Chapter 10 - Molecular Biology of a Gene

Question 1

what is molecular biology?

Answer 1

the study of DNA, its properties, and its role within the cell at the molecular level.

Question 2

primary structure of DNA

Answer 2

4 types of nitrogenous bases:
single ring pyrimidines: cytosine and thymine
double ring purines: guanine and adenine

Question 3

primary structures of polynucleotides

Answer 3

includes a nucleotide monomer which consists of a phosphate group, sugar, and nitrogenous base.

Question 4

what is the sugar phosphate backbone?

Answer 4

same basic structure in all polynucleotides. it is read from 3’ (sugar) end to 5’ (phosphate) end.
sugars are either ribose (RNA) or deoxyribose (DNA).

Question 5

primary structure of RNA

Answer 5

almost the same as DNA, sugar is a ribose, thymine is replaced by uracil and it does not form a double helix.

Question 6

what are base pairing rules?

Answer 6

A to T and C to G. with these rules, each strand of DNA can serve as a template for synthesis of new copy of its compliment.

Question 7

what is DNA polymerase?

Answer 7

enzyme which forms new chain of nucleotides against template, adding monomers at 3’ end. can synthesis smoothly against one strand, must rely upon DNA ligase joining up interrupted new segments against other strand.

Question 8

what is the central dogma?

Answer 8

the genotype (DNA) encodes instructions for the primary structures of proteins = sequence of amino acids. 
RNA transmits genetic information (translation & transcription) to protein ~ synthesis mechanism.
proteins produce phenotype.

Question 9

gene and protein relationship

Answer 9

one gene = one protein (poly peptide).

Question 10

What is DNA?

Answer 10

linear sequence of DNA bases; in a gene, exact sequence very important as it specifies order of amino acids in primary structure of a protein.

Question 11

what is RNA?

Answer 11

linear sequence of RNA nucleotides synthesized upon the plate of DNA bases; complementary RNA bases = transcription of a gene.

Question 12

what is a polypeptide?

Answer 12

sequence of amino acids corresponding to linear sequence of bases in RNA molecule - translation of RNA codons to specific amino acid.

Question 13

triplet codon of bases

Answer 13

codes for each of 20 amino acids in amino acid pool used by terrestrial organisms, with abundant redundancy = room for mistakes.

Question 14

what are substitution mutations?

Answer 14

one nucleotide replaces another (one way of forming alleles). may make a little or great difference.

Question 15

what are deletions and insertions?

Answer 15

generally distort reading frame. sequence of poly peptide changes from that point on.

Question 16

What are the 3 types of RNA?

Answer 16

mRNA: transcribed from DNA, carries codons for linear sequence of amino acids. codons are a series of 3 RNA bases, compliments to DNA triplet code.
rRNA: makes up bulk of ribosome
tRNA: attaches to ribosome, carries anticodon (compliment to specific codon on mRNA) at one end and appropriate amino acid at the other.

Question 17

what is transcription initiation?

Answer 17

promoter DNA sequence on chromosome. RNA polymerase attaches to promoter on “unzipped” sequence of DNA. RNA monomers line up against corresponding DNA monomers, held by hydrogen bonds. RNA polymerase joins RNA monomers into polypeptide mRNA.

Question 18

what is transcription elongation?

Answer 18

mRNA strand elongates and peels away?

Question 19

what is transcription termination?

Answer 19

terminator DNA sequence on chromosome. RNA polymerase attaches to terminator on “unzipped” sequence of DNA. mRNA detaches from RNA polymerase = transcription complete.

Question 20

Eukaryotic Transcription

Answer 20

takes place in nucleus: mRNA must pass through nuclear membrane to ribosomes in cytoplasm or rough ER = translation. various transcript factors involved.
processing in nucleus: cap and tail added to promote translation.

Question 21

what is splicing?

Answer 21

intron sequences clipped out from between exons (coding sequences), exons joined together to form continuous coding mRNA. Allows for regulation.

Question 22

what are the two meanings of translation?

Answer 22

1. rendering a message from one language to another.

2. moving an object from one place to another.

Question 23

what happens during translation?

Answer 23

the mRNA moves from the transcription site to the site where the codons will be read and amino acids polymerized. the information encoded down the length of the mRNA is rendered into a sequence of amino acids.

Question 24

what is the role of tRNA?

Answer 24

the interface between amino acid pool in cytoplasm and RNA sequence along length of mRNA. one end carries anticodon = bases complementary to the codon for a particular amino acid on mRNA. other end: sites for attachment of amino acid specified by codon/anticodon by specific enzymes. enzyme recognizes anticodon and binds correct amino acid to tRNA.

Question 25

what is the role of ribosomes?

Answer 25

function: protein synthesis site. composed of rRNA and proteins. holds mRNA and complementary tRNA close together, allows peptide bonds to form between adjacent amino acids.
when not in use, two separate subunits, large and small.
assembled, there are two tRNA binding sites, with one mRNA binding site.

Question 26

what is translation initiation?

Answer 26

isolated ribosomal small subunits bind with mRNA poly nucleotide. start codon of mRNA binds with initiator tRNA in P site. large ribosomal subunit binds with complex.

Question 27

what is translation elongation?

Answer 27

sequential attachment of appropriate tRNAs to complementary sections of mRNA as it moves along mRNA binding site. peptide bonds formed between successive amino acids as they are brought to the ribosomes.

Question 28

what is translation termination?

Answer 28

stop codon on mRNA encountered. polypeptide released from ribosome. subunits separate and translation is complete.