most of the species reproduce sexually. in sexual reproduction, both male and female gametes are involved. in order to maintain the number of chromosomes in offsprings, sex cells in parents undergo meiosis, which reduces the chromosomal number to half. for instance, we take human sex cells with 46 chromosomes undergo miosis, and produce 4 haploid daughter cells having 23 chromosomes each.
now, the question is how meiosis reduces the chromosomal number to half.in meiosis’ different stages, homologous pair of chromosome and non-sister chromatids segregate,leaving daughter cells with only 23 chromosomes(half no. of chromosomes) known as gametes;male gamete=sperm,female gamete=ovum.
fusion of male and female gametes to form a zygote, is known as fertilization. when sperm fertilizes an egg, conception occurs in mother womb with a zygote having 46 chromosomes (receiving 23 chromosomes from each parent)which gradually develops into a fetus and then offspring not identical to parents but with the same no. of chromosomes as parents do have.
be produced by meosis.
simple, meiosis reduce the chromosome number in half while fertilization doubles the chromosome number. n=chromosome number meiosis = 2n (primordial germ cells) ----> n (sperm cell/egg cell/polar bodies) fertilization = sperm (n) + egg (n) ----> 2n (zygote)
its haploid. number of chromosome is reduced to half in meosis i.
the gamates each have half the number of chromosome in the species
the chromosome number doubles. 1 set from the egg, and 1 set from the sperm.
i don't know why don't you pay attention in class more
if the chromosome number was not reduced during meiosis, what would happen during fertilization is that the fetus would then have either an extra chromosome or have an extra chromosome. the resulting baby would then have some form of developmental problem.
before fertilisation it is 23 & afterwards it is 46.
why it is important to keep chromosome number consistent
it multiplies itself
it doubles (or goes from "n" to "2n", with "n" being the number of sets of chromosomes).
the zygote's number of chromosomes is double that of the two sex cells
the number of genes varies from chromosome to chromosome and the number of chromosomes varies from species to species (from as few as 1 single chromosome per cell to as many 30,000 chromosome pairs per cell). human cells have 23 chromosome pairs per cell.
meiosis is results in gametes (or sex cells) that have half the number of choromosomes as non-sex cells.this means that when fertilization occurs, each gamete is carrying half the number of chromosomes - so when they combine, you end up with the number of chormosomes found in somatic (non-sex) cells.
gametes, sex cells, are haploid because they make diploid zygotes. in sexual reproducing species, meiosis, the halving of chromosome number along sexual lines, male and female. is necessary so that when the sperm and egg meet in fertilization a proper chromosome number is maintained.
fertilization will never happen
the chromosome number is specific for each type of organism. the exact chromosome number must be maintained for the species to continue. this means that as cells reproduce, the new cells must have the same number of chromosomes as did the original cells
it is a reductional division so that at time of fertilization baby get half number of chromosome from the parents.
during mitosis the daughter cells receive the same number of chromosomes as in the parental cell. in meiosis the chromosomes are reduced by 1/2 and during fertilization it gets redoubled.
well if human chromosomes number 21 does not separate during fertilization the baby will be with down syndrome. at fertilization of the egg with a normal sperm the zygote contain three chromosome number 21 (trizomic 21) hence the zygote contain 47 chromosome instead of 46.
68 pairs .