Sex-linked diseases like hemophilia are often carried on the X chromosome. Males have only one X chromosome, so if they inherit the recessive allele on that X, they will express the disease. Females have two X chromosomes, so they must inherit two copies of the recessive allele (one on each X) to express the disease, making it less common for them to be affected.
More Questions on Heredity
1Briefly explain how DNA and chromosomes work together to store and transmit genetic information.
→ 2In a large, randomly mating population, if the allele frequencies for a particular gene remain constant from one generation to the next, what does this suggest about the evolutionary forces acting on that gene?
→ 3While not strictly a Class 10 topic, how would you briefly describe the concept that environmental factors can influence gene expression without changing the underlying DNA sequence, and its relevance to heredity?
→ 4In a family pedigree, a trait appears in every generation, and affected individuals always have at least one affected parent. It also affects males and females equally. What is the most likely mode of inheritance?
→ 5Many genetic disorders arise from a mutation in a gene that codes for an enzyme. How might this lead to the symptoms of the disorder?
→ 6If two genes A and B show 50% recombination frequency, what can be inferred about their location relative to each other?
→ 7Differentiate between complete dominance and incomplete dominance using an example for each.
→ 8How does meiosis contribute to maintaining the chromosome number across generations while also promoting genetic variation?
→ 9A weightlifter develops large, strong muscles through rigorous training. If this weightlifter has children, will their children automatically inherit these large muscles? Justify your answer.
→ 10Cystic fibrosis is an autosomal recessive genetic disorder. If two carrier parents (heterozygous) have children, what is the probability that their second child will be unaffected and not a carrier?
→ 11In Mendel's experiments, what did he call the first generation of offspring resulting from a cross between two true-breeding parents, and what did he call the generation resulting from self-pollinating these offspring?
→ 12Give two reasons why Gregor Mendel chose pea plants (Pisum sativum) for his experiments on heredity.
→ 13Arrange the following terms in increasing order of complexity: DNA, gene, chromosome, nucleotide.
→ 14While humans use the XX/XY system, some animals like birds use a ZW/ZZ system where females are ZW and males are ZZ. If a male bird mates with a female bird, which parent determines the sex of the offspring?
→ 15Genetic screening can identify carriers of certain genetic disorders. While beneficial, what is a potential ethical concern associated with widespread pre-natal genetic screening?
→ 16Apart from recombination during sexual reproduction, what is another significant source of new alleles and genetic variation in a population?
→ 17If a cross between two individuals results in offspring with a phenotypic ratio of approximately 3 dominant : 1 recessive for a single trait, what must be the genotypes of the parents?
→ 18Genes are located on chromosomes at specific positions. What is the term for this specific physical location of a gene on a chromosome?
→ 19Explain the difference between a homozygous and a heterozygous individual for a particular gene.
→ 20In humans, attached earlobes (a) are recessive to free earlobes (A). If a woman with attached earlobes marries a man who is heterozygous for free earlobes, what is the probability that their first child will have free earlobes?
→ 21A scientist is studying a population of butterflies where wing color is determined by a single gene. However, they observe that butterflies raised in colder temperatures have darker wing colors than those raised in warmer temperatures, even if they have the same genotype. What does this indicate?
→ 22Why is Gregor Mendel considered the 'Father of Genetics'?
→ 23How many different types of gametes can be produced by an individual with the genotype AaBb?
→ 24If a genetic disorder affects males and females equally, and an affected child can have unaffected parents, which of the following is the most probable mode of inheritance?
→ 25Consider a population of bacteria exposed to an antibiotic. Only a small fraction of the bacteria survive and multiply, leading to a resistant population. Which concept of heredity is best illustrated by this scenario?
→ 26In a monohybrid cross, if the F2 phenotypic ratio is 1:2:1, what type of dominance pattern is indicated?
→ 27How does sexual reproduction contribute more to variation in a population compared to asexual reproduction?
→ 28What is the primary definition of 'heredity' in biology?
→ 29If genes for two different traits are located very close together on the same chromosome, what can be inferred about their inheritance pattern compared to genes on different chromosomes?
→ 30Briefly explain how genetic information is transmitted from one generation to the next.
→ 31A breeder has a pea plant that produces purple flowers. Since purple is dominant over white, the plant's genotype could be PP or Pp. How can the breeder determine the exact genotype of this purple-flowered plant?
→ 32A pea plant has the genotype RrYy, where R is round, r is wrinkled, Y is yellow, and y is green. What is its phenotype?
→ 33Why is variation crucial for the survival of a species in a changing environment?
→ 34How do 'gene' and 'allele' differ in their meaning within the context of heredity?
→ 35In humans, what determines the sex of an offspring?
→ 36A sudden change in the genetic material of an organism, which may be beneficial, harmful, or neutral, is called a:
→ 37Can environmental factors modify the expression of inherited traits? Give an example.
→ 38In a cross between two pea plants heterozygous for two traits: tall (T) dominant over dwarf (t) and purple flowers (P) dominant over white (p). What proportion of the offspring are expected to be dwarf with white flowers?
→ 39Mendel's Law of Segregation states that:
→ 40Explain the fundamental role of DNA in heredity and how it relates to protein synthesis.
→ 41A genetic disorder is observed in a family. Both parents are unaffected, but their son has the disorder. Their daughter is unaffected. This pattern suggests which type of inheritance?
→ 42Which of the following processes is primarily responsible for creating new combinations of alleles on a chromosome, contributing to genetic variation?
→ 43If a pure dominant tall pea plant (TT) is crossed with a pure dwarf pea plant (tt), and the F1 generation is then backcrossed with the dwarf parent. What will be the genotypic ratio in the progeny of this backcross?
→ 44A geneticist crossed purebred red-flowered snapdragons with purebred white-flowered snapdragons. The F1 generation had pink flowers. If the F1 plants are self-pollinated, what phenotypic ratio is expected in the F2 generation?
→ 45Distinguish between acquired and inherited traits, providing one example for each in humans.
→ 46If a recessive allele is expressed only when present in two copies, what would be the phenotypic outcome in a heterozygous individual carrying one dominant and one recessive allele for a particular trait?
→ 47In guinea pigs, black coat (B) is dominant over white coat (b), and short hair (S) is dominant over long hair (s). A dihybrid cross is performed between a homozygous black, short-haired guinea pig and a white, long-haired guinea pig. What will be the genotype of the F1 generation?
→ 48Assertion (A): Human males are heterogametic. Reason (R): They produce two different types of gametes, X-bearing and Y-bearing.
→ 49A tall pea plant (TT) is crossed with a dwarf pea plant (tt). What percentage of the F2 generation plants will be dwarf?
→ 50How is the equal genetic contribution of male and female parents ensured in the progeny?
→ 51A study found that children with light-coloured eyes are likely to have parents with light-coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not?
→ 52A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short. This suggests that the genetic make-up of the tall parent can be depicted as (a) TTWW (b) TTww (c) TtWW (d) TtWw
→ 53How is the sex of the child determined in human beings?
→ 54A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?
→ 55How do Mendel’s experiments show that traits are inherited independently?
→ 56How do Mendel’s experiments show that traits may be dominant or recessive?
→ 57How does the creation of variations in a species promote survival?
→ 58If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
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