Answer:
The final product is four gametes, two of them with 5 chromosomes, and the other two with 3 chromosomes each.
Explanation:
If nondisjunction occurs during meiosis 1, a pair of homologous chromosomes fail to separate, and one of the daughter cells will have the two chromosomes while the other cell will not get any chromosome from the pair.
If meiosis 1 occurs normally, but nondisjunction occurs in meiosis 2, sister chromatids fail to separate.
The usual process of meiosis produces four daughter haploid cells (n) from a diploid germ cell (2n). Each daughter cell is haploid because they have half the number of chromosomes of the original one.
If the diploid number of the original cell is 8 (2n=8), then under normal conditions, each haploid daughter cell should have 4 chromosomes (n = 4).
But in the exposed example, one pair of homologous chromosomes experiences nondisjunction during meiosis I (in the attached file, you will recognize this pair as the red one). The other chromosomes separate as usual. So one of the daughter cells will have one extra chromosome than expected (five instead of four), and the other daughter cell will lack one chromosome (three instead of four). Meiosis II occurs normally. The final result is the formation of four gametes, two of them with 5 chromosomes, and the other two with 3 chromosomes each.
Answer:
a. Heterozygous individuals may pass on their copy of the disease-causing allele to offspring.
Explanation:
Tay-Sachs, which is a recessive lethal disease ---- Let say the recessive lethal diseases is s
∴ it only results when an individual posses two copies of the diseases-causing allele i.e two copies of the disease will be ss.
Now, when two hetrozygous individuals crossed , it is obvious that each can pass on their copy of the disease-causing allele to the offspring.
Let show an illustration for the above statement.
Let the heterozygous individual be Ts, if Ts cross with another Ts;
we will have:
Ts × Ts
T s
T TT Ts
s Ts ss
the offspring are TT,Ts,Ts,ss
We can now see how the Heterozygous individuals pass on their copy of the disease-causing allele to the offspring (Ts).
Answer:
Adaptive immune defense system consists of lymphocytes like B-lymphocytes and T- lymphocytes. B-lymphocytes provides humoral immunity while T- lymphocytes provide cell-mediated immunity to the body.
99% of lymphocytes circulate freely in the blood and lymph. B lymphocytes differentiate into plasma B cells and B memory cells when interact with antigen presented by T helper cells.
Then plasma cells secrete antibodies in the circulation which binds to extracellular antigens through antigen-binding site. Then the bounded antigen is recognized by receptors present on phagocytic cells. This receptor binds the Fc region of antigen bounded antibody and destroy the antigen by phagocytosis.