Chapter 5.2 Genetics Today ✓ Flashcards
Define monohybrid
An organism that is heterozygous for a single gene
Define monohybrid cross
A cross between two monohybrids ( parents with genotypes consisting of one dominant and one recessive allele) that differ in only one characteristics
Distinguish between dominant and recessive allele in terms of expression
A dominant allele produces a dominant phenotype in individuals who have one copy of the allele, which can come from just one parent.
For a recessive allele to produce a recessive phenotype, the individual must have two copies, one from each parent.
State the purpose of a Punnett square
Can be used to determine the likelihood of producing offspring with particular genotypes and phenotypes from known parental genotypes.
What is the ratio of F2 in a monohybrid cross?
3:1
Describe the relationship between the process and products of meiosis and Mendel’s 3:1 ratio in monohybrid crosses
During meiosis homologous chromosomes separate so each new gamete receives only one allele for a gene. In cross between two heterozygous individuals (e.g Tt x Tt) meiosis produces equal numbers of T and t gametes. When these gametes combine randomly at fertilisation, the offspring have a genotypic ratio of 1xTT, 2xTt, 1xtt, resulting in a phenotypic ratio of 3 tall:1 short.
Construct a punnett square, determine the genotype and phenotype ratios, and provide an answer for the following questions.
The presence of freckles is a dominant characteristics. An unborn child’s mother has no freckles and its father is heterozygous for freckles. What is the probability that this child will have freckles?
