D
Cos Dna contains deoxyribose, Rna ribose
Gravity increases as mass increases.
Gravity decreases when distance decreases
Answer:
(a) crossing over: Meiosis I, Recombination
(b) chromatids separate at their centromeres and migrate to opposite poles: Meiosis II, Anaphase II
(c) chromosomes become aligned in pairs at the equator: Meiosis II, Metaphase II
Explanation:
Homologous recombination is a type of genetic recombination that occurs during meiosis (formation of ovum and sperm cells). The paired chromosomes of the male and female parents are aligned so that similar DNA sequences intersect. This crossing over produces an exchange of genetic material, which is an important cause of the genetic variability observed in the offspring.
Meiosis II: Anaphase II. The centromeres separate and the daughter chromatids - now individual chromosomes - move to the opposite poles of the cell. The centromeres separate, and the two chromatids of each chromosome move toward the opposite poles in the spindle.
Meiosis II: Metaphase II. Chromosomes are accommodated in the equatorial plate of metaphase, similar to what happens in mitosis. They are attached to the already fully formed meiotic spindle. Each chromosome is aligned in the equatorial plate of the metaphase, as it happens in mitosis.
Answer:
Estrogen and progesterone are both involved in preparing the endometrium for embryo implantation. Estrogen helps to ensure conception by increasing the amount of secretory glands in the uterus. Estrogen also increases blood supply to the endometrium.
Progesterone is crucial for embryo implantation and maintenance of pregnancy. Progesterone also enlarges secretory glands that produce carbohydrates, proteins and mucin that are required for embryo nourishment before implantation. Progesterone stabilizes endometrial muscles to prevent them from contracting during pregnancy.
Explanation:
- Estrogen and progesterone are steroid hormones of the reproductive system. Estrogen helps in conception whereas progesterone maintains pregnancy.
- Estrogen is secreted during the follicular phase of the menstrual cycle that promotes the growth and maturation of follicles in the ovary.
- Estrogen also induces oestrous behavior in females.
- Secreted by the corpus luteum, progesterone is also a steroid hormone, responsible for implantation of the embryo in the uterus.
