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In photosynthetic organisms, NADPH is produced by ferredoxin-NADP+ reductase in the last step of the electron chain of the light reactions of photosynthesis. It is used as reducing power for the biosynthetic reactions in the Calvin cycle to assimilate carbon dioxide.
Answer: C. Homologous chromosomes are separated in meiosis but not in mitosis.
Explanation: There are two main types of division that take place in eukaryotic cells, mitosis, and meiosis. Mitosis is the type of division that is used for growth, repair, and replacement of tissues. Therefore it is not necessary that the cells have different chromosome numbers or are varied genetically in the daughter cells in the case of mitosis.
Meiosis is the division that takes place to form the gametes for sexual reproduction. It is important in the first stages of meiosis I, to introduce variation and to halve the chromosome number.
Chromosomes numbers are halved (from 46 to 23) during meiosis I because the gametes (sperm and egg) come together and fuse during fertilization to form a zygote. When this fusion occurs (23 from the zygote and 23 from the egg), the chromosome number needs to be returned to that of the parent cell (46).
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Genetic variation is introduced during synapsis which only occurs in meiosis, not mitosis. Homologs exchange genetic information during crossing over of synapsis. Entire chromosomes also separate during meiosis I.
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At the end of meiosis, four genetically unique cells are produced with half the number of chromosomes as the parent cell (23 cromosomes) . After the process of mitosis is completed, two cells genetically identical to each pther are produced and have the same number of chromosomes as the parent cell (46 cromosomes).
Genetic variation is actually important because of changing environmental conditions.
Answer:
1) In the first step, we need to predict the possible alleles for the cross. The dominant allele will be written with a capital letter. The recessive allele will be written with a small letter. Hence, the allele for brown hair colour will be B and the allele for red hair colour will be b.
2) In the second step, we need to determine the genotype of the parents. The genotype of the homozygous dominant parent will be BB. The genotype of the heterozygous brown hair colour will be Bb.
3) The punnet square for cross between these parents can be shown as follows:
B b
B BB Bb
B BB Bb
4) In the fourth step, lets determine the phenotype of the children. The phenotype of all the offsprings born will be brown hair colour.
5) The genotype from the punnet square shows that there is a 50% chance that the offsprings will be heterozygous dominant (Bb) for brown hair colour and their will be a 50% chance that the child born will be homozygous dominant (BB).
