Chapter 15 From Gene to Protein

Question 0

What is transcription? Translation?

Answer 0

Transcription is the synthesis of RNA using information in the DNA. Translation is the synthesis of a polypeptide using information in the mRNA.

Question 1

What is gene expression?

Answer 1

The process by which DNA directs the synthesis of proteins.

Question 2

What is messenger RNA (mRNA)? Transfer RNA (tRNA)?

Answer 2

mRNA is a type of RNA produced using a DNA template. tRNA is an RNA molecule that transfers amino acids from the cytoplasm to the growing polypeptide in a ribosome.

Question 3

What is a codon?

Answer 3

A series of three nucleotides that together form a unit of genetic code in a DNA or RNA molecule.

Question 4

How does base pairing differ between DNA strands and RNA strands?

Answer 4

In RNA, thymine is replaced with Uracil.

Question 5

What is RNA polymerase?

Answer 5

An enzyme that separates the two DNA strands and joins RNA nucleotides complementary to the DNA template strand.

Question 6

What is a promoter?

Answer 6

A DNA sequence where RNA polymerase attaches and initiates transcription.

Question 7

What is a terminator?

Answer 7

The sequence that signals the end of transcription. It is only found in bacteria.

Question 8

What is a transcription unit?

Answer 8

The stretch of DNA that is transcribed into RNA.

Question 9

What is a transcription initiation complex?

Answer 9

The complex of transcription factors and RNA polymerase bound to the promoter is called the transcription initiation complex.

Question 10

What is an anticodon?

Answer 10

A sequence of 3 nucleotides forming a unit of genetic code in a tRNA molecule, corresponding to a complementary codon in mRNA.

Question 11

Describe the process of transcription?

Answer 11

Once the transcription initiation complex is assembled, the RNA polymerase can unwind the DNA molecule and begin transcription. RNA polymerase exposes 10-20 DNA nucleotides at a time for transcription. Transcription takes place at the rate of 40 nucleotides/sec. Multiple enzymes can transcribe the same gene simultaneously allows the cell to make protein in large amounts.
Transcription stops when a specific sequence is reached.

Question 12

What is RNA processing?

Answer 12

Enzymes in a eukaryotic nucleus may modify the pre-mRNA is specific ways before it enters the cytoplasm.

Question 13

What is RNA splicing? Alternative RNA splicing?

Answer 13

RNA splicing is the removal of large portions of the RNA molecule. The alternative RNA splicing is the process by which different mRNA molecules are produced from the same transcript, depending on what is treated as the introns and the exons.

Question 14

What are introns? Exons?

Answer 14

Introns are noncoding, intervening segments of nucleic acid. Exons are regions of nucleic acids that are expressed by being translated into amino acids.

Question 15

What are the 3 binding sites for tRNA on the ribosome?

Answer 15

1. P site
2. A site
3. E site

Question 16

Describe the process of translation.

Answer 16

The small ribosomal subunit binds to mRNA near the “start” codon and the initiator tRNA binds to the start codon (P site). The large ribosome subunit then binds to complete the translation initiation complex. tRNA carrying amino acids specified by mRNA are brought in one by one (A site) and the amino acids are joined by peptide bonds. Empty tRNA are moved to he E site and exit the ribosome. This continues until the stop codon is reached.

Question 17

What has to happen for a protein to become functional after translation?

Answer 17

It must be folded to acquire it’s 3-D shape.

Question 18

What is a mutation?

Answer 18

A change in the nucleotide sequence of DNA.

Question 19

What is a point mutation?

Answer 19

A mutation on a small scale.

Question 20

What is nucleotide-pair substitution?

Answer 20

The replacement of one nucleotide and its partner with another pair of nucleotides.

Question 21

What is a silent mutation?

Answer 21

Has no observable effect on the phenotype.

Question 22

What is a missense mutation?

Answer 22

Changes one amino acid to another.

Question 23

What is a nonsense mutation?

Answer 23

Causes translation to be terminated prematurely.

Question 24

What is insertion?

Answer 24

Addition of a nucleotide pair in a gene.

Question 25

What is a deletion?

Answer 25

Loss of a nucleotide pair in a gene.

Question 26

What is a frameshift mutation?

Answer 26

Alters the reading frame of the triplet grouping of nucleotides on mRNA during translation.

Question 27

What is an operon?

Answer 27

An operon includes the operator, the promotor, and the genes that they control.

Question 28

What is a repressor?

Answer 28

Prevents gene transcription.

Question 29

What is differential gene expression?

Answer 29

The expression of different genes by cells with the same genome.

Question 30

What role does chromatin structure play in gene expression?

Answer 30

Genes with heterochromatin (highly condensed DNA) are usually not expressed. Chemical modifications to histones and DNA of chromatin influence both chromatin structure and gene expression.

Question 31

What three processes transform a zygote into an adult?

Answer 31

1. Cell division
2. Cell differentiation
3. Morphogenesis

Question 32

What are cytoplasmic determinats? Induction?

Answer 32

Cytoplasmic determinants are maternal substances in the egg that influence the course of early development. Induction is a process where signal molecules from embryonic cells cause transcriptional changes in nearby targets.

Question 33

What are homeotic genes?

Answer 33

They control pattern formation in the late embryo, larva, and adult stages.

Question 34

What are oncogenes? Proto-oncogenes? Tumor-suppressor genes?

Answer 34

Oncogenes are cancer causing genes. Porto-oncogenes are the corresponding normal cellular genes that are responsible for normal cell growth and division. Tumor-suppressor genes prevent uncontrolled cell growth.