Pleiotropy - class-XII

Pleiotropy occurs when one gene will code and control the phenotype or expression of several different and unrelated traits. Phenylketonuria is an autosomal recessive disorder controlled by a mutant gene present on the 12th chromosome. This mutant gene fails to code for the enzyme phenylalanine hydroxylase required for normal metabolism of amino acid phenylalanine to tyrosine. Due to this, there is an accumulation of phenylalanine in body fluids such as blood, sweat, CSF. An abnormal breakdown product phenyl ketone is found in urine A higher level of phenylalanine and pheylketone cause severe brain damage leading to mental retardation. Thus phenylketonuria is the best example to explain pleiotropy.

In Drosophila, the vestigial gene is a classic example of pleiotropy, affecting not only wing size but also haltere size, bristle orientation, and reproductive fitness.

Mutations in the human gene for fibrillin-1 (FBN1) in the Marfan syndrome and related disorders. Mutations in FBN1 produce Marfan syndrome, a pleiotropic autosomal dominant connective tissue disorder with prominent manifestations in the skeleton, eye and cardiovascular system.

When there are three or more alternative forms of a gene, it is called multiple allelism. Polygeny suggests that humans evolved from several different ancestors. When a single gene has more than one effects, it is called pleiotropy.

Pleiotropy occurs when one gene influences two or more unrelated phenotypic traits. So, pleitrophy cannot play a role in gene controlling starch synthesis.

Though Mendel through his experiments showcased inheritance of a trait as genetic, some traits results from the combined effect of more than one pair of genes. Contrary to this, a single gene may also be responsible for a variety of traits. This phenomenon is called pleiotropy.

The ability of a gene to produce more than one phenotype in an organism is called Pleoitrophy and the genes are called Pleiotripic genes. It is not essential that the traits are equally influenced. Sometimes, the effect of the gene is more evident in case of one trait and less evident in case of another trait.

So,
the correct option is ‘Pleiotropic gene’.

The ability of a gene to have multiple phenotypic effects is known as pleiotropy and the genes are called Pleiotropic genes. These genes influence the number of characters simultaneously. These genes are present on same loci on two homologous chromosomes and produce different phenotypes.

So, the correct option is ‘Pleiotropic genes’.

The ability of a gene to produce more than one phenotype in an organism is called Pleoitrophy and the genes are called Pleiotripic genes. It is not essential that the traits are equally influenced. Sometimes, the effect of the gene is more evident in case of one trait and less evident in case of another trait.

So,
the correct option is ‘Affects more than one character’.

A.Codominant – appearance of genotypes of both parents in the progeny is called codominance.

B.Pleiotropic - The ability of a gene to have a multiple phenotypic effects is known as pleiotrophy and the gene is called Pleiotropic gene.

C.Epistatic - A gene which masks the action of another gene is termed as epistasis. The gene is called epistatic gene and the gene whose effect is masked is termed as hypostatic gene.

D.Supplementary - genes which include two pairs of non-allelic genes. Both of them are involved in affecting the same character. Out of the non-allelic genes, one gene is dominant and can express by itself. Second gene is also dominant but expresses only when it is supported by the presence of the first gene.

So,
the correct option is ‘Pleiotropic’.

The ability of a gene to have a multiple phenotypic effects is known as pleiotrophy and the gene is called Pleiotropic gene.

So,
the correct option is ‘Pleiotrophy’.

• Pleiotropy occurs when one gene influences two or more seemingly unrelated phenotypic traits. 
• Such a gene that exhibits multiple phenotypic expression is called a pleiotropic gene.
• So, (A) is the correct answer.

Phenylketonuria is a recessive autosomal disorder related to phenylalanine metabolism. It is controlled by a single gene having  multiple phenotypes. So it is a pleiotrophy. This disorder is due to the absence of a liver enzyme phenylalanine hydroxylase. Due to the lack of this enzyme, phenylalanine follows another pathway and gets converted into phenyl pyruvic acid. This phenyl pyruvic acid upon accumulation in joints causes arthritis. If it hits the brain, it causes mental  retardation known as phenyl pyruvic idiocy.

So,
the correct option is ‘Pleiotrophy’

The ability of a gene to have a multiple phenotypic effects is known as pleiotrophy and the gene is called Pleiotropic gene and the inheritance is called Pleiotropic inheritance. In Drosophila, a gene is responsible in controlling the colour of the eye and depigmentation of body parts. It is a pleiotropic gene.

So,
the correct option is ‘Pleiotropic gene’.

a)Dominance – In a heterozygous organism only one allele express itself

b)Codominance – in a heterozygous organism both alleles express themselves fully

c)Pleiotrophy – A single gene influences many characters.

d)Polygenic inheritance – Many genes govern a single character.

So,
the correct option is ‘a-ii b-iii c-iv d-I’.

A.Sickel cell anaemia – Pleiotropic alleles

B.Cystic fibrosis – Pleiotropic alleles

C.Phenylketonuria – it is autosomal recessive disorder.

D.Erythroblastosis foetalis – It is also called hemolytic disease of the newborn, type of anemia in which the red blood cells (erythrocytes) of a foetus are destroyed in a maternal immune reaction resulting from a blood group incompatibility between the foetus and its mother.

So, the correct option is ‘Erythroblastosis foetalis’.

A.Complmentary genes - Two genes present on separate loci that interact together to produce a dominant phenotype is called Complementary gene.

B.Pseudogenes – Genomic DNA sequences similar to normal genes but non-functional; they are regarded as defunct relatives of functional genes.

C.Pleiotrophic genes - The ability of a gene to have a multiple phenotypic effects is known as pleiotrophy and the gene is called Pleiotropic gene and the inheritance is called Pleiotropic inheritance. Eg:Sickle cell anaemia.

D.Cistrons – Functional parts of the DNA is called Cistron.

So,
the correct option is ‘Pleiotropic genes’.

The ability of a gene to have multiple phenotypic effects or as it influences a number of characters simultaneously is pleiotrophy and the genes are called Pleiotropic genes.

So,
the correct option ‘Multiple phenotypes’.

The ability of a gene to have a multiple phenotypic effects is known as pleiotrophy and the gene is called Pleiotropic gene and the inheritance is called Pleiotropic inheritance.

eg:Sickel cell anaemia

So,
the correct option is ‘sickle cell anaemia’.

The gene having multiple phenotypic effects is called pleiotropic genes. Eg: Sickel cell anaemia. This is caused by a gene HbS. When it is a homozygous condition, sickle cell anaemia occurs or if it is in the homozygous condition, act as a carrier.

So, the correct option is 'Hb^S’