Biology

Human Genetics and Disorders

844 Questions

Human Genetics and Disorders covers the inheritance patterns, genetic mutations, and molecular basis of hereditary diseases. Topics include sex-linked traits, cancer genetics, and metabolic disorders. This section tests knowledge critical for biology exams and general science papers.

Genetic mutationsInherited disordersCancer geneticsGenetic testingMendelian inheritance

Human Genetics and Disorders Questions

Multiple choice zoology selection and evolution extinction extinctions environmental science

Choose the correct answers from the alternatives given.
The continued occurrence of sickle-cell disease in parts of Africa with malaria is due to

  1. Disruptive selection

  2. Continual mutation

  3. Fitness of the heterozygote

  4. Gene flow between populations
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Sickle cell anemia is an inherited blood disease where red blood cells show an abnormal crescent (or sickle) shape. It is an autosomal recessive disease in which one gene of allele codes for a normal protein and the other one codes for defective hemoglobin (sickle-celled). 


Heterozygous individuals ie., carrying just one copy of the sickle mutation (inherited from either the father or mother), do not develop sickle cell anemia. However, such individuals are protected against malaria. This defective hemoglobin cause sickling of RBC in which malarial parasite cannot survive. This explains the high prevalence of this mutation in parts of Africa, where malaria is endemic.

So the correct answer is "Fitness of the heterozygote"

Multiple choice biology mendel's law of inheritance determination of sex sex determination sex determination in humans

The sex chromosomes of .......... determine the sex of an unborn baby.

  1. Male

  2. Female

  3. Grand parent

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The sex of a human baby is determined by the composition of its sex chromosomes (a single distinct pair among humans 23 pairs of chromosomes). Females possess two copies of the same chromosome (referred to as the 'X' chromosome); males have one copy of the X chromosome and one copy of the smaller, hook-shaped Y chromosome.
When fertilization occurs, the new gamete (the initial cell from which a fetus grows) always inherits one of the mother's X chromosomes, and either a X or a Y from the father, depending on which chromosome the fertilizing sperm cell happened to inherit. One could say, then, that the father—or, at least, his sperm—determines the sex of the child. 
Multiple choice biology mendel's law of inheritance determination of sex sex determination sex determination in humans

A zygote which has inherited a Y chromosome from the father will develop into

  1. A boy

  2. A girl

  3. Anyone of the above

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

XY type of sex determination is seen in humans. Genetic makeup of female is XX and that of male is XY. A female ovum always carries a X chromosome and male sperm can carry either X or Y chromosome.

Multiple choice biology mendel's law of inheritance determination of sex sex determination sex determination in humans

The human which has an XX pair of chromosomes is called 

  1. Male

  2. Female

  3. Hybrid

  4. Pure breed
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Humans have X and Y sex chromosomes. A human with 22 pairs of autosomes and two copies of X chromosomes as sex chromosomes are females while those with 22 pairs of autosomes and XY chromosomes as sex chromosomes are males. A pure breed refers to individual that have a pair of identical alleles for a particular locus while a hybrid carries unlike alleles for a particular locus. The correct answer is B.

Multiple choice biology mendel's law of inheritance determination of sex sex determination sex determination in humans

The karyotype of a normal male is

  1. 22 AA + XY

  2. 44 AA + XY

  3. 22 A + XY

  4. Both A and B
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The karyotype of a normal human contains 22 pairs of autosomal chromosome and one pair of sex chromosome called as allosomes. Female contains 2 X chromosomes and 46 autosomes and male contains 1 X and 1 Y chromosome and 46 autosomes.

Multiple choice biology mendel's law of inheritance determination of sex sex determination sex determination in humans

The sex chromosomes of both male and female are respectively

  1. YY, XX

  2. YX, XY

  3. XY, XX

  4. All of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Humans have 22 pairs of chromosome of which one pair of sex chromosome is not always a perfect pair. Women have a perfect pair of X chromosome but, men have a mismatched pair of X and Y chromosome. Therefore, (c) is the correct answer.

Multiple choice biology mendel's law of inheritance determination of sex sex determination sex determination in humans

The sex of every animal depends on the _______ fusion.

