B. Is the correct answer.
1. The main aim of the Human Genome Project was to determine the DNA Sequence of every human gene.
2. Variation in skin colour is an example of polygenic inheritance
This Human Karyotype is unusual because it has an extra chromosome at chromosome 21.
Klinefelters syndrome is shown in the second figure
Explanation:
1. The Human Genome Project's main goal was to sequence all the 30,000 genes and 3 million base pairs in their makeup for the early detection of diseases, gene therapy and molecular level studies.
2. Human skin colour is determined by the pigment melanin. The Dominant allele is responsible for dark colours as it produces more melanin. The melanocortin 1 receptor (MC1R) gene and Tyrosinase enzyme codes for the human skin colour. Polygenic inheritance are the traits which are controlled by one or more genes.
<u>figures:</u>
<u>The extra chro</u>mosome at the 21st chromosome pairs is called trisomy 21 or Down's Syndrome. It is due to the abnormal cell division/meiosis resulting in an extra X chromosome. This leads to thechanges the in physical development of the individual.
Klinefelter's Syndrome: There are 47 chromosomes and 2 or more X chromosomes in this syndrome of males. The resulting male suffering from Klinefelter would be sterile and have poorly developed testicles.
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.
The sun is the source for photosynthesis
