Answer To Biology Questions - Definition, Short Essay, And Multiple Choice

Definition/Comparison Questions

A. Definition/Comparison Questions

Instructions: In your own words, define the pairs of terms given below. Write in complete sentences, stating the differences and relationships between the two terms, and give specific examples where appropriate. A complete answer usually requires four to eight sentences.

1. gene / chromosome
2. chiasmata / non-disjunction
3. Barr body / sex chromosomes
4. topoisomerase / DNA polymerase
5. leading strand / Okazaki fragment
6. miRNA / RNA interference
7. inducible operon / repressor
8. gene therapy / DNA fingerprinting
9. transduction / conjugation
10. cytoplasmatic inheritance / genomic imprinting

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B. Short Answer/Short Essay Questions

Instructions: Answer each of the questions given below in your own words. Write in complete sentences where appropriate. A complete answer usually requires one to two sentences per mark, so a three-mark question would be answered in three to six sentences. This section is worth a total of 40 marks.
1. Draw two cells, one showing the arrangement of chromosomes at metaphase of mitosis, and the other showing the chromosomes at metaphase I of meiosis. Describe how the arrangements differ and how this relates to variation in the daughter cells.
2. Compare and contrast DNA synthesis in prokaryotes and eukaryotes.
3. What are restriction enzymes? How are they used in cloning?
4. Gene regulation in eukaryotes occurs on several levels. Which level of gene regulation is most important? Describe one example of the the most important level of gene regulation.
5. The lac operon in E. coli is subject to both positive and negative regulation. Describe and explain both in detail.
6. What are the three main types of RNA, and what are their roles?
7. What is the proofreading mechanism of DNA, and which enzymes are involved?
8. Using the following DNA template strand sequence, answer the questions below: 3’–TACCGGCACGATTAG–5’ a. What is the mRNA sequence? b. List the anticodons for each tRNA involved in translation of the sequence. c. What is the final sequence of amino acids in the peptide produced?


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C. Multiple Choice Questions

1. Interrupted coding sequences include long sequences of bases that do NOT code for amino acids. These noncoding sequences, called ________, are found in ________ cells.

a. exons; prokaryotic

b. introns; prokaryotic

c. exons; eukaryotic

d. introns; eukaryotic

e. none of these are correct

2. Which of the following is TRUE about cytoplasmic inheritance?

a. It refers to chromosomal genes.

b. It is independent of the gender of the parent.

c. It follows Mendel’s law of segregation.

d. It originates from plasmids in the cytoplasm.

e. It is based on the widely different amount of cytoplasm that male and female parents provide when gametes are formed.

3. Aneuploidy describes

a. a phenomenon that only occurs in plants.

b. a condition in which an extra chromosome is present or one is absent.

c. a disomy in somatic cells.

d. an uncommon condition in humans.

e. a mutation with a beneficial effect.

4. If cultured normal human cells are treated with telomerase, the cells are most likely to

a. undergo more cell divisions than normal.

b. undergo fewer cell divisions than normal.

c. die almost immediately.

d. undergo more active gene expression.

e. enter meiosis.

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5. Which of the following are produced by meiosis?

a. haploid cells

b. eggs

c. sperm

d. plant spores

e. all of these

6. A mutation that replaces one amino acid in a protein with another is called a ________ mutation.

a. frameshift

b. recombinant

c. nonsense

d. missense

e. neutral

7. In a repressible operon under negative control, the repressor protein functions to

a. stimulate transcription in the presence of a corepressor.

b. turn off transcription in the presence of an inducer.

c. stimulate transcription in the presence of a coactivator.

d. turn off transcription in the presence of a corepressor.

e. It doesn’t function in this situation.

8. Which of the following is TRUE about X-linked recessive genetic diseases?

a. They affect more males than females.

b. They affect more females than males.

c. The disease phenotype is not gender correlated.

d. Males may have the corresponding allele on the Y chromosome.

e. An individual with two copies of the gene may not be symptomatic for the given disease.

