Question 1

Which of the following best describes the role of Short Tandem Repeats (STRs) in forensic DNA profiling?

Accepted Answer

STRs are short, repeated DNA sequences that vary in number among individuals, making them useful for identification.

Question 2

A DNA profile is generated using PCR amplification of STR loci. If an individual is heterozygous at a locus, what would you expect to see in the electropherogram?

Accepted Answer

Two peaks, each corresponding to a different allele.

Question 3

The probability of two unrelated individuals having the same genotype for all 13 original CODIS STR markers is approximately:

Accepted Answer

$$1/10^{10}$$

Question 4

Which of the following scenarios would NOT be distinguishable by DNA profiling using 20 STR markers?

Accepted Answer

Identical twins.

Question 5

In the context of DNA packaging in eukaryotes, which structure consists of DNA wrapped around histone proteins?

Accepted Answer

Nucleosome

Question 6

What is the effect of histone acetylation on chromatin structure and gene transcription?

Accepted Answer

It makes DNA more loosely packed and increases transcription.

Question 7

Which enzyme is responsible for maintaining DNA methylation patterns during DNA replication?

Accepted Answer

Maintenance methyltransferase

Question 8

If a person’s DNA profile shows two peaks at 8 out of 13 STR loci, how many loci is this person heterozygous for?

Accepted Answer

8

Question 9

Which of the following is TRUE regarding the CODIS system used in law enforcement?

Accepted Answer

It allows electronic access to DNA profiles across the US using STR loci.

Question 10

A crime scene sample is analyzed for 13 STR markers. The suspect’s DNA matches all 13 markers. What is the probability that this match is due to chance, assuming the population probability for each marker is independent and $$1/10^8$$ for all 13 markers combined?

Accepted Answer

$$1/10^8$$

Question 11

Which of the following best explains why DNA must be tightly packed in the nucleus?

Accepted Answer

Because the total length of DNA in a human cell is about 2 meters, which must fit into a nucleus of about $$10 \mu m$$ diameter.

Question 12

Which of the following is a real-world application of DNA profiling?

Accepted Answer

Identifying missing persons and crime scene suspects.

Question 13

Which of the following statements about DNA methylation is correct?

Accepted Answer

DNA methylation is heritable and does not change the DNA sequence.

Question 14

In a paternity test, the child has an STR allele that is not present in the alleged father. What does this indicate?

Accepted Answer

The alleged father can be excluded as the biological father.

Question 15

Which of the following is a consequence of DNA being tightly packed into chromatin?

Accepted Answer

Genes are less accessible for transcription.

Question 16

What is the main difference between DNA phenotyping and traditional STR profiling in forensic investigations?

Accepted Answer

DNA phenotyping uses SNPs to predict physical traits, while STR profiling uses repeat numbers for identification.

Question 17

Which of the following best describes epigenetics?

Accepted Answer

Heritable changes in gene expression that do not involve changes to the DNA sequence.

Question 18

If a DNA sample is tightly packed and highly methylated, what is the expected level of gene transcription?

Accepted Answer

Low transcription.

Question 19

Which of the following is TRUE about nucleosomes?

Accepted Answer

They consist of DNA wrapped around a core of histone proteins.

Question 20

A forensic scientist is analyzing a DNA sample using fluorescent dye-labeled STR primers. What is the purpose of the fluorescent dye?

Accepted Answer

To visualize the amplified DNA fragments during electrophoresis.

DNA Profiling, Chromosome Structure, and Epigenetics: Genetics Study Notes

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