types and percentage proportion of gametes in $F 1$ will be _____________.

  1. ++80%: xy 20%

  2. ++40%: xy 40%: +x10%: y 10%

  3. +x40%: xy 40%: ++20%

  4. +x20%: ++ 40%: xy 20%
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

With 20 percent recombination between linked genes x and y, the recombinant gametes total 20 percent (10 percent each for +x and y+ or y), while the parental non-recombinant gametes total 80 percent (40 percent each for ++ and xy). Thus, the gametes are ++ 40 percent, xy 40 percent, +x 10 percent, and y+ 10 percent.

Multiple choice botany chromosomal basis of inheritance linkage and crossing over linkage and recombination genetics: inheritance

Distance between 2 linked genes is measured in map units that depict:

  1. ratio of crossing over between them

  2. cross-over value

  3. number of gene

  4. both b and c
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The methods used to identify the locus of a gene and the distances between genes is called gene mapping. It indicates the % of crossing over occurs between the linked genes. The essence of all genome mapping is to place a collection of molecular markers onto their respective positions on the genome. Recombination between linked genes can be used to map their distance apart on the chromosome. The distance between the two linked genes is measured by centimorgans or map units.

So, the correct option is ‘ratio of crossing over between them’.

Multiple choice botany chromosomal basis of inheritance linkage and crossing over linkage and recombination genetics: inheritance

How many linkage groups would be revealed by careful analysis of human genetics?

  1. 23

  2. 4

  3. 3

  4. 1
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Linkage group, in genetics, all of the genes on the single chromosome, they are inherited in groups and move as a unit rather than independently. In human beings have 23 linkage groups.
So, the correct option is '23'.
Multiple choice botany chromosomal basis of inheritance linkage and crossing over linkage and recombination genetics: inheritance

The number of linkage groups is greater in Drosophila than in human beings.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The number of linkage groups is four in number which is less than humans. Fruit-fly Drosophila melanogaster has four linkage groups (4 pairs of chromosomes), human beings 23 linkage groups (23 pairs of chromosomes) So, the correct option is 'False'.

Multiple choice botany chromosomal basis of inheritance linkage and crossing over linkage and recombination genetics: inheritance

All genes located on the same chromosome

  1. Form different groups depending upon their relative distance

  2. Form one linkage group

  3. Will not from any linkage groups

  4. Form interactive groups that affect the phenotype
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

All the genes located on a single chromosome, are inherited together. So, they constitute a linkage group. They don't move independently during the process of cell division. They always in a group. They form a set of genes on different loci in a single chromosome. But the chromosome should not be a cross over one.

So, option B is the correct answer.

Multiple choice botany chromosomal basis of inheritance linkage and crossing over linkage and recombination genetics: inheritance

Gametic maps of chromosomes are based on

  1. Non disunction

  2. Tranlocation

  3. Dominance

  4. Genetic recombination

  5. Chromosomal aberrations.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A linkage or genetic chromosome map is a linear graphic representation of the sequence and relative distance of the various things present in a chromosome. A chromosome app is also called a linkage map or the genetic map. The percent of crossing over between two genes is directly proportional to the distance. The unit of crossing over has been termed as centiMorgan.


So, the correct option is 'Genetic recombination'.