Genetics Exam 4: Mendelian Genetics pt2

What is a dihybrid cross?

Two pairs of contrasting traits

Examines 2 characteristics simultaneously

What is the ratio of a dihybrid cross?

9:3:3:1

What is Mendel’s 4th postulate?

Independent assortment: the two sets of traits are being inherited independently of each other

What is product law?

Used to predict frequency of two independent events occurring simultaneously

What is an example of the 9:3:3:1 ratio?

9/16 yellow, round seeds

3/16 yellow, wrinkled seeds

3/16 green, round seeds

1/16 green, wrinkled seeds

What is a trihybrid cross?

Segregation and independent assortment applied to three pairs of constraining traits

Mendel theorized discontinuous variation, the dominant-recessive relationship. What did Darwin and Wallace’s continuous variation suggest?

offspring are a blend of parental phenotypes

Where did Walter Flemming discover chromosomes?

in the nuclei of salamander cells

What is the chromosomal theory of inheritance?

Genetic material in living organisms is contained in the chromosomes

What served as the basis for Mendel’s principles of segregation & independent assortment?

the separation of chromosomes during meiosis

Where can Mendel’s postulates be found during chromosome separation?

unit factors in pairs = first meiotic prophase

segregation = first meiotic anaphase

independent assortment = nonidentical homologous chromosomes

What is the requirements for homologous pairs?

same size & identical centromere location

synapse during meiosis

have identical order of gene loci

one is derived from either maternal or paternal parent

What is sum law?

Calculates probability of outcomes independent of each other

What two factors are used in predicting genetic outcomes?

independent assortment & sample size

What does the null hypothesis measure in Chi-Square analysis?

Assumes there is no real difference between measured values and predicted values

How do we decide in chi-square analysis?

if P < 0.05 = there is a statistical difference

if P > 0.05 = there is not a statistical difference

degrees of freedom is n - 1. What are some examples of this in relation to the ratios?

3:1 > n = 2, df = 1

9:3:3:1 > n = 4, df = 3

What is a pedigree?

Family tree with respect to given trait

-reveals patterns of inheritance of human traits

What is a proband in a pedigree?

The individual whose phenotype first brought attention to the family

How can we tell when a recessive trait is seen in a pedigree?

they typically skip generations

How can we tell if a dominant trait is seen in a pedigree?

they almost always appear in each generation