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What contribute to the success of Mendel ?
Consideration of one character with two contrasting conditions at one time contributed to Mendel's success in proposing the laws of inheritance of traits. His choice of experimental plant as pea and use of statistical methods also contributed to his success.
Haploids are able to express both recessive and dominant alleles/mutations because there are
In haploid organisms every gene, irrespective of dominant or recessive and every mutation finds expression because there is only one allele for each gene in the haploid individual. Recessive allele is able to express as there is no alternative dominant allele for producing its masking effect on recessive allele.
A mother in a family of five daughters is expecting her sixth baby. The chance of its being a son is
Humans have 22 pairs of autosomes and 1 pair of sex chromosomes which are XX in females and XY in males. So, everytime the chances of son or daughter is 50-50% depending upon which sex chromosome is contributed by father in sperm.
Mutations used in agriculture are commonly
Induced mutations are produced in response to external factors of chemicals called mutagens. In agriculture mutagens are used to induce desired mutations in crop plants.
Diploid chromosome number in humans is
Chromosomes occur in homologous pairs. Somatic cells have diploid number of chromosomes. Humans have 23 pairs i.e. 46 chromosomes. 22 pairs of autosomes and 1 pair of sex chromosomes ie. XX in females and XY in males.
Two linked genes a and b show 20 % recombination. The individuals of a dihybrid cross between + +/ + + × ab/ab shall show gametes
Two linked genes a and b show 20% recombination. The individuals of a dihybrid cross between + + / + + × ab/ ab shall show gametes + + 40 : ab40: + a 10 : +b : 10.
Triticale has been evolved by intergeneric hybridization between
Triticale is a man made cereale produced by crossing two generate wheat (Triticum) and rye (Secale). Hexaploid Triticale was obtained by crossing Triticum durum and Secale cereale.
A normal green male maize is crossed with albino female. The progeny is albino because
Besides nucleus some genes are also present in the cytoplasm of the female parent, these genes are called plasmogenes. In the given example the progeny is albino because of inheritance of plastids from female parent.
tt mates with Tt. What will be characteristic of offspring ?
On mating tt with Tt, 50% individual offsprings are recessive and 50% are heterozygous dominant.
ABO blood group system is due to
A gene may have more than two alternative forms occupying the same locus on a chromosome such alleles are known as multiple alleles and the phenomenon is turned as multiple allelism. ABO blood group has 3 alleles. IO, IA or A, IB or B.
In a genetic cross having recessive epistasis, F2 phenotypic ratio would be
In recessive epistasis, the recessive alleles suppress the expression of a trait. Recessive epistasis is a type of intergenic interaction in which one non allelic gene can produce its effect independently in the dominant state but second gene can produce its effect when they are present together. Here homozygous recessive allele for a gene mask the expression of dominant allele of another gene.
Cross between AaBB and aaBB will form
AaBB × aaBB on crossing gives 50% individuals having genotype AaBB and 50% individuals having genotype aaBB.
An octamer of 4 histones complexed with DNA forms
Nucleosomes are oblate spherical structure having an octamer of four histone proteins (constituting 2 molecules of each type).
Both husband and wife have normal vision though their fathers were colour blind. The probability of their daughter becoming colour blind is
The probability of the daughter becoming colour blind arises only when the father is also colour blind.
Husband – XY Wife – XXC (wife is carrier because her father is colour blind)
So, probability of their daughter becoming colour blind is 0%.
Which one is a hereditary disease ?
Phenylketonuria is a human genetic disorder in which the body does not contain the enzyme phenylalanine hydroxylase, necessary to metabolize phenylalanine to tyrosine, and converts phenylalanine instead to phenylpyruvic acid. As PKU is an autosomal recessive genetic disorder each parent must have at least one defective allele of the gene for PAH, and the child must inherit a defective allele from each parent. As such, it is possible for a parent with a PKU phenotype to have a child without PKU if the other parent possesses at least one functional allele of the gene for PAH. A child of two parents with the PKU phenotype will always receive two defective alleles so will always have PKU. The gene for PAH is located on chromosome 12, at location 12q22-q24.2.
Haemophilia is more common in males because it is a
Haemophilia is a sex linked recessive trait carried by X chromosome (also known as bleeder’s disease).
Bateson used the terms coupling and repulsion for linkage and crossing over. Name the correct parent of coupling type alongwith its cross repulsion
Bateson and Punnett (1906) discovered coupling and repulsion in sweet pea (Lathyrus odoratus).
In Down’s syndrome of a male child, the sex complement is
Down’s syndrome is due to trisomy of 21st chromosome and is an autosomal abnormality.
Red (RR) Antirrhinum is crossed with white (WW) one. Offspring RW are pink. This is an example of
Incomplete dominance is the phenomenon of none of the alleles being dominant, with the effect that the hybrid produced by crossing two pure individuals is a mixture between the parents.
The allele which is unable to express its effect in the presence of another is called
The allele which can not impressits effect in the hybrid or in the presence of dominant allele is termed as recessive. It is denoted by small letter.
Blue eye colour is recessive to brown eye colour. A brown eyed man whose mother was blue eyed marries a blue-eyed women. The children shall be
The brown eyed man will have the genotype Bb and his wife bb. Hence Bb × bb = Bb : bb. Hence ratio is 1 : 1.
A dihybrid condition is
Dihybrid condition involves simultaneous inheritance of two pairs of mendelian factors or genes.
Mendel’s last law is
According to the law of Independent Assortment, alleles of different characters located in different pairs of homologous chromosomes are independent of one another in their separation or segregation during gamete formation.
First geneticist/ father of genetics was
Gregor Johann Mendel formulated the laws of heredity and is regarded as the father of genetics.
The contrasting pairs of factors in Mendelian crosses are called
Two allelomorphs are the different forms of a gene which are responsible for different expression of same characters, e.g. for colour of flower is R and r.