Question 1

During meiosis some chromosomes do not separate from each other. This is called
A) diplotene
B) nondisjunction
C) diakinesis
D) zygotene
E) leptotene

Accepted Answer

Nondisjunction results in the failure of chromosome pairs to separate during meiosis, leading to abnormal chromosome numbers in daughter cells. This can result in genetic disorders such as Down syndrome (trisomy 21) or Turner syndrome (monosomy X). The other choices refer to different stages of meiosis.

Question 2

A patient with cancer possesses cells that are undergoing mitosis at a very rapid rate. The contractile rings that are formed during cytokinesis are composed of
A) thin filaments
B) intermediate filaments
C) thick filaments
D) microtubules
E) neurofilaments

Accepted Answer

The contractile ring is composed mainly of actin filaments, which are also known as thin filaments. These filaments interact with myosin to produce the constriction necessary for cytokinesis, which separates the two daughter cells. This process occurs during the final stage of mitosis, and its rate is often elevated in cancer cells due to mutations or dysregulation of cell cycle control mechanisms.

Question 3

A patient with a chromosomal complement of XXX has
A) a male phenotype
B) a female phenotype
C) a very short life span
D) a higher IQ than his/her siblings
E) trisomy of autosomes

Accepted Answer

A chromosomal complement of XXX indicates the presence of three X chromosomes, which is a type of sex chromosome aneuploidy. This condition typically results in a female phenotype.

Question 4

A 2-month old infant is brought to the physician's office to be examined, and the physician notices that he has flaccid muscles, a smaller head than usual, a large tongue, and a short nose and broad face. The parents say that the baby is very quiet and hardly ever cries. The pediatrician suspects aneuploidy. The baby probably has which of the following chromosomal configurations?
A) monosomy
B) trisomy
C) normal diploid complement
D) haploid complement
E) tetraploid complement

Accepted Answer

The flaccid muscles, smaller head, large tongue, short nose, broad face, and quiet demeanor are all symptoms of Down syndrome, which is caused by trisomy of chromosome 21.

Question 5

Which RNA synthesis is catalyzed by RNA polymerase II?
A) tRNA
B) rRNA that codes for the large ribosomal subunit
C) rRNA that codes for the small ribosomal subunit
D) mRNA
E) tRNA that carries the start codon

Accepted Answer

RNA polymerase II catalyzes the synthesis of messenger RNA (mRNA) in eukaryotic cells, which carries the genetic information from DNA to ribosomes for protein synthesis.

Question 6

In Fig. Img_010, the cell at the tip of the pointer is in which of the following phases of mitosis? 
A) prophase
B) prometaphase
C) metaphase
D) anaphase
E) telophase

Accepted Answer

The answer of In Fig. Img_010, the cell at the...

Question 7

A patient with a chromosomal complement of XO has
A) trisomy of the sex chromosomes
B) Turner's syndrome
C) monosomy of the autosomes
D) Klinefelter syndrome
E) a male phenotype

Accepted Answer

XO is indicative of having only one X chromosome and no Y chromosome, which is a characteristic of Turner's syndrome. This results in a female phenotype with underdeveloped ovaries, short stature, and other physical abnormalities.

Question 8

Chiasmata formation
A) occurs during metaphase II
B) results in the exchange of genetic material between nonhomologous chromosomes
C) occurs during the pachytene phase
D) results in nondisjunction
E) results in the formation of the synaptonemal complex

Accepted Answer

Chiasmata formation occurs during the pachytene phase of meiosis I, when homologous chromosomes pair up and exchange genetic material through crossing over.

