Genetics - Exam 1 Practice Q's

In a DNA double helix each type of base forms a stable base pair with only one type of base. When bases on an RNA strand are involved in base pairing, which bases can form stable base pairs with more than one type of base?

Guanine and uracil

T/F pyrimidines have a single heterocyclic ring consisting of 4 carbon atoms + 2 nitrogen atoms that are linked to the same carbonyl group

True

T/F purines have 2 heterocyclic rings, each with 2 N atoms

True

T/F Thymine = 5-methyluracil

True

T/F Purines carry an amino group, unlike pyrimidines

False

T/F In nucleic acids, the sugar is always base on a heterocyclic ring that consists of one O atom and 4 C atoms, one of which is connected to a fifth C atom, the 5’ carbon atom

True

T/F In nucleic acids, the internal sugar residues in a DNA strand normally have free hydroxyl groups, unlike those in an RNA strand

False

T/F In nucleic acids, bases are covalently linked to the C 1’ atoms of the sugars

True

T/F In nucleic acids, neighboring sugar residues are linked to each other by a phosphodiester bond that connects the 3’ carbon atom on one sugar to the 5’ carbon atom of its neighbor

True

T/F regarding DNA replication, DNA replication is said to be semi-conservative b/c for each DNA helix only one strand serves as a template for new DNA synthesis

False

T/F Regarding DNA replication, the two DNA strands of the parental DNA helix are unwound using a DNA helicase

True

T/F Regarding DNA replication, the replication fork marks the point at which DNA is actively being replicated from a single DNA duplex to form new DNA strands

True

T/F Regarding DNA replication, the synthesis of new DNA strands always proceeds in the 5’ → 3’ direction

True

T/F Regarding DNA replication and synthesis, the leading strand is replicated continuously

True

T/F Regarding DNA replication and synthesis, the lagging strand is replicated discontinuously: the new DNA is synthesized as short pieces of DNA that must be linked together

True

T/F Regarding DNA replication and synthesis, a DNA polymerase always requires a DNA template to synthesize a complementary DNA

False

T/F Regarding DNA replication and synthesis, a DNA polymerase requires a short RNA primer when synthesizing new DNA strands using a DNA template

True

which is the best definition of noncoding RNA?

a functional RNA that is not translated to make a protein

If we take the number of chromosomes in a haploid sperm cell or egg cell to be n and the total content of genomic DNA to be C, what is the number of chromosomes and the total genomic DNA content of a diploid G₁ phase cell and in a diploid G₂ phase cell from the same organism.

2n chromosomes, DNA content of 2C in G1; 2n chromosomes, DNA content of 4C in G2

T/F Regarding the cell cycle, the M phase and the S phase are the critically important phases of the cell cycle, according to circumstance, the G2 phase and G1 phase are dispensable

False

T/F Regarding the cell cycle, the M phase is the only phase in the cell cycle when chromosomes stained w/ chemical dyes are visible under the light microscope

True

T/F Regarding the cell cycle, the G0 phase is a specialized phase that allows terminally differentiated cells to irretrievably exit the cell cycle and become most-mitotic cells

True

T/F Regarding the cell cycle, the G0 phase is a modified version of the G2 phase

False

When one of our chromosomes undergoes replication, the very long double helix within the chromosome DNA must also _____1_____. To do that the DNA double helix must be unwound using a dedicated enzyme known as a ____2_____. The individual parental DNA strands serve as ____3_____ for new DNA synthesis to generate new ____4____ daughter DNA strands. Because each parental double helix generates two daughter double helixes that contain one parental strand plus one newly synthesized DNA strand, DNA replication is said to be _____5______.

1. replicate

2. helicase

3. template

4. complementary

5. semi-conservative

Different types of DNA polymerase work in our cells, and in each case the new DNA strand is synthesized in the ___1___ prime to ____2___ prime direction. Most of our DNA polymerases use a DNA template from which a complementary new DNA strand is made. To help initiate DNA synthesis, a DNA polymerase requires an _____3____ primer that must first be synthesized by an _____3____ polymerase. A few DNA polymerases , known as ____4____ ______5_____ , use an _____3____ template to synthesize DNA. For example, an enzyme known as _____6_____ uses an _____3____ template to replicate DNA at the very ends of our chromosomes.

