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Genetics > Chapter 4: Extensions of Mendelian Inheritance > Flashcards

Chapter 4: Extensions of Mendelian Inheritance Flashcards

1
Q

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

A

heterozygote; phenotype

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2
Q

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

A

phenotype

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3
Q

Define overdominance

A

inheritance pattern in which the heterozygote has greater reproductive successes

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4
Q

T/F: Alleles cannot be codominant

A

False - AB blood type

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5
Q

Lethal alleles most commonly occur in __ genes

A

essential

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6
Q

Define pleiotropy

A

genes that exert multiple phenotypic effects

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7
Q

What two characteristics does Simple Mendelian inheritance involve?

A

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

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8
Q

What two laws do Mendelian Inheritance obey?

A

Law of Segregation
Law of Independent Assortment

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9
Q

Define incomplete dominance

A

phenotype of a heterozygote is intermediate between that of the homozygotes

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10
Q

What is an example of incomplete dominance?

A

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

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11
Q

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

A

False - becomes 1:2:1

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12
Q

Incomplete dominance is easier seen on a __ or __ level

A

cellular; microscopic

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13
Q

Define codominance

A

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

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14
Q

What is an example of codominance?

A

AB Blood Type - both A and B antigens are expressed

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15
Q

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

A

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

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16
Q

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

A

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

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17
Q

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

A

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

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18
Q

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

A

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

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19
Q

A and B are __ to O

A

dominant

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20
Q

Incompatible blood samples result in ?

A

agglutination

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21
Q

What is the code for Rh antigens?

A

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

22
Q

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

A

sugar; lipids; RBC

23
Q

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

A

True - why there’s no antigens

24
Q

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

A

antigen; anti

25
Q

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

A

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

26
Q

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

A

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

27
Q

Define a lethal allele

A

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

28
Q

Lethal alleles are usually inherited in a __ manner

A

recessive

29
Q

How do lethal alleles typically result?

A

mutations in essential genes

30
Q

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

A

recessive

31
Q

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

A

dominant

32
Q

Who first observed a lethal allele pattern in mice?

A

Lucien Cuenot

33
Q

Who confirmed Cuenot’s observation of lethal alleles?

A

Castle and Little

34
Q

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

A

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

35
Q

Lethal alleles can also be __ and __

A

conditional - temperature
semilethal

