Lecture 12- Mendelian Genetics

Question 1

What is the difference between a phenotype and a genotype?

Answer 1

Phenotype is the traits expressed by an organism whereas genotype encompasses both physically visible and non-expressed alleles

Question 2

What did the Blending Inheritance hypothesis state?

Answer 2

Progeny (offspring) inherit characteristics as the average of their parents. For example: under Blending Inheritance, the offspring of a purple flower crossed with a white flower would yield a pink flower

Question 3

What was the result of Gregor Mendel’s cross of two true-breeding parental (P) generation?

Answer 3

Crossed violet and white flowers-> yielded 100% violet F1 (first filial) generation

Question 4

Gregor Mendel allowed self-fertilization of the first filial (F1) generation. What were the results of this experiment?

Answer 4

Yielded 3:1 ratio of purple:white F2 generation (75% purple:25% white)

Question 5

How did Gregor Mendel’s experiments reject the Blending Inheritance hypothesis?

Answer 5

No intermediate phenotypes appeared & lost phenotypes reappeared

Question 6

What did the Particulate Inheritance hypothesis state?

Answer 6

Phenotypic traits can be passed from generation to generation through discrete particles/heritable factors known as genes & each trait is controlled by two factors (genes) from parents

Question 7

What did Mendel’s Law of Independent Assortment state?

Answer 7

Alleles for different genes get sorted into gamete’s independently of one another

Question 8

What did Mendel’s Law of Segregation state?

Answer 8

Only one of the two gene copies present in an organism is distributed to each gamete that it makes, and the allocation of the gene copies is random

Question 9

Which probability rule predicts combined probabilities of independent events?

Answer 9

Multiplication rule

Question 10

Which probability rule predicts combined probabilities of mutually exclusive events?

Answer 10

Addition rule

Question 11

Concept 1- Alleles

Answer 11

One of two or more alternative forms of a gene. Each allele at same locus (location) on homologous chromosomes

Question 12

What is true-breeding?

Answer 12

All individuals of line have the same characteristics (same phenotype)

Question 13

What are the 4 concepts in Mendel’s model that support discrete inheritance?

Answer 13

1. Alleles are discrete units of information
2. 2 alleles from each parent (2n)
3. Dominant and recessive alleles
4. Mendel’s two laws of inheritance

Question 14

Concept 2- Two alleles: 1 from each parent

Answer 14

The two alleles may be identical (homozygous) or different (heterozygous)

Question 15

Concept 3- Dominant and recessive alleles

Answer 15

If an organism is heterozygous, the dominant allele determines the organism’s appearance. The recessive allele has no effect on appearance.

Question 16

Concept 4- Mendel’s 2 Laws

Answer 16

1. Law of Segregation- The 2 copies of each gene (alleles) segregate (separate) during meiosis. Egg or sperm gets only 1 of the 2 alleles.
2. Law of Independent Assortment- Genes on different chromosomes assort randomly and independently during gamete formation due to random orientation of tetrads during metaphase I. Each are equally likely, this leads to genetic recombination and more variation