1. 5

2. 3

3. RNA

4. reverse

5. transcriptase

6. telomerase

When a DNA double helix is replicated, the point at which active DNA replication is occurring (where two double helices are being generated from one parental double helix) is known as a ____1____ ____2____. As DNA synthesis occurs, one of the DNA strands that is being produced, known as the ____3_____ ____4______ , is synthesized continuously in the same direction as the movement of the ____1____ ____2____. But the other strand, known as the ____5_____ ____4______ is synthesized in the opposite direction to the movement of the ____1____ ____2____. As a result it must be synthesized in short pieces (known as ____6_____ fragments, each synthesized using an RNA ____7____ ); each RNA_____7_____ binds to the DNA template a short distance in advance, allowing DNA synthesis in the backward direction. As a result of this asymmetry in DNA synthesis, DNA replication is said to be semi-____8______.

1. replication

2. fork

3. leading

4. strand

5. lagging

6. Okazaki

7. primer

8. discontinuous

A chromosome has one long DNA molecule. When a chromosome replicates, it forms two ____1_____ ____2_____, each containing a copy of the original DNA molecule, that are held together initially across their lengths by multi-subunit protein complexes called ____3_____. At a later stage, most of the ____3_____ are removed but some remain at the centromere to keep the two ____1_____ ____2_____ together until the _____4_____ stage of mitosis. At this point the remaining ____3____ begin to be removed so that the ____1_____ ____2_____ dissociate to become separate chromosomes. The _____5_____ attached to the _____6_____ at the centromeres of the two chromosomes ensure that the two chromosome copies migrate to opposite poles of the dividing cell (the identical chromosome copies normally ____7_____ equally into the daughter cells).

1. sister

2. chromatids

3. cohesins

4. anaphase

5. microtubules

6. kinetochore

7. segregate

____1_____ is the usual form of cell division and occurs after a previous round of chromosome (and DNA) ____2_____. The point of this type of cell division is to allow an increase in cell ___3____. As might be expected, ____1____ is particularly prevalent during periods of growth, but even in a fully grown adult there is a need for cell divisions in order to replace certain cells that have ___4____ lifespans, such as ___5____ cells and some types of epithelial cells, notably those in the _____6_____ tract.

1. mitosis

2. replication

3. number

4. short

5. blood

6. gastrointestinal

____1_____ is a specialized type of cell division that is exclusively used to produce ____2_____, and so occurs only in cells required for that purpose in the ____3_____ and ____4____. It really comprises two successive cell divisions following a single round of DNA synthesis. As a result, what was a single diploid germ cell precursor cell gives rise to ____5____ haploid ___6____ cells in men. In women, however, the two cell divisions are each asymmetric, producing one large cell plus a smaller cell (called a _____7_____ _____8_____) that is discarded, and so ultimately generating just a single ____9_____ cell.

1. meiosis

2. gametes

3. testis

4. ovary

5. four

6. sperm

7. polar

8. body

9. egg

The whole point of meiosis is to increase genetic ___1___ . That occurs in two ways. First, as a result of independent ___2____ of homologous chromosomes, sperm and egg cells contribute only one of the two alleles at each diploid locus in the two parents. Secondly, the process of ____3_____ ensures that the individual chromosomes in a sperm or egg cell are a mixture of alleles present on both homologs of the paternal or maternal grandparents. _____3______ involves breakage and re-joining of DNA strands on _____4_____ chromatids that can be observed under the microscope. The point of ___5____ (at which the chromatids have broken and re-joined) can be visualized under the microscope, when it is referred to as a _____6____ .

