| Talk about Mendel's experimental approach. | He experimented on garden pea (Pisum sativum) which were easy to grow and to hybridize artificially. He followed seven different features each representing a different trait. |
| Talk about the monohybrid cross. | Simplest one, involved in only one pair of contrasting traits. Each experiment is called monohybrid cross, made by true breeding individuals from two parent strains, each exhibiting a different trait under study, we study the first generation firstly and then the second one (selfing) which is the result of self fertilization.
Parents are P1, first filial generation is F1 second generation is F2 ... |
| Talk about the results obtained from monohybrid cross. | (tall and dwarf stems for example)
Crossed together P1 tall x dwarf
F1 are all tall
F2 some are tall others are dwarf 3:1 or 2.8:1
Same for smooth and wrinkled pea. |
| What is reciprocal cross? | Same genetic results if sexes are swapped. (non-sex dependant) |
| Talk about Mendel's first postulate. | Unit factors in pairs:
Genetic characters are controlled in pair manner, there is a specific unit factor for each trait, each diploid organism receives one unit factor from each parent having a pair of unit factors. So there are three possible combinations: tall tall, tall dwarf, dwarf dwarf. |
| Talk about Mendel's second postulate. | Dominance and Recessive, When two different unit factors are present one is phenotypically dominant and the other is recessive. (All F1 were tall meaning that the tall unit factor is dominant) |
| Talk about Mendel's third postulate. | Segregation: During formation of gametes, paired unit factors separate, or segregate randomly so that each gamete has one unit factor with equal likelihood
If an individual is homozygous each gamete receives one unit factor (tall tall each)
If heterozygous each one receives also one (tall dwarf equally) |
| Talk about modern genetics terminology. | Trait = phenotype
unit factors= genes
each gene has a certain characteristic = allele
First letter of recessive allele is the one considered to study the monohybrid cross (for example d dwarf allele and D tall allele)
the combination of alleles = genotype
homozygous= same allele
heterozygous= different alleles. |
| Talk about Punett square. | Table representing different phenotypes and genotypes
ratio 1:2:1 and 3:1 is shown on it. |
| Talk about test cross. | To discover the genotype of plants and animals, ones with dominant allele shown but may have a recessive allele that is masked, should be crossed with an homozygous recessive individual. If it results in some recessive descendants then the unknown one is heterozygous |
| What is a backcross? | cross of F1 with homozygous recessive parent. |
| What is a dihybrid cross? | Cross involving two pairs of contrasting traits, AKA two-factor cross, e.g: pea plants having yellow and rounded peas cross plants having green and wrinkled peas (homozygous) or green rounded with yellow wrinkled.
They give F1 which is all yellow round (meaning that yellow and round are dominant) |
| Talk about Mendel's fourth law. | We can understand dihybrid crosses as two independent events, fourth postulate is Independent assortments, "During gamete formation, segregation of pairs of unit factors assort independently of each other" |
| Talk about the observed phenotype of dihybrid cross. | 9:3:3:1 (9 dominant dominant, 3 dominant recessive for both, 1 recessive recessive)
We can obtain it by the method (branched diagram) of showing the probabilities of each independently and multiplying them (P(A and B)= P(A) * P(B) for each recessive and dominant) (2^n total where n is the number of total alleles.) |
| Talk about the genotypes. | same as phenotypes method. (3^2 in total) |
| Talk about the testcross of dihybrid. | We can know if each gene is homo or heterozygous by test cross with recessive recessive homozygous individual. |
| Talk about trihybrid cross. | Segregation is independent also for trihybrid cross (unlinked genes) AKA three factor cross. Somewhat complex, parents make 8 F1 gametes |
| Talk about the fork line method. | AKA branch diagram, combination of different probabilities of each trait alone whether phenotype (3:1) or genotype (1:2:1) last trihybrid ratio of phenotype is 27:9:9:9:3:3:3:1 |
| Talk about unit factors genes and chromosomes. | Mendel's conclusions were observed by the process of chromosome segregation during meiosis were the genes are present in all body cells and no cell doesn't have the gene, and the heredity depends on how the chromosomes segregate during meiosis. |
| What does the independent assortment of genes lead to? | Production of genetically dissimilar gametes, making genetic diversity. (extensive) |
| Talk about the product law. | Probability of two events happening in the same time is the product of the probability of each. |
| Talk about the sum law. | Probability to get two events independent but in many possible ways is by sum of probabilities of the events. |
| Talk about the binomial theorem. Pascals triangle | (a+b)^n=a^n+a^b-1b+...
-->probability of event 1 is a and probability of event 2 is b
-->according to the outcome of the events we choose the suitable part of the polynomial. |
| Give another formula for probability. | p=n!*a^s*b^t/(t!*s!) where s and t are the number of times each event occurs and n is the total times of the events. |
