deck_2878276 Flashcards
Gene
a factor of inheritance for a particular trait or characteristic of an organism. It is composed of a specific nucleotide sequence in the DNA. This sequence acts as a template for RNA synthesis and ultimately the formation of a specific protein in a cell.
Alleles
different forms that a gene can come in. For example, a gene may code for seed colour in corn plants, while different alleles of this gene could include green, yellow, or purple seed colour.
Recessive Allele
an Allele that is not expressed phenotypically in the heterozygous condition
Dominant Allele
One whose phenotypic effect is the same in both the heterozygous and homozygous conditions
Heterozygous
A diploid organism with particular gene(s) having two different alleles for the gene(s)
Homozygous
A diploid organism with particular gene(s) having two identical alleles for the gene(s)
Genotype
the genetic makeup of an organism. Always use descriptive words to indicate genotypes
Phenotypes
expressed traits of an organism. Always use descriptive words to indicate phenotypes.
Frequency
the proportion of one type if thing (e.g. a genotype of phenotype) to the total population. Frequencies will range between 0 and 1, and a total of frequencies will add up to 1.
If there are 56 students in a class and 26 are male and 30 are female, what is the frequency of males and females
males: 26/56=0.46females: 30/56=0.54
Ratio
The proportion of one type of thing to another. In genetics, you will use both genotypic and phenotypic ratios
Genotypic frequency example
0.5 Dd, 0.25 DD, 0.25 dd
Phenotypic frequency example
0.75 green seeds, 0.25 white seeds
Genotypic ratio
the relative numbers of each different genotype in a given generation of offspring are expressed in ratio form e.g. 1 DD: 2 Dd: 1 dd
Phenotypic ratio
The relative numbers of each different phenotype in a given generation of offspring are expressed in ratio form. e.g. 3 green seeds: 1 white seed
Punnett Square
Is used to simulate the combinations of male and female gametes to form diploid zygotes (the offspring of the next generation).
Monohybrid cross
is between two organisms that differ with respect to one characteristic.
Dihybrid cross
Is between two organisms that differ with respect to two characteristics. In the following experiments, the characteristics of interest are plant height and plant colour (for this particular experiment)
Mendel’s 2nd Law
Alleles of different genes assort independently of one another during gamete formation.
Test cross
Involves crossing an individual of unknown genotype with a homozygous recessive individual. A homozygous recessive individual contributes only recessive alleles to any offspring from the test cross, making it easier to determine what the unknown genotype must be. Test crosses can also be used to test known genotype to determine if the genes in question are on different chromosomes (independent assortment) or the same chromosomes (gene linkage)
Test-cross progeny
Can be predicted using two scenarios, depending on whether the genes are on different chromosomes or are linked on the same chromosome. Each scenario demonstrates two different results.
Mendel’s 1st Law
Alleles of one gene segregate from one another during the formation of gametes
Principle of Dominance
When parents differ in one characteristic, their hybrid offspring resemble only one of the parents and are not a blend of the two parent phenotypes.
Principle of Segregation
When a hybrid reproduces, it produces two kinds of reproductive cells- half passing on the dominant character of one parent, and the other half passing on the recessive character of the other parent
