TO GENETIC DISORDERS AND MUTATIONS MCQs

Question 1

What is the lifetime frequency of genetic disease per 1000 individuals?

Accepted Answer

670 — The lifetime frequency of genetic disease is thought to be 670 per 1000 individuals, which is higher than widely appreciated, meaning approximately 67% of people will develop some genetic-related condition. ---

Question 2

Approximately how many genes do human beings have?

Accepted Answer

30,000 — Human beings have approximately 30,000 genes, though less than 2% of these actually code for proteins, with more than half being repetitive nucleotide sequences. ---

Question 3

What percentage of human DNA codes for proteins?

Accepted Answer

Less than 2% — Less than 2% of human DNA codes for proteins. More than half of the genome consists of repetitive nucleotide sequences of mysterious function. ---

Question 4

What percentage of DNA sequence do individuals share with each other?

Accepted Answer

99.9% — Individuals share 99.9% of their DNA sequence with each other, with only 0.1% (about 3 million base pairs) accounting for the diversity in the human race. ---

Question 5

Approximately what percentage of early pregnancy miscarriages have demonstrable chromosomal abnormalities?

Accepted Answer

50% — Approximately 50% of early pregnancy miscarriages have demonstrable chromosomal abnormalities, highlighting the significant impact of genetic disorders on early development. ---

Question 6

What is a point mutation?

Accepted Answer

Substitution of a single nucleotide base by a different base — A point mutation is the substitution of a single nucleotide base by a different base, resulting in substitution of an amino acid within a protein, such as in sickle cell anemia. ---

Question 7

What type of mutation is exemplified by sickle cell anemia?

Accepted Answer

Point mutation — Sickle cell anemia is caused by a point mutation where a single nucleotide substitution leads to the replacement of glutamic acid with valine in the β-globin chain. ---

Question 8

What is a frameshift mutation?

Accepted Answer

Insertion or deletion of one or two base pairs altering the reading frame — A frameshift mutation involves insertion or deletion of one or two base pairs that alters the reading frame of the DNA strand, changing all subsequent amino acids in the protein. ---

Question 9

What type of mutation involves dynamic amplification of a sequence of three nucleotides?

Accepted Answer

Trinucleotide repeat mutation — Trinucleotide repeat mutations involve dynamic amplification of a sequence of three nucleotides (often guanine and cytosine), with the degree of amplification increasing at gametogenesis. ---

Question 10

Which disorder is an example of trinucleotide repeat mutation?

Accepted Answer

Fragile X syndrome — Fragile X syndrome is the classic example of a trinucleotide repeat mutation, involving expansion of CGG repeats in the FMR1 gene. ---

Question 11

What are the three major categories of genetic disorders?

Accepted Answer

Mutant genes, multifactorial inheritance, chromosomal aberrations — The three major categories of genetic disorders are: diseases related to mutant genes of large effect, diseases with multifactorial (polygenic) inheritance, and diseases arising from chromosomal aberrations. ---

Question 12

Which type of mutation affects germ cells?

Accepted Answer

Mutations causing cancer — Mutations affecting germ cells are transmitted to progeny and cause inherited diseases, unlike somatic mutations which are not transmitted to offspring. ---

Question 13

What do somatic cell mutations typically cause?

Accepted Answer

Cancers and some congenital malformations — Mutations affecting somatic cells are not transmitted to progeny but can cause cancers and some congenital malformations in the affected individual. ---

Question 14

What is functional cloning (classic approach) in molecular genetics?

Accepted Answer

Starting with known affected protein to isolate and clone normal gene — Functional cloning starts with a known affected protein (clinical phenotype), then isolates and clones the normal gene, and determines molecular changes affecting the gene. ---

Question 15

What is positional cloning (candidate gene approach)?

Accepted Answer

Mapping disease phenotype to chromosome location and cloning DNA from region — Positional cloning involves mapping a disease phenotype to a particular chromosome location, cloning several DNA pieces from the region in vitro, and identifying aberrant proteins from mutated genes. ---

Question 16

Which of the following is produced using recombinant DNA technology by inserting genes into bacteria?

Accepted Answer

Growth hormone and erythropoietin — Human biologically active agents like soluble TNF receptor, tissue plasminogen activator, growth hormone, and erythropoietin are produced by inserting requisite genes into bacteria or suitable cells in tissue culture. ---

Question 17

What is gene therapy?

Accepted Answer

Treating genetic diseases by transfer of somatic cells transfected with normal genes — Gene therapy involves treating genetic diseases by transferring somatic cells that have been transfected with normal genes, though questions remain about whether benefits outweigh risks. ---

Question 18

What is a missense mutation?

Accepted Answer

A missense mutation — A missense mutation is a type of point mutation where nucleotide substitution results in a different amino acid being incorporated into the protein, potentially affecting protein function. ---

Question 19

What is a nonsense mutation?

Accepted Answer

A nonsense mutation — A nonsense mutation is a point mutation that creates a premature stop codon, leading to truncated protein production and usually loss of protein function. ---

Question 20

Which diseases are now considered to have genetic components beyond "classic" genetic disorders?

