Origins of Genetic Variation

• the ratio for 2 heterozygous parents will be 3:1
• carrying out genetic experiments on peas is easy and cheap and has a short life cycle but is largely to chance and ineffective sampling technique
• law of segregation says that 1 allele is inherited from both parents so you have 2 alleles for each trait
• law of independent assortment is the fact that inheritance of characteristics occur independantly of each other
• A and B blood group are dominant but O is recessive
• blood group AB are codominant
• chi-squared test is when you look at the frequency of something occurring
• degrees of freedom = number of categories- 1
• $x^2=$$sum of (O-E)^2/ E$
• for normal crosses, you get a 3:1 ratio
• a double cross results in 9:3:3:1 ratio
• carrying out genetic experiments on peas are good because its easy and cheap and can produce large numbers of offspring
• carrying out genetic experiments on peas are bad because offspring die quickly and is an ineffective sampling techniques
• law of segregation says that 1 allele is inherited from each parent to give 2 alleles for each trait. in gamete formation a pair of alleles separate in 2 sex cells and some dominate each other
• law of independent assortment says that inheritance of characteristics occur independently of each other but sometimes you have multiple alleles for 1 gene
• A and B blood group are dominant and co-dominate together
• blood group O is recessive and has no antigens on the outside the red blood cells
• chi squared is used when looking at observed results and frequency of something occurring
• degrees of freedom is number of categories - 1
• if your value of degrees of freedom is greater than the critical value, then the null hypothesis is rejected
• crossing over is when large enzymes cut and join bits of chromatids to make genetic variation
• independent assortment is when chromosomes pair randomly and can result in genetic variation and new combinations of alleles
• mutations mostly produce little to no effect but can help survival and increase genetic variation
• random fertilisation is when males mate with females from non related people so causes genetic variation
• dihybrid crosses is when you have 2 different chromosomes
• dihybrid crosses produces 9:3:3:1 ratio
• colour blindness is when there are defects and mutations in the cones of your eyes, found in the retina
• colour blindness is carried from the mother and is almost always passed down to the son
• haemophilia is a lack of protein for blood clotting and is normally passed down from the mother
• if 2 or more genes are located on the same chromosome, then inheritance is linked and more likely to be inherited together
• recombinants are new combinations of phenotype that weren't seen in the phenotype of parents
• a large number of the original parental phenotype must show there is linkage and presence of recombinants proves linkage wasn't complete
• $cross over value =$$recombinant offspring/ total offspring$
• the lower the percentage of recombinants the closer the gene loci on the chromosome
• girls have xx chromosomes and are homogametic. they have 200 million base pairs and controls blood clotting
• boys have xy chromosome and are heterogametic. they have 23 million base pairs
• if a gene is passed from the mother the son always expresses is because the y chromosome doesn't have enough alleles to counteract
• barr body is when the x chromosme inactivates to prevent males having 2 x chromosomes
• population is a breeding group of individuals of the same species
• the hardy-weinberg equilibrium works if a population is not evolving, no mutations, random mating and the population is large