Gene Expression

Question 1

What is gene expression?

Answer 1

The transcription and translation of DNA sequences

Gene expression involves the processing of the genetic code found in all forms of life.

Question 2

What determines an organism’s phenotype?

Answer 2

The proteins produced as a result of gene expression

The phenotype is the observable characteristics of an organism.

Question 3

What is the genome of an organism?

Answer 3

Its entire hereditary information encoded in DNA

Not all genes are expressed in every cell of an organism.

Question 4

True or false: Only a fraction of the genes in a cell are expressed.

Answer 4

TRUE

This indicates that gene expression is regulated and varies by cell type.

Question 5

What is the structure of RNA compared to DNA?

Answer 5

• Single stranded
• Contains uracil instead of thymine
• Has ribose sugar

RNA plays a crucial role in protein synthesis.

Question 6

What are the three differences between RNA and DNA?

Answer 6

• RNA is single stranded; DNA is double stranded
• RNA has uracil; DNA has thymine
• RNA has ribose; DNA has deoxyribose

These differences affect their functions in the cell.

Question 7

What are the bases found in RNA?

Answer 7

• Adenine
• Uracil
• Cytosine
• Guanine

RNA has the same bases as DNA except for uracil replacing thymine.

Question 8

What sugar is found in RNA?

Answer 8

Ribose

DNA contains deoxyribose sugar.

Question 9

What are the main forms of RNA?

Answer 9

• Messenger RNA (mRNA)
• Ribosomal RNA (rRNA)
• Transfer RNA (tRNA)

Each type of RNA plays a crucial role in protein synthesis.

Question 10

What is the function of Messenger RNA (mRNA)?

Answer 10

Carries a copy of the DNA code from the nucleus to the ribosome

mRNA is a single-stranded molecule that contains codons.

Question 11

What does Ribosomal RNA (rRNA) do?

Answer 11

Forms protein structures called ribosomes

rRNA works with ribosomal proteins in the synthesis of proteins.

Question 12

What is the role of Transfer RNA (tRNA)?

Answer 12

Carries specific amino acids to the ribosome

tRNA has a folded shape with an anticodon at one end and an attachment site for an amino acid at the other.

Question 13

What is the process of Transcription?

Answer 13

The first phase of gene expression where DNA is transcribed into mRNA

Transcription occurs in the nucleus of a cell.

Question 14

List the steps involved in Transcription.

Answer 14

• RNA polymerase unwinds the DNA double helix
• Breaks hydrogen bonds between base pairs
• Synthesizes a primary transcript of mRNA using free RNA nucleotides
• Forms a primary RNA transcript

The RNA nucleotides bond with exposed DNA bases through complementary base pairing.

Question 15

In transcription, what does RNA polymerase do?

Answer 15

Moves along the DNA and unwinds the double helix

It also synthesizes mRNA from the DNA template strand.

Question 16

What replaces thymine in RNA?

Answer 16

Uracil

This is a key difference between DNA and RNA.

Question 17

What is the primary transcript in transcription?

Answer 17

The initial mRNA formed from the DNA template

This primary transcript undergoes further processing before becoming mature mRNA.

Question 18

What is the primary transcript made of?

Answer 18

• Introns
• Exons

The primary transcript is processed to remove introns and join exons.

Question 19

What are introns in the primary transcript of mRNA?

Answer 19

Non-coding regions that are removed

Introns do not code for proteins and are spliced out during RNA processing.

Question 20

What are exons in the context of mRNA?

Answer 20

Coding regions that are joined together

Exons are retained in the mature mRNA transcript after splicing.

Question 21

What is the process called when introns are removed and exons are joined?

Answer 21

RNA splicing

This process results in the formation of a mature mRNA transcript.

Question 22

After leaving the nucleus, where does the mature mRNA transcript travel?

Answer 22

To a ribosome

The mature transcript travels through the cytoplasm for translation.

Question 23

What is the role of tRNA during translation?

Answer 23

• Carries specific amino acids
• Matches anticodons to mRNA codons

tRNA brings the correct amino acids to the ribosome based on the mRNA sequence.

Question 24

What determines the starting and end points of the polypeptide chain during translation?

Answer 24

• Start codons
• Stop codons

Start codon AUG codes for methionine; stop codons UAA, UGA, and UAG terminate the chain.

Question 25

What is the **start codon** in mRNA?

Answer 25

AUG ## Footnote AUG codes for methionine and signals the beginning of translation.

Question 26

What are the **stop codons** in mRNA?

Answer 26

* UAA * UGA * UAG ## Footnote Stop codons do not code for amino acids and signal the termination of polypeptide synthesis.

Question 27

What is the **start codon** in the translation process?

Answer 27

The first codon of the mRNA ## Footnote It signals the beginning of translation.

Question 28

What role does **tRNA** play in translation?

Answer 28

Transports specific amino acids to the ribosome ## Footnote The anticodon on a tRNA molecule is specific to only one amino acid.

Question 29

What forms the **polypeptide chain** during translation?

Answer 29

Amino acids joined together by peptide bonds ## Footnote The polypeptide chain is essential for protein structure and function.

Question 30

What is the last codon of the mRNA called that stops the translation process?

Answer 30

Stop codon ## Footnote This codon signals the termination of protein synthesis.

Question 31

What happens to **tRNA** after it delivers its amino acid?

Answer 31

Leaves the ribosome ## Footnote The tRNA departs after its specific amino acid is joined to the growing polypeptide chain.

Question 32

How does the assembly of **polypeptide chains** affect proteins?

Answer 32

Determines the structure and function of the finished protein ## Footnote The sequence and arrangement of amino acids are crucial for protein functionality.

Question 33

What is **gene expression**?

Answer 33

The process by which information from a gene is used to synthesize a functional gene product, typically a protein ## Footnote Gene expression involves transcription and translation processes.

Question 34

What is the result of **alternative RNA splicing**?

Answer 34

Different proteins can be expressed from one gene ## Footnote This process leads to the production of different mature mRNA molecules from the same primary transcript.

Question 35

What do **mature mRNA transcripts** contain?

Answer 35

Different exons ## Footnote These exons are the coding sequences that remain after splicing.

Question 36

What modifications can be made to proteins during processing?

Answer 36

* Addition of phosphate * Addition of carbohydrate * Cutting or combining polypeptide chains ## Footnote These modifications can affect the protein's function and activity.

Question 37

Where does **translation** occur in the cell?

Answer 37

Cytoplasm ## Footnote Translation is the process of synthesizing proteins from mRNA.

Question 38

What determines the **structure and function** of a protein?

Answer 38

The sequence of amino acids in a polypeptide chain ## Footnote The specific arrangement of amino acids leads to unique protein structures.

Question 39

How many different types of **amino acids** are there?

Answer 39

20 ## Footnote These amino acids are the building blocks of proteins.

Question 40

What causes the **folding** of polypeptide chains?

Answer 40

Hydrogen bonds and interactions between amino acids ## Footnote This folding creates three-dimensional shapes essential for protein function.

Question 41

Proteins are usually folded to form a **3D shape** held together by what?

Answer 41

Hydrogen bonds and other interactions ## Footnote The 3D shape of proteins is crucial for their biological activity.