3 Basic Principles of Heredity

What rule is implied with “OR”/ ‘EITHER”

Addition Rule

What rule is implied with “AND”

Multiplication Rule

Revealed the Law of Segregation and the principle of dominance

Monohybrid Crosses

Revealed the principle of independent assortment

Dihybrid Crosses

Is phenotype inherited?

No only the alleles of the genotype are inherited

Which of the following factors did not contribute to Mendel’s success in his study of heredity?

a. his use of the pea plant

b. his study of plant chromosomes

c. his adoption of an experimental approach

d. his use of mathematics

B.

All alleles for any particular gene found at a specific place on a chromosome is called

Locus or loci

True or False: How the phenotype develops within those limits is determined by the joint effects of genes and environmental factors

True. Some characteristics are not heavily influenced by environment others are.

True or False: organisms transfer their phenotypes to the next offspring

False

In a monohybrid cross what did the P generation consist of?

Pure bred round (AA) x pure bred wrinkled (aa)

In a monohybrid cross what did the F₁ generation consist of?

All possessed heterozygous for the round and wrinkle (Aa). All had the phenotype of round.

In a monohybrid cross what did the F₂ generation consist of?

A phenotype ratio of 3:1 and a genotype ratio of 1:2:1

What was the first conclusion Mendel had after doing a monohybrid cross?

Concluded that each plant must possess two alleles that encoded a character

What was the second conclusion Mendel had after doing a monohybrid cross?

Two alleles in each plant separate when gametes are formed, and one allele goes into each gamete. In other words a parent cannot pass down two of its alleles into its gametes (ex:AA) but rather an A from it and an a/A from the other parent.

What was the third conclusion Mendel had after doing a monohybrid cross?

The concept of dominance

What was the fourth conclusion Mendel had after doing a monohybrid cross?

The two alleles of an individual plant separate with equal probability into the gametes which was shown in the F₂ generation (Phenotype of 3:1)

What was Mendel’s First Law?

The Law of Segregation

What was the Law of Segregation

• Each individual diploid organism possesses two alleles for any particular characteristic, one from the maternal parent and one from the paternal parent.

• The two alleles segregate into gametes in equal proportions

• These two alleles segregate (separate) when gametes are formed, and one allele goes into each gamete.

• in other words a gamete cannot get two alleles from one parent. One has to come from each parent

What was the concept of dominance?

When two different alleles are present in a genotype, only the dominant allele is observed in the phenotype

How did Mendel know that each of his pea plants carried two alleles encoding a characteristic?

In the F₂ generation, both traits were shown in the progeny either being wrinkled or round.

What is the enzyme that causes round peas and what does it have to do with wrinkled peas?

SBEI enzyme is responsible for converting starch into a highly branched form. Wrinkled peas have a mutation that prevents the formation of branched starch and thus results in accumulation of starch. Over time as the seed matures, it loses a lot of water causing it to look wrinkled.

A cross with between an F₁ genotype with either of the parental genotypes (monohybrid ex: Rr x RR or rr)

Backcross

In animals, the most common allele for a characteristic and is symbolized by + or with letters accompanied with (ex: ye⁺). Is not necessarily correlated as dominant

Wild type

Crossing an unknown dominant genotype (AA or Aa) with a homozygous recessive genotype (aa)

Testcross

In animals, what is the opposite of wild type and usually only has letters?

Mutant (ex: ye)

What may be used to distinguish the two alleles present in an individual genotype

Slash (cn⁺/cn)

In addition to a slash, if multiple genotypes are on the same locus of the chromosome, what is added?

A space (cn⁺/cn G/g)

In the dihybrid cross what was the ratio of PHENOTYPE in the F₂ generation?

9:3:3:1

What was Mendel’s Second Law

Law of independent assortment

Alleles at different loci separate independently of one another meaning that the separation of an an allele does not dictate where the separation of another allele at a different loci on a chromosome will go

Law of independent assortment

In what scenario would the law of independent assortment not work?

When genes are on the same chromosome unless the genes are far apart enough that crossing over can take place.

What rule is used to determine the probability of two alleles at different loci on separate chromosomes sorting together during meiosis?

Law of multiplication