2.2 Genetics and Chromosomal Abnormalities

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Questions and Answers

What is a key characteristic of a sex-limited trait?

It is influenced by environmental factors.

It can only occur in one sex due to anatomical or physiological differences. (correct)

It occurs much more often in one sex than the other.

It is determined by genes located on the sex chromosomes.

Which of the following best defines a sex-influenced trait?

A trait that is passed down only through the maternal line.

A trait that is equally expressed in both sexes.

A trait that is only expressed in the presence of specific hormones.

A trait that occurs much more often in one sex than the other. (correct)

What is the significance of germline DNA in the context of genetic diseases?

It is only useful for studying disease symptoms and not the disease genetics.

It is tissue derived from non-reproductive cells and is responsible for most diseases.

It is derived from reproductive cells and incorporated into every cell of the offspring, potentially passing on disease mutations. (correct)

It is only found in somatic cells and not involved in disease transmission.

Why is sequencing the entire germline DNA becoming more common for identifying diseases?

The cost of sequencing has decreased, making it feasible to search for disease-causing variations. (A) Signup and view all the answers

How does personalized medicine utilize a person's genetic and environmental factors?

It takes into account both unique genetic and environmental risk factors for diagnosis and management. (A) Signup and view all the answers

How is genetics currently influencing therapeutic drug prescriptions?

By using genetic testing to guide administration and dosing based on individual metabolism variances. (A) Signup and view all the answers

What is the role of the CYP2D6 gene in drug metabolism?

It encodes for an enzyme that influences the metabolism of more than 25 percent of all prescribed drugs. (D) Signup and view all the answers

What is the potential benefit of pre-anesthetic genetic testing related to drug metabolism?

It helps predict the length of time a drug will remain effective, based on metabolic rate. (B) Signup and view all the answers

What differentiates germline and somatic mutations?

Germline mutations can be passed to the next generation, but somatic mutations cannot. (A) Signup and view all the answers

Which of the following is true regarding human sex chromosomes?

Females have a homologous pair of X chromosomes, while males have a non-homologous pair of X and Y chromosomes. (D) Signup and view all the answers

What is the term for a cell having more than the diploid number of chromosomes?

Polyploidy (A) Signup and view all the answers

Which of the following best describes a triploid zygote?

A zygote with three copies of each chromosome. (B) Signup and view all the answers

How does aneuploidy differ from polyploidy?

Polyploidy involves a change in the total number of sets of chromosomes, while aneuploidy involves a change in the number of particular chromosomes. (D) Signup and view all the answers

Which of the following is TRUE regarding monosomy?

It is a form of aneuploidy, always lethal, where there is only one copy of a chromosome in diploid cells. (A) Signup and view all the answers

What is the primary reason for trisomies like Trisomy 13, 18, and 21?

Failure of sister chromatids to separate during mitosis and meiosis. (A) Signup and view all the answers

How do duplications differ from deletions in chromosome structure abnormalities?

Duplications typically have less serious consequences than deletions (A) Signup and view all the answers

What is the key characteristic of an inversion chromosomal abnormality?

Reinsertion of a chromosome fragment in reverse order. (C) Signup and view all the answers

Which type of translocation involves the fusion of long arms of two non-homologous chromosomes at the centromere?

Robertsonian translocation (D) Signup and view all the answers

What is the primary cause of fragile X syndrome?

A fragile site on the long arm of the X chromosome. (B) Signup and view all the answers

What is the most common chromosomal abnormality that causes Down Syndrome?

Non-disjunction (C) Signup and view all the answers

Which of the following is NOT a characteristic of Turner Syndrome?

Elevated stature (A) Signup and view all the answers

What is the recurrence risk for a child when one parent is heterozygous affected and the other is unaffected for an autosomal dominant condition?

50% (A) Signup and view all the answers

Which of the following describes the chromosomal makeup of an individual with Klinefelter syndrome?

Two X chromosomes and a Y chromosome (A) Signup and view all the answers

In autosomal recessive inheritance, how many copies of the recessive allele must an individual have to express the disease?

Two (B) Signup and view all the answers

The term locus refers to which of the following?

The location of a gene on a chromosome. (C) Signup and view all the answers

What is the definition of a 'phenotype'?

The observable traits resulting from the interaction of genotype and environment. (A) Signup and view all the answers

What is the term for a person who carries a disease-causing allele without exhibiting symptoms?

Heterozygous carrier (D) Signup and view all the answers

A new gene mutation is most likely the cause of a dominant disease when:

There is no history of the disease in the family. (A) Signup and view all the answers

What type of gene is described as one whose effects mask the other gene present at the same locus?

Dominant gene (D) Signup and view all the answers

What does incomplete penetrance mean in the context of genetic disease?

An individual with the disease-causing allele may not exhibit the disease phenotype. (D) Signup and view all the answers

What is a 'carrier' in the context of genetics?

An individual with one copy of a disease-causing allele who does not express the phenotype. (B) Signup and view all the answers

What principle states that homologous genes separate during reproduction, with each reproductive cell carrying only one gene?

