Chapter 17

Question 1

point mutations

Answer 1

single nucleotide changes (ex: sickle cell disease results in protein sequence change that results in whole cell structure change)

Question 2

redundancy

Answer 2

protective that helps the genetic code so point mutations dont always cause amino acid changes

Question 3

silent mutations

Answer 3

DNA change that does not cause protein change (ex: GCC->GCA, both code for alanine)

Question 4

misense mutations

Answer 4

one amino acid is changed to a diff, amino acid (ex: GCC->CCC, alanine to proline)

Question 5

nonsense mutations

Answer 5

amino acid is changed to a stop codon, causes the protein to be shorter or truncated (ex: AAA->UAA, lysine to stop)

Question 6

reading frame

Answer 6

mRNA is read as non-overlapping sequence, established when ribosome finds the AUG start codon

Question 7

changes in reading frame

Answer 7

can cause drastic changes in amino acid sequence, insertion/deletions have more drastic change then a single substitution (making 3 new vs just 1)

Question 8

eukaryotic mRNA processing

Answer 8

1. 5’ cap (protects mRNA from degradation and aids in translation initiation by binding to ribosome) 2. 3’ poly-A tail (enhances stability and translation efficiency) 3. Splicing, introns (non-coding sequences are removed from pre-mRNA) exons (coding sequences are joined to form continuous sequence)

Question 9

snRNAs and proteins

Answer 9

make lariat structure (intermediate structure when introns are removed), they remove introns and join exons

Question 10

mRNA export

Answer 10

need assistance to leave through nuclear pores, only when mRNA is completely processed and ready to go

Question 11

RNA synthesis

Answer 11

1. Initiation- transcription factors identify promoter and bring RNA pol to promoter site once transcription is ready, promoter contains TATA box recognized by tfs, tfs pull DNA strands apart at the box and RNA pol is placed there, ribosome small unit scans until dind start codon, tRNA enters at P site and large subunit attaches
2. Elongation- RNA pol moves down DNA strand and adds nucleotides to growing RNA strand, 10-20 nucleotides are pulled apart in enzyme, RNA pol unzips and rezips DNA as it moves down strand, RNA pol adds 3’ end and moves twrds 5’ end, RNA pol is slower than DNA pol and proofread but less carefully, RNA mistakes are less harmful than DNA
3. Termination- eukaryotic and prokaryotic have diff methods

Question 12

prokaryotic termination

Answer 12

rho-dependent, a protein that binds to RNA transcript and moves up strand, RNA pol moves slow and rho catches up and bumps it off and makes it stop, rho independent termination involves the RNA transcript forming complicated base paired structures and interfering with RNA pols movement

Question 13

eukaryotic termination

Answer 13

relies on specific sequence, enzyme cuts RNA transcript at this sequence, another enzyme binds and adds polyAtail, RNA pol keeps going down DNA strand, another enzyme binds to RNA and degrades it heading towards RNA pol and dislodges it

Question 14

translation of soluble vs membrane proteins

Answer 14

soluble proteins translated in cytosol, transmembrane and anything entering the endomembrane system are cotranslationally inserted into ER using translocon complex channel