Cell Biology and Genetics Quiz

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Questions and Answers

What is a characteristic feature of chimerism in humans?

Fusion of two zygotes forms a single embryo (correct)

A single fertilized egg develops into a mosaic individual

A mutation in a single gene causes a gain of function

A duplication of a gene leads to a new function

How is chimerism typically proven?

Through the identification of a specific cell surface receptor

Through the presence of a single mutation in a regulatory sequence

By the presence of too many parental alleles at several loci (correct)

By a gain of function mutation in a specific gene

What is the distinguishing feature of XX/XY chimerism?

A duplication of a gene leading to a new function

The presence of both XX and XY cells in the same individual (correct)

A mutation in a regulatory sequence causing a gain of function

A specific inherited neurological disorder

What is the result of the fusion of two embryos after in vitro fertilization?

A chimera with two sets of cells Signup and view all the answers

What is the term for the colonization of one twin by cells from a non-identical co-twin?

Limited colonization Signup and view all the answers

What is the term for the mixing of two cell lines, one XX and one XY, in a single individual?

Chimerism Signup and view all the answers

What is the likely consequence of a gain of function mutation in a cell surface receptor?

The cell responds as if the signaling compound is continuously present Signup and view all the answers

What is the underlying genetic mechanism leading to Jansen's disease?

Gain of function mutation in the parathyroid hormone receptor gene Signup and view all the answers

What is the consequence of duplication of the PMP22 gene?

Recombination between repeat sequences on chromosome 17 Signup and view all the answers

Which of the following is NOT a characteristic of trinucleotide repeat expansions?

Results in growth defects Signup and view all the answers

What is the mechanism by which a mutation in a cell surface receptor can lead to a gain of function?

The receptor becomes constitutively active in the absence of the signaling compound Signup and view all the answers

What is the name of the inherited disorder caused by a trinucleotide repeat expansion in the Huntingtin gene?

Huntington's disease Signup and view all the answers

What is the characteristic of a locus with paternal expression and maternal silencing?

It is an example of genomic imprinting Signup and view all the answers

What is the term for the presence of two or more genetically different sets of cells in an individual's body?

Mosaicism Signup and view all the answers

What type of mutation is NOT associated with the syndromes mentioned in the text?

Gain of function mutation Signup and view all the answers

What is the characteristic of an individual with Mosaic Down syndrome?

They have some cells with 46 chromosomes and others with a different number of chromosomes Signup and view all the answers

What is the normal range of repetition of the sequence 5’-CAG-3’ in the HD gene?

What is the effect of the expansion of the CAG repeat in Huntington’s disease?

It results in a loss of function of the HD protein Signup and view all the answers

What is the role of the HD protein in the nerve cells of the brain?

Its biochemical role is not yet discovered Signup and view all the answers

What is a characteristic of dominant inherited diseases?

They can be inherited from either parent Signup and view all the answers

What is a characteristic of Huntington’s disease?

It is a dominant inherited disease Signup and view all the answers

Why do many dominant inherited diseases have incomplete penetrance or delayed onset?

Because they are not severe enough to prevent reproduction Signup and view all the answers

What is an example of a dominant inherited disease?

Huntington’s disease Signup and view all the answers

What is the result of the expansion of the CAG repeat in the Huntingtin gene?

A loss of function of the HD protein Signup and view all the answers

What is the term used to describe traits that are influenced by multiple genes?

Polygenic Signup and view all the answers

What is the leading cause of death worldwide?

Heart disease Signup and view all the answers

What is the most common underlying cause of heart disease?

Coronary artery disease Signup and view all the answers

What is atherosclerosis?

A narrowing of the coronary arteries Signup and view all the answers

What is a common consequence of atherosclerosis in the arteries that supply blood to the brain?

Stroke Signup and view all the answers

What is a risk factor for coronary artery disease?

Elevated cholesterol level Signup and view all the answers

What is the result of inadequate supply of oxygen to the heart tissue?

