Higher Biology

• DNA consists of 2 strands made up of units called nucleotides
• Genome is composed of units called nucleotides.
• Nucleotides are made of 3 parts: phosphate group, base, deoxyribose sugar.
• 5' end = phosphate
• Bases can be: adenine, thymine, guanine and cytosine.
• A pairs with T and G pairs with C.
• Bases in adjacent strands are held together by hydrogen bonds.
• A strand of DNA is held together by a strong sugar phosphate backbone.
• A strand of DNA is held together by a strong sugar phosphate backbone.
• DNA replication takes place before cell division.
• DNA is replicated by DNA polymerase.
• DNA replication requires a template DNA strand, free DNA nucleotides, primers, DNA polymerase, and ligase.
• Primers are short strands of nucleotides that bind to the 3' end of the template strand to allow DNA polymerase to add free nucleotides.
• DNA polymerase adds free DNA nucleotides to the 3' end of the new DNA strand in both leading and lagging strand.
• In the first step of DNA replication, DNA is unwound and the hydrogen bonds between the bases break.
• A primer is needed to start the replication.
• DNA polymerase adds free DNA nucleotides to the 3' end of the new DNA strand being formed.
• The leading strand can be replicated in fragments, ligase joins the fragments together.
• The DNA is unwound and the hydrogen bonds between the bases break to make two template strands.
• A primer is needed to start the replication, it binds to the 3’ end of the template DNA strand.
• DNA polymerase adds the free DNA nucleotides to the 3’end of the new DNA strand being formed.
• The leading strand can be replicated continuously because DNA Polymerase can only add nucleotides in the one direction.
• The lagging strand is replicated in fragments.
• Ligase joins the fragments together.
• Eukaryotes have linear chromosomes in the nucleus which are tightly coiled and packed around a protein called a histone.
• Eukaryotes have circular chromosomes in their mitochondria and chloroplast.
• Yeast is a special example of a eukaryote as it also has plasmids.
• Prokaryotes have a singular circular chromosome and circular plasmids.
• PCR amplifies DNA by using complimentary primers that target specific sections of DNA.
• PCR primers are short strands of nucleotides which are complementary to specific sections of the DNA to be amplified.
• PCR can be used to help solve crimes, settle paternity suits and diagnose genetic disorders.
• DNA is heated to between 92 and 98 to separate the strands (break hydrogen bonds).
• DNA is cooled to between 50 and 65 degrees Celsius to allow primers to bind to target sequences.
• DNA is heated to between 70 and 80 degrees for heat-tolerant DNA polymerase to replicate the region of DNA.
• Gene expression involves the transcription and translation on DNA sequences.
• To make a protein, three types of RNA are needed: messenger RNA, transfer RNA, and ribosomal RNA.
• RNA is single stranded and is composed of nucleotides containing: ribose sugar, a phosphate and a base.
• RNA bases are Uracil, Adenine, Guanine and Cytosine.
• Transcription is the first stage in gene expression.
• Transcription takes place in the nucleus.