In-depth summary for content covered in the Populations and Evolution topic of A-level AQA Biology, covering content on the Hardy-Weinberg principle, speciation types, selection and more.
This will still be applicable to other exam boards, but take caution when looking at key-words and the order...
• This determines the limits characteristics of an individual
• Excluding the effect of the environment – e.g. diet
Phenotype is the observable characteristics of an organism
-> therefore, influenced by both environment and genotype
Genes and Alleles:
A gene is a length of DNA / sequence of nucleotide bases
-> these code for the 1o structure of a polypeptide or functional RNA
• Genes exist in different forms, coding for variations of the same structure
• Due to different sequence of bases
• These are called alleles
The position of a gene on a strand of DNA is known as a locus
-> all of these features influence the inheritance for the offspring of an organism
• Only one allele of a gene can occur at a specific locus of a chromosome
• However, in diploid organism (2 chromosomes)
• Homologous pairs of chromosomes mean there are two alleles for the same gene
These can be of a few variations –
1. Homozygous – two of the same alleles carried; either dominant or recessive usually
2. Heterozygous – two different alleles carried
Heterozygous characteristics are usually determined by a
dominant allele
-> these express themselves over their recessive
counterpart
• Usually represented by alternating letters e.g. Bb
, Oliver Dyson
Notation for genetics:
Genetic crosses are usually represented by using standard shorthand
-> this is described by the table below
Figure 1 – reproduced from [1]
Monohybrid inheritance: (e.g. in pea pod colour)
Monohybrid describes the inheritance of a single gene
-> for example pea pod colour can be modelled
• The colour green is dominant – GG or Gg
• And yellow is recessive - gg
Each generation of inheritance is called a ‘filial’
• For example the first filial is called the F1 generation
for shorthand
• The notation for this is shown on the right Figure 2 – reproduced from [1]
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 oliverdyson. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £2.99. You're not tied to anything after your purchase.