Question 9

During a routine examination of a 3-year-old child, the pediatrician notes that the color of the pupil is white and that the child is cross-eyed. She asks the child's father if there are any cases of retinoblastoma in the family, and when the answer is in the affirmative she calls in a pediatric ophthalmologist. The ophthalmologist knows that retinoblastoma is due to the mutation of the Rb gene (retinoblastoma gene) and that it is a recessive trait. Not all cases of retinoblastoma have a familial component. In the sporadic form of retinoblastoma, the child's normal genetic complement does not predispose the child to have retinoblastoma. If this child had the sporadic form of retinoblastoma, then
A) one copy of the Rb gene mutated
B) both copies of the Rb gene mutated
C) the patient's future children will most probably will have one mutated Rb gene
D) the patient's future children will most probably have two mutated Rb genes
E) the mutated Rb gene is known as a protooncogene

Accepted Answer

In sporadic cases of retinoblastoma, both copies of the Rb gene are mutated, as opposed to the familial form where only one copy is mutated. Therefore, the best choice is B - both copies of the Rb gene mutated. Choices A, C, D, and E are all incorrect based on the genetic basis of sporadic retinoblastoma.

Question 10

During a routine examination of a 3-year-old child, the pediatrician notes that the color of the pupil is white and that the child is cross-eyed. She asks the child's father if there are any cases of retinoblastoma in the family, and when the answer is in the affirmative she calls in a pediatric ophthalmologist. The ophthalmologist knows that retinoblastoma is due to the mutation of the Rb gene (retinoblastoma gene) and that it is a recessive trait. Retinoblastoma can metastasize to the brain via the
A) optic nerve
B) superior division of the oculomotor nerve
C) trochlear nerve
D) abducent nerve
E) inferior division of the oculomotor nerve

Accepted Answer

Retinoblastoma can metastasize to the brain via the optic nerve, which connects the eye to the brain. The Rb gene mutation causes uncontrolled cell growth in the retina, leading to the development of retinoblastoma. If left untreated, the cancer can spread to other parts of the body, including the brain. Cross-eyedness and the appearance of a white pupil are both common signs of retinoblastoma, and a family history of the disease can increase the risk of developing it.

Question 11

In Fig. Img_009, the cell at the tip of the pointer is in which of the following phases of mitosis? 
A) prophase
B) prometaphase
C) metaphase
D) anaphase
E) telophase

Accepted Answer

The answer of In Fig. Img_009, the cell at the...

Question 12

A patient with a chromosomal complement of XXY has
A) trisomy of the autosomes
B) Turner's syndrome
C) monosomy of the sex chromosomes
D) Klinefelter syndrome
E) a female phenotype

Accepted Answer

XXY chromosomal complement is found in individuals with Klinefelter syndrome, which involves the presence of an additional X chromosome in males. They typically have underdeveloped testes, reduced fertility, and may have language and learning difficulties.

Question 13

In the Fig. Nucleus, the cell depicted in this electron micrograph synthesize 
A) short-chain lipids
B) proteins destined for the cytosol
C) cholesterol
D) proteins destined to be packaged
E) long-chain lipids

Accepted Answer

The electron micrograph shows a cell with extensive rough endoplasmic reticulum (ER), which is responsible for protein synthesis and packaging. Therefore, the best choice is D, proteins destined to be packaged.

Question 14

The binding of cyclin B to CDK1 (cyclin-dependent kinase 1) permits the cell to progress from
A) S phase into G2 phase
B) G2 phase into M phase
C) G1 phase into G2 phase
D) G1 phase into S phase
E) prometaphase into metaphase

Accepted Answer

Cyclin B binding to CDK1 activates the complex and allows for progression from G2 phase into M phase, also known as mitosis.

Quiz 2: Nucleus

During meiosis some chromosomes do not separate from each other. This is called

A patient with cancer possesses cells that are undergoing mitosis at a very rapid rate. The contractile rings that are formed during cytokinesis are composed of

A patient with a chromosomal complement of XXX has

Which RNA synthesis is catalyzed by RNA polymerase II?

In Fig. Img_010, the cell at the tip of the pointer is in which of the following phases of mitosis?

A patient with a chromosomal complement of XO has

Chiasmata formation

In Fig. Img_009, the cell at the tip of the pointer is in which of the following phases of mitosis?

A patient with a chromosomal complement of XXY has

In the Fig. Nucleus, the cell depicted in this electron micrograph synthesize

The binding of cyclin B to CDK1 (cyclin-dependent kinase 1) permits the cell to progress from