Explanation
The traits that Mendel studied are listed below:
It may be used to establish the genotype of an individual with the dominant phenotype.
e.g: Genotype could be AA or Aa so crossing with aa will give us different results.
AA x aa = All Aa (All one phenotype)
Aa x aa = 1 Aa: 1 aa (half one phenotype, half other)
The appearance of the recessive phenotype in the offspring of a test cross indicates that the unknown genotype was heterozygous.
A test cross can also occur with 2 or more genes involved.
Mendel did not know about genes or discover genes, but he did speculate that there were two factors for each basic trait and that one factor was inherited from each parent.
We now know that Mendel's inheritance factors are 'genes', more specifically 'alleles', different variants of the same gene.
Olins and Olins discovered nucleosomes. A nucleosome is a basic unit of DNA packaging in eukaryotes, consisting of a segment of DNA wound in sequence around eight histone protein cores. This structure is often compared to thread wrapped around a spool. Nucleosomes form the fundamental repeating units of eukaryotic chromatin, which is used to pack the large eukaryotic genomes into the nucleus while still ensuring appropriate access to it.
Mendel picked pea plants for his experiment. The reasons for the selection of pea plants for the genetic experiments are: 1) Easy to grow in the garden.2) Pea plants can be self-fertilized (easy to obtain pure breed plants).3) The generation time of pea plants is less. 4) Pea plants have easily identifiable traits.Thus, the correct answer is option D.
Klinefelter syndrome is a condition related to the X and Y chromosomes (the sex chromosomes). People typically have two sex chromosomes in each cell: females have two X chromosomes (46, XX), and males have one X and one Y chromosome (46, XY). Most often, Klinefelter syndrome results from the presence of one extra copy of the X chromosome in each cell (47, XXY). Extra copies of genes on the X chromosome interfere with male sexual development, often preventing the testes from functioning normally and reducing the levels of testosterone. Most people with an extra X chromosome have the features described above, although some have few or no associated signs and symptoms. Some people with features of Klinefelter syndrome have more than one extra sex chromosome in each cell (for example, 48, XXXY or 49, XXXXY). These conditions, which are often called variants of Klinefelter syndrome, tend to cause more severe signs and symptoms than classic Klinefelter syndrome. In addition to affecting male sexual development, variants of Klinefelter syndrome are associated with intellectual disability, distinctive facial features, skeletal abnormalities, poor coordination, and severe problems with speech. As the number of extra sex chromosomes increases, so does the risk of these health problems. Some people with features of Klinefelter syndrome have the extra X chromosome in only some of their cells; in these individuals, the condition is described as mosaic Klinefelter syndrome (46, XY/ 47, XXY). Individuals with mosaic Klinefelter syndrome may have milder signs and symptoms, depending on how many cells have an additional X chromosome.
$$\bullet$$ Sex-linked disorders are any disorders or abnormality that is determined by the sex chromosomes and are generally recessive in nature.
$$\bullet$$ X-linked recessive diseases usually occur in males. Males have only one X chromosome. A single recessive gene on that X chromosome will cause the disease.
$$\bullet$$ Diseases such as haemophilia are the sex linked disease and occur from a recessive gene on the X chromosome.
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