Summary
AQA A Level Biology Summary Notes - DNA, Genes and Protein Synthesis
Summarised notes for AQA A Level Biology DNA, Genes and Protein Synthesis for students studying A Levels.
[Show more]
Connected book
Book Title:
Author(s):
- Edition:
- ISBN:
- Edition:
Seller
Follow
Content preview
DNA, genes & protein synthesis● A gene is a section of DNA that codes for a protein.
● They are found in chromosomes.
● Different versions of the same gene are called alleles - can be
dominant or recessive.
Redundancy of the genetic code:
● 3 bases/a triplet code = 1 amino acid.
● There are 64 combinations but only 20 amino acids can be
made so there is excess.
● Chain always starts with AUG, ends with stop codon.
Features of the genetic code:
● Code is degenerate because there is always more than 1 triplet code for each amino
acid. Code is universal in all organisms - code the same way.
● Non-overlapping - each base is part of only 1 triplet e.g. 123456 not 123,234.
Protein that packages DNA is called a histone. DNA is found in a chromosome.
Homologous pair:
● They are chromosomes that carry the same gene.
● How can you tell - same size/length, same gene location/loci
● Diploid number = total number of homologous pairs e.g. humans 46. Haploid - single.
Structure of a chromosome:
Eukaryotes - DNA is in the nucleus, DNA in chromosomes are coiled and packed tighter
because of histones so take up less space
Prokaryotes - DNA found as a free circular DNA/chromosome in the cytoplasm/plasmids that
contain DNA, no histones
Structure - DNA + histones = chromosome
Transcription: (making pre-mRNA)
1. The relevant section of DNA uncoils through the enzyme DNA helicase
2. One of the strands acts as a template strand
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller sumayyah2. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £3.99. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
52355 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now