***Bio Lec Chap 16 & 17*** Flashcards

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Chap 16

Describe the structure of DNA.

Nitrogenous bases: Thymine (T), Adenine (A), Cytosine (C), Guanine (G).

Sugar Phosphate (negatively charged) backbone, Deoxyribose (5-carbon sugar, pentose). 5’-3’.


Describe the process of DNA replication, including the role of the origins of replication and replication forks.

a. Replication begins at specific sites, origins, where two parental strands separate to form replication bubbles
b. Bubbles expand laterally as DNA replication proceeds in both direction; end of bubbles are called replication forks (Y-shaped region)
c. Replication bubbles fuse, and synthesis of daughter strands is completed


Explain the role of DNA polymerases in replication.

The main function of DNA polymerase is to make DNA from nucleotides, the building blocks of DNA. There are several forms of DNA polymerase that play a role in DNA replication and they usually work in pairs to copy one molecule of double-stranded DNA into two new double stranded DNA molecules.


Explain what energy source drives the polymerization of DNA.

It comes from two of the three total phosphates attached to each unincorporated base. (Free bases with their attached phosphate groups are called nucleoside triphosphates.)


Distinguish between the leading strand and the lagging strand.

Leading Strand: Goes into the 5’-3’ direction, lays down a single primer using primase it makes a continues complimentary copy.

Lagging Strand: Goes 3’-5’ direction, lays down multiply primer using primase and DNA is made in a discontinuous fashion.


Explain how the leading and lagging strands are synthesized.

Okazaki Fragments. At a replication fork, both strands are synthesized in a 5′ → 3′ direction. The leading strand is synthesized continuously, whereas the lagging strand is synthesized in short pieces termed Okazaki fragments.


Explain the roles of DNA ligase, primase, helicase, topoisomerase and single-strand binding proteins in DNA replication.



Chap 17

Briefly explain how information flows from gene to protein.

The sequence of nucleotides in DNA holds the instructions for making proteins but must first be transcribed into RNA nucleotides. RNA then takes the message out of the nucleus to the ribosomes, the site of protein synthesis.


Distinguish between transcription and translation.

Transcription- is the process where DNA language is converted into mRNA language (using a nucleotide language; DNA = CATG, RNA = CAUG

Translation- process where RNA language is covered into a protein (amino acid language). The use of the genetic code.


Compare where transcription and translation occur in bacteria and in eukaryotes.

Bacteria- Prokaryotic cell has no membrane bound DNA which causes both transcription and translation to occur in cytoplasm.

Eukaryotes- DNA is in nucleus, Transcription and RNA processing occurs in the nucleus, Transcription (where ribosomes are) occurs in the cytoplasm.


Define “codon” and explain the relationship between the linear sequence of codons on mRNA and the linear sequence of amino acids in a polypeptide.

Codon: is a three nucleotide sequence and equals one amino acid.

61 of the codons, code for amino acids; 3 of the 61 code for stop (stop the process of translation) and 1 of the 61 codes for start.


Explain what it means to say that the genetic code is redundant and unambiguous.

Redundant- codons can code for the same amino acid.

Unambiguous- No condo will code for another amino acid.


Explain the significance of the reading frame during translation.



Explain the evolutionary significance of a nearly universal genetic code.

The genetic code is used by almost all organisms.


Explain how RNA polymerase recognizes where transcription should begin.

The start site, +1


Describe the role of the promoter, the terminator and the transcription unit.

The promotor- contains base sequences that an enzyme called RNA polymerase.

The terminator- Location where transcription stops.

The Transcription unit-


Explain the general process of transcription, including the three major steps of initiation, elongation and termination.

RNA polymerase recognize and bind to specific base sequences in the promoter reign. Then RNA polymerase moves down DNA to +1 (start site) and opens up DNA to make transcript. RNA polymerase will make a complimentary copy of mRNA.


Explain how RNA is modified after transcription in eukaryotic cells.

-10 and -35 TATA box and require transcription factors (proteins that assist RNA).


Describe the structure and function of tRNA and of ribosomes.



Describe the process of translation, including the three major steps of initiation, elongation, and termination.