Question 1

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

Accepted Answer

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

Question 2

In the context of DNA profiling, what is the probability that two unrelated individuals will have the same alleles for each of the 13 original STR markers?

Accepted Answer

$$1/10^{10}$$

Question 3

Which of the following statements about the Combined DNA Index System (CODIS) is correct?

Accepted Answer

CODIS allows electronic access to DNA profiles across the US using STR markers.

Question 4

A DNA profile shows two peaks for a given STR marker. What does this indicate about the individual's genotype at that locus?

Accepted Answer

The individual is heterozygous at that locus.

Question 5

Why are identical twins not distinguishable by traditional STR-based DNA profiling?

Accepted Answer

They have identical STR alleles at all loci.

Question 6

Which equation correctly represents the probability $$P of $$two unrelated individuals sharing the same genotype at $$n$$ independent STR loci, if the probability for one locus is $$p$$?

Accepted Answer

$$P = p^n$$

Question 7

In a paternity test, which STR marker result would most strongly exclude a man as the biological father?

Accepted Answer

The child has an allele at an STR locus that is not present in either the mother or the alleged father.

Question 8

Which of the following best explains why histone acetylation leads to increased gene transcription?

Accepted Answer

Acetylation neutralizes positive charges on histones, loosening DNA packing and allowing transcription machinery access.

Question 9

Which process is responsible for heritable changes in gene expression that do NOT alter the DNA sequence?

Accepted Answer

Epigenetics

Question 10

If a cell's chromosomal DNA is tightly packed and highly methylated, what is the expected level of gene transcription?

Accepted Answer

Low transcription

Question 11

Which of the following is TRUE regarding the packing of DNA in eukaryotic cells?

Accepted Answer

DNA is loosely packed in nucleosomes and tightly packed in metaphase chromosomes.

Question 12

A forensic scientist is analyzing a DNA sample using 20 STR markers. If the sample is heterozygous at 8 markers, how many peaks should be observed for those markers?

Accepted Answer

16 peaks

Question 13

Which of the following is a key difference between STR and SNP-based DNA profiling?

Accepted Answer

STR profiling analyzes the number of repeat units, while SNP profiling analyzes single base changes.

Question 14

What is the combined length of DNA in a human cell, given 46 chromosomes and an average chromosome length of $$1.9 	imes 10^8$ base pairs?

Accepted Answer

$$2$$ meters

Question 15

Which of the following best describes the function of nucleosomes in eukaryotic cells?

Accepted Answer

Nucleosomes are protein complexes that tightly wrap DNA, aiding in its compaction.

Question 16

Which of the following is TRUE about DNA methylation?

Accepted Answer

DNA methylation is heritable and involves methyltransferases copying methylation patterns during DNA replication.

Question 17

In a rape case, a suspect's DNA profile matches the crime evidence at all tested STR loci. What is the most likely conclusion?

Accepted Answer

The suspect's DNA is consistent with the crime evidence, supporting a charge.

Question 18

Which of the following is a limitation of traditional STR-based DNA profiling in criminal investigations?

Accepted Answer

It cannot distinguish between identical twins.

Question 19

Which of the following best explains why genes must be 'unpacked' from chromatin to be transcribed?

Accepted Answer

Transcription factors cannot access tightly packed DNA.

Question 20

Which of the following approaches uses SNPs plus genealogical research to identify suspects from DNA evidence?

Accepted Answer

Forensic Genomics

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

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