9. Bacterial gene regulation occurs mainly at the ________ level.

a. translational

b. transcriptional

c. posttranscriptional

d. feedback inhibition

e. posttranslational


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10. Mitosis results in two daughter cells. When comparing the genetic information

Definition/Comparison Questions

A. Definition/comparison

1. Gene: It is unit of hereditary and a fragment of DNA on a chromosome code for protein
2. Chromosome: DNA  in the nucleus of each cell packaged by a thread like structure called the chromosome  

Differences	Chromosome	Gene
	Chromosomes can be seen under microscope	Not visible under microscope
	Composed of DNA, RNA, and histones	Composed of either RNA or DNA
Similarities
	Two sets of chromosomes are in each diploid cell	Two copies of a gene in each diploid cell
	During meiosis chromosome duplicates	Gene duplication also occurred during meiosis (Finegold, 2018)

2.Chiasmata

During synopsis, the non-sister chromatids break and recombine with the homologous chromosome. The chromatids remain attached at the single point of exchange which is called chromatin

Nondisjunction

It is the Failure of chromosomes to divide at meiosis stage in karyokinesis, which results in chromosome having only one daughter cell.

Divergences

Nondisjunction is characterized as an abnormal distribution of the chromosomes to the cell poles during mitotic division.   

Chiasmata are the point at which two chromosomes remain in contact with one another during the first metaphase of the meiosis.

3.Bar Bodies and sex chromosome

A female shut off one of their x chromosomes during the development of the embryo. This inactivation of X chromosome is called Barr body.

Sex chromosomes X and Y are chromosomes that play an important role to determine whether the person is male or female.

Relationship

Barr bodies are actually inactivated X chromosomes

4.Topoisomerase

Topoisomerase is a class of enzymes that changes the supercoiling of dsDNA. Example: DNA topoisomerase1, 2, 3, 4

DNA polymerase

DNA polymerase is an enzyme that synthesizes DNA, molecule by assembling nucleotides. Example DNA polymerase 1, 2, 3, and 4

Differences

• Functions of DNA topoisomerase include DNA replication, transcription, and recombination
• DNA polymerase takes part in DNA replication

5.Leading strand

Leading strand is the one replicated strand of DNA double-strand that grows continuously without gaps

Okazaki fragments are the small fragments of newly synthesized DNA formed on lagging strand

Differences

• Leading strait is a complete strand without any gaps  
• Okazaki fragments a are short and located on lagging strand

6.RNA Interference

It is a set of pathways that takes part in regulation of gene expression

miRNA

These are small endogenous RNA takes part in degradation and translation repression of a specific mRNA.

Differences

• miRNA is 21-25 nucleotides in length
• RNAi is 20 nucleotides in length

7.Inducible operon and suppressor

An inducible operon is a type of operon in which a key metabolic element induces the transcription process of the structural genes. Example: lac operon

Suppression

It is an operon that transcribes the structural genes in the absence of repressor. Example: trp operon

Similarities

Both inducible operon and suppressor have structural genes with the same function are operated by a single promoter https://www.123helpme.com/view.asp?id=114172

8.Gene therapy and DNA fingerprinting

• Gene therapy is defined as an experimental technique where genes are used to treat a disease.
• DNA fingerprinting is a genetic method of isolating and finding out variable elements within the DNA sequence.

Differences

• In gene therapy mutated or disease-causing gene is replaced with health copy of a gene.
• In DNA fingerprinting, a fragment of DNA has been used to solve issues such as criminal cases, paternity tests

9.Transduction and conjugation

• Transduction involves the transfer of genetic substances form on bacteria to another by using bacteriophage
• Conjugation is the short term direct contact between the two bacterial cells results in an exchange of DNA.

Differences

• In Transduction Phage’s are used to transfer the genetic information
• In conjugation, the genetic material is transferred by a direct contact 

10.Cytoplasmic inheritance and genomic imprinting

• When the characteristics are transferred from parents to their offspring which controlled by cytoplasmic genes is known as cytoplasmic inheritance
• Genomic imprinting is a phenomenon or process whereby a gene is biochemically marked with genetic information of its parents  

Differences

• In cytoplasmic inheritance, the pattern of inheritance or mitochondria is followed
• In genomic imprinting, an allele from one of the parent is inherited and another one is silent

B. Short answers

1.

