A2 biology new spec genetics

Genetics, populations, evolution, and ecosystems

·         Genotype is the genetic constitution of an organism

·         Phenotype are the observable or biochemical characteristics of an organism as a result of the environment and the expression of genotype.

·         Gene is a length of DNA that codes for a sequence of nucleotide bases that normally codes for a particular polypeptide.

·         Locus is the position of a gene on a DNA molecule.

·         Allele is an alternative form of a gene

·         Homologous chromosomes are a pair of chromosomes, one maternal, 1 paternal, that have the same gene loci and determine the same features.

·         Homozygous means both alleles are the same on each chromosome, recessive or dominant

·         Heterozygous means 2 different alleles- 1 of these alleles will present in the phenotype

·         Diploid means 2 sets of chromosomes

·         Codominant means both alleles contribute to the phenotype in equal amounts

·         Multiple alleles are if there are more than 2 allelic forms of a gene

·         Monohybrid inheritance is the inheritance of a single gene and you can work out the possible genotypes of offspring using genetic crosses.

·         State the parent pheno and genotype, the gametes produced, put them in a punnet square, show the results and indicate the number of each of the offspring.

·         Pure breeds have homozygous chromosomes.

·         The F1 generation are the first generation of parental breeding and the F2 generation is if the F1 generation had offspring

·         The law of segregation is in a diploid organism’s characteristics are determined by alleles that occur in pairs, only 1 of each allele can be present in a single gamete.

·         Dihybrid inheritance is with 2 genes. If you have identical phenotypes, the ratio is 9:3:3:1

·         Law of independent assortment- each member of a pair of alleles may combine randomly with either of another pair.

·         Sex linkage is when a gene carried by an X or Y chromosome. If it is a recessive allele, it will be more apparent is males as they only have 1 X chromosome. E.g. haemophilia

·         Pedigree charts are used to trace inheritance of sex linked characteristics

·         Autosomal linkage- 2 genes on the same chromosome are linked- non-sex chromosomes are called autosomes.

·         Autosomal linkage means that as long as crossing over does not occur, alleles cannot segregate due to the law of independent assortment

·         Epistasis is when the allele for 1 gamete masks the of another in a phenotype

·         degrees of freedom are the number chosen – 1

·         Critical value is usually 0.05 and so if the deviation is less than 5% the results are significant, above means not significant

·         A population is a group of organisms of the same species that occupy a particular space at a…