Chapter 4: Extensions of Mendelian Inheritance

Question 1

Incomplete dominance is an inheritance pattern in which the __ has an intermediate __

Answer 1

heterozygote; phenotype

Question 2

Whether we consider an allele to be dominant of incompletely dominant may depend on how closely we examine the __

Answer 2

phenotype

Question 3

Define overdominance

Answer 3

inheritance pattern in which the heterozygote has greater reproductive successes

Question 4

T/F: Alleles cannot be codominant

Answer 4

False - AB blood type

Question 5

Lethal alleles most commonly occur in __ genes

Answer 5

essential

Question 6

Define pleiotropy

Answer 6

genes that exert multiple phenotypic effects

Question 7

What two characteristics does Simple Mendelian inheritance involve?

Answer 7

a single gene with two different alleles
alleles display a simple dominant/recessive relationship

Question 8

What two laws do Mendelian Inheritance obey?

Answer 8

Law of Segregation
Law of Independent Assortment

Question 9

Define incomplete dominance

Answer 9

phenotype of a heterozygote is intermediate between that of the homozygotes

Question 10

What is an example of incomplete dominance?

Answer 10

Flower color in four-o’ clock plants; red, pink, white

Question 11

T/F: The 3:1 phenotypic ratio is observed in Incomplete dominance

Answer 11

False - becomes 1:2:1

Question 12

Incomplete dominance is easier seen on a __ or __ level

Answer 12

cellular; microscopic

Question 13

Define codominance

Answer 13

phenotype of the heterozygote is a mixture of the phenotypes of the homozygotes - both alleles are expressed

Question 14

What is an example of codominance?

Answer 14

AB Blood Type - both A and B antigens are expressed

Question 15

List the genotype, surface antigen, and serum antibodies for blood type O

Answer 15

Genotype: ii
Surface antigen: neither A or B
Serum antibodies: against A and B

Question 16

List the genotype, surface antigen, and serum antibodies for blood type A

Answer 16

Genotype: I(A)I(A) or I(A)i
Surface antigen: A
Serum antibodies: against B

Question 17

List the genotype, surface antigen, and serum antibodies for blood type B

Answer 17

Genotype: I(B)I(B) or I(B)i
Surface antigen: B
Serum antibodies: against A

Question 18

List the genotype, surface antigen, and serum antibodies for blood type AB

Answer 18

Genotype: I(A)I(B)
Surface antigen: A or B
Serum antibodies: none

Question 19

A and B are __ to O

Answer 19

dominant

Question 20

Incompatible blood samples result in ?

Answer 20

agglutination

Question 21

What is the code for Rh antigens?

Answer 21

D - directs synthesis of the Rh antigen
d - Rh antigen is absent

Question 22

A and B antigens are __ groups that are bound to __ and protrude from the __ membrane

Answer 22

sugar; lipids; RBC

Question 23

T/F: O cannot add any terminal sugar, and only possesses the H substance

Answer 23

True - why there’s no antigens

Question 24

The B __ on the RBC reacts with the __ B body

Answer 24

antigen; anti

Question 25

People with the Bombay phenotype are homozygous for a rare recessive mutation that prevents them from?

Answer 25

synthesizing the complete H substance resulting in no expression of A or B

Question 26

Discuss the dominance hierarchy for coat color in rabits: full coat color, albino, chinchilla, and himalayan

Answer 26

C - full coat c(ch) - chinchilla; partial defect in pigmentation c(h) - himalayan; pigmentation only in certain areas c - albino; no pigmentation

Question 27

Define a lethal allele

Answer 27

one that has the potential to cause the death of an organism

Question 28

Lethal alleles are usually inherited in a __ manner

Answer 28

recessive

Question 29

How do lethal alleles typically result?

Answer 29

mutations in essential genes

Question 30

If the heterozygous state of a lethal allele is tolerated, then the lethal allele is __

Answer 30

recessive

Question 31

If the heterozygous state of a lethal allele leads to death, then the allele is __

Answer 31

dominant

Question 32

Who first observed a lethal allele pattern in mice?

Answer 32

Lucien Cuenot

Question 33

Who confirmed Cuenot's observation of lethal alleles?

Answer 33

Castle and Little

Question 34

T/F: Lethal alleles result in a Mendelian Inheritance Pattern

Answer 34

False - 2:1 ratio, homo recessive leads to death

Question 35

Lethal alleles can also be __ and __

Answer 35

conditional - temperature semilethal

Question 36

Huntington disease is caused by a __ __ allele

Answer 36

dominant lethal

Question 37

Discuss the phenotype based on the genotype for Huntington's Homozygous dominant

Answer 37

die in utero

Question 38

Discuss the phenotype based on the genotype for Huntington's Heterozygous

Answer 38

develop normally; get disease later in live

Question 39

Discuss the phenotype based on the genotype for Huntington's Homozygous recessive

Answer 39

phenotypically normal

Question 40

Define pleiotropy

Answer 40

phenomenon in which a single gene affects a number of seemingly unrelated characters

Question 41

What are three reasons pleiotropy occurs?

Answer 41

gene product can affect cell function in more than one way gene may be expressed in different cell types gene may be expressed at different stages of development

Question 42

What is an example of pleiotropy?

Answer 42

sickle cell anemia

Question 43

Sickle cell anemia is a __ __ disorder

Answer 43

autosomal recessive

Question 44

What are the two alleles affected in Sickle Cell Anemia?

Answer 44

Hb(A) Hb(S)

Question 45

Sickle cell anemia results from a defect in the?

Answer 45

mutation in the gene for the beta chain of hemoglobin

Question 46

What are the two major productions of sickle cell anemia?

Answer 46

sickled red blood cells are destroyed - causing anemia odd-shaped cells clump - blocks in capillary circulation

Question 47

Define overdominance

Answer 47

phenomenon in which a heterozygote is more vigorous than both of the corresponding homozygotes

Question 48

What are three possible explanations for overdominance at the molecular/ cellular level?

Answer 48

Disease resistance homodimer formation variation in functional activity

Question 49

What is an example of overdominance?

Answer 49

Sickle cell anemia + malaria

Question 50

Discuss the overdominance pattern of sickle cell

Answer 50

Hb(A)Hb(A) - normal - dies to malaria Hb(A)Hb(S) - sickle cell trait - protected from both Hb(S)Hb(S) - sickle cell anemia - death from sickle cell anemia