Awild-type trihybrid soybean plant is crossed to a pure-breeding soybean plant with the recessive phenotypes pale leaf l, oval seed (r), and short height (t). the results of the three-point test cross are shown in the table. traits not listed are wild type.

Pale - 648 - Parental

Pale, oval - 64 - Single recombinant (recombination between T and R)

Pale, short - 10 - Double recombinant

Pale, oval, short - 102 - Single recombinant (recombination between T and L )

Oval - 6 - Double recombinant

Oval, Short - 618 - Parental

Short - 84 - Single recombinant (recombination between T and R)

Wild type - 98 - Single recombinant (recombination between T and L )

Total 1630

A). From the given table, the genotype of the parents is lTR and Ltr. Double cross over gave rise to the offspring with the phenotypes oval and plale, short. Thus, the gene order is L-T-R.

B). The recombination fraction between T and L pair of genes. = number of gametes produced by single crossover of T and L + number of double crossover gametes*100/ total number of gametes.

= [(102+98) + (10+6)]* 100/ 1630 = 13.25 map units.

The genetic distance between genes T and L = 13.25 map units.

C). The recombination fraction between T and R pair of genes. = number of gametes produced by single crossover of T and R + number of double crossover gametes*100/ total number of gametes.

= [(64+84) + (10+6)]* 100/ 1630 = 10.06 map units.

The genetic distance between genes T and R = 10.06 map units.

fertilization, pictured in figure 24.23a is the process in which gametes (an egg and sperm) fuse to form a zygote. the egg and sperm each contain one set of chromosomes. to ensure that the offspring has only one complete diploid set of chromosomes, only one sperm must fuse with one egg. in mammals, the egg is protected by a layer of extracellular matrix consisting mainly of glycoproteins called the zona pellucida. when a sperm binds to the zona pellucida, a series of biochemical events, called the acrosomal reactions, take place. in placental mammals, the acrosome contains digestive enzymes that initiate the degradation of the glycoprotein matrix protecting the egg and allowing the sperm plasma membrane to fuse with the egg plasma membrane, as illustrated in figure 24.23b. the fusion of these two membranes creates an opening through which the sperm nucleus is transferred into the ovum. the nuclear membranes of the egg and sperm break down and the two haploid genomes condense to form a diploid genome.

explanation:

c

explanation: