Question 1

Which of the following best describes the difference between euchromatin and heterochromatin?

Accepted Answer

Euchromatin is less condensed, gene rich, and stains lighter; heterochromatin is more condensed, gene poor, and stains darker.

Question 2

A karyotype is most useful for detecting which of the following genetic abnormalities?

Accepted Answer

Large chromosomal rearrangements such as deletions, duplications, and translocations

Question 3

Which type of chromosomal mutation involves the gain of a single chromosome, resulting in a karyotype of $$2n+1$$?

Accepted Answer

Trisomy

Question 4

A patient is diagnosed with Down syndrome due to a Robertsonian translocation. Which of the following best explains this genetic event?

Accepted Answer

A fusion of the long arms of two acrocentric chromosomes, creating a single large chromosome and loss of short arms.

Question 5

Which of the following is a consequence of nondisjunction during meiosis I?

Accepted Answer

Half of the gametes will be monosomic and half will be trisomic.

Question 6

Polyploidy in crop plants such as wheat is often beneficial because:

Accepted Answer

Allopolyploid species are evolutionary successful, aggressive, and efficient colonizers.

Question 7

A terminal deletion is best described as:

Accepted Answer

A deletion that occurs towards the end of a chromosome.

Question 8

Which of the following statements about mitochondrial DNA (mtDNA) is TRUE?

Accepted Answer

mtDNA is circular, generally small, and codes for rRNAs, tRNAs, and some polypeptides.

Question 9

A child presents with symptoms of MERRF (Myoclonic Epilepsy with Ragged Red Fibers). Which genetic principle explains the variable severity of this disease among affected individuals?

Accepted Answer

Heteroplasmy, where the proportion of mutant mtDNA varies among tissues and individuals.

Question 10

Which of the following best describes extranuclear inheritance?

Accepted Answer

Transmission of genetic information from parent to offspring through the cytoplasm, often involving organelles such as mitochondria and chloroplasts.

Question 11

In a cross between a variegated branch and a green branch in a plant, which type of inheritance pattern would allow offspring to be white, green, or variegated?

Accepted Answer

Cytoplasmic (maternal) inheritance

Question 12

Which of the following is NOT a property shared by mitochondrial and chloroplast DNA with eubacterial DNA?

Accepted Answer

Organization into nucleosomes

Question 13

A dicentric chromosome is characterized by:

Accepted Answer

A chromosome with two centromeres due to fusion events.

Question 14

Which of the following is a feature of the human mitochondrial genetic code that differs from the universal genetic code?

Accepted Answer

Some codons that are stop codons in the universal code code for amino acids in mitochondria.

Question 15

Which of the following best explains why monosomy of autosomes is usually not tolerated in humans?

Accepted Answer

Unmasking of lethal recessive alleles and haploinsufficiency.

Question 16

Which of the following is an example of a gene fusion event?

Accepted Answer

A translocation that creates a chimeric gene from two previously separate genes.

Question 17

Which of the following statements about cooperation between nuclear and organellar genomes is TRUE?

Accepted Answer

Some subunits of mitochondrial enzymes are encoded by nuclear genes, while others are encoded by mitochondrial DNA.

Question 18

A plant cell contains up to 16 sets of chromosomes in its liver cells. This is an example of:

Accepted Answer

Endopolyploidy

Question 19

Which of the following is a plausible mechanism for the origin of triploidy in humans?

Accepted Answer

Simultaneous fertilization of an egg by two sperm (dispermy)

Question 20

Which of the following best describes the concept of 'promiscuous DNA'?

Accepted Answer

DNA that is exchanged between the nucleus, mitochondria, and chloroplasts.

Lecture 7 (ch8&9)

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