Inheritance part 2 Flashcards
What is a monohybrid cross?
a genetic cross performed to observe the inheritance of alleles and phenotypes for a single gene
show how certain traits are passed down from parents to
their offspring. By completing a Punnett square, we can predict the genotypes and phenotypes of offspring
What does a cross between two heterozygotes result in?
three possible genotypes in the offspring
What is a punnet square?
a square diagram used to predict the genotypes of offspring
How is a sex-linked trait different on a punnet square?
sex-linked traits involve alleles on sex chromosomes.
the method is the same, however, the way alleles are written and the genotypic and phenotypic proportions differ from that of an autosomal Punnett square
it is important to notice for proportions are calculated with respect to sex.
What is a test cross?
performed by crossing an individual with an unknown genotype with a homozygous recessive individual.
when an individual expressing the dominant phenotype but with an unknown genotype is crossed with a homozygous recessive individual. The results indicate whether the individual with the dominant phenotype is homozygous dominant or heterozygous
What is a dihybrid cross?
a genetic cross used to observe the inheritance of alleles and phenotypes for two genes
What is an unlinked gene?
genes located on different chromosomes, or far apart on the same chromosome. Unlinked genes have less chance of being inherited together
What are the steps to complete a dihybrid cross?
1 Assign letters to each allele
2 Draw a 4 × 4 grid
3 Write each of the father’s allele combinations above one column
4 Write each of the mother’s allele combinations beside one row
5 Complete the cross to determine the potential offspring genotypes. Ensure you write the dominant allele first in heterozygous offspring
6 Calculate the fractional proportions of each potential genotype by determining the frequency of each genotype then dividing it by the total number of squares. Multiply this fraction by 100 to determine the percentage of each genotype
7 Determine the phenotype of each offspring by looking at the genotypes. To calculate the fractional proportions of each phenotype, determine the frequency of each phenotype then divide it by the total number of squares. Multiply this fraction by 100 to determine the percentage of each phenotype.
What does FOIL stand for?
F – First alleles
O – Outside alleles
I – Inside alleles
L – Last alleles
How many combinations of alleles can a gamete have?
there can be up to four different possible combinations of alleles in any one gamete.
When performing a dihybrid cross and crossing two heterozygous individuals, what will the ratio be?
whenever you cross two heterozygous individuals, you will always finish with the same ratio of 9 : 3 : 3 : 1.
What are linked genes?
Genes that are located more closely together on the same chromosome. This means that during meiosis, because they are on the same chromosome, they are inherited together and are not separated during independent assortment. They can occasionally be separated through crossing over
What is independent assortment?
the random orientation of homologous chromosomes along the metaphase plate during metaphase I
What is crossing over?
the exchange of genetic material between non-sister chromatids during prophase I of meiosis, resulting in new combinations of alleles in daughter cells
What are map units?
a measure of the distance between two genes on the same chromatid. Genes that are closer together are more likely to be linked genes
One map unit equates to a one per cent chance of crossing over and the offspring containing a recombinant chromosome. This means crosses with linked genes can result in strange ratios like 11.5 : 1 : 1 : 11.5
