Q: During Sanger sequencing, why does incorporation of a dideoxynucleotide (ddNTP) terminate DNA synthesis?

ddNTPs lack a $$3'\text{-OH}$$ group.

Question 1

In a complementation test, two true-breeding Drosophila mutants with black bodies are crossed and all F1 offspring have wild-type body color. What does this result indicate?

Accepted Answer

The mutations are in two different genes.

Question 2

A bacterial strain that cannot synthesize methionine and requires it in the medium is described as:

Accepted Answer

Auxotrophic

Question 3

If two genes are 20 cM apart, what percentage of recombinant gametes is expected from a testcross?

Accepted Answer

$$20\%$$

Question 4

In a three-point testcross, genes a and b are 10 map units apart, b and c are 20 map units apart, and a and c are 30 map units apart. If 1,000 progeny are produced and there is no interference, how many double crossovers are expected?

Accepted Answer

$$30$$

Question 5

Which of the following statements about DNA replication is correct?

Accepted Answer

DNA replication is semiconservative.

Question 6

During Sanger sequencing, why does incorporation of a dideoxynucleotide (ddNTP) terminate DNA synthesis?

Accepted Answer

ddNTPs lack a $$3'	ext{-OH}$$ group.

Question 7

A bacterial cell with the phenotype F$$^-$$:

Accepted Answer

Can receive the F factor during conjugation.

Question 8

Which of the following enzymes is responsible for removing RNA primers and filling gaps during completion of Okazaki fragments in E. coli?

Accepted Answer

DNA polymerase I

Question 9

If a double-stranded DNA molecule is $$28\%$$ guanine, what percent of the bases is adenine?

Accepted Answer

$$22\%$$

Question 10

In a complementation analysis of Drosophila eye color mutants, eight mutant strains are tested and form five complementation groups. What does this indicate?

Accepted Answer

There are five genes involved.

Question 11

Which of the following is a purine base found in nucleic acids?

Accepted Answer

Adenine

Question 12

In a PCR reaction, which step is responsible for the separation of DNA strands?

Accepted Answer

Denaturation

Question 13

The melting temperature of DNA increases as the:

Accepted Answer

G+C content increases.

Question 14

In a testcross involving two genes, the observed frequency of double crossovers is $$6$$ and the expected frequency is $$15. $$What is the coefficient of coincidence ($$CoC$$)?

Accepted Answer

$$0.4$$

Question 15

Which process involves the transfer of bacterial DNA from one cell to another via a bacteriophage?

Accepted Answer

Transduction

Question 16

In a Sanger sequencing gel, the smallest DNA fragments are found:

Accepted Answer

At the bottom of the gel, farthest from the origin.

Question 17

Which enzyme creates the final covalent bond to join Okazaki fragments on the lagging strand?

Accepted Answer

DNA ligase

Question 18

In a four-point testcross, how many phenotypic classes of progeny are expected?

Accepted Answer

$$16$$

Question 19

Which of the following will result in modifications to the expected Mendelian ratios in a dihybrid cross?

Accepted Answer

Epistasis

Question 20

In a gene mapping experiment, the observed double crossover frequency is $$0.006$$ and the expected is $$0.015. $$What is the interference ($$I$$)?

Accepted Answer

$$I = 1 - \frac{0.006}{0.015} = 0.6$$

Genetics Exam 2 Study Guide: Linkage, Mapping, Complementation, and DNA Biology

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