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A woman with two genes for haemophilia and a gene for colour blindness on one of the 'X' chromosomes marries a normal man. How will the progeny be
Albinism is known to be due to an autosomal recessive mutation. The first child of a couple with normal skin pigmentation was an albino. What is the probability that their second child will also be an albino? [
A child will be albino only if it is homozygous for albinism genes (since albinism is a recessive character). As parents have normal skin, it means they are hetrozygous. As a result of cross between two heterozygous parents, 25% of the children will be homozygous recessive. The nature of the second child is not affected in any way by the nature of the first child because both are independent events.
Crossing over in diploid organism is responsible for
Crossing over involves physical exchange of genetic material between non sister chromatids of homologous chromosomes, which leads to recombination.
How many genome types are present in a typical green plant cell?
Three types of genome, occur in a typical green plant cell - nuclear genome, mitochondrial genome and chloroplast genome.
If Mendel had studied the 7 traits using a plant with 12 chromosomes instead of 14, in what way would his interpretation have been different ?
If Mendel had studied a plant with 12 chromosomes, he would have encountered linked genes, and hence he would not have arrived at principle of independent assortment
How many different types of genetically different gametes will be produced by a heterozygous plant having the genotype : AABbCc?
Different types of gametes produced will be ABC, AbC, ABc, Abc
Molecular weight of chromosome of yeast cell is
Molecular weight of chromosome of yeast cell is 2.56 × 109.
Which of the following is the main category of mutation?
Somatic mutation is the mutation occurring in somatic or body cells. Mutations occurring in germ cells which are transferable to the progeny is called germinal mutation. Mutation occuring in genes is called genetic mutation.
In hybridisation Tt × tt gives rise to the progeny of ratio
Phenomenon of ‘ Industrial melanism ’ demonstrates
During industrial revolution in England the frequency of melanic forms of species of Peppered Moth (Biston betularia) increased in polluted areas. Generally the moths are light coloured. This change in colour is known as "Industrial melanism". The change was presumed to be a result of natural selection since the melanic moths better matched the blackened tree trunks where they rest during day.
One child is haemophilic (sex-linked trait), while its fraternal twin brother is normal. Which one of the following informations is most appropriate?
The mother must have been a haemophilic carrier (XhX). One of the twins would have inherited the normal X chromosome and the other would have received the X chromosome carrying the gene for haemophilia.
Red-green colour blindness in humans is governed by a sex-linked recessive gene. A normal woman whose father was colour blind marries a colour blind man. What proportion of their daughters is expected to be colourblind?
Normal woman whose father was colour blind would have received the X will be chromosome from her father − XcY →
How many base pairs are found in one genome of man? 
The number of base pairs (bp) found in one genome of man is 3 × 109.
Drosophila flies with XXY genotype are females but in case of humans, such individuals are abnormal males (Klinefelter's syndrome). This indicates that
In human the Y chromosome bears the androgenic factor or the male determining factor. Whereas in Drosophila the ratio of sex chromosomes to autosomes is the factor determining sex of the individual.
Mongoloid idiocy in humans is also known as
Downs syndrome develops due to trisomy of the 21st chromosome. Affected individual possess a characteristic appearance. They have short stature, small round heads, broad forehead, open mouth and projecting lower lip (Mongoloid idiocy).
Which one pair of the following parents is most likely to get a child who suffer from hemolytic disease of new born?
Hemolytic disease of the newborn occurs when a Rh– mother conceives a Rh+ child. Mother’s blood starts producing antibodies against the foetal red blood cells.
Which character studied by Mendel in garden pea (Pisum sativum) was dominant
Round seed shape is dominant over wrinkled. Yellow seed colour is dominant over green seed colour Axial flower position is dominant over terminal.
In a certain plant, red fruit (R) is dominant over yellow fruit (r) and tallness (T) is dominant over shortness (t) .If a plant with RRTt genotype is crossed with a plant rrtt genotype , what will be the percentage of tall plants with red fruits in the progeny ?
Independent assortment of genes does not take place when
Independent assortment of genes takes place only when they are located on separate non-homologus chromosomes. Where two or more than two genes are located on same chromosome, independent assortment will not be possible.
When dominant and recessive alleles express itself together it is called 
According to principle of dominance, out of the two factors of alleles representing different traits of a character, only one expresses itself. But when both express themselves it is codominance.
Ratio of complementary genes
In complementary gene action, both the non allelic pair independently produce similar phenotypes and when present together produce a new phenotype. So, that F2 ratio 9 : 3 : 3 : 1 would become 9 : 7.
Forthcoming generation are less adaptive than their parental generation due to
Natural selection operates through differential reproduction. Genetic drift is random change in the allele number and frequency in a gene pool.
Extranuclear inheritance occurs in
In eukar yotic cells, two cytoplasmic organelles, mitochondria and chloroplast of green plants, contain their own genetic materials.
Two non-allelic genes produce new phenotype when present together but fail to do so independently are called?
Probability of four sons to a couple is