Bio 141 Exam 3

Question 1

What was Crick’s adapter molecule and how was it discovered?

Answer 1

The adapter molecule is tRNA and it was discovered by accident by biologists.

Question 2

What is an “anticodon”?

Answer 2

An anticodon is a set of 3 ribonucleotides that forms base pairs with the mRNA codon

Question 3

How many different codons are there?

Answer 3

61

Question 4

How many different anticodons are there?

Answer 4

40

Question 5

Why is there a difference between number of codons and anticodons?

Answer 5

Wobble hypothesis- nonstandard base pairing is acceptable in third position of codon as long as it doesn’t change the amino acid that the codon specifies

Question 6

There must be at least how many different “aminoacyl tRNA synthetases?”

Answer 6

20 to account for each of the 20 major amino acids

Question 7

What do aminoacyl tRNA synthetases do?

Answer 7

These enzymes catalyze the addition of amino acids to tRNA.

Question 8

What are the three phases of protein synthesis (translation)?

Answer 8

initiation, elongation, and termination

Question 9

Initiation in translation?

Answer 9

a small ribosomal subunit binds to the mRNA ribosome binding site. In eukaryotes, initiation factors bind to the 5’ cap on mRNAs and guide it to the ribosome.The initiator aminoacyl tRNA bearing f-met binds to the start codon, then to finish off initiation a large ribosomal subunit binds

Question 10

Elongation in translation?

Answer 10

new tRNA moves into A site where its anticodon base pairs with the mRNA codon, then a peptide bond forms between amino acid attached to the tRNA in P site and A site, the tRNA attached to polypeptide chain moves into the P site, while the A site is now empty

Question 11

Termination in translation?

Answer 11

translocation opens the A site and exposes one of the stop codons, a release factor then fills the A site, a reaction that frees the polypeptide

Question 12

How do mRNAs and ribosomes get together to start the process of translation?

Answer 12

A section of ribosomal RNA in a small ribosomal subunit bins to a complementary sequence on an mRNA, also known as the ribosome binding site. It is six nucleotides upstream from the AUG start codon.

Question 13

What is a “ribozyme” and how do we know that a ribozyme catalyzes peptide bond formation?

Answer 13

A ribozyme is RNA that catalyzes protein synthesis. We know that a ribozyme catalyzes peptide bond because it is known that the active site in the ribosome catalyzes this process. Also, it was discovered that this active site is composed of rRNA.

Question 14

How does protein synthesis conclude when the ribosome reaches the end of the message?

Answer 14

It concludes when translocation exposes the stop codon in an mRNA strand. A release factor then enters the A site and breaks the bond between the P-site tRNA and the polypeptide, releasing the polypeptide.

Question 15

What processes take place after the translation of mRNA into a linear sequence of amino acids (i.e., into a polypeptide or protein) has been completed?

Answer 15

protein folding, some proteins receive sorting signals, some gain sugar/lipid groups crucial for normal functioning, many are altered by enzymes that add or remove phosphate groups

Question 16

What is meant by the term “phenotypic plasticity”?

Answer 16

Phenotypic plasticity allows plants to grow in ways that respond to their environmental condition.

Question 17

What is meant by the term “morphological diversity”?

Answer 17

Morphological diversity refers to differences in inner and outer structure.

Question 18

Where are apical meristems located?

Answer 18

Apical meristems are located at the tip of each root and shoot.

Question 19

difference between primary growth and secondary growth

Answer 19

purpose of primary growth is to increase the length of the root and shoot systems, Secondary growth increases the width of the plant body

Question 20

difference between determinate growth and indeterminate growth

Answer 20

Indeterminate growth means to grow throughout their lives, while determinate growth means to stop growing at a certain point.

Question 21

What is the difference between sexual reproduction and asexual reproduction?

Answer 21

Sexual reproduction involves meiosis, the production of gametes, fertilization and the resulting genetically different offspring. Asexual reproduction involves mitosis and results in identical offspring.

Question 22

What are the four primary organs that make up a flower?

Answer 22

sepals, petals, stamens, and one or more carpels

Question 23

function of sepal?

Answer 23

leaflike structures that make up the outermost parts of a flower; they enclose the flower bud as it develops and grows, protecting young buds from damage by insects or disease-causing agents

Question 24

function of petals?

Answer 24

function to advertise the flower to pollinators.

Question 25

function of stamens?

Answer 25

reproductive structures that produce male gametophytes.

Question 26

function of carpels?

Answer 26

produces female gametophytes.

Question 27

What is the “alternation of generations” in plants?

Answer 27

It is the life cycle in which a diploid multicellular sporophyte alternates with a haploid multicellular gametophyte.