CfE Higher Biology

Expectations….. A lot of content to be covered, so self study is required. Everyone to try their best and put in 100% Research project within this course so be prepared for write up at home, not during class time. Homework will be given regularly………..Check homework board! Open classroom…….no question is a stupid question!!!

And most importantly……

Consolidate our knowledge of DNA structure and function Learning Intention Consolidate our knowledge of DNA structure and function

Success Criteria All pupils will….. Most pupils will….. State the basic structure of DNA and base pair matches. Most pupils will….. Identify the 3’ and 5’ end of DNA along with phosphate group, deoxyribose sugar, and hydrogen bond. Some pupils will…… Explain the function of DNA and its role.

Recap Because before the holidays seems like such a long time ago………..! DNA True or False

DNA is found in some living things.

False DNA is found in all living things as it contains the information needed for a living thing to develop, survive and then reproduce itself.

DNA is the heredity material – it is passed on from one generation to the next.

True

Your DNA is the same as the DNA of the person sitting next to you.

False Everyone's DNA is different as we are all different. These differences in DNA, which are differences in its chemical sequence, create individual differences.

DNA is found in the cytoplasm of the cell.

DNA is found in the nucleus. False DNA is found in the nucleus.

The DNA sequence – the chemical language – doesn’t matter as it doesn’t change anything about the living thing.

False The DNA sequence provides the heredity information for the living thing to develop and survive.

The DNA sequence of a living thing is called its genotype.

True

Structure of DNA You will be given sheets of paper that have cut outs of nucleotides. Your task (in pairs) is to cut and construct the molecular structure of DNA. You must label the 5’ and 3’ ends along with the other labels on the sheet.

CfE Higher Biology Lesson 2

Starter Question: If there is 30% Adenine, how much Cytosine is present?

Answer: There would be 20% Cytosine Adenine (30%) = Thymine (30%) Guanine (20%) = Cytosine (20%) Therefore, 60% A-T and 40% C-G

Consolidate our understanding of DNA replication. Learning Intention Consolidate our understanding of DNA replication.

Success Criteria All pupils will….. Most pupils will….. State what the nucleus must contain in order for replication to occur. Most pupils will….. Describe the steps and process of PCR. Some pupils will…… Explain or draw a diagram to show what happens to DNA during PCR. (must include the words ; leading strand, replication fork, direction of replication, primers and ligase.)

Replication of DNA What does the cell need to replicate DNA? A DNA template Primers (short bits of DNA that are complementary to the DNA being copied) A supply of DNA nucleotides (all 4 types – ATGC) Enzymes – DNA polymerase and Ligase ATP for energy

Formation of the leading strand The double helix unwinds Hydrogen bonds between the bases are broken and the molecule ‘unzips’ exposing the bases. This point where the bases are exposed is called the ‘replication fork’

Formation of the leading strand 2. The primer binds to the 3’ end. New hydrogen bonds form between the complementary base pairs of the primer and DNA. Free DNA nucleotides align themselves so they bond with the exposed bases of the DNA.

Formation of the leading strand 3. DNA polymerase catalyses the reaction DNA polymerase catalyses the formation of the sugar phosphate bond between the 3’ end of the primer. DNA polymerase can only ADD nucleotides to the to the 3’ end of the strand.

Formation of the leading strand 4. DNA polymerase moves along the strand DNA polymerase moves along the 3’ end continuously adding nucleotides. This strand is called the leading strand.

Formation of the Lagging strand Because DNA polymerase can only add nucleotides from the 3’ end that leaves the 5’ end exposed. The enzyme LIGASE is able to add nucleotides in this direction. This strand is called the lagging strand and its formation known as discontinuous. After both strands have been joined by their complementary bases 2 new DNA molecules are formed. These then coil to make 2 new identical Double helix. As both molecules have one of the original strands it is known as Semi-conservative.

Replication forks Many chromosomes are very long. So to ‘unzip’ the entire DNA molecule to replicate a small sequence would be silly. Also, sometimes more than one part of the molecule needs to be replicated at the same time. To overcome this several replication forks will open at one time like in the diagram above.

Video

Polymerase Chain Reaction (PCR) PCR has many uses. The most well known probably being to identify an individual that committed a crime. It can also be used for Paternal/maternal DNA tests ( like on Jeremy Kyle) Identify strains of infectious diseases. Medical use to look for genetic diseases. Historical/Antrapological uses

PCR – How do you do it? Denature original sample at 95 oC Sample is then cooled at 55 oC for one min to allow primers to bind (anneal) to target sequence. Sample is then heated again to 72 oC. This allows the heat tolerant DNA polymerase to add nucleotides to the 3’ end. DNA polymerase continues to add nucleotides until replication is complete.

Answer Stage 1 separates strands or breaks H bonds (1) Stage 2 allows primer to bond/anneal to strand/target sequence (1)

Answer (b) 7 (1) (c) Identical set up but without primers (1)