Starter What do you know about DNA and gene expression?

1.5 The Structure of the Genome

1.5 Learning Outcomes State what is meant by the term ‘genome’. State what is meant by the term ‘gene’. Describe the structure of the genome in terms of coding and non-coding sequences. Explain the difference between coding and non- coding sequences. Describe some functions of the non-coding sequences. Name 3 forms of non-translated RNA State that some non-coding sequences have no known functions.

Fact Finding Task Structure of The Genome Fact Finding Task Research: Research: Using page 57 & 58 of the Higher Biology for CFE text book research the structure of the genome. Produce: Produce: Using any paper resources you wish produce a learning tool that explains each of the learning outcomes for Key Area 1.5 ‘The Structure of the Genome’ Present: Present: Share your learning tool with a classmate who will assess your research against the learning outcomes.

The Genome The genome of an organism is its hereditary information encoded in DNA. The study of an organisms genome is called genomics. A human genome consists of about 3 BILLION nucleotides! It would take 9.5 years, non-stop, to read aloud a person’s genome base by base!! A human genome consists of about 3 BILLION nucleotides! It would take 9.5 years, non-stop, to read aloud a person’s genome base by base!!

A Gene Genes are sequences of DNA bases that code for protein. The study of single genes or groups of genes is called genetics. A human has around THOUSAND genes!

Coding and Non-Coding Regions The genome is not made up exclusively of genes. The parts of the genome that carry the instructions for making proteins are described as ‘coding regions’. These coding regions actually only make up around 2% of the whole genome in eukaryotes! The remaining 98% of the genome in is made-up of non-coding regions.

Non-Coding Regions Non-coding regions of the genome are long sequences of DNA that do not code for protein. These regions are often DNA sequences that are repeated many times over. These non-coding regions have a variety of functions, e.g: – Regulation of transcription – Transcription of RNA Some of the non-coding regions have no known function.

Some non-coding sequences of DNA are used to regulate transcription. This means that they can bind proteins that promote or prevent transcription of a gene. Regulation of Transcription

Some non-coding sequences code for forms of RNA other than mRNA. These forms of RNA have specific functions but they are not translated into protein. Some of the non-translated forms of RNA include: – tRNA – rRNA – RNA fragments Transcription of non-translated RNA

Transfer RNA (tRNA) Produced to transport specific amino acid molecules to a ribosome to be used during the translation process. However, the tRNA itself is never translated.

ribosomal RNA (rRNA) rRNA is produced by non-coding regions of DNA and combines with a protein molecule to form a ribosome. A ribosome with the protein part coloured purple and RNA coloured orange.

RNA Fragments These are small sections of RNA which are involved in splicing, and other processes such as post- transcriptional regulation of genes.

The function of many large sections of the genome are still unknown. Originally, this was thought of as ‘junk DNA’ but nowadays scientists think that this DNA does must play an important role. Non-coding regions with no known function

1.5 You should now be able to…. State what is meant by the term ‘genome’. State what is meant by the term ‘gene’. Describe the structure of the genome in terms of coding and non-coding sequences. Explain the difference between coding and non- coding sequences. Describe some functions of the non-coding sequences. Name 3 forms of non-translated RNA State that some non-coding sequences have no known functions.