Genetics and Cell Biology

It is described as a phase where the chromosomes at each pole uncoil and enlarges to form chromatin. Nucleolus and nuclear membrane are re- formed surrounding each chromatin network. Asters and spindle fibres disappear and centrioles divide. Daughter nuclei are formed.

He was an English geneticist. He is famed for first using the term genetics & explaining the study of heredity and biological inheritance.

This is described as the process when a segment of chromosome splits and relocates within a non- homologous chromosome.

This type of sex determination occurs in insects and mammals including human beings. Here, the females bear two identical homologous sex chromosomes designated as XX and the males bear two dissimilar sex chromosomes designated as X and Y. Thus, females are homogametic, producing only one type of ovum, and males are heterogametic, producing two types of gametes.

These are defined as the chromosomes which are found in the salivary gland cells of the fruitfly Drosophila. They are many times bigger than the normal chromosomes attaining a length of 2000 micro meters and are visible even under a compound microscope.

Here the centromere is located far away from the centre of the chromosome so that the two arms are highly unequal. The chromosome acquires the shape of 'J' during anaphase.

It leads to the new genetic combinations as a result of crossing over. This situation brings about variations.

Out of 64 codons, the two codons namely AUG and GUG are called the initiation codons as they begin the synthesis of polypeptide.

 It is described as the stage where each chromosome breaks into two chromatids forming four chromatids; two paternal and two maternal which are known as tetrads. Chiasma is the site of an exchange of genetic material between the two chromatids. It occurs due to breakage and reunion between the two non-sister chromatids. This process is called genetic recombination.

It is described as the 3' end of the tRNA. Here a particular amino acid gets associated. The tRNA molecule has a base triplet CCA with OH group at the tip. The COOH of amino acid conjoins the OH group.

It is defined as the step where the amino acid AMP-enzyme complex conjoins with the amino acid binding site of its specific tRNA, where its COOH group bonds with the OH group of the terminal base triplet CCA. This reaction is catalyzed by the same enzyme, aminoacyl tRNA synthetase.

It is described as the phase where chromosomes become short & visible as single structure. It contains the dense stained chromomeres.

Here DNA replication takes place. Protein molecules namely histones are synthesised and cover each DNA strand. 

Homozygous recessive is defined as a diploid carrying two copies of the recessive allele of the examined gene. Since the ability to taste PTC is a dominant allele, therefore this genotype will be least expressed by this person.

Because the child was born with dwarfism, the recessive alleles must be present in the parents.

The sickle cell is an example of a mutation that is beneficial when maintained in heterozygotes. When you are homozygous for the trait you get sickle cell anemia. When a person is heterozygous for the sickle cell gene they have some added protection from malaria.

Out of total progenies, 25 % will have O blood group. When both parents have blood types BO, then it is possible that they can produce a child of O blood group.

Since white flowers are the recessive traits in Pisum sativum, the genotype of the parents would be pp x pp, where P= gene for a purple flower and p= gene for a white flower. Because it is a recessive trait, both white flowered parents must be homozygous recessive. Therefore, all of their offsprings will also have white flowers, because that is the only gene available.

XXY is Klinefelter's syndome. It is described as an inequality in X chromosomes where a male (dubbed by inheriting a X chromosome) also inherits an extra X chromosome, giving them female qualities. This can include a more slender shape, more refined hips, breast development, absence of facial hair, etc.

The output of the genes is the phenotypic character which physically observed. Eye colour, skin colour, hair colour, earlobe shape, etc. are all phenotypic traits of an individual.

The random shuffling of homologous chromosomes is the process that causes the most variation. It is like taking the 46 chromosomes you have, and paring them together by like ones, and flipping a coin to see if the one you inherited from your mother or father will go with each gamete produced.

In the above question one parent is homozygous recessive, pp, while the other is heterozygous, Pp. With the help of Punnett square, you can see that half of the offspring will be homozygous, thus purple, and half will be white.

Since colour blindness is a recessive trait, men, who have only 1 copy of the X chromosome, will always be color blind if they inherit the defective gene. Women must inherit two defective copies in order to be color blind.

In genetics, knocking out a gene implies that particular gene would not be expressed. Altering the genotype of an individual normally alters the phenotype. For example, if you knocked out a particular gene and found out that the resulting fly has underdeveloped wings compared to the wild-type, it could suggest the gene has a role in embryonic wing development.

As per the question, by constructing the Punnet square for two heterozygous parents, you can observe that 25% will be homozygous dominant, 25% homozygous recessive, and 50% heterozygous. Thus, 75% will be purple.