What are extension strategies in a lesson plan?

What are extension strategies in a lesson plan?

Extension strategies (to help activities take up a little more time) To extend a discussion activity, towards the end, ask each pair or group to prepare a brief report back to the rest of the class on the most important or interesting things that have been said.

What is the extension phase?

Extension is content “cement” The teacher selects activities that engage higher-level thinking skills within the students’ brains. These activities help the students to develop maturity in their thinking. They can draw even broader conclusions. This is a critical phase of the 5E process.

What happens during extension in PCR?

Denaturing – when the double-stranded template DNA is heated to separate it into two single strands. Annealing – when the temperature is lowered to enable the DNA primers to attach to the template DNA. Extending – when the temperature is raised and the new strand of DNA is made by the Taq polymerase enzyme.

What is the temperature used for extension step?

The annealing temperature (typically between 48-72°C) is related to the melting temperature (Tm) of the primers and must be determined for each primer pair used in PCR. During the extension step (typically 68-72°C) the polymerase extends the primer to form a nascent DNA strand.

What does extension do in PCR?

Extension is achieved by using the loosened nucleotides of each base to grow the complementary DNA strand. The end result is two double-stranded products of DNA. The temperature that is used during the extension phase is dependent on the DNA polymerase that is used.

What happens at 72 degrees in PCR?

Since the Taq polymerase, which is usually added to the PCR, works the best at around 72 degrees centigrade, the temperature of the test tube is raised (Scheme – Elongation). At the end of a cycle of these three steps, each target region of DNA in the vial has been duplicated. This cycle is usually repeated 30 times.

Why are 2 primers needed for PCR?

Two primers are used in each PCR reaction, and they are designed so that they flank the target region (region that should be copied). That is, they are given sequences that will make them bind to opposite strands of the template DNA, just at the edges of the region to be copied.

What is final extension step in PCR?

The final stage is the extension step (20 sec to 1 min at 72 °C), which is performed so that the DNA polymerase extends the primer sequences from the 3′ of each primer to the end of the amplicon. A 1 min extension is typically sufficient to synthesize PCR fragments up to 2 kilobases (kb).

What does Primer do in PCR?

​Primer. A primer is a short, single-stranded DNA sequence used in the polymerase chain reaction (PCR) technique. In the PCR method, a pair of primers is used to hybridize with the sample DNA and define the region of the DNA that will be amplified.

How long is extension in PCR?

1 min/kb

Why is the DNA heated to 94 degrees C?

Magnetic Zippers. One reason DNA is heated to the high temperature of 95 degrees Celcius is that the longer the DNA double strand is, the more it wants to stay together. The A-T and G-C base pairs in the double-stranded DNA bond with each other to hold the double-strand structure together.

Why is DNA heated to 95 degrees?

Heat to 95 degrees. At this temperature the DNA will denature, splitting the double standed DNA by breaking thy hydrogen bonds holding the bases together. This results in two separate strands with exposed bases. At this temperature teh DNA primers will attach to their complementary sequences of bases.

What are the 3 major steps of PCR?

PCR is based on three simple steps required for any DNA synthesis reaction: (1) denaturation of the template into single strands; (2) annealing of primers to each original strand for new strand synthesis; and (3) extension of the new DNA strands from the primers.

At what temperature does annealing of DNA and primer takes place?

At what temperature do annealing of DNA and primer takes place? Explanation: After the denaturation of the two strands the temperature is decreased to 50 – 60˚C. At this temperature the primers anneal to their complementary segments.

What is the annealing process?

Annealing is a heat treatment process that changes the physical and sometimes also the chemical properties of a material to increase ductility and reduce the hardness to make it more workable.

Are primers complementary to DNA?

Primers. – short pieces of single-stranded DNA that are complementary to the target sequence. The polymerase begins synthesizing new DNA from the end of the primer.

How do you calculate annealing temperature?

The optimal annealing temperature (Ta Opt) for a given primer pair on a particular target can be calculated as follows: Ta Opt = 0.3 x (Tm of primer) + 0.7 x (Tm of product) – 14.9; where Tm of primer is the melting temperature of the less stable primer-template pair, and Tm of product is the melting temperature of the …

What are the three stages of annealing?

The three stages of the annealing process that proceed as the temperature of the material is increased are: recovery, recrystallization, and grain growth.

What is primer annealing temperature?

To copy DNA, polymerases require a short sequence called a primer. They cannot “anneal” to the strand of DNA at temperature 95 degrees centigrade, so the test tube is cooled to 45 – 60 degrees C. The temperature of this step depends on the melting temperature of the primer – template hybrid.

What happens if extension temperature is too high?

If the temperature is too high, no annealing occurs, but if it is too low, non-specific annealing will increase dramatically. Primer-dimers will form if the primers have one or more complementary bases so that base pairing between the 3´ ends of the two primers can occur.

How do I calculate my extension time?

Extension Time

1. Extensions are normally performed at 68°C.
2. As a general rule, use extension times of one minute per 1000 base pairs (e.g. 3 minutes for a 3 kb product)
3. For products less than 1 kb, use 45-60 seconds.
4. Products greater than 3 kb, or reactions using more than 30 cycles, may require longer extensions.

What happens if annealing temp is too high?

If the annealing temperature is too high, primers are unable to bind to the template. The annealing temperature should not exceed the extension temperature. Denaturation temperature was too low. If the denaturation temperature is too low, the DNA will not completely denature and amplification efficiency will be low.

What happens if primers are too short?

Short primers produce inaccurate, nonspecific DNA amplification product, and long primers result in a slower hybridizing rate. On average, the DNA fragment that needs to be amplified should be within 1-10 kB in size.

Why is it recommended to have a 40% 60% G C content?

Aim for the GC content to be between 40 and 60% with the 3′ of a primer ending in G or C to promote binding. The shorter the primers are, the more efficiently they will bind or anneal to the target. Try to make the melting temperature (Tm) of the primers between 65°C and 75°C, and within 5°C of each other.

How short can primers be?

Primer Length: It is generally accepted that the optimal length of PCR primers is 18-22 bp. This length is long enough for adequate specificity and short enough for primers to bind easily to the template at the annealing temperature.

What does self complementarity mean in a blast primer?

Self-complementarity is the likelihood that the primer will bind to itself and to the other primer in the pair. Self 3′-complementarity is the likelihood that the primer will bind to itself and to the other primer in the pair at the 3′ end. High scores are a good predictor of primer dimer formation.