CPA #12 Questions

Question 1

what are ribosomes made of?

Answer 1

polypeptides/proteins + rRNA

Question 2

describe a prokaryotic ribosome

Answer 2

5S rRNA + 23S rRNA + 34 polypeptides = 50S subunit
16S rRNA + 21 polypeptides = 30S subunit

total size = 70S

Question 3

describe a eukaryotic ribosome

Answer 3

5S rRNA+5.8S rRNA+28S rRNA+49 polypeptides = 60S subunit

18S rRNA+ >33 polypeptides = 40S subunit

total size = 80S

Question 4

how many amino acids exist

Answer 4

21-22

Question 5

define: codone

Answer 5

a triplet of mRNA nucleotides

Question 6

how do codons code for amino acids

Answer 6

each triplet of nucleotides (codon) specifies a specific amino acid (fig. 7.12)

Question 7

how many stop codons exist? what is function?

Answer 7

3 ; UAA, UAG, UGA (stop translation)

Question 8

how many start codons exist?

Answer 8

1 ; AUG (also methionine)

Question 9

explain how the genetic code is both redundant and specific

Answer 9

redundant: more than one codon is associated with every amino acid, except for methionine and tryptophan; the 1st two nucleotides are the same for coding for a specific amino
specific: the 3rd nucleotide base specifies which amino acid it codes for; one codon = one amino acid

Question 10

define: frameshift mutation (insertion or deletion)

Answer 10

following the insertion/deletion mutation, nucleotide triplets are displaced, creating new sequences of codons

Question 11

define: silent mutation

Answer 11

redundancy in the genetic code prevents the substitution from altering the amino acid sequence

Question 12

define: missense mutation

Answer 12

a change that specifies a different amino acid; info makes sense, but not the right sense; seriousness depends on where this occurs; changes first or second nucleotide base

Question 13

define: nonsense mutation

Answer 13

base pair amino substitution that changes amino acid codon into a stop codon

Question 14

define: mutagens

Answer 14

physical or chemical agents; radiation, DNA-altering chemicals

Question 15

exchange of nucleotide sequences between two DNA molecules and often involves segments that are composed of identical or nearly identical nucleotide sequences (homologous sequences)

Answer 15

genetic recombination

Question 16

when a recipient cell inserts part of a donors DNA into its own chromosome

Answer 16

recombinant cell

Question 17

what are the 3 types of horizontal gene transfer?

Answer 17

transformation, transduction, bacterial conjugation

Question 18

define: transformation

Answer 18

recipient bacterial cell takes up DNA from the environment, such as DNA released from dead organsisms

Question 19

define: transduction

Answer 19

transfer of DNA from one bacterial cell to another via a replicating virus (virus aka phage)

Question 20

define: bacterial conjugation

Answer 20

donor cell remains alive; requires physical contact between donor and recipient (F & R plasmids)

Question 21

define: sex pilus

Answer 21

thin, proteinaceous tubes extending from the surface of a cell

Question 22

define: F & R plasmids

Answer 22

fertility and resistance plasmids