Crossing over is a process that produces new combinations (recombinations) of genes by interchanging and exhanging of corresponding segments between non-sister chromatids of homologous chromosomes. It occurs during pachytene of prophase I of meiosis. The term crossing over was coined by Morgan. The mechanism of crossing over consists four sequential steps such as synapsis, tetrad … Read more
Allosomes are the chromosomes that are responsible for determination of sex (gender). In humans, they are typically denoted as X and Y chromosomes, with females having two X chromosomes (XX) and males having one X and one Y chromosome (XY).
The cross of F1 hybrid with the homozygous recessive parent is known as a test cross. It is used to test whether an individual is homozygous (pure) or heterozygous (hybrid). Test cross is easy, simple, repeatable and predictable.
An individual possessing contrasting alleles for a particular trait, is called heterozygous. Heterozygous does not breed true for that trait and produces two types of gametes e.g. F1 generation hybrids (Tt). Heterozygous individual is also called hybrid.
An individual possessing identical allels for a particular trait, is called homozygous or pure for that trait. Homozygous breeds true to the trait and produces only one type of gametes e.g., tall with TT and dwarf with tt.
A cross between parents differing in two heritable traits, is called dihybrid cross e.g. cross of pure tall, round seeded plant with dwarf, wrinkled seeded plant.
Mendel’s “Law of dominance is not universal” reflects the complexities in genetic inheritance. Real-world genetics presents instances like co-dominance and incomplete dominance, where alleles don’t strictly adhere to dominance or recessiveness. These exceptions add shade to visible outcomes, challenging the simplicity of Mendelian principles. The dynamic interplay of alleles in these scenarios reveals a spectrum … Read more
The concept “Test cross is a back cross, but a back cross is not necessarily a test cross” highlights differences in genetic approaches. A test cross unveils genotype by breeding with a homozygous recessive individual. It observes phenotypic ratios in offspring. A back cross mates an organism with a parent or a genetically similar individual. … Read more
After syngamy, the zygote becomes active and starts dividing. 1. Cleavage: Cleavage is the initial mitotic division of the zygote, forming a hollow multicellular blastula. Blastomeres, the cells produced, decrease in size with each cleavage due to the absence of a growth phase. As size reduces, metabolic rates increase, leading to faster successive cleavages. This demands … Read more
Fertilization is the amazing process of combining male and female gametes to form a diploid zygote, crucial for human reproduction. This complex event usually happens in the ampulla of the fallopian or uterine tube, paving the way for the embryo’s development in the protective environment of the uterus. Sperm Movement towards Egg: The journey commences … Read more