Ch 11

Question 1

What did Gregor Mendal study at the University of Vienna?

Answer 1

• Gregory Mendal studied math and science
• 1822-1884
• Worked as a substitute teacher at a local high school
• First scientist to apply math to biology
• he applied statistics and probability to breeding experiments

Question 2

Describe the blending concept of inheritance.

Answer 2

Mendal theory: particulate theory

• he thought minute particles ( hereditary units) were reshuffled in parents and passed on to offspring
• he proposed the law of segregation
• he proposed the law of independent assortment
• Mendal did not know about DNA or genetic material

Question 3

Is it the F1 generation or the F2 generation that disproves this theory of inheritance?

Answer 3

F1 generation: this was the offspring from the cross of two true-breeding varieties chosen to be different by only one trait

• blending theory rejected
• when tall plants were crossed with short plants: the offspring were all tall.

Question 4

What is Mendels Law of segregation?

Answer 4

To test the blended vs particulate nature of inheritance Mendal selected true-breeding pea varieties that differed in only one trait
-tall vs short (everything else is the same)
- red vs white (everything else is the same)
If blended theory was correct: tall crossed with short would give medium offspring and red vs white would give pink offspring

Question 5

What is Mendals law of independent assortment?

Answer 5

Two or more characteristics are inherited, individuals hereditary factors as sort independently during gamete production, giving different traits an equal opportunity of occurring together

Question 6

What is a true-breeding organism?

Answer 6

• self-pollination for many plant generations produces offspring plants that look exactly like the parent plant
• tall plants always produce tall offspring
• red plants always produce red offspring

Question 7

What does the genotype look like or a true-breeding organism and what is the phenotype of an example organism for 1 trait?

Answer 7

Genotype for true-breeding organism is either TT or tt

Phenotype of F1 generation is Tt

Question 8

What does the genotype look like and what is the phenotype of an example organism for two traits?

Answer 8

F2 generation phenotype: always produces a 3:1 ratio of the true-breeding phenotypes
F2 generation genotype: Ff and Ff produce FF, Ff, Ff, and ff

Question 9

Why was it necessary for Mendel to remove the anthers from a pea plant in some of his experiments?

Answer 9

For some of the plants to self-pollinate like in F2 generations

Question 10

Which of the generations could be produced by self-fertilization? Why is this called a monohybrid cross?

Answer 10

F2 generation: generation allowed to self-pollinate

Monohybrid cross: Letting the offspring from the true-breeding cross self-pollinate

Question 11

Which generation produces a 3:1 ratio of dominant to recessive phenotype so in the offspring?

Answer 11

F2 generation always produces a 3:1 ration of the true-breeding phenotypes

Question 12

Describe the purpose of a test cross with offspring of the F1 generation of a monohybrid cross. What are the genotype a of both parents for this test cross?

Answer 12

F1 generation: this was the offspring from the cross of two true-breeding varieties chosen to be different by only one trait
Monohybrid cross: letting the offspring from a true-breeding cross self-pollinate

Question 13

Define locus.

Answer 13

A specific area on a chromosome

Question 14

Define allele.

Answer 14

• two traits, segregated in gametes, brought together again in offspring
• each trait can be called an allele

Question 15

Define homozygous.

Answer 15

The alleles are identical

• both dominant: TT
• both recessive: tt

Question 16

Define heterozygous.

Answer 16

One dominant and one recessive: Tt

Question 17

What is a dihybrid cross?

Answer 17

Looking at 2 traits

Question 18

For dihybrid crosses, what is the genotype of the homozygous dominant parent in the P generation?
What is the phenotype for this parent?

Answer 18

Parent 1: a tall (homozygous dominant) plant with green pods ( homozygous dominant) TTGG
Phenotypes:
1. Tall plants with green pods
2. Tall plants with yellow pods 
3. Short plants with green pods
4. Short plants with yellow pods

Question 19

What is the genotype for the homozygous recessive parent in the P generation?
What is the phenotype for this parent?

Answer 19

Parent 2: a short ( homozygous recessive) plant with yellow pods ( homozygous recessive) ttgg
Phenotype:
1.Short plants with green pods
2.Short plants with yellow pods

Question 20

For dihybrid crosses, what would the genotype of the offspring of the F1 generation if both parents are heterozygous for both traits?
What are the possible genotypes and phenotypes of the F2 generation from this cross?
What is the expected ratio of phenotypes from this cross?

Answer 20

If the F1 generation was heterozygous (Tt) then the test cross will produce offspring that have a phenotype ration of 1:1
-TT, Tt, Tt, tt

Question 21

Describe the purpose of a test cross with offspring of the F1 generation of a dihybrid cross.
What are the genotypes of both parents for this test cross?

Answer 21

.

Question 22

Some genes have multiple alleles, although each individual only inherits two. Is this true or false?
What was the example of this in the lecture?

Answer 22

.

Question 23

A person has a blood type AB. Is this an example of codominance or incomplete dominance?

Answer 23

Codominance

Question 24

Define codominance.

Answer 24

Pattern of inheritance in which both alleles of a gen are expressed

Question 25

Define incomplete dominance.

Answer 25

Offspring show traits intermediate between two parental phenotypes

Question 26

Some traits that are know to be dominant are not expressed for unknown reasons. Is this codominance, incomplete dominance, or incomplete penetrance? What was example in the lecture?

Answer 26

Incomplete penetrance - dominant allele not always expressed - polydactyl ( extra fingers)

Question 27

What is a pedigree diagram?

Answer 27

shows the occurrence and appearance or phenotypes of a particular gene or organism and its ancestors from one generation to the next

Question 28

Why are pedigree diagrams useful to determine inheritance patterns of human traits and diseases?

Answer 28

.

Question 29

Know the characteristics of inheritance for autosomal recessive disorders.

Answer 29

The affected individual must have the genotype as aa (homozygous recessive) 1. Parents can be affected or carriers 2. Carriers are heterozygous and unaffected 3. Most children have unaffected parents 4. Two affected parents will always have an affected child 5. Close relatives who reproduce are more likely to have affected children 6. Both males and females are affected with equal frequency

Question 30

Know the characteristics of inheritance for autosomal dominant disorders.

Answer 30

The affect individual can have the genotype AA. (homozygous dominant) or Aa (heterozygous) 1. Affected children will usually have an affected parent 2. Two affected parents can have an unaffected child 3. Two unaffected parents will not have affected child 4. Both males and females are affected with equal frequency

Question 31

Know the characteristics of inheritance for sex-linked disorders.

Answer 31

``` Color blindness Menkes syndrome Duchene muscular dystrophy Adrenoleukodystrophy Hemophilia ```

Question 32

Know the details of the diseases covered in lecture that are autosomal recessive.

Answer 32

Methemoglobinemia Cystic fibrosis Phenylketonuria

Question 33

Know the details of the diseases covered in lecture that are autosomal dominant.

Answer 33

Osteogenesis imperfecta Hereditary spherocytosis Huntington disease

Question 34

Know the details of the diseases covered in lecture that are sex-linked recessive.

Answer 34

1. Color blindness 2. Menkes syndrome 3. Duchene muscular dystrophy 4. Adroenoleukodydtrophy 5. Hemophilia

Question 35

What is a pleiotropic effect?

Answer 35

A single gene exerts an effect on many aspects of an individual's phenotype Ex-sickle cell traits Ex- porphyria Ex- Marfan syndrome