1. variation (or diversity)

2. assortment

3. recombination

4. non-sister

5. crossover

6. chiasma

The ends of linear chromosomes have specialized nucleoprotein structures known as ____1_____. The DNA component of a ____1_____ consists of short ____2____ repeats that have been highly ____3_____ during evolution. In humans and other vertebrates the DNA repeat is a hexanucleotide, with the sequence ____4_____. As a result, one of the two DNA strands is rich in guanines (G-rich) and one that is rich in cytosines (C-rich). At the very end of the ___1____ DNA, the G-rich strand has about 30 repeats that are ____5____. This short ____5____ overhang is able to bend backwards to base pair with complementary repeat sequences on the C-strand (after displacing the G-rich strand over a short region). The resulting structure, known as a ___6____ protects the ____1____ DNA from natural cellular _____7_____ that naturally remove some nucleotides from broken DNA strands during DNA repair.

1. telomere(s)

2. tandem

3. conserved

4. TTAGGG

5. single-stranded

6. T-loop

7. exonucleases

T/F Regarding exons, some exons in protein-coding genes consist of noncoding DNA

True

T/F Regarding exons, the first exon of a protein-coding gene always contains the translational start site

False

T/F Regarding exons, the last exon of a protein-coding gene always contains the normal termination codon

False

T/F Regarding exons, a coding exon is always translated in just one of the three possible forward reading frames

False

T/F Regarding the structures of amino acids, the general formula for a nonionised a.a. is H2N-CH(R)-COOH, that is, a central C atom is linked to an amino group, a carboxyl group, and H atom, and a side chain, R

True

T/F Regarding the structures of amino acids, the identity of the a.a. is determined by the side chain that is connected to the central C atom

True

T/F Regarding the structures of amino acids, the side chain of an amino acid is based on a branch that contains one or more C atoms

False

T/F Regarding the structures of amino acids, proline is unique in having a side chain that is connected to both the central C and also to the N atom of the amino group

True

T/F Regarding polypeptide structure, a polypeptide is a polymer composed of a linear sequence of amino acids

True

T/F Regarding polypeptide structure, a polypeptide normally adopts a rod-like conformation, with the side chains orientated in the same direction relative to the polypeptide backbone

False

T/F Regarding polypeptide structure, the a.a’s w/i a polypeptide are joined by a covalent bond known as a peptide bond

True

T/F Regarding polypeptide structure, peptide bonds form by a condensation rxn between the amino group of an a.a. and the carboxyl group of its neighbor

True

T/F Regarding protein structure, the primary structure is the linear sequence of amino acids

True

T/F Regarding protein structure, the secondary structure is the path followed by the polypeptide backbone over its length

True

T/F Regarding protein structure, the secondary structure of every protein contains an alpha helix

False

T/F Regarding protein structure, the structure of an alpha-helix is primarily determined by hydrogen bonding between chemical groups on the side chains

False

T/F Unlike DNA, RNAs are unmethylated, and only the four standard bases -A, C, G, U - are found in RNAs

False

T/F the primary structure of an RNA is the linear sequence of nucleotides

True

T/F the secondary structure of an RNA is dominated by H bonding between bases on the same strand

True

T/F Stem-loop structures are common in RNA and consist of complementary sequences that form stable base pairs, separated by a short sequence of unpaired bases

True

T/F a ribosome is a large ribonucleoprotein that contains multiple different types of RNA but just one type of protein

False

T/F During translation, a ribosome binds to the 5’ end of a mRNA, slides along it until the initiator AUG codon is identified, and continues until reaching an in-frame termination codon

True

T/F the single type of ribosomal protein is a crucially important peptidyltransferase

False

T/F the peptidyltransferase catalyzes the condensation reaction that allows joining of amino acids using peptide bonds

True

T/F During translation, the individual codons of an mRNA are “read” by transient H bonding to a complementary anticodon sequence on a transfer RNA

True

T/F According to their anticodon, transfer RNAs usually have a specific amino acid attached to their 3’ end

True

T/F When the anticodon of a tRNA binds to a codon w/ a suitably complementary sequence, the amino acid is released and becomes a part of a polypeptide

True

T/F Translation terminates at an in-frame termination codon (UAA, UAG, or UGA in the universal genetic code) because for these codons, there are no transfer RNAs w/ a complementary anticodon sequence

True