Genetics Review

Semi-conservative replication

Correct theory
-proposed by Watson and Crick
-the double helix is split, and a new strand of DNA is built on each of the original parent strands

Helicase

unzips DNA, also causing it to unwind

Enzyme responsible for relieving tension in the unwinding DNA by untwisting it.

Gyrase

Adds DNA nucleotides during replication.

DNA polymerase III

Stabilizes the unzipped strands to prevent reannealing.

Single Strand Binding Proteins

Name of fragments that are formed on lagging strand.

Okazaki

The direction in which new DNA is built.

Your Answer: 5'-3'

Adds RNA nucleotides.

Primase

Replaces RNA nucleotides with DNA.

DNA polymerase I

Breaks bonds between nitrogenous bases, unzipping DNA.

Helicase

A lesser known enzyme, thought to be responsible mainly for proofreading new DNA.

DNA polymerase II

Which of the following is found in the nucleolus?

rRNA

Which of the following is not found in the cytoplasm?

DNA

Which of the following best represents the mRNA that would result from the following template strand? AATTAACCGGCGAATT

UUAAUUGGCCGCUUAA

Which enzyme is responsible for transcription?

RNA polymerase

A section of mRNA 6 codons long would code for how many amino acids?

6

Which statement is correct regarding the flow of information in the cell?

DNA - mRNA - ribosome - tRNA - protein

What is the function of the poly(A) tail that is added to mRNA?

To prevent degradation of the mRNA

The degeneracy of the genetic code means:

If a mutation occurs, it is more likely to be silent

Which of the following statements is correct?

the promoter region must be easy to unzip

How is mRNA prepared for it's entry into the cytoplasm?

A methyl guanosine cap is added

What is the function of a spliceosome?

remove introns

What is responsible for delivering amino acids to the ribosome?

tRNA

What is responsible for transferring genetic information from the nucleus into the cytoplasm?

mRNA

What is responsible for building protein by making peptide bonds?

ribosome

What is complementary to the mRNA codon?

anticodon

What is the end product of transcription?

mRNA

What is the end product of translation?

polypeptide

Gyrase (topoisomerase)

relieves tension in the DNA that builds up as a result of the unzipping

Single strand binding proteins (SSB's)

proteins that stabilize the unzipped single strands

Replication fork

the opening where DNA is unzipped. There are several i eukaryotic DNA, resulting in replication bubbles

Primase

Adds RNA primers to the single DNA strands to initiate polymerization

DNA polymerase III

Adds DNA nucleotides in the 5' to 3' direction (moves from 3' to 5' direction on the parent strand)

The lagging strand is built in what direction

5 to 3 direction

The leading strand

The faster strand that is made continuously in the direction that the DNA is unzipping

DNA ligase

glues the Okazaki fragments together

DNA polymerase I

Replaces RNA primers with DNA nucleotides.

DNA polymerase II

Involved in proofreading the newly formed strands

The genetic code is DEGENERATE

this means that more than one triplet or codon codes for the same amino acid or stop command...why is this important? (allows small errors to go unnoticed)

Codons

3 nitrogenous bases on DNA or mRNA = a codon. A codon codes for an amino acid.

Start Codon

AUG (methionine, or met)
The codon that signals the start of a polypeptide chain and initiates translation

Stop codon

UAA, UAG, UGA
A codon that signals the end of a polypeptide chain and causes the ribosomes to stop translation

What do the ribosomes do?

Produce polypeptides

rRNA

Ribosomal RNA; normally located in the nucleolus of the cell, where ribosomes are formed
Ribosomes are made of rRNA and proteins

tRNA

transfer RNA; each tRNA carries a particular amino acid - this is dictated by its anticodon (which is complementary to the codon found on the mRNA)

mRNA

molecular expression of the DNA ge

Direction genetic code is read in

5 - 3 direction on mRNA

Small Scale mutations

Small scale mutations include mutations of an individual base pair called point mutations, and of small groups of base pairs. There are several different types of point mutatoins including: substitution, insertion or deletion, and inversion.

Large Scale Mutation

Large-scale mutations can involve multiple nucleotides, entire genes, or whole regions of chromosomes. Translocation? and Inversion occur.

