Chapter 14

Question 1

2 possible explanations for how genes/heredity are passed down from parent to offspring

Answer 1

1) Blending hypothesis

2) “Particulate” hypothesis or Gene Idea

Question 2

Blending Hypothesis

Answer 2

genetic material contributed by two parents mixes

i.e blue + yellow paint = green

Question 3

“Particulate” Hypothesis

Gene Idea

Answer 3

parents pass on discrete heritable units, called genes, that retain their identities in future offspring

Question 4

Gregor Mendel

Answer 4

• discovered the principles of heredity
• 1st to document particulate inheritance
• utilized an experimental and quantitive approach to genetics

~1857, studied principle of heredity by breeding garden peas

Question 5

Why Mendel worked with peas

Answer 5

1) available in many varieties
provided both distinctive heritable features or characters with different traits
2) control cross breeding
4) food source
4) easily observable
5) grow relatively quickly in cooler climates

Question 6

Character

Answer 6

a heritable feature

i.e. hair or eye color

Question 7

Trait

Answer 7

a variant of a character

i.e. brown, blond, red hair color

Question 8

Mendel’s Experiments

Answer 8

• began breeding “true-breeds”
• then would mate the two contrasting, true-breeds
• used pea plants, studying petal color (purple vs. white)
• 3:1 phenotype ratio
• 1:2:1 genotype ratio

Question 9

“True-Breeding”

Answer 9

the same variety

always produce the same color

Question 10

Hybridization

Answer 10

• mating two contrasting, true-breeding varieties

- studied the process of inheritance

Question 11

What did Mendel use to determine the process of inheritance in future generations?

Answer 11

pea plant Petal Color

-purple vs. white

Question 12

“P” generation

Answer 12

the true-breeding parents

Question 13

Hybrid Offspring

from the “P” generation

Answer 13

create F1 generation

had all dominant trait, regardless of source of pollen

i.e. all purple flowers

Question 14

F1 cross with F1

Self-polination

Answer 14

• create F2 generation
• disproved the hybridization theory

i. e. 3/4 purple; 1/4 white
- 3:1 ratio

Question 15

Dominant

Answer 15

i.e. purple petals

if dominant trait was present, that was the trait that was seen

Question 16

Recessive

Answer 16

i.e. white petals

only seen if both recessive genes were passed down

Question 17

4 related concepts that make up Mendel’s 3:1 ratio model (long version)

Answer 17

1) Alternative versions of genes account for variations in inherited characters, called alleles
2) Each character an organism inherits 2 alleles, one from each parent (genetic locus is represented twice)
3) If 2 alleles at a locus differ then one, the dominant allele, determines the organism’s appearance and the other, the recessive allele, has no noticeable effect on the organism’s appearance
4) the Law of Segregation: 2 alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes

Question 18

4 related concepts that make up Mendel’s 3:1 ratio model (short version)

Answer 18

1) alternative version of genes (alleles)
2) 2 alleles per character are inherited
3) Dominant allele will determine appearance
4) Law of Segregation: alleles separate in meiosis

Question 19

Alleles

Answer 19

inherited characters

found on chromosomes

Question 20

Law of Segregation

Answer 20

2 alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes

• for a single trait

Question 21

Pungent Square

Answer 21

can be used to predict the results of a genetic cross between individuals of known genotype

Question 22

Homozygous organism

Answer 22

a pair of identical alleles for that gene and exhibits true-breeding

Question 23

Heterozygous organism

Answer 23

a pair of alleles that are different for that gene

Question 24

Phenotype

Answer 24

an organism’s physical character

Question 25

Genotype

Answer 25

an organism’s genetic makeup

Question 26

2 organisms can have ….

Answer 26

the same phenotype but different genotype

- one homologous, one heterologous

Question 27

Testcross

Answer 27

allows us to determine the genotype of an organism with the dominant phenotype, but unknown genotype

crosses an individual with the dominant phenotype with an individual that is homozygous recessive for a trait

Question 28

Monohybrid Cross

Answer 28

• law of segregation for a single trait

- heterozygous for one character

Question 29

Dihybrid Cross

Answer 29

• looking at 2 inherited characters at the same time
• crossing two, true-breeding characters that produces dihybrids in the F1 generation
• produces 4 phenotypes
• 9:3:3:1 ratio
• are the two characters transmitted from the parents as a package?

Question 30

Law of Independent assortments

Answer 30

alleles are sorted into gametes and inherited independently

-each pair of alleles segregates independently during gamete formation

Question 31

Laws of probability govern…

Answer 31

Mendelian inheritance and Mendel’s law of segregation and independent assortment reflect the rules of probability

can use these rules of probability to predict the outcome of crosses involving multiple characters

Question 32

Multiplication Rule

Answer 32

the probability that two or more independent events will occur together is the product of their individual probabilities

in calculating the chances for various genotypes from crosses, each character first is considered separately and then the individual probabilities are multiplied together

Question 33

The relationship between genotype and phenotype is

Answer 33

Rarely Simple and the inheritance of characters by a single gene may Deviate from Simple Mendelian patterns

Question 34

3 types of dominance

Answer 34

Complete dominance, Co-dominance, Incomplete dominance

Question 35

Complete Dominance

Answer 35

Dominant character is shown, recessive character is suppressed

i.e. Mendel’s pea plants

Question 36

Co-Dominance

Answer 36

both phenotypes are fully expressed

i.e. ABO blood type

Question 37

Incomplete dominance

Answer 37

the phenotype of F1 hybrids is somewhere between the phenotypes of the two parental variations

i.e. snapdragons
Red + White => Pink F1s

Question 38

Recessive Inherited Disorders

Answer 38

many genetic disorders are inherited in a recessive manner and show up only in individuals homozygous for the allele

Question 39

Carriers (parents) are heterozygous individuals who carry the recessive allele but are phenotypically normal…

Answer 39

can give their offspring a recessive gene and giving them a recessive inherited disorder

Question 40

2 types of recessive inherited disorders

Answer 40

1) Cystic fibrosis

2) Sickle Cell Disease

Question 41

Cystic Fibrosis

Answer 41

include mucus buildup and abnormal absorption of nutrients in internal organs

transduction channel doesn’t pump water and protein correctly

• mostly Caucasian, descendants from Europe

Question 42

Sickle Cell Disease

Answer 42

a mutation that affects the hemoglobin protein in red blood cells
- hemoglobin protein in RBCs that transport oxygen is not folded correctly

• symptoms: physical weakness, pain, organ damage, even paralysis
• affects 1 out of 400 African-Americans