Dna Model Kit

Abstract

A kit for constructing a DNA (deoxyribonucleic acid) molecule, and for demonstrating replication during mitosis, comprises, a plurality of groups of chips, each group designating a component of the DNA molecule, interlocking connectors carried by the chips enabling them to be snap-fitted into others according to certain predetermined combinations, a common base supporting the lower end of the DNA molecule and carrying a supporting bar supporting the upper end of the DNA molecule, the supporting bar being rotatable 180.degree. or 360.degree. and lockable in the rotated condition. The common base carries four equally-spaced supporting elements, such that a double-strand molecule may first be constructed by supporting the lower ends of the strands on the two middle elements, and then replication by mitosis may be demonstrated by splitting the molecule into two strands, pivoting the two strands supported on the middle elements, so that each faces one of the remaining two elements, and then constructing two double-strand molecules from the two strands.

Description

BACKGROUND OF THE INVENTION

The present invention relates to kits for constructing DNA (deoxyribonucleic acid) molecules and for demonstrating their replication by mitosis.

A number of different types of kits are available for demonstrating the construction of the DNA molecule and also its replication during mitosis. One type, for example, uses a supporting rod and two stretchable rubber strands, representing sugar and phosphate chains which join the ends of the bases forming the molecule. The stretchable rubber strands enable the molecules to be given the double-twist characteristic of such molecules. To demonstrate replication, the DNA molecule is assembled on a stand, and the molecule is then split and placed on another stand for reassembling two complete DNA molecules. Such an arrangement, however, is not convenient in constructing the DNA molecule and also in demonstrating replication.

SUMMARY OF THE PRESENT INVENTION

The present invention provides a kit enabling chemical molecules in general, and DNA molecules in particular, to be constructed, and also to be replicated, in a much more convenient manner than the known arrangement described above.

According to the present invention, there is provided a kit for constructing a double-strand chemical molecule having a twist therein, and for demonstrating its replication by mitosis, the kit comprising a plurality of groups of chips, each group designating a component of the molecule, interlocking connectors carried by the chips enabling them to be detachably assembled together according to certain predetermined combinations, each combination including two molecular strands; a plurality of lower supporting elements for supporting the lower ends of the molecular strands; and a plurality of upper supporting elements for supporting the upper ends of the strands. One of the plurality of supporting elements, preferably the upper plurality, are rotatably mounted about a vertical axis for applying a twist to the molecular strands supported thereby. The plurality of lower supporting elements are supported on a common base there being at least four of such lower supporting elements, equally spaced from each other on the common base.

The arrangement is such that a double-strand molecule may first be constructed by supporting the lower ends of the strands on the middle two lower supporting elements, and then replication by mitosis may be demonstrated by splitting the molecule into two strands, pivoting the two strands supported on the middle lower supporting element so that each faces one of the remaining two lower supporting elements, and then constructing from the two strands two double-strand molecules.

The kit is particularly intended for constructing a DNA (deoxyribonucleic acid) molecule, in which case the plurality of groups of chips designate components of the DNA molecule and include a group of S-chips each designating the sugar chain, a group of P-chips each designating the phosphate chain, a group of T-chips each designating the thymine base, a group of C-chips each designating the cytosine base, a group of A-chips each designating the adenine base, and a group of G-chips each designating the guanine base. The S-chips and the P-chips include interlocking connectors enabling a P-chip to be attached at either end of an S-chip and to be pivoted with respect thereto along a pivotable axis extending lengthwise of the S-chip. The S-chip and the four base-chips include other interlocking connectors enabling any one of the base-chips to be attached at one end thereof to a mid-portion of the S-chip and to be pivoted with respect thereto along a pivotable axis extending widthwise of the S-chip and at right angles to the first pivotable axis. The four base-chips include further interlocking connectors enabling a T-chip to be attached to an A-chip, and a C-chip to be attached to a G-chip.

