Neurogenetics

Question 1

What is the term for the complete “book” of DNA containing our genetic code?

Answer 1

The complete “book” of DNA containing our genetic code is called the DNA sequence.

Question 2

How similar is the DNA sequence between different individuals?

Answer 2

The DNA sequence is 99.9% identical between people.

Question 3

What are SNPs, and how do they contribute to genetic variation?

Answer 3

SNPs (single nucleotide polymorphisms) are the most common type of genetic variation. They are differences in DNA sequence at a single nucleotide level, and they can lead to variations between individuals

Question 4

What are the characteristics of Mendelian disorders?

Answer 4

Mendelian disorders exhibit a direct relationship between a gene and a disease, display recognizable inheritance patterns, and are caused by mutations in a single gene.

Question 5

Can you provide examples of Mendelian disorders?

Answer 5

Examples of Mendelian disorders include Huntington’s disease and Familial Alzheimer’s disease.

Question 6

What are the characteristics of complex disorders?

Answer 6

Complex disorders involve genes that confer an increased risk but do not always cause the disease. They may exhibit a familial pattern of inheritance and are often due to interactions between multiple genes or genes and the environment.

Question 7

Can you provide examples of complex disorders?

Answer 7

Complex disorders include psychiatric disorders, cardiovascular diseases, and behavioral disorders.

Question 8

What are some examples of very large changes to DNA at the level of chromosomes?

Answer 8

chromosome deletions, chromosome duplications, and chromosome rearrangements.

Question 9

What genetic abnormality is associated with Down’s syndrome?

Answer 9

Down’s syndrome is associated with the duplication of chromosome 21 (trisomy 21).

Question 10

Which genetic abnormality is linked to DiGeorge syndrome/VCFS and an increased risk of schizophrenia and autism?

Answer 10

Deletion of chromosome 22q11.2, which affects 43 genes,

Question 11

What are small changes to DNA involving deletions?

Answer 11

Deletions involve the removal of 1 to thousands of nucleotides (base pairs, bp) from the DNA sequence.

Question 12

What genetic change can cause Alzheimer’s disease?

Answer 12

Deletions in the PSEN1 gene can cause Alzheimer’s disease.

Question 13

What type of change alters the protein coding region of a gene, leading to a frameshift and premature truncation?

Answer 13

occur when there are insertions or deletions in the DNA sequence, disrupting the reading frame of the gene.

Question 14

What repeat length of a certain sequence is considered normal, and what length is associated with disease?

Answer 14

A repeat length of <35 is considered normal, while a repeat length of >37 is associated with disease.

Question 15

How many different missense mutations in the PSEN1 gene are known to cause Alzheimer’s disease?

Answer 15

Approximately 93 different missense mutations in the PSEN1 gene are associated with Alzheimer’s disease.

Question 16

What type of disease requires only one copy of the mutated gene to be inherited for the condition to be expressed?

Answer 16

Dominant diseases require only one copy (50% chance) of the mutated gene to be inherited for the condition to be expressed.

Question 17

In which type of disease does an individual need to inherit two copies of the mutated gene (one from each parent) to express the condition?

Answer 17

Recessive diseases require an individual to inherit two copies (25%) of the mutated gene (one from each parent) to express the condition.

Question 18

What does genetic risk in a population entail?

Answer 18

involves the number of risk alleles, including multiple risk alleles in a gene, contributing to the disease in the population.

Question 19

What factors determine genetic risk in a population regarding the frequency of risk alleles?

Answer 19

determined by the frequency of each risk allele, which can be the major or minor alleles.

Question 20

What role does the interaction between alleles play in genetic risk?

Answer 20

The interaction between alleles, whether additive or multiplicative, influences the overall genetic risk for a particular disease.

Question 21

What is observed in the distribution of the trait in relatives of patients with schizophrenia?

Answer 21

Relatives of patients with schizophrenia exhibit a shifted distribution for the trait, reflecting their increased liability, meaning the curve is shifted to the right.

Question 22

What is the probability that alleles at two loci will be inherited together by chance?

Answer 22

50% of the time, represented by θ = 0.5.

Question 23

How is linkage determined between two loci?

Answer 23

If alleles at two loci are inherited together more than 50% of the time, they are considered linked.

Question 24

What does it mean if the recombination fraction (θ) between two syntenic genes is 0.5?

Answer 24

If two syntenic genes, located on the same chromosome, have a recombination fraction (θ) of 0.5, they may be so far apart that they are inherited independently of each other.

Question 25

How does the recombination fraction (θ) indicate the proximity of two genes?

Answer 25

If the recombination fraction (θ) between two genes is less than 0.5, it indicates that they are close together on the chromosome and are inherited together more often than expected by chance.

Question 26

What are Genome Wide Association Studies for (GWAS)?

Answer 26

Compares differences in the frequencies of specific alleles between diseased individuals and healthy controls