Mendelian Genetics
What is a phenotype?
A phenotype is the physical expression of a trait
What is codominance?
Codominance occurs when both alleles are expressed equally in the phenotype
What is the purpose of meiosis?
Meiosis reduces chromosome number by half and creates genetic diversity.
What is a pedigree chart?
A pedigree chart shows the inheritance of a trait within a family.
In a certain species of plants, the stems can either be tall or short. Hybrids for this trait will be tall. This is an example of
Complete dominance
What is a homozygous genotype?
A homozygous genotype has two identical alleles for a trait.
What is incomplete dominance?
Incomplete dominance results in a blend of parental traits in the phenotype.
What happens during Prophase I?
Homologous chromosomes pair up and exchange genetic material during crossing over.
How do you calculate genotypic ratios?
Divide the number of each genotype by the total number of offspring. (Punnet Squares).
Trisomy 21 also known as Downs Syndrome, is caused by an error made during meiosis where homologous chromosomes fail to separate from one another during anaphase. This is known as
Non disjunction
Describe the law of segregation
The law states that allele pairs separate during gamete formation and randomly unite at fertilization
Describe polygenic inheritance
Polygenic inheritance involves multiple genes influencing a trait.
Explain crossing over.
Crossing over is the exchange of genetic material between homologous chromosomes, increasing variation.
Explain a test cross result.
A test cross result can reveal if an individual is homozygous or heterozygous for a trait.
You have a Chi Squared value of 5.95. You compare this number to the Chi-Square Table and see the significant number is 5.99. What does this mean?
You accept the null hypothesis - any difference between observed and expected is due to random chance.
Explain a dihybrid cross
A dihybrid cross examines the inheritance of two different traits simultaneously
How does mitochondrial inheritance work?
Mitochondrial inheritance is passed from mother to offspring through the cytoplasm of the egg cell.
What is independent assortment?
Independent assortment is the random distribution of chromosomes during meiosis.
What does a chi-square test measure?
The difference between observed frequencies in data and the frequencies that would be expected if there was no relationship between variables
Explain why a rabbit's fur color will change based on the season? How is this a survival adaptation?
The changing of the season acts as an environmental cue, and changes the gene expression of the rabbit. The change in pigments produced in each season will aid the rabbit in camouflage
How does a test cross work?
A test cross determines the genotype of an organism by crossing it with a homozygous recessive
What is Epistasis?
Epistasis occurs when one gene masks the expression of another, such as albinism.
How does nondisjunction affect genetic variation?
Nondisjunction results in gametes with abnormal chromosome numbers, leading to disorders like Down syndrome.
Two individuals RrTtYy are crossed. What is the probability their offspring has the genotype RRttyy?
1/64
in your own words, describe the three ways in which meiosis can lead to genetic variation?
Random fertilization of sperm and egg
Crossing over
Independent assortment of chromosomes