Genetics Single Nucleotide Polymorphisms Quiz

Questions and Answers

How many chromosomes are present in a normal male?

48 chromosomes

46 chromosomes (correct)

44 chromosomes

23 chromosomes

What type of cells undergo spermatogenesis?

Muscle cells

Gametes (correct)

Neurons

Erythrocytes

What is the significance of the term 'haploid' in genetics?

It refers to cells with 46 chromosomes.

It describes cells that have two sets of chromosomes.

It characterizes organisms with no chromosomes.

It indicates cells that have one set of chromosomes. (correct)

In terms of chromosome structure, what does 'sister chromatids' refer to?

Identical halves of a duplicated chromosome Signup and view all the answers

How many chromosomes are indicated when stating '46.xx' for a normal female?

46 chromosomes Signup and view all the answers

What is a single nucleotide polymorphism (SNP)?

An alteration in DNA sequence affecting one nucleotide Signup and view all the answers

Which type of mutation results in a truncated protein?

Nonsense mutation Signup and view all the answers

What distinguishes a missense mutation from a silent mutation?

Missense mutations change an amino acid, silent mutations do not Signup and view all the answers

Which of the following is an example of an insertion mutation?

Adding an extra nucleotide into the sequence Signup and view all the answers

What is the main result of a frameshift mutation?

It alters the entire amino acid sequence downstream Signup and view all the answers

How are conservative and non-conservative missense mutations different?

Conservative mutations result in similar amino acids, non-conservative do not Signup and view all the answers

Which mutation can involve complete removal of a nucleotide?

Deletion mutation Signup and view all the answers

What does a silent mutation signify in genetic terms?

It has no effect on the amino acid sequence Signup and view all the answers

Which type of genetic alteration leads to the formation of new alleles?

Mutations Signup and view all the answers

What type of mutation results in the substitution of a single amino acid in the polypeptide chain?

Missense mutation Signup and view all the answers

What characterizes a nonsense mutation?

It produces a stop codon resulting in a truncated protein. Signup and view all the answers

When is a mutation considered a frameshift mutation?

When the number of inserted or deleted bases is not a multiple of 3. Signup and view all the answers

What effect do loss-of-function mutations typically have on proteins?

They cause a decrease in protein activity or a missing protein product. Signup and view all the answers

What occurs if nucleotide bases are inserted or deleted in quantities that are multiples of 3?

The mutation is classified as in-frame. Signup and view all the answers

What is a common result of mutations in promoter or regulatory regions of genes?

They can increase or decrease protein production. Signup and view all the answers

Which of the following best defines gain-of-function mutations?

Mutations that enhance protein function or create new protein functions. Signup and view all the answers

What is the primary consequence of a frameshift mutation?

The entire downstream amino acid sequence is altered. Signup and view all the answers

What is the primary cause of retinoblastoma?

Mutations in the RB gene Signup and view all the answers

What is pleiotropy in the context of genetics?

The ability of one gene to influence multiple traits. Signup and view all the answers

What is the pattern of inheritance for mutations in the RB1 gene?

Autosomal dominant Signup and view all the answers

What is the impact of modifier genes on gene transcripts?

They can alter transcription and expression of other genes. Signup and view all the answers

What does incomplete penetrance mean in the context of retinoblastoma?

Some carriers do not develop the disease Signup and view all the answers

What is one possible outcome of alternative splicing?

Production of protein isoforms with different functions. Signup and view all the answers

Which of the following diseases is known to exhibit incomplete penetrance?

Huntington's disease Signup and view all the answers

Which of the following is NOT a common type of alternative splicing?

Gene duplication. Signup and view all the answers

What role does the Rb protein play in relation to the cell cycle?

Controls the cell cycle negatively Signup and view all the answers

In patients with thalassemia, how does the expression of the beta-globin gene vary?

Some patients have mild symptoms while others experience severe anemia. Signup and view all the answers

What characterizes the disorder achondroplasia?

Abnormal bone growth and dwarfism Signup and view all the answers

What is the role of exons in alternative splicing?

They are coding sequences that can be arranged in different combinations. Signup and view all the answers

How does the Rb protein affect cell survival?

Influencing apoptosis Signup and view all the answers

What happens during the process of intron retention?

Introns are kept in the final mRNA transcript. Signup and view all the answers

Which of the following statements is true regarding complete penetrance?

All carriers show symptoms of the disease Signup and view all the answers

Why might alternative splicing be significant for protein diversity?

It leads to the production of different protein isoforms. Signup and view all the answers

Study Notes

Mutations

Mutations are alterations in DNA sequences that produce new alleles.
Types of mutations include point mutations, which consist of single nucleotide changes, and can further be classified as:
- Silent mutations: No change in amino acid sequence.
- Missense mutations: One amino acid is substituted; e.g., sickle cell disease involves substitution of valine for glutamic acid.
- Nonsense mutations: Introduces a premature stop codon, leading to truncated proteins.

Mutational Categories

Conservative missense mutations: Do not significantly alter protein function.
Non-conservative missense mutations: Result in proteins with altered functions.
Insertions and deletions can lead to frameshifts, altering downstream codons and potentially producing nonfunctional proteins if not in multiples of three.

Effects on Gene Expression

Mutations in regulatory regions impact gene product levels.
Mutations are classified by their phenotypic effects:
- Loss-of-function: Results in reduced or absent protein function.
- Gain-of-function: Produces proteins with new or increased activity.

Penetrance and Clinical Examples

Penetrance describes the proportion of individuals with a mutation that exhibit the corresponding phenotype.
- Incomplete penetrance: Not everyone carrying a mutation develops the associated condition (e.g., retinoblastoma).
- Complete penetrance: Every individual with the mutation presents the phenotype (e.g., achondroplasia linked to FGFR3 mutations).

Modifier Genes and Variable Expressivity

Modifier genes can influence the expression of other genes, leading to varied clinical presentations.
Variable expressivity: Different individuals with the same genotype exhibit a range of symptoms; thalassemia patients showcase this with differing severities of symptoms.

Alternative Splicing

Alternative splicing modifies pre-mRNA, creating diverse mRNA transcripts from a single gene.
This process allows for different combinations of coding sequences (exons), leading to protein isoforms with varied functions.
Common types of alternative splicing include:
- Exon skipping: Removal of certain exons and flanking introns.
- Alternate 5’ or 3’ splicing: Joining of exons at different splice sites.
- Intron retention: Retaining non-coding regions in the final mRNA transcript.

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Description

Test your knowledge on single nucleotide polymorphisms (SNPs) and their role in genetics. This quiz covers key concepts including mutations such as deletions and substitutions. Sharpen your understanding of genetic variations and their implications.