I created these notes throughout y12&13 and used them for my A level 2022 exams. I got a grade 9 in GCSE and am awaiting for my a level biology result. These notes were made using the CGP revision guide, AQA Biology textbook and class notes in order to cover everything in the course. I have also ad...
17.1 STUDYING INHERITANCE
04 October 2021
16:30
Genotype - The genetic constitution of the organism.
Phenotype - Observable or biochemical characteristics due to expression of the
genotype and its interaction with the environment.
Gene - Length of DNA that codes for a specific protein.
Allele - Different version of the same gene.
Locus - the position of the gene on a particular DNA molecule.
Homologous chromosomes - Chromosoes in diploid cells that contain the same
sequence of genes, derived from both parents.
● May have different alleles, but genes are at the same loci.
Homozygous - Genotype having the same alleles for a particular gene.
Heterozygous - Genotype having different alleles for a particular gene.
Dominant allele - The allele will always be expressed if present, even if heterozygous.
Recessive allele - The allele is only expressed in the homozygous genotype.
Co-dominant alleles - Both expressed in the heterozygous genotype to give a
phenotype different to either allele.
Multiple alleles - More than 2 alleles for a gene.
● Only 2 of the alleles can be present in the organism.
17.2 MONOHYBRID INHERITANCE
04 October 2021
17:02
Monohybrid inheritance - Inheritance of one characteristic.
17.3 PROBABILITY & GENETIC CROSSES
04 October 2021
21:16
A ratio is a measure of the relative size of two or more groups expressed as a
proportion.
Results of genetic crosses are rarely the same as predicted results.
● Fertilisation is random.
● Small sample size.
● Crossing over
, 17.4 DIHYBRID INHERITANCE
04 October 2021
21:22
Dihybrid inheritance - Inheritance of two characteristics.
Mendel investigated the seed shape and colour of pea plants at the same time.
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