Class Notes 4 - Genetics and Inheritance 2 Flashcards
what is a gene?
a specific region of a chromosome/DNA that is capable of determining the development of a specific trait through the coding for a regulation of a polypeptide or RNA product.
what is an allele?
a particular variation of a gene e.g., gene for flower colour in pea plants : F= purple flowers and f= white flowers. F/f represents flower colour.
what is a dominant trait/ allele?
an allele or trait that is expressed over its recessive form. E.g., Purple flowers expressed over white.
what is a recessive allele/trait?
an allele or trait that is only expressed in the absence of a dominant allele. E.g., white flowers only if ‘ff’.
what is a phenotype?
the trait/characteristic that is expressed (or often visible). E.g., purple flowers vs. white flowers
what is a genotype?
the combination of alleles that gives rise to the phenotype. E.g., ‘FF’ or ‘Ff’ = purple flowers vs. ‘ff’ = white flowers.
what is homozygous?
having the same alleles, e.g., ‘FF’ or ‘ff’
what is heterozygous?
having diferent alleles, e.g., ‘Ff’.
what is the parent generation?
homozygous individuals that produce the F1 generation
what is the F1 generation?
heterozygous offspring arising from two homozygous individuals.
what is the F2 generation?
offspring arising from two heterozygous (F1) individuals
what are the three basic patterns of inheritance being studied?
complete dominance
co-dominance and incomplete dominance
epistasis
what is complete dominance? give example
one allele completely masks the presence of the other. E.g., flower colour in pea plants.
what is a monohybrid cross?
crosses involving only one trait.
what is a dihybrid cross?
crosses involving two traits.
what do you have to assume in dihybrid crosses?
non-linkage. E.g., Flower colour and seed shape are found on diferent chromosomes, i.e., not linked on the same chromosomes.
what is the null hypothesis?
any deviation from the expected outcome is probably due to chance.
what is the discussion ?
the null hypothesis is Accepted/supported OR rejected. the chi square value of ____ is less/more than the critical value of ____ at 5% probability level. therefore, the deviation from the expected outcome seen in these results has at least a 5% probability of being due to chance/ not due to chance. Therefore, the deviation between the observed and expected results is not significant/ is significant.
what is a test cross?
when an individual expressing the dominant phenotype (e.g., F-R-) is crossed with a recessive individual in order to determine whether, or not, the dominant individual is homozygous or heterozygous for the traits.
what is linkage?
linkage is when genes for different traits are formed on the same chromosome.
what happens when cross over occurs?
the majority of the gametes in a AaBb meiosis with the linkage pattern A to B and a to b are AB and ab. however, when cross over occurs, some of the gametes will have the recombinant chromatids, with Ab and aB.
what is the name of the point of cross-over?
chiasma
what happens when you cross a normal linkage parent with a normal linkage parent where some recombinant linkage has occurred?
The ratio of dominant both traits to recessive both traits is 3:1, however, a small number will produce offspring showing one dominant trait and one recessive trait. these, however, make up a very small number of the offspring as they result from the recombinant linkage.
what is sex linkage?
sex linkage refers to genes that are located on (or linked to) the sex chromosomes. Typically this involves the X chromosome.