Translocation

Occurs when entire genes or sequences are moved to a different chromosome. This can change the regulation of the gene or even the protein that results.

Inversion

Occurs when a section of the DNA is flipped. This results in a mutation only if the inversion occurs in a section that codes for protein.

Silent mutation

a change in a non-coding part of DNA or the third base of a codon that is redundant in its coding for an amino acid. Silent mutations have no effect on the amino acid made by translation.

Misence Mutation

a change in a codon so that a different amino acid is produced. This can either be small scale (one or two amino acids) or large (entire protein changes).

Nonsense mutation

a change in a codon so that the codon acts as a punctuation, stopping a transcription prematurely.

How do mutations occur

Some are spontaneous, arising in the duplication actions of DNA. There are also that occur because of the presence of particular chemicals or radiation, mutagenic agents. Their presence induces mutations at a far higher rate than found normally.

Transcription

Copying information from DNA into mRNA

Initiation stage

RNA polymerase binds to the DNA at a promoter region (a region that is 'upstream', or a bit before, the actual gene). It is often a string of A's and T's - since they each only have 2 hydrogen bonds, it takes less energy for RNA polymerase to break them a

Elongation stage

The mRNA is built on only one of the strands - the template strand is the one that the mRNA is built on, and the coding strand is the one that is not used. Note: the coding strand is identical to the resulting RNA, except that the DNA contains T's and the

Termination stage

Terminator sequence tells RNA polymerase to stop transcription. The mRNA detaches itself, and can leave the nucleus.

What are biological molecules responsible for?

- the storage and transmission of inherited information
- providing structure for cells and organisms
- carrying out functions necessary for life

Translation

Utilization of mRNA as a blueprint to make polypeptide(s)

Substitution mutation

? a substitution occurs when one base is replaced with another - this can result in silent, missense, nonsense mutations

Insertion or deletion mutation

? an insertion or deletion occurs when a base is inserted or deleted - this results in a frameshift, which in turn will result in multiple missense, or nonsense mutations. (insertion of 3 bp does not cause frameshift)

DNA mutations

Changes in DNA base sequence

Bio technology

the use of a living organism to develop useful products (alcohol, insulin).

Recombinant DNA

fragment of DNA composed of sequences from at least 2 different sources. .

Restriction Endonucleases:

enzymes that cleave double-stranded DNA into fragments at a particular point called a "recognition site". (only come from bacteria!)

EcoR1

lways cleaves DNA at:
� This type of cleavage results in "sticky ends" (a series of unpaired bases).

Suma1

Sma1 - always cleaves DNA at:
� Other enzymes such as Sma1 produce "blunt ends" which are fully paired.

Lac Operon

The lac operon is a cluster of three genes that code for the proteins involved in the metabolism of lactose. The lac operon consist of a promoter (the site where DNA transcription begins), an operator (the sequence of bases that contron transcription), an

methylase

� Bacterial cells produce the enzyme methylase that will add methyl groups (CH3) to their DNA to prevent the naturally occurring restriction enzymes from cleaving their own DNA.
� Molecular biologists can also use DNA methylase to protect a DNA fragment f

Prokaryotic cell

Prokaryotes can be divided into two domains, Archaea and Bacteria.
-translation (synthesis of proteins) starts while transcription of the mRNA is occurring (ie. Prokaryote ribosomes don't even wait for transcription to be done before they start using the

Eukaryotic cell

These are plant and animal cells
- takes hours or days for protein synthesis to take place
- -mRNA must be transported from nucleus to cytoplasm before proteins can be synthesized

Nucleic acids

Nucleic acids are polymers that are made up of nucleotide monomers. Examples of nucleic acids include deoxyribonucleic acids (DNA) and ribonucleic acid (RNA).

Polymer Structure

� backbone of double helix is sugar / phosphate (backbone of ladder)
� 2 strands attached through H bonding on base pairs (rungs of ladder)
� Ladder is twisted into what is referred to as a double helix

Denaturation of DNA

Heat can break H bonds between N bases, unzipping DNA. If the damage is not too great, the DNA can "rezip" itself once it is cooled.

Nucleotide structure

nucleotide contains ribose sugar (or deoxyribose, seen in DNA), phosphate group, and one of 4 possible nitrogenous bases.