Further features and advantages of the invention will be apparent from the description below.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described by way of example only, with reference to the accompanying drawings, wherein:

FIG. 1 illustrates one chip of each of the component groups used in constructing the DNA molecule; namely an S-chip designating the sugar chain; a P-chip designating the phosphate chain; a T-chip designating the thymine base; a C-chip designating the cytosine base; an A-chip designating the adenine base; and a G-chip designating the guanine base;

FIG. 2 illustrates the attachment of a C-chip to a G-chip;

FIG. 3 illustrates the use of the foregoing chips in constructing a DNA molecule;

FIG. 4 illustrates the DNA molecule so constructed and given a double-twist; and

FIG. 5 illustrates the construction of two DNA molecules in side-by-side relationship to demonstrate replication by mitosis.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The kit illustrated in the drawings comprises a plurality of groups of flat chips each group designating a component of the DNA molecule. Thus, there are six groups of chips, one of each being shown in FIG. 1, namely; a group of S-chips 2 each designating the sugar chain; a group of P-chips 4 each designating the phosphate chain; a group of T-chips 6 each designating the thymine base; a group of C-chips 8 each designating the cytosine base; a group of A-chips 10 each designating the adenine base; and a group of G-chips 12 each designating the guanine base. These chips are preferably all made of plastic material and are colour-coded to distinguish the different groups.

The S-chips 2 are shaped according to the approximate shape of a sugar chain, being formed with two opposed short sides 2a, 2b, joined at one end by a long straight side 2c and joined at the opposite end by two further sides 2d, 2e forming an obtuse angle juncture with each other at the midportion 2' of the chip. The two short sides 2a, 2b are each formed with a central pin-socket 22a, 22b, and the midportion 2' is formed with a third pin-socket 22c. In addition, the S-chip carries the numbers "3" and "5" adjacent to the sockets 22a, 22b, respectively, and the number "1" adjacent to socket 22c, these numbers representing the carbon atoms of the sugar chain approximately at these positions.

The P-chips 4 are of square shape to approximate the shape of the phosphate chain, and each carries pins 24a, 24b at the centre of two opposed sides. These pins form interlocking connectors with sockets 22a, 22b of the S-chips 2, being snap-fitted therein when constructing the DNA molecule.

Both the T-chips 6 and the C-chips 8 are of the same hexagonal shape to approximate the shape of the thymine and cytosine bases, respectively, and carry pins 26 28 centrally of one side. At the opposite side of the respective hexagons, T-chip 6 is formed with two spaced pins 30 each terminating in a ball 32, and C-chip 8 is formed with three spaced pins 34 each terminating in a ball 36. These pins represent the chemical valences of these bases.

Both the A-chips 10 and the G-chips 12 are components the form of a hexagon joined at one side to a pentagon, thereby approximating the shape of the chemical componets they represent. One end of each of the two chips is formed with a pin 40, 42 respectively. The opposite end of the A-chip is formed with two spaced pins 44, each terminating in a ball 46, and the opposite end of G-chip 12 is formed with three spaced pins 48, each terminating in a ball 50 to represent the chemical valences of these bases.

Pins 24a, 24b of the P-chips 4 form an interlocking connector with sockets 22a, 22b of the S-chips 2, enabling a P-chip to be attached at either end of an S-chip and to be pivoted with respect thereto along a pivotable axis extending lengthwise of the S-chip. Pins 26, 28, 40, 42 of the base chips 6, 8, 10, 12, each form an interlocking connector with socket 22c of the S-chips 2 enabling any one of the base chips to be attached to mid-portion 2' of the S-chip and to be pivoted with respect thereto along a pivotable axis extending widthwise of the S-chip, i.e., at right angles to the first-mentioned pivotable axis of the P-chips 4. The two pins 30 and balls 32 of the T-chips 6 form an interlocking connector with the two pins 44 and balls 46 of the A-chips 10 and permit these two chips to be attached together at that end; whereas the three pins 34 and balls 36 of the C-chips 8 form an interlocking connector with the three pins 48 and balls 50 of the G-chips 12 and permit these two chips to be attached together at that end, as shown in FIG. 2. The rules accompanying the use of the kit may specify that chips containing two pins and two balls may only be attached to each other, and chips containing three pins and three balls may only be attached to each other, although the spacing between the pins and balls, or the shape of such spacing, may be designed to enforce this requirement.