Myocardial infarction Signup and view all the answers

What is the term used to describe traits that are influenced by multiple genes and environmental factors?

Multifactorial Signup and view all the answers

What determines the threshold for phenotypic expression of mitochondrial gene mutations?

Energy requirements of the cell or tissue Signup and view all the answers

Which tissue has considerable energy requirements and is highly susceptible to mitochondrial gene mutations?

Brain Signup and view all the answers

What is the incidence of mitochondrial disorders in live births?

1 in 10,000 Signup and view all the answers

What is an indication of a non-Mendelian process in mitochondrial genetics?

Lack of phenotypic equivalence from reciprocal matings Signup and view all the answers

What is a biological consequence of mitochondrial mutations?

Myopathy Signup and view all the answers

Why are cells with low energy requirements less affected by homoplasmy for mutant mitochondrial DNA?

They have lower energy requirements Signup and view all the answers

What is the result of the combination of mitochondrial mutations and high energy requirements?

Increased risk of disease Signup and view all the answers

Which organs are highly susceptible to mitochondrial gene mutations due to their high energy requirements?

Brain and skeletal muscles Signup and view all the answers

What is the chromosome associated with Prader-Willi and Angelman syndromes?

15q Signup and view all the answers

What is the term for the presence of two or more cell types or lines in an individual, resulting from an error during mitosis?

Mosaicism Signup and view all the answers

What is a characteristic of a person with Mosaicism?

Some cells have 46 chromosomes, while others have a different number of chromosomes Signup and view all the answers

Which of the following syndromes is associated with paternal deletion and obesity?

Prader-Willi syndrome Signup and view all the answers

What is the role of genomic imprinting in the inheritance of certain syndromes?

It prevents the expression of certain genes Signup and view all the answers

How many human genes are known to be imprinted?

At least 80 Signup and view all the answers

What is the characteristic of Angelman syndrome?

All of the above Signup and view all the answers

What is the result of mosaicism in an individual?

Both A and B Signup and view all the answers

What is the main difference between a chimera and a mosaic?

The number of fertilized eggs involved Signup and view all the answers

What is the result of limited colonization of one twin by cells from a non-identical co-twin?

Chimerism Signup and view all the answers

How do blood-grouping centers occasionally discover chimeras?

Among normal donors Signup and view all the answers

What is the term for the fusion of two embryos after in vitro fertilization?

Embryo amalgamation Signup and view all the answers

What is the characteristic of the 46,XY/46,XX boy described in the study by Strain et al.?

He is a chimera Signup and view all the answers

What is the main difference between a chimera and a Greek mythological creature?

The physical characteristics Signup and view all the answers

What is a chimera in Greek mythology?

A fire-breathing creature with physical traits of a lion, goat, and dragon Signup and view all the answers

What is the result of fusion of two zygotes to form a single embryo?

Chimerism Signup and view all the answers

What is a characteristic of an XX/XY chimera?

Presence of two cell lines, one 46,XX and the other 46,XY Signup and view all the answers

What is the name of the study that described a 46,XY/46,XX boy?

Strain et al. Signup and view all the answers

What is the result of in vitro fertilization in which three embryos were transferred into the mother’s uterus?

Chimerism Signup and view all the answers

What is the term used to describe the colonization of one twin by cells from a non-identical co-twin?

Limited colonization of one twin by cells from a non-identical co-twin Signup and view all the answers

What is the term used to describe a single embryo that develops from the fusion of two zygotes?

Chimerism Signup and view all the answers

What is a characteristic of blood-grouping centers?

Discovery of chimeras among normal donors Signup and view all the answers

What is the most favored explanation for families with autosomal dominant disorders where parents are phenotypically normal but their children are affected?

Gonadal mosaicism in one of the parents Signup and view all the answers

Which of the following disorders is an example of an X-linked recessive disorder?

