Mendel's Principles of Heredity

Question 1

What is the basic unit of heredity?

Answer 1

Genes

Question 2

What are genes?

Answer 2

A region of DNA that encodes a protein or RNA

Question 3

What is heredity?

Answer 3

The way that genes transmit traits from parents to offspring.

Question 4

What was the first applied genetic technique?

Answer 4

Artificial selection

Question 5

What is artificial selection?

Answer 5

Purposeful control of mating by choice of parents for the next generation.

Question 6

What was the issue with artificial selection?

Answer 6

Unpredictable

Question 7

What were the two misleading theories of inheritance at the time of Mendel’s studies?

Answer 7

1. The homunculus
2. Blended inheritance

Question 8

What was the humunculus?

Answer 8

Inherited features of offspring are contributed by the male parent via fully formed miniature offspring in the sperm.

Question 9

What was blended inheritance?

Answer 9

Parental traits become mixed and permanently changed in the offspring

Question 10

What were the keys to the success of Mendel’s experiments?

Answer 10

• Used pure-breeding lines of peas
• Used antagonistic pairs of traits
• Was a brilliant experimentalist (carefully planned, use of reciprocal crosses, mathematical analysis)

Question 11

How did Mendel disprove the blending hypothesis?

Answer 11

Crossed pure-breeding lines that differed in only one trait.

Question 12

What were the phenotypes of Mendel’s F1 and F2 progeny?

Answer 12

F1: have only one of the parental traits
F2: Both parental traits appear in F2 progeny in a 3:1 ratio

Question 13

In modern terminology, what are the “unit factors” Mendel refers to: Genetic characters are controlled by unit factors existing in pairs in individual organisms

Answer 13

Genes

Question 14

Differentiate between dominant and recessive traits.

Answer 14

Trait that appears in the F1 progeny is dominant.
Trait that is hidden in F1 progeny is recessive.

Question 15

What are alleles?

Answer 15

Alternative forms of a single gene.

Question 16

What are monohybrids?

Answer 16

Individuals with two different alleles for a single trait.

Question 17

What are gametes?

Answer 17

The specialized cells that carry genes across generations.

Question 18

What is Mendel’s law of segregation?

Answer 18

The two alleles for each trait separate during gamete formation. Two gametes, one from each parent, unite at random at fertilization.,

Question 19

What is the product rule?

Answer 19

Probability of to independent events occurring together is product of individual probabilities.

Question 20

What is the sum rule?

Answer 20

Probability of either of two mutually exclusive events occurring is the sum of their individual probabilities.

Question 21

What is the genotypic ratio in F2 progeny? Phenotypic?

Answer 21

G - 1:2:1
P - 3:1

Question 22

How would you determine whether the genotype of an individual with a dominant phenotype is heterozygous or homozygous?

Answer 22

Testcross with a homozygous recessive individual.

Question 23

What are dihybrids?

Answer 23

INdividuals heterozygous for two genes.

Question 24

What is the phenotypic ratio of crosses of F1 dihybrids? Genotypic?

Answer 24

p - 9:3:3:1
g - 1:1:1:1

Question 25

What is Mendel’s law of independent assortment?

Answer 25

During gamete formation, different pairs of alleles segregate independently of each other.

Question 26

What is the molecular explanation for Mendel’s pea colour?

Answer 26

The Y allele encodes the stay green enzyme (Sgr). Sgr helps break down chlorophyll.
The y allele does not make Sgr. Chlorophyll is not broken down and the pears remain green.

Question 27

What are the two general molecular principles of genetics?

Answer 27

1. A specific gene determines a specific protein, whose activity may affect the phenotype.
2. A dominant allele usually determines a normally functioning protein and a recessive allele does not encode a functional protein.

Question 28

Why do many heritable traits in humans not show simple Mendelian inheritance patterns?

Answer 28

Caused by interaction of multiple genes

Question 29

Why is it difficult to determine the inheritance patterns of traits in humans (as compared to Mendel’s peas)?

Answer 29

Long generation time
Small numbers of progeny
No controlled matings
No pure-breeding lines

Question 30

Look at the single-gene traits tables.

Answer 30

chicken licken

Question 31

What are pedigrees?

Answer 31

Orderly diagrams of a family’s relevant genetic features.

Question 32

Is Huntington disease allele dominant or recessive?

Answer 32

Dominant

Question 33

What does a vertical pattern of inheritance indicate?

Answer 33

Rare dominant trait.

Question 34

What does a horizontal pattern of inheritance indicate?

Answer 34

Rare recessive trait

Question 35

How does the protein CFTR lead to cystic fibrosis?

Answer 35

CFTR regulates passage of chloride ions across cell membrane. Heterozygotes produce enough for normal lung function. Homzygous recessive is what cause CF.

Question 36

What are the 3 key aspects of pedigrees with dominant traits?

Answer 36

1. Affected children always have at least one affected parent
2. As a result, dominant traits show a vertical pattern of inheritance
3. Two affected parents can produce unaffected children if both parents are heterozygotes.

Question 37

What are the 4 key aspects of pedigrees with recessive traits?

Answer 37

1. Affected individuals can be the children of 2 unaffected carriers, particularly as a result of consanguineous mating
2. All the children of 2 affected parents should be affected
3. Rare recessive traits show a horizontal pattern of inheritance
4. Recessive traits may show a vertical pattern of inheritance if the trait is extremely common in the population.