Molecular Genetics

Question 1

DNA

Answer 1

comprised of chains of molecules called nucleotides

-nucleotides consist of:
~5 carbon cyclic structure called deoxyribose sugar
~a phosphate group
~one of 4 nitrogen bases

Question 2

4 Nitrogen Bases

Answer 2

• Adenine
• Thymine
• Guanine
• Cytosine

A&T always together
C&G always together

Question 3

4 enzymes used in DNA replication

Answer 3

DNA helicase -unwinds double helix
DNA polymerase III - synthesizes complimentary strand
DNA polymerase I - removes RNA primers & replaces with nucleotides
DNA ligase- joins DNA fragments together

Question 4

Gene expression

Answer 4

conversion of a gene into a specific trait through the production of a particular polypeptide

-help from RNA

Question 5

Polypeptide

Answer 5

long chain of amino acids

-make up proteins

Question 6

DNA vs RNA

Answer 6

• RNA is single stranded
• RNA contains ribose sugar
• uracil instead of thymine

Question 7

Transcription

Answer 7

DNA->RNA

Initiation
-RNA polymerase binds to a segment of DNA called the promoter
~this Sequence tells the enzyme where transcription should begin
~The promoter will sit upstream of the DNA sequence to be transcribed

Elongation

• RNA polymerase starts building single-stranded mRNA in the 5 to 3 direction
• Adenine in the DNA are paired with uracil in mRNA
• Exons are expressed introns are not

Termination

• RNA polymerase will continue to transcribe DNA until it reaches a termination sequence
• RNA polymerase falls off the DNA molecule an mRNA separates from DNA

Question 8

Translation

Answer 8

• During translation RNA is read in groups of three nucleotides, called codons
• Each codon calls for a specific amino acid to be placed in the polypeptide chain
• Codons can consist of any combination of the 4 nitrogen bases, so there are 64 possible codons for the 20 amino acids

Initiation

• Ribosome recognizes a specific sequence on the mRNA and binds to it
• In eukaryotes, The ribosome consist of two subunits large and small – the subunits clamp the mRNA between them
• The ribosome read the mRNA 5 to 3

Elongation

• tRNA brings amino acids to the ribosome - tRNA in a molecules have an anti-codon that is complementary to the code on in the mRNA
• amino acids keep adding on

Termination

• Eventually the ribosome reaches one of the three stop codons
• These codons do not code for an amino acid, there are no corresponding tRNAs
• A protein known as release factor recognizes that the ribosome has stalled and releases the polypeptide chain and the mRNA

Question 9

Point Mutation

Answer 9

a mutation at a specific base pair (substitution)

Question 10

Silent Mutation

Answer 10

Does not result in a change in the amino acid coded for (same sense)

Question 11

Missense (gene) mutation

Answer 11

Results in the single substitution of one amino acid in the polypeptide

Question 12

Nonsense mutations

Answer 12

convert a codon for an amino acid into a stop codon

Question 13

Frameshift mutation

Answer 13

a mutation that causes the reading frame of codons to change (insertion or deletion)

Question 14

Translocation

Answer 14

A transfer of a fragment of DNA from one side of the genome to another

Question 15

Inversion

Answer 15

Reversal of a segment of DNA within a chromosome

Question 16

Spontaneous mutation

Answer 16

A mutation occurring as a result of errors made in DNA replication

Question 17

Induced mutation

Answer 17

A mutation caused by chemical agent or radiation

Question 18

Recombinant DNA

Answer 18

A fragment of DNA composed of sequences originating from at least two different sources

organisms becoming factories for a hormone

Question 19

Restriction endonucleases

Answer 19

(restriction enzyme)

-Are like molecular scissors that can cut double-stranded DNA at a specific base pair sequence