Genetics and Recombinant DNA CA

What is label a?

The leading strand

What is label b?

The lagging strand

What is label c?

DNA ligase

What is label d?

Okazaki fragment

What is label e?

DNA polymerase

What is label f?

DNA primer

What is label g?

Helicase

What is label h?

Single stranded binding proteins

What is label i?

Topoisomerase

What’s label j?

Parent DNA

What is label k?

Replication fork

What are the enzymes involved in DNA replication?

Helicase

Primase

Polymerase

Ligase

Topoisomerase

What is the function of Helicase in DNA replication?

To unwind the double helix by breaking the hydrogen bonds between complementary base pairs

What is the function of Primase in DNA replication?

To make short RNA primers that give a starting point for polymerase to start building.

What is the function of polymerase in DNA replication?

Responsible for building new DNA strands by adding nucleotides to the 3’ end of the primer and proofreads the newly made strand to make sure it is accurate.

What is the function of ligase in DNA replication?

To join up the Okazaki fragments fragments on the lagging strand by speeding up the making of phosphodiester bonds between fragments, creating a continuous DNA strand.

What is the function of Topoisomerase in DNA replication?

To relieve the stress on DNA when it is unwound by cutting and rejoining to stop it tangling.

What does replicon mean?

A region of DNA that replicates on its own

What does replication bubble mean?

Open area of chromosome between two replication forks

What does discontinuous synthesis mean?

The way that the lagging strand is made in short fragments (Okazaki fragments) and later joined together

Why is replication referred to as semi-conservative?

Because when the double helix replicates each of the two daughter molecules will have one old strand taken from the parent molecule and one newly made one from the feee nucleotides in the solution using the parent strands as templates

What’s the difference between the three different types of RNA?

mRNA carries the code, tRNA brings the amino acids and rRNA makes up the ribosome

What is one similarity between replication and transcription?

They both take place in 5’ to 3’ direction

What are three differences between replication and transcription?

Transcription uses RNA polymerase instead of DNA polymerase

Only one strand of DNA is copied in transcription both is copied in replication

The product of transcription is single stranded RNA, the product of replication is double stranded DNA

What is the general structure of a prokaryotic RNA polymerase enzyme?

It is made up of the core enzyme which consists of two alpha, one beta and one beta prime and a sigma factor

Describe the features of a prokaryote promoter

They have two key features the -10 sequence and the -35 sequence. These are short DNA sequences located 10 and 35 base pairs upstream from the transcription start site. They act as recognition and binding sites for RNA polymerase, helping to initiate transcription.

Is this a prokaryote or eukaryote promoter?

Prokaryote

Is this a prokaryote or eukaryote promoter?

Eukaryote

How does chain termination occur in prokaryote transcription?

The stopping of transcription occurs at terminators signalling the end of the gene. Self complementary sequences at the terminators cause hairpin structures to form in the RNA causing the release of mRNA transcript this is Rho independent termination there is also rho dependent termination where the rho protein binds to the RNA transcript releasing it

How is chain termination different in eukaryotes than prokaryotes?

Eukaryotes have no strong termination sequences like prokaryotes. RNA continues transcribing up to 1000 to 2000 nucleotides beyond where the 3’ end of the mature mRNA will be.

What does intron mean?

Sequences of nucleotides transcribed for non coding DNA and don’t contain information needed for protein synthesis

What does exon mean?

Sequences of nucleotides coding for amino acids therefore are needed for protein synthesis

What does splicing mean?

The removal of introns front the primary mRNA transcript and the joining of exons to produce the mature mRNA transcript

What is polyadenylation?

The cleavage of the RNA to produce the proper 3’ end and the adding of a string of adenine nucleotides

What are the steps involved in mRNA transcript processing in eukaryotes?

1. Capping- the 5’ end of the mRNA transcript is capped by adding methylated guanine nucleotide.

2. Polyadenylation- the cleavage of the RNA to produce proper 3’ end and add a string of adenine nucleotides

3. Splicing- the removing of introns from the primary mRNA transcript and the joining of exons to produce mature mRNA transcript.

What is the general structure of a tRNA molecule?

Has a 3 base anticodon that can base pair with a specific mRNA codon and has a molecular hook which is an attachment site for a specific amino acid

Why are point mutations in the third nucleotide of a codon often silent?

They are often silent because of the genetic code degeneracy which means the amino acids therefore often doesn’t change

What does open reading frame mean?

A set of codons that run continuously and is bounded by a start codon and a stop codon

What does anticodon mean?

A group of 3 nucleotides on a tRNA molecule that is complementary to a codon in mRNA which codes for the amino acids that particular tRNA is carrying

What does silent mutation mean?

A codon change to one that encodes the same amino acid and causes no change to the protein produced

What does frame shift mutation mean?

A mutation where the entire reading frame of a gene is changed and a functional protein is not made.

What is label A?

mRNA binding site

What is label B?

Small ribosomal subunit

What is label C?

mRNA

What is label D?

Initiator tRNA

What is label E?

P site

What is label F?

Large ribosomal subunit

What is label G?

Translation imitation complex

What is the difference between a repressible and inducible system in gene regulation?

Repressible system is when the end product of the system increases the transcription of the coding region needed for synthesis is shut off whereas inducible system is when a substance is present and genes are expressed when the substance is gone the genes are no longer expressed

What is label A?

Promoter

What is label B?

Regulatory gene

What is label C?

mRNA

What is label D?

Protein

What is label E?

Inactive repressor

What is label F?

RNA polymerase

What is label G?

mRNA

What is label H?

Start codon

What is label I?

Stop codon

What is label J?

Promoter

What is label K?

Genes of operon

What is label L?

trp operon

What is label M?

Polypeptide subunits that makeup enzymes for tryptophan synthesis

What are the different ways bacteria may gain new genetic information? And where does the DNA originate?

Transformation- from environment

Transduction- from bacteriophages

Conjugation-from another bacterium

What is meant by competent cells in transformation?

Be able to take up the exogenous DNA

How is transformation achieved in the lab?

• a fragment of foreign DNA is located into a plasmid vector

• the recombinant plasmid is mixed with competent bacterial cell

• bacteria has now gained new genetic information

What does F+ mean in conjugation?

F+ is the donor strain of bacteria because it contains the fertility factor

What does F- mean in conjugation?

The F- is the recipient strain of bacteria because it lacks the fertility factor

What does Hfr mean in conjugation?

When the fertility factor (F factor) integrates into a random position in the bacterial chromosome the bacterial cell is called Hfr instead of F+

What is the difference between specialised and generalised transduction?

Generalised transduction is when the lytic phage destroys chromosome, general or random pieces are picked up, any gene is transferred.

Specialised transduction is when temperate phage is inserted at a specific spot, only special or adjacent genes are picked up during faulty excision