Chapter 14: Gene Expression

Question 1

What is gene expression?

Answer 1

DNA directs the synthesis of a protein or in some cases, just RNA

Most genes are controlled at the transcription (making of mRNA level)

Question 2

What is transcription?

Answer 2

synthesis of RNA using the information in DNA

Question 3

What is messenger RNA?

Answer 3

carries the genetic message from the DNA to the protein-synthesizing machinery of the cell

Question 4

What is translation?

Answer 4

synthesis of a polypeptide using the information in the mRNA

Question 5

What is the central dogma? Who stated this?

Answer 5

DNA to RNA to protein

Francis Crick

Question 6

triplet code

Answer 6

RNA is read in groups of 3 bases.

ex. UUU

This is called a codon.

Each codon codes for an amino acid. (except for stop codons)

Question 7

template strand

Answer 7

one of the DNA strands that is transcribed

determined by the promoter.

For any given gene, the same strand is used as the template. But the opposite strand may be used as the template for a different gene.

Question 8

codon

Answer 8

ex. UUU

mRNA

Can be translated to phenylalanine

Question 9

reading frame

Answer 9

Reading the symbols in the correct grouping

By groups of three/nonoverlapping

Question 10

What are the three stages of transcription?

Answer 10

initiation, elongation and termination

Take a look at the Mastering Biology animations!

Question 11

TATA box

Answer 11

a crucial promoter DNA sequence (25 nucleotides) which is part of the eukaryotic promoter

Question 12

RNA processing in Eukaryotes

Answer 12

5’ cap is added (modified guanine)

3’ tail (50-250 A)

introns are removed, exons are spliced together

Question 13

Why the cap and tail?

Answer 13

Help move message to cytoplasm

longer the tail? protect message from degradation

ribosome binding

Question 14

alternative RNA splicing

Answer 14

depending on which segments are treated as exons, a number of polypeptides can be made.

Reason for 100 000 proteins and 20 000 genes

Question 15

spliceosome

Answer 15

large complex made of proteins and small RNAs

Question 16

tRNA

Answer 16

transfer amino acids from cytoplasmic pool to a growing polypeptide in a ribosome

Question 17

wobble

Answer 17

flexible base pairing at the 3’ end of the mRNA codon.

For example. the U at the 5’ end of anticodon can pair with A or G at 3’ end of codon.

Question 18

What are the three sites of a ribosome and their functions?

Answer 18

P= holds tRNA carrying the growing polypeptide chain

A= holds tRNA carrying the next amino acid to be added to the chain

E= discharged tRNA

Question 19

What is initiation?

Answer 19

brings together an mRNA, a tRNA bearing the first amino acid (met), and the two subunits of the ribosome.

Question 20

Reverse transcriptase

Answer 20

The enzyme that makes a copy of DNA from RNA

Backward (Reverse) Transcription!

HIV virus has this!