                                                                                                    

 

                                                           

• At metaphase stage, there are 8 chromosomes and line up in a single file on a metaphase plate
• In metaphase 1 of Meiosis 16 Chromosomes (pair) are aligned on the different side of the metaphase plate  

2.Similarities between prokaryotic and eukaryotic DNA Synthesis  

• The steps of DNA replication are same in both eukaryotes and prokaryotes
• DNA helicase enzyme is associated with the unwinding of DNA
• DNA polymerase takes part in Formations of NEW DNA strand
• Both types of organisms follow semiconservative replication

Differences

• In prokaryotes, replication takes place in two opposite directions but in a prokaryotic cell, the replication is unidirectional (Taylor, 2018).

3.Restriction enzymes are the DNA cutting enzymes. They cut the DNA at one or more sites of sequence

Example – restriction endonucleases, ligase

The restriction endonuclease enzyme is used in recombination with the help of plasmid. Restriction enzyme recognizes a specific site at DNA sequence and cleaves it. DNA ligase works to join the strands.

4.Gene regulation

Steps involved in gene regulation

• Chromatin accessibility
• Transcription
• RNA processing
• RNA stability
• Translation
• Protein activity

Transcription is the most important level of the gene regulation where the protein binds to a particular DNA sequence and promotes or stops transcription (Khan Academy, 2018).

5.Negative and positive regulation of lac operon in E. coli

A negative regulation takes place when repressor protein that binds to the nucleotide sequence present within the lac-operator site. After binding of lac repressor, transcription of LacZ, LAcY, and LacA by RNA polymerase is prevented. In the absence of lactose, the repressor binds to O site and block RNA polymerase from binding to the p site and stops transcription

Lac operon is positively regulated when lactose is bind to the repressor site to allow RNA polymerase to transcript a gene of interest.

6.Types of RNA

.mRNA: it carries the genetic information from the nucleus of a cell to the cytoplasm

.rRNA: It triggers regulate the translation of messenger RNA into protein

.tRNA: they bring to transfer the amino acid to a ribosome in order to make polypeptide (Albert, 2017)

7.DNA proofreading

DNA proofreading is a mechanism for correcting errors such as unpaired bases in the nucleic acid or protein synthesis (Seeberg, 2012).

• DNA polymerase is the enzyme that plays a major role in this mechanism.

8.DNA Template

mRNA sequence

5’ – AUGGCCGUGCUAAUC– 3’

Anticodon

UAC, CGG, CAC, GAU, UAG

Final sequence

AUG GCC GUG CUA AUC

Methionine, Alanine, Valine, Leucine, Isoleucine

C. Multiple choices

1.d 
introns; eukaryotic

2.e 

It is based on the widely different amount of cytoplasm that male and female parents provide when gametes are formed.

3.d 

an uncommon condition in humans.

4.a 

undergo more cell divisions than normal.

5.a

haploid cells

6.d 

missense

7.b

turn off transcription in the presence of an inducer.

8.b

They affect more females than males.

9.b

 transcriptional

10. 

During mitosis on cell is divided in to two daughter cells at Telophase stage

• Numbers of chromosome are same as parent cell
• Nucleus also divided in two and each daughter cell has one nucleus.

References:

Albert, B. (2017). Molecular biology of the cell. (6^th ed.). San Francisco: Garland Science.  

DAT Bootcamp (2018). Chromosome and chromatid numbers during mitosis and meiosis. Retrieved from: https://datbootcamp.com/biology-strategy/chromosome-and-chromatid-numbers-during-mitosis-and-meiosis/

Finegold, D. N. (2018). Genes and chromosome. Retrieved from: https://www.msdmanuals.com/home/fundamentals/genetics/genes-and-chromosomes

Hasunuma, K. (2009). Genetics and molecular biology. Oxford, UK: EOLSS publications.

Helmenstine, A. M. (2018). What are the three types of RNA? What are their functions?. Retrieved from: https://www.thoughtco.com/types-of-rna-and-their-functions-606386

Khan Academy (2018). Overview of Gene Regulation. Retrieved from: https://www.khanacademy.org/science/biology/gene-regulation/gene-regulation-in-eukaryotes/a/overview-of-eukaryotic-gene-regulation

Seeberg, E. (2012). Chromosome damage and repair. New York: Springer Science & Business Media.

Taylor, S. (2018). Compare and contrasting DNA replication in prokaryotes & eukaryotes. Retrieved from: https://sciencing.com/comparing-contrasting-DNA-replication-prokaryotes-eukaryotes-13739.html