Principle of Segregation (A) Signup and view all the answers

Which of the following situations provides the greatest chance of a child developing an autosomal recessive disease?

Both parents are carriers for the disease. (C) Signup and view all the answers

Why are males more frequently affected by X-linked recessive diseases?

Males only receive one X chromosome. (A) Signup and view all the answers

What does a pedigree chart primarily show?

Family relationships and which members are affected by a genetic disease. (C) Signup and view all the answers

In an autosomal dominant inheritance pattern, what is the likelihood of an affected heterozygous parent passing the trait to their child?

50 percent (A) Signup and view all the answers

An affected father with an X-linked recessive condition will pass the allele to which of the following?

All of his daughters. (B) Signup and view all the answers

Which of the following is a characteristic of autosomal recessive inheritance?

The disease is seen in siblings, but usually not their parents. (A) Signup and view all the answers

Which is a key characteristic of autosomal dominant inheritance?

Both sexes are affected in equal proportion. (B) Signup and view all the answers

What is the role of consanguinity in autosomal recessive inheritance?

It increases the likelihood of recessive diseases. (B) Signup and view all the answers

Why is it relatively rare for two individuals affected with the same autosomal dominant disease to produce offspring?

The population frequency of these diseases is relatively low. (B) Signup and view all the answers

In X-linked recessive inheritance, a carrier mother will pass the disease-causing allele to which of the following offspring?

Half of her sons and half of her daughters (D) Signup and view all the answers

What does the term 'age dependent penetrance' refer to in genetic disorders?

The disease symptoms are seen only in older individuals. (A) Signup and view all the answers

What is the function of the SRY gene?

It initiates gonadal differentiation towards male characteristics. (A) Signup and view all the answers

A female with one X chromosome carrying a recessive allele will

be a carrier for the x-linked disease. (B) Signup and view all the answers

What is the average age of death for someone affected by cystic fibrosis?

40 years. (A) Signup and view all the answers

Study Notes

Genes and Genetic Diseases

Genes occupy specific locations (loci) on chromosomes.
Different forms of a gene at a locus are alleles.
Alleles determine characteristics/traits, like hemoglobin types.
Polymorphic alleles occur at appreciable frequencies in a population.
Genotype: the combination of alleles at a given locus.
Phenotype: the result of genotype and environment.
Dominant genes mask recessive genes in heterozygotes.
Carriers: individuals with a disease-causing allele but are phenotypically normal.

Chromosomal Abnormalities

Somatic cells: diploid, 23 pairs of chromosomes (22 homologous pairs + sex chromosomes).
Germline cells: transmit traits to next gen.
Aneuploidy: abnormal chromosome number.
Triploidy: three copies of each chromosome; often results in spontaneous abortion.
Monosomy: one copy of a chromosome (lethal).
Trisomy: three copies of a chromosome; some survivable (e.g., Down syndrome).
Chromosome structural abnormalities: deletion, duplication, inversion, translocation, fragile sites.
Deletion: loss of a chromosome segment (e.g., Cri-du-chat syndrome).
Duplication: extra copies of a chromosome segment.
Inversion: reversal of a chromosome segment.
Translocation: swapping parts between nonhomologous chromosomes (e.g., Robertsonian translocation).
Fragile sites: areas prone to breaks; some are associated with diseases (e.g., Fragile X syndrome).

Chromosomal Disorders

Down syndrome (Trisomy 21): increased risk with maternal age. Affects approximately 1 in 800 live births.
- Characteristics: low nasal bridge, flat face, protruding tongue, heart defects, Alzheimer's disease risk.
Turner syndrome (45, X): only one X chromosome (female, sterile).
Klinefelter syndrome (XXY): additional X chromosome (male, sterile).

Modes of Inheritance

Autosomal dominant: equal frequencies in both sexes; no skipping generations.
Autosomal recessive: equal frequencies in both sexes; skipping generations possible; high carrier frequency.
X-linked recessive: more common in males; not from father to son; skipping generations possible.
Y-linked traits affect male fertility.

Pedigree Charts

Used to analyze inheritance patterns within families.
Shows relationships and affected individuals.

Penetrance

Penetrance: percentage of individuals with a genotype who express the phenotype.
Incomplete penetrance: individuals with the genotype may not show the phenotype.

Age-Dependent Penetrance

Symptoms not apparent until later in life.

Genetic Testing

Germline DNA sequencing is used to detect disease-causing variants.
Causes for thousands of genetic conditions are discovered.
Used for diagnosis, treatment, and for drug prescription guidance.

Personalized Medicine

Takes individual genetic and environmental factors into account.
Drug metabolism testing used to help prescribe the right dose.

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Description

This quiz covers key concepts related to genes, genetic diseases, and chromosomal abnormalities. It explains terms such as loci, alleles, genotype, phenotype, aneuploidy, and various genetic conditions. Test your understanding of how genetic traits are inherited and the implications of chromosomal changes.