  1. Chromosomal

  2. Blood

  3. RNA

  4. None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

All animals do not contain chromosomes. In some cases, sex is determined by environmental variables (such as temperature) or social variables (e.g. the size of an organism relative to other members of its population). Therefore, (d) is the correct answer.

Multiple choice biology mendel's law of inheritance determination of sex sex determination sex determination in humans

A zygote which has an X chromosome inherited from the father will develop into a

  1. Boy

  2. Girl

  3. X chromosome does not determine the sex of a child

  4. Either boy or girl
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

XX chromosomal pair determines that a child is a female. XY combination determines that the child is a male. Thus, an egg of a female will always contain and X chromosome. 50% of the sperms contain X chromosome and 50% of sperms contain Y chromosome. Thus when an egg is fertilized by a sperm containing X chromosome, the combination of XX is paired thus giving birth to a girl child.

Multiple choice biology mendel's law of inheritance determination of sex sex determination sex determination in humans

Structure present in a cell which is responsible for determination of the sex of a baby is

  1. Cytoplasm

  2. Cell membrane

  3. Nucleus

  4. Chromosome
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In humans, males and females have differences in sex chromosomes. Human cells are having two types of chromosomes: autosomes and allosomes. Allosomes present in a male is XY and those present in a female are XX. There are no differences in the cytoplasm or membrane. The chromosome is present inside a nucleus, so you can think of the nucleus also as the correct answer but when a chromosome is given as an option, it is a better choice.

Multiple choice biology mendel's law of inheritance determination of sex sex determination sex determination in humans

The human offspring can be of two types with XX and .......... chromosomes.

  1. XY

  2. XX

  3. XXX

  4. YY
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The sex of an individual is determined by which paternal sex chromosome (X or Y) is inherited during fertilization. Eggs and sperm, as reproductive cells, each contain only one of the two sex chromosomes as a result of having undergone meiosis, a form of cell division that produces daughter cells containing only one member of each chromosome pair. All eggs therefore, contain an X chromosome, but half of the sperms contain an X chromosome and the other half a Y chromosome. 
If an egg is fertilized by a sperm carrying an X chromosome, an XX or female embryo will result, while fertilization of the egg by a Y-bearing sperm will produce an XY or male embryo. In some organisms, including birds, the female contains the unlike pair of sex chromosomes. Thus, in these cases, the mother determines the sex of the offspring.
Thus, the offspring can be of two types, XX and XY.
Multiple choice biology variation variation and its type natural selection introduction to genetics

Which of the following is not heritable?

  1. Point mutation

  2. Chromosomal mutation

  3. Somatic mutation

  4. Gene mutation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

  • Point mutation is a genetic mutation where a single nucleotide base is changed, inserted or deleted from a sequence of DNA or RNA. Each triplet codon corresponds to an amino acid when translated to protein. When one of these codons is changed by a point mutation, the corresponding amino acid of the protein is changed.
  • Chromosomal mutation is presence or absence of one or more set of chromosomes in a cell or a structural abnormality in the normal set of chromosomes.
  • Somatic mutation is the occurrence of a mutation in the somatic cells (cells other than sperm and egg) of the organism. These are frequently caused by environmental factors like exposure to UV rays or to certain chemicals. 
  • Gene mutation is a permanent alteration in the DNA sequence that makes up a gene. They are of two types: Hereditary mutations (inherited from parents) and Acquired mutation (occur at some time during a person's life).
So, the correct answer is 'Somatic mutation'

Multiple choice zoology excretory system of human disorders of excretory system disorders related to the excretory system functions and disorders of kidney

Assertion  :  Phenylketonuria is a recessive hereditary disease caused by the body's failure to oxidize an amino acid phenylalanine to tyrosine, because of a defective enzyme

Reason    :    It results in the presence of phenylalanine in the urine


  1. If both the assertion and the reason are true and the reason is a correct explanation of the assertion

  2. If both the assertion and reason are true but the reason is not a correct explanation of the assertion

  3. If the assertion is true but the reason is false

  4. If both the assertion and reason are false

  5. If the assertion is false but reason is true
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Phenylketonuria results when there is a deficiency of liver enzyme phenyl alanine hydroxylase that converts phenyl alanine into tyrosine. It results with a high level of phenyl alanine in blood, tissue fluids and urine.

So, the correct answer is 'If both the assertion and reason are true but the reason is not a correct explanation of the assertion'