Genetic Engineering and Biotech

What is artificial selection?

Selective breeding of a species by humans resulting in a change in allele frequency.

What is inbreeding?

Breeding of closely related individuals.

Describe a problem with inbreeding.

It reduces the gene pool and hence genetic diversity, which reduces their chance to evolve and adapt to environmental changes and increases the chance of inheriting recessive alleles that may cause genetic disorders.

What is the effect of artificial selection on genetic diversity?

It decreases genetic diversity.

What is a gene bank?

Storage of genomes within organisms to provide possible new alleles for future artificial selection.

What are the 2 main ethical objections to artificial selection?

Loss of a species' natural characteristics/behaviour, and inbreeding depression.

What is a DNA probe?

A single-stranded piece of DNA that is complementary to a gene of interest and is attached to a marker (tag) to identify the presence of specific genes.

Which regions of the genome are compared in DNA profiling for forensics?

Non-coding regions including introns, STRs, VNTRs, minisatellites, and microsatellites.

Put these steps for creating a DNA profile in the correct order: Amplification, Visualisation, Extraction, Digestion, Separation.

Extraction, Amplification, Digestion, Separation, Visualisation.

Give 2 uses of DNA profiles.

Paternity testing, forensic investigations.

State three potential sources of DNA at a crime scene.

Hair, blood, skin cells, semen, saliva.

What is a primer in PCR?

A short, single-stranded DNA fragment used to 'tell' the DNA polymerase which part of DNA to copy.

What happens during the first step of a PCR cycle when heated to 95°C?

Double-stranded DNA is separated into two single strands as hydrogen bonds break.

What is special about Taq polymerase compared to other DNA polymerases?

Taq polymerase is very stable at high temperatures so it does not denature.

What is the purpose of cooling to around 55°C in PCR?

To allow primers to anneal (bind) to the target DNA.

What must a PCR mixture contain besides DNA polymerase, free nucleotides, buffer, primers?

The target DNA sequence to be amplified.

If the number of DNA fragments doubles in each PCR cycle, how many fragments will there be after 15 cycles starting with one piece of DNA?

32768 fragments.

What does PCR stand for?

Polymerase chain reaction.

In gel electrophoresis, is DNA attracted to the anode or cathode?

DNA is attracted to the anode (positively charged side) because it is negatively charged.

Describe the movement of small fragments compared to larger fragments in gel electrophoresis.

Smaller fragments move further and faster than larger fragments.

What are DNA markers in gel electrophoresis?

Mixtures of DNA molecules of known size used to estimate the sizes of other DNA samples.

What is the gel in gel electrophoresis made of?

Agarose.

What is the purpose of gel electrophoresis?

To separate DNA fragments in order of size.

What is a genome?

The genes or genetic material present in a cell or organism.

Give two reasons why new DNA sequencing techniques have improved upon old methods.

They are quicker and cheaper.

What are the four other chemicals needed for the Sanger sequencing method?

Taq DNA polymerase, a primer, normal nucleotides, and chain terminator nucleotides (ddNTPs).

How is a terminator base different from a normal nucleotide?

A terminator base has a hydrogen instead of a hydroxyl group on C3 of the deoxyribose sugar.

How are terminator bases altered for detection in DNA sequencing?

They are tagged with a colored fluorescent marker, with four different colors for different bases.

Why does the addition of a terminator base stop further DNA strand extension in sequencing?

Terminator bases do not have a hydroxyl group on C3 of deoxyribose, preventing the formation of phosphodiester bonds with the next nucleotide.

What is the first step in sequencing a whole genome?

Cut the genome into smaller fragments and clone into BACs to create a clone library.

How are DNA fragments separated and read in DNA sequencing?

Using gel electrophoresis in minute capillary tubes, which separate DNA fragments by size and allow reading through a laser detecting the color as they pass.

Briefly describe how next-generation sequencing works.

It is an automated, high-throughput sequencing process where millions of DNA fragments are attached to a surface and sequenced as clusters simultaneously.

Explain how genome sequencing can help identify evolutionary relationships.

Closer % match of genome sequence indicates less time since two species diverged from a common ancestor.