Biological Science: Definitions, Comparisons, Short Answers, Multiple Choices

This article covers definitions, comparisons, short answers, and multiple choices related to biological science. Topics include genes, chromosomes, chiasmata, bar bodies, topoisomerase, RNA interference, inducible operon, gene therapy, transduction, and more.

Running Head: BIOLOGICAL SCIENCE 0
Biological science
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Table of Contents
A Definition/comparison.......................................................................................................................1
B. Short answers................................................................................................................................5
C. Multiple choices................................................................................................................................9
References...........................................................................................................................................11

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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.

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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

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 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

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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 http://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 (

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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.
Figure 1 cell during metaphase of mitosis (8 chromosomes)

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Figure 2 Cell during Metaphase 1 of meiosis (8 chromosomes and 16 chromatids)
(DAT Bootcamp, 2019)
 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).

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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

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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
1. mRNA: it carries the genetic information from the nucleus of a cell to the cytoplasm
2. rRNA: It triggers regulate the translation of messenger RNA into protein
3. 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

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Methionine, Alanine, Valine, Leucine, Isoleucine
C. Multiple choices
1
Answer: D
2
Answer: E
3
Answer: D
4
Answer: A
5
Answer: A
6
Answer: D
7
Answer: B
8
Answer: B
9

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Answer: B
10
Answer
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.

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References
Albert, B. (2017). Molecular biology of the cell. (6th 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