Mendelian Genetics

Question 1

What is the complete complement of an organism’s DNA?

Answer 1

Genome

Question 2

How is cellular DNA organized?

Answer 2

In chromosomes

Question 3

What have specific places on chromosomes (loci)?

Answer 3

Genes

Question 4

What is the genetic composition of an organism?

Answer 4

Genotype

Question 5

What is the physical expression of an organism’s traits?

Answer 5

Phenotype

Question 6

What are variations of a gene?

Answer 6

Alleles - Represented with letters for different types of alleles (PP, Pp, pp)

Question 7

What is a pair of identical alleles for a character (PP, pp)?

Answer 7

Homozygous

Question 8

What is two different alleles for a gene (Pp)?

Answer 8

Heterozygous

Question 9

What is a heritable feature?

Answer 9

A character

Question 10

What is a variant for a character?

Answer 10

A trait

Question 11

What are all offspring of the same variety called?

Answer 11

Purebred

Question 12

What is the crossing of two different true-bred organisms called?

Answer 12

Hybrid

Question 13

What are the different generations of a cross called?

Answer 13

-P generation (parents)
-F1 generation (1st filial generation)
-F2 generation (2nd filial generation)

Question 14

What type of genotype is it when both recessive alleles are present (rr)?

Answer 14

Recessive

Question 15

What type of genotype is it when at least one dominant allele is present (R-)?

Answer 15

Dominant

Question 16

Who was Gregor Mendel?

Answer 16

Austrian monk from the 1800’s who suggested that when crossed, organisms had heritable traits

Question 17

What did Gregor Mendel do?

Answer 17

He examined pea plants over many generations

Question 18

What did Mendel discover? What were these things called?

Answer 18

-Three laws of inheritance.
-They are called:
- Law of Dominance
- Law of Segregation
- Law of Independent Assortment

Question 19

What happened in Mendel’s Pea Plant Experiments?

Answer 19

• Mendel examined plants of varying heights (tall or short 🡪 T = tall, t = short)
• In the experiment he crossed two parent (P) plants (short x tall) and got ALL tall plants in the F1 generation
• He crossed the F1 plants and found that ¾ were tall in the F2 generation

Question 20

What is a monohybrid cross?

Answer 20

The examination of one trait (height)

Question 21

What did the results of these experiments mean?

Answer 21

• Mendel went on to examine other traits on pea plants (round x wrinkled, yellow x green) and got similar results
• Ratio of ~3:1 in F2 generation
• He concluded that there must be a dominant trait that is always expressed when present, and a recessive trait that is expressed only when the dominant trait is not present

Question 22

Explain Mendel’s Law of Dominance

Answer 22

• In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the F1 generation
• The dominant trait will be expressed (phenotype), while the recessive trait will be hidden
• Factor that remained hidden in F1 generation but is present in the F2 generation is the “recessive factor”

Question 23

Explain Mendel’s Law of Segregation (3 points)

Answer 23

• Alleles (one from each parent) result in variations in inherited characteristics
• For each character, an organism inherits two alleles (1/parent)
• The alleles for each character segregate during meiosis
• Alleles for a trait are recombined at fertilization → genotype of offspring

Question 24

Explain Mendel’s Law of Independent Assortment

Answer 24

Alleles for different traits are distributed to sex cells (and offspring) independent of one another

Question 25

How do you predict patterns of inheritance?

Answer 25

- Punnett Squares: Tool for diagramming possible genotypes of offspring - Laws of Probability: When you flip a coin, what is the likelihood that you will get heads? Tails? Basic genetics problems can be solved using the foundational laws of probability

Question 26

How do you determine if an organism is homozygous dominant or heterozygous?

Answer 26

- When the above information is not given, a test cross must be done to confirm - Always performed between the unknown genotype and a homozygous recessive genotype - Cross the individual with the dominant trait with an individual that exhibits the recessive trait -Results reveal the genotype: All offspring display the dominant phenotype, then the the individual in question is homozygous dominant. Offspring display both dominant and recessive phenotypes, then individual is heterozygous

Question 27

What are test crosses?

Answer 27

- When the genotype of an organism is not known, one can cross this organism with another that is homozygous recessive for the traits in question - This is called a test cross