Accepted Answer

Cardiovascular diseases, immunity disorders, cancers — Beyond classic genetic disorders, cardiovascular diseases, disorders of immunity, and cancers are now recognized to have significant genetic components. ---

Question 21

What characterizes diseases with multifactorial (polygenic) inheritance?

Accepted Answer

Single gene defect — Diseases with multifactorial or polygenic inheritance result from the interaction of multiple genes along with environmental factors, rather than a single gene defect. ---

Question 22

What is the key characteristic of trinucleotide repeat mutations?

Accepted Answer

They only affect somatic cells — Trinucleotide repeat mutations are dynamic, meaning the degree of amplification increases during gametogenesis, which can lead to anticipation (worsening severity in successive generations). ---

Question 23

What is genomic imprinting?

Accepted Answer

Genomic imprinting — Genomic imprinting is an epigenetic phenomenon where the expression of certain genes depends on whether they were inherited from the mother or father, affecting disease transmission. ---

Question 24

Which category of genetic disorders involves mitochondrial DNA mutations?

Accepted Answer

Other category beyond three major types — Diseases resulting from mutations in mitochondrial DNA constitute a separate category beyond the three major categories, with unique maternal inheritance patterns. ---

Question 25

How can molecular probes be used in disease diagnosis?

Accepted Answer

For both genetic and nongenetic (e.g., infectious) diseases — Molecular probes can be used in diagnosis of both genetic diseases and nongenetic diseases such as infectious diseases, making them versatile diagnostic tools. ---

Question 26

What is a permanent change in DNA called?

Accepted Answer

Mutation — Mutations are permanent changes in the DNA sequence that can be transmitted to progeny (if in germ cells) or cause disease in the individual (if in somatic cells). ---

Question 27

What percentage of DNA is responsible for human diversity?

Accepted Answer

0.1% — Only 0.1% of DNA (approximately 3 million base pairs) accounts for diversity in the human race, while individuals share 99.9% of their DNA sequence. ---

Question 28

Which nucleotides are typically involved in trinucleotide repeat mutations?

Accepted Answer

Guanine and cytosine — Trinucleotide repeat mutations typically involve sequences containing guanine and cytosine nucleotides, such as CGG repeats in Fragile X syndrome. ---

Question 29

What application of genetics involves producing tissue plasminogen activator?

Accepted Answer

Tissue plasminogen activator — Tissue plasminogen activator is a human biologically active agent produced using recombinant DNA technology by inserting genes into bacteria or tissue culture cells. ---

Question 30

What is the extremity range of genetic disorders?

Accepted Answer

Varies from mild/hidden to severe/lethal — The extremity of genetic disorders varies widely - some may be mild or remain hidden, while others cause early miscarriage or serious disease in young individuals. ---

Question 31

What is the main difference between functional and positional cloning?

Accepted Answer

Functional starts with protein; positional starts with chromosome location — Functional (classic) cloning starts with a known affected protein and works toward the gene, while positional (candidate gene) cloning starts by mapping disease to a chromosome location and works toward the protein. ---

Question 32

What proportion of human genes consists of repetitive nucleotide sequences?

Accepted Answer

More than 50% — More than half ( 50%) of human genes consist of repetitive nucleotide sequences of mysterious function, with less than 2% actually coding for proteins. ---

Question 33

What raises the question "Do the benefits outweigh the risks?" in medical genetics?

Accepted Answer

Gene therapy — Gene therapy raises important ethical and safety questions about whether the benefits of treating genetic diseases by transferring normal genes outweigh the potential risks. ---

Question 34

What happens in a frameshift mutation involving deletion of two base pairs?

Accepted Answer

Reading frame altered affecting all downstream amino acids — Deletion of two base pairs in a frameshift mutation alters the reading frame, changing the coding of all amino acids downstream from the mutation site, usually severely affecting protein function. ---

Question 35

Which genetic disorder category includes diseases like Down syndrome?

Accepted Answer

Chromosomal aberrations — Down syndrome (trisomy 21) is a disease arising from chromosomal aberrations, specifically having an extra copy of chromosome 21. ---

Question 36

What is the significance of unknown genetic disorders being mild or hidden?

Accepted Answer

True burden of genetic disease may be underestimated — The fact that an unknown number of genetic disorders may be mild or remain hidden suggests that the true burden of genetic disease is likely higher than currently recognized. ---

Question 37

What type of cells must be affected for a mutation to be inherited?

Accepted Answer

Germ cells — Only mutations affecting germ cells (sperm or egg cells) can be transmitted to progeny and cause inherited diseases. Somatic cell mutations affect only the individual. ---

Question 38

Which application of genetics helps in understanding the molecular basis of human disease?

Accepted Answer

Functional and positional cloning approaches — Both functional cloning and positional cloning approaches help understand the molecular basis of human disease by identifying genes and proteins involved in disease processes. ---

Question 39

What is the clinical implication of 50% of early miscarriages having chromosomal abnormalities?

Accepted Answer

Chromosomal abnormalities are major cause of pregnancy loss — The fact that approximately 50% of early pregnancy miscarriages have demonstrable chromosomal abnormalities indicates that chromosomal abnormalities are a major cause of early pregnancy loss and many are incompatible with continued development.

TO GENETIC DISORDERS AND MUTATIONS MCQs

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