Duchenne muscular dystrophy Signup and view all the answers

What is the term for the presence of two or more genetically different sets of cells in an individual's body?

Chimerism Signup and view all the answers

What is the characteristic of families with X-linked recessive disorders where parents are phenotypically normal but their children are affected?

Gonadal mosaicism in one of the parents Signup and view all the answers

What is a characteristic feature of Bardet-Biedl syndrome (BBS)?

All of the above Signup and view all the answers

What is the minimum number of mutant alleles required to give rise to the BBS phenotype in some cases?

3 Signup and view all the answers

Which of the following is NOT a clinical feature of Bardet-Biedl syndrome (BBS)?

Heart defects Signup and view all the answers

What is the pattern of inheritance of Bardet-Biedl syndrome (BBS)?

Autosomal recessive Signup and view all the answers

How many loci have been identified for Bardet-Biedl syndrome?

At least eight Signup and view all the answers

What is a characteristic of Bardet-Biedl syndrome?

A combination of retinal dystrophy, obesity, polydactyly, kidney defects, underdeveloped testes, and cognitive impairment Signup and view all the answers

What is required to give rise to the Bardet-Biedl syndrome phenotype in some cases?

Three mutant alleles at the BBS2 and BBS6 loci Signup and view all the answers

What is the term for Bardet-Biedl syndrome?

A heterogeneous recessive disorder Signup and view all the answers

What are the possible consequences of having multiple mutant alleles at the BBS2 and BBS6 loci?

The Bardet-Biedl syndrome phenotype Signup and view all the answers

Study Notes

• Multifactorial diseases are caused by the combined effects of multiple genes and environmental factors, and include heart disease, which is the leading cause of death worldwide, accounting for approximately 25% of all deaths in the United States.

• Heart disease is often caused by coronary artery disease (CAD), which is a result of atherosclerosis, a narrowing of the coronary arteries due to the formation of lipid-laden lesions, impeding blood flow to the heart and potentially leading to a myocardial infarction.

• Risk factors for CAD include obesity, cigarette smoking, hypertension, elevated cholesterol levels, and a positive family history, usually defined as having one or more affected first-degree relatives.

• Genomic imprinting is a phenomenon where the expression of a gene depends on its parental origin, with at least 80 human genes known to be imprinted, including those involved in Prader-Willi and Angelman syndromes, and Beckwith-Wiedemann and Russell-Silver syndromes.

• Mosaicism occurs when an individual or a particular tissue consists of more than one cell type or line, resulting from an error during mitosis, and can account for unusual patterns of inheritance or phenotypic features in an affected individual.

• Huntington's disease is a dominant inherited disease caused by an expansion of a repeat sequence in the HD gene, leading to a loss of function of the HD protein, which is thought to act within the nerve cells of the brain.

• Mitochondrial diseases are caused by mutations in mitochondrial DNA and can result in a range of symptoms, including myopathy, cardiomyopathy, dementia, and loss of cerebral blood supply, with an incidence of about 1 in 10,000 live births.

• Chimerism is a rare phenomenon where a single individual is composed of cells from two or more fertilized eggs, which can be detected by the presence of multiple parental alleles at several loci.

• A chimera can result from the fusion of two zygotes to form a single embryo, or the colonization of one twin by cells from a non-identical co-twin, and can be proven by karyotyping of peripheral-blood lymphocytes.

• Cystic fibrosis is an autosomal recessive disorder affecting approximately 8000 people in the UK and 30,000 in the USA, caused by any one of 1400 different mutations, which can affect the body's cells, tissues, and glands, leading to faulty mucus and sweat production.

• Bardet-Biedl syndrome is a multifactorial disease that is thought to be caused by the combined effects of multiple genes, with at least 12 different genes implicated in the disorder.

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Description

Test your knowledge of genetics and cell biology with this quiz, covering topics such as gene duplication, mutation, and cell signaling. Learn about the effects of genetic changes on cell function and more.