Answer:
These include your skin, tears, mucus, cilia, stomach acid, urine flow, 'friendly' bacteria and white blood cells called neutrophils. Pathogenic (disease-causing) microorganisms must make it past this first line of defence. If this defence is broken, the second line of defence within your body is activated.
Explanation:
1) Four Helixes in a double chromosome [ 2 for each strand ]
2) Centromere is t<span>he region of a chromosome to which the microtubules of the spindle attach, via the kinetochore, during cell division.
3) </span><span>A </span>homologous pair<span> is a </span>pair<span> of chromosomes containing a maternal and paternal chromatid joined to together at the centromere
4) End result = 12 pair of chromosome which is unindentical to each other.
5) Crossing over is </span><span>the exchange of genes between homologous chromosomes, resulting in a mixture of parental characteristics in offspring.
Crossing over occurs during prophase I in nucleus of the cell [ as it is operation of chromosomes ]
</span>Crossing over<span> creates new combinations of genes in the gametes that are not found in either parent, contributing to genetic diversity. So, it is so important for Genetic diversity
</span>
Hope this helps!