The kit further includes a common base 52 (FIG. 3) in the form of a hollow box 53 for housing all the chips as well as the other parts of the kit. The common base supports four equally spaced tightly-coiled vertical springs 54 (two of which are shown in FIG. 3) which serve as pivotable pins receivable in sockets 22a or 22b of the S-chips 2 in order to support the lower end of the constructed DNA molecule. In addition, a pair of end-rods 56 are removably attached to the base, the upper ends being bridged by a horizontal beam 58 of rectangular section. End rods 56, which may comprise telescoping tubes to permit disassembly, form with bridging beam 58 a frame for supporting a bar 60, which bar supports the upper end of the DNA molecule. For this purpose, bar 60 is formed with a pair of end openings 61 into which may be snap-fitted the pins 24b of the P-chips 4. Bar 60 is fixed to the lower end of a square rod 62 the upper end of which passes through a circular opening (63) formed in beam 58. Bar 60 may thus be rotated with respect to the vertical axis of the constructed DNA molecule, and is fixed in its rotated position (180.degree. or 360.degree.) by means of a channel member 64 having a square opening through which square rod 62 passes, the sides of the channel member straddling the sides of beam 58. Thus, rod 62 and bar 60 carried at its lower end may be raised or lowered by moving same within the square opening of channel member 64. In addition, the channel member may be lifted to permit the bar to be rotated, e.g. 360.degree. to provide a double-helix in the constructed DNA molecule, and then the bar may be locked in its rotated position by lowering channel member so that it engages the sides of beam 58.

To construct the DNA molecule, the two centre pins 54 are first used as shown in FIG. 3. First, a single strand is assembled of alternating S-chips 2 and P-chips 4 by snap-fitting the pins 24a, 24b of the P-chips into sockets 22a, 22b of the S-chips. The lowest chip is an S-chip 2 and its lowermost socket is snap-fitted into the spring pin 54 of stand 52, whereas the top chip in the string is a P-chip 4 and its pin is snap-fitted into one of the end openings 61 in cross-bar 60. 10 S-chips 2 alternating with 10 P-chips 4 are thus assembled forming a single strand of 10 mucleotides. A second strand of 10 nucleotides is formed in a similar manner between the adjacent centre pin 54 and the other end of cross-bar 60. The sugar chains in the first strand should point in the direction opposite to those in the second strand, i.e., the "5" hydrogen should be down in one strand and up in the other strand.

Next, the appropriate base chips 6, 8, 10 and 12 are assembled between the centre sockets 22c of the S-chips 2 in both strands. As one way of accomplishing this, a T-chip 6 is paired with an A-chip 10 by interconnecting pins 30 of one with pins 44 of the other, and the pair is then snap-fitted into the centre sockets 22c of a pair of aligned S-chips 2 in the two strands; similarly, a C-chip 8 is paired with a G-chip 12 by interlocking pins 34 and 48, and the pair is snap-fitted into the centre sockets 22c of another pair of aligned S-chips 2 in the two strands. Another way of accomplishing this is to attach the appropriate base chips to the S-chips of one strand, and then of the other strand (as shown) in FIG. 3; then to rotate the two strands to face each other; and finally to attach together the pins 30, 34, 44, 48 of the base chips to be paired.

After the DNA molecule is thus assembled, channel member 64 is lifted off of beam 58, and rod 62 carrying cross-bar 60 is rotated 360.degree. to form a double helix in the DNA molecule as shown in FIG. 4. The channel member 64 is then returned onto beam 58 to lock the bar in this twisted condition.

During this twisting operation, it will be seen that the interlocking connector arrangements described above permit the P-chips to be pivoted with respect to the S-chips, and the S-chips to be twisted with respect to the base chips. In addition, pins 54 supporting the lower ends of the DNA molecule permit some pivoting of the S-chips, and pins 24b of the P-chips at the upper end of the molecule permit pivoting of the P-chips.

To demonstrate replication of the DNA molecule by mitosis, the molecule is straightened (i.e., untwisted) by reversing the process described above. The molecule is then split in half by disconnecting the connectors between the two base chips of each pair between the two strands. Then, each strand is pivoted 180.degree. (to the position illustrated in FIG. 3), and two further strands are assembled between the end pins 54 of the common base. The original cross-bar 60 including its supporting rod 62 and locking channel member 64 is moved over to one side of the frame and is used for assembling one of the new DNA molecules, and a second cross-bar 60' including rod 62' and locking channel member 64' is used for assembling the second DNA molecule.

Many variations, modifications and other applications of the illustrated embodiment will be apparent.

Claims

What is claimed is:

1. A kit for constructing a double-strand chemical molecule having a twist therein, and for demonstrating its replication by mitosis, comprising: a plurality of groups of chips, each group designating a component of the molecule; interlocking connectors carried by the chips enabling them to be detachably assembled together according to certain predetermined combinations, each combination including two molecular strands; a plurality of lower supporting elements for supporting the lower ends of the molecular strands; and a plurality of upper supporting elements for supporting the upper ends of the molecular strands; one of said plurality of supporting elements being rotatably mounted about a vertical axis for applying a twist to the molecular strands supported thereby; characterized in that said plurality of lower supporting elements are supported on a common base, and that there are at least four of such lower supporting elements equally spaced from each other on the common base, so that a double-strand molecule may first be constructed by supporting the lower ends of the strands on the middle two lower supporting elements, and then replication by mitosis may be demonstrated by splitting the molecule into two strands, pivoting the two strands supported on the middle lower supporting elements so that each faces one of the remaining two lower supporting elements, and then constructing from the two strands two double-strand molecules.

2. A kit as defined in claim 1, wherein said lower supporting elements comprise tightly-coiled vertical springs to be received in sockets in the lowermost chips of the molecular strands, and wherein said upper supporting elements are in the form of openings to receive pins in the uppermost chips of the molecular strands.

3. A kit as defined in claim 1, wherein the kit includes a frame having a horizontal beam supported by and over said common base, said horizontal beam including at least one opening therethrough; and wherein said plurality of upper supporting elements are carried on a horizontal bar having a vertical arm passing through said opening in the horizontal beam of the supporting frame, said vertical arm being rotatable in said opening to apply the twist to the molecular strands and being fixable in a predetermined position within the opening to fix the twist in the molecular strands.

4. A kit as defined in claim 3, wherein said horizontal beam of the supporting frame includes three equally-spaced openings, and said kit includes at least two of said horizontal bars, the middle opening in the beam being used for receiving the vertical arm of one horizontal bar to construct the double-strand molecule, and the remaining two openings in the beam being used for receiving the vertical arms of two horizontal bars to construct the two double-strand molecules when demonstrating replication by mitosis.

5. A kit as defined in claim 1 for constructing a DNA (deoxyribonucleic acid) molecule, wherein said plurality of groups of chips designate components of the DNA molecule and include a group of S-chips each designating the sugar chain, a group of P-chips each designating the phosphate chain, a group of T-chips each designating the thymine base, a group of C-chips each designating the cytosine base, a group of A-chips each designating the adenine base, and a group of G-chips each designating the guanine base; the S-chips and the P-chips including first interlocking connectors enabling a P-chip to be attached at either end of an S-chip and to be pivoted with respect thereto along a first pivotable axis extending lengthwise of the S-chip; the S-chip and the four base-chips including second interlocking connectors enabling any one of the base-chips to be attached at one end thereof to a mid-portion of the S-chip and to be pivoted with respect thereto along a second pivotable axis extending widthwise of the S-chip and at right angles to said first pivotable axis; the four base-chips including third interlocking connectors at their ends opposite to said one end thereof enabling said opposite end of a T-chip to be attached to an A-chip, and said opposite end of a C-chip to be attached to a G-chip.

6. A kit as defined in claim 5, wherein said first interlocking pivotable connections comprise sockets formed at both ends of the S-chips and adapted to receive pins carried at both ends of the P-chips.

7. A kit as defined in claim 5, wherein said second interlocking pivotable connection comprise further sockets formed in said mid-portion of the S-chips adapted to receive pins carried at said one end of each of the four base chips.

8. A kit as defined in claim 5, wherein said third interlocking connections comprise two pins each terminating in a ball carried at said opposite ends of the T-chips and A-chips, and three pins each terminating in a ball carried at said opposite ends of the C-chips and G-chips.

9. A kit as defined in claim 5, wherein the S-chips are each formed with two opposed short sides joined at one end by a long straight side at right angles to the opposed short sides, and joined at the opposite end by two further sides forming an obtuse angle juncture with each other at said mid-portion of the S-chip, said first interlocking connectors of the S-chips being at said opposed short sides, and said second interlocking connectors of the S-chips being at said obtuse angle juncture.

10. A kit as defined in claim 9 wherein said P-chips are each in the form of a square; said T-chips and C-chips are each in the form of a hexagon; and said A-chips and G-chips are each in the form of a hexagon joined at one side to a pentagon.