Smeltz BIO 101 CH 11A

Distinguish between the terms homozygous and heterozygous.

*Homozygous*: When an organism has identical alleles for a gene *Heterozygous*: When an organism has different alleles for a gene

Distinguish between the terms phenotype and genotype.

*Phenotype*: An organism's physical appearance for a specific character. (e.g., purple flowers) *Genotype*: An organism's genetic makeup (e.g., PP or Pp) for a specific character

Genetics problem: In certain plants, tall is dominant to short. If a heterozygous plant is crossed with a homozygous plant, what is the probability that the offspring will be short? Provide the genotypic and phenotypic ratios of the offspring.

0% chance of a short offspring. Genotypic ratio: 1TT: 1Tt Phenotypic ratio: 4 tall: 0 short (1 tall: 0 short)

Given that the rule of addition states that the probability that either one of two independent events will occur is the sum of the individual probabilities, what is the probability of rolling either a 5 or a 6 using a 6-sided die?

1/3 1/6 (probability of rolling a 5) + 1/6 (probability of rolling a 6) = 2/6 = 1/3

Given that the rule of multiplication states that the probability that two or more independent events will occur together is the product of their individual probabilities, in the cross AaBbCc x AaBbCc, what is the probability of producing the genotype AABBCC?

1/4 x 1/4 x 1/4 = 1/64 To solve, determine the probabilities of each event independently using monohybrid crosses (Aa x Aa; Bb x Bb; Cc x Cc), and then multiply those probabilities together to get the probability of those events occurring together.

In which percentage of the F2 generation does the recessive trait reappear?

25%

How many squares does a 1 character Punnett square have?

4^1 = 4 squares

How many squares does a 2 character Punnett square have?

4^2 = 16 squares

How many squares does a 3 character Punnett square have?

4^3 = 64 squares

What is the expected phenotypic ratio of a dihybrid cross: AaBb x AaBb ?

9:3:3:1 9 offspring with dominant phenotypes for both characters 3 offspring with dominant phenotypes for 1 character, but recessive phenotypes for the other character 3 offspring with recessive phenotypes for 1 character but dominant phenotypes for the other character 1 offspring with recessive phenotypes for both characters

What is a Punnett square?

A diagram for predicting the results of a genetic cross between individuals of known genetic makeup.

What is a testcross?

A mating between an individual of unknown genotype and an individual homozygous recessive for the trait of interest. Used to determine if the unknown genotype is homozygous dominant or heterozygous.

Mendel's second law of independent assortment has its basis in which meiotic event?

Alignment of homologs (tetrads) at the equator during Metaphase I

What are alleles?

Alternative versions of a gene

Which phase of meiosis accounts for Mendel's observation of the segregation of alleles in gamete formation?

Anaphase I of meiosis when homologous chromosomes separate from each other

What are distinct heritable features called?

Characters

Individuals that are heterozygous for two characters are called ____________________________.

Dihybrids

How are the dominant and recessive traits represented?

Dominant trait with a capital letter and recessive trait with a lowercase of the same letter.

What ratios of dominant to recessive traits are observed in the F1 and F2 generations?

F1: 4:0 F2: 3:1

With reference to the pea plant, what is an example of a character that was studied?

Flower color

What is the F1 generation?

Hybrid offspring of the P generation

How did Mendel explain the disappearance of a trait during the F1 generation, and its reappearance during the F2 generation?

Mendel said that traits can be dominant or recessive; the recessive traits were masked by the dominant ones in the F1 generation.

Individuals that are heterozygous for one character are called __________________________.

Monohybrids

What model did Gregor Mendel use to study patterns of inheritance?

Pea Plant (sweet pea plant)

What are true-breeding plants?

Plants that self-fertilize to produce offspring identical to the parent.

What is the F2 generation?

Produced from the cross between two F1 generations

With reference to the pea plant, what is an example of traits that were studied?

Purple and white flowers

What are the different varieties of a character called?

Traits

What is the P generation?

True-breeding parents

What is the difference between a dominant trait and a recessive trait?

When crossing two true-breeding plants, the trait that is expressed in the F1 generation is the *dominant trait* and the trait that is hidden is the *recessive trait*.

Solve the following genetics problem: Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to long tails (t). What fraction of the progeny of crosses BbTt (male) x BBtt (female) will be expected to have black fur and long tails? a. What are the male gametes? b. What are the female gametes? c. Fraction of black fur, long tail offpring?

a. Male gametes: BT, Bt, bT, bt b. Female gametes: Bt c. 1/2

According to Mendel's principle of segregation, gametes have how many copies of each allele?

one