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A and B genes are linked what shall be genotype of progeny in a cross between AB/ab and ab/ab?
Parents : AB/ab × ab/ab
In humans, male XXY and female XXXX occur due to
Aneuploidy is numerical change in the chromosome number in the genome. Euploidy is the phenomenon of having multiple or more than twice the number of genome.
No. of barr body present in each somatic cell of a female is
One bar body is present in each somatic cell of female (XX).
Which of the following is correct match?
Sickle cell anaemia is a genetic disorder caused by a defective allele on chromosome 11. Hemophilia is a sex linked recessive disorder. Down's syndrome is caused by trisomy of the 21st chromosome.
Which of the following is an example of sex linked disease?
AIDS is a viral disease. Syphilis and gonorrhoea are both sexually transmitted diseases. Colour blindness is a sex linked disease.
Which of the following is an example of pleiotropic effect?
A gene is said to be dominant if
A dominant gene would lead to the expression of its phenotype irrespective of the fact whether its allelic gene is dominant or recessive.
A diseased man marries a normal woman. They have three daughters and five sons. All the daughters were diseased and sons were normal. The gene of this disease is
Sex linked disorders follow criss-cross inheritance pattern that affected father passes it on to their daughters. The daughters receive one of their X - chromosome from their fathers.
On selfing a plant of F1 generation with genotype “AABbCC”,the genotypic ratio in F2 generation will be
There are three genes a, b, c. Percentage of crossing over between a and b is 20%, b and c is 28% an a and c is 8%. What is the sequence of genes on chromosome?
a − b = 20 %, b − c = 28 %, a − c = 8%
Percent crossing over between two genes is proportional to the distance between them.
In Drosophila, the sex is determined by
Calvin Bridges demonstrated that in Drosophila, the sex is determined by ratio of the number of X chromosomes to the sets of autosomes.
Genes for cytoplasmic male sterility in plants are generally located in
Male sterility in plants can be controlled by nuclear genes or cytoplasm or by both. Three different mechanisms for control of male sterility in plants are :
(i) Genetic male sterility;
(ii) Cytoplasmic male sterility;
(iii) Cytoplasmic genetic male sterility. In Maize the genes for cytoplasmic control of male sterility are located in cytoplasm.
Nicotiana sylvestris flowers only during long days and N. tabacum flowers only during short days. If raised in the laboratory under different photoperiods, they can be induced to flower at the same time and can be cross fertilized to produce self – fertile offspring. What is the best reason for considering N. sylvestris and N. tabacum to be separate species ?
Correct option is
They cannot interbreed in nature.
The term species evolves from word specific means only those group of plants or animals come under one species which can interbreed and produce fertile offsprings naturally. N. tobacum and N. sylvestris cannot produce flowers naturally have different photoperiods, hence they cannot belong to the same species. Thus the correct answer is 'They can not interbreed in nature.'
Which one of the following traits of garden pea studied by Mendel was a recessive feature ?
Yellow seed colour is dominant over green seed colour.
The genes controlling the seven pea characters studied by Mendel are now known to be located on how many different chromosomes ?
The seventraits are now know to be present on 4 chromosome. But they do not show linkage, because of large distances between them on the chromosome.
Two crosses between the same pair of genotypes or phenotypes in which the source of the gametes are reversed in one cross, is known as
Dihybrid cross is made between individuals having contrasting traits in order to study the inheritance of two pairs of alleles. Test cross is a back cross between individual with a dominant trait and its recessive parent to know whether the individual is homozygous or heterozygous for the trait.
The linkage map of X-chromosome of fruit fly has 66 units, with yellow body gene (y) at one end and bobbed hair (b) gene at the other end. The recombination frequency between these two genes (y and b) should be
Mapping of genes on chromosomes is based on the assumption that genes are arranged on the chromosome and that the percentage of crossing over (recombination frequency) between two genes is an index of their distance apart. Distances between genes is expressed as map units, where, one map unit
Christmas disease is another name for
Pattern baldness, moustaches and beard in human males are examples of
Traits or characters which develop only in one sex are called sex-limited characters. They are produced and controlled by the genes which may be located on autosomes in only one sex, eg. Moustaches and beards in human males, breast in human females, milk secretion in human females.
Down's syndrome is caused by an extra copy of chromosome number 21. What percentage of offspring produced by an affected mother and a normal father would be affected by this disorder?
50% of ova will have (n + 1) chromosome which would, on fertilisation, yield abnormal zygotes (n + 1) + (n) = 2n + 1.
Lack of independent assortment of two genes A and B in fruit fly Drosophila is due to
The lack of inde pendent assor tment in sweet pea and Drosophila is due to linkage.
The recessive genes located on X-chromosome in humans are always
Males have only one X - chromosome. Hence any gene present on the lone X - chromosome expresses itself in males. Females have two X- chromosomes . The mutant allele must be present on both the X-Chromosomes to express itself phenotypically. If only one copy of allele present, then the female only becomes a carrier showing no external manifestation of the gene. Sublethal condition can never arise in males.
A male human is heterozygous for autosomal genes A and B and is also hemizygous for hemophilic gene h. What proportion of his sperms will be abh?
Chance of getting a = 1/2
Chance of getting b = 1/2
Chance of getting h = 1/2
Chance of getting sperms with
A normal woman, whose father was colourblind is married to a normal man. The sons would be
Normal woman with colour blind father would be a carrier
50% of the sons would be colour blind.
One of the parents of a cross has a mutation in its mitochondria. In that cross, that parent is taken as a male. During segregation of F2 progenies that mutation is found in
Mitochondria is an organelle present in the cytoplasm. A zygote receives its cytoplasm from the female parent gamete. Hence in the given question, the F2 progenies do not receive the mitochondrial genome from the male parent and mutation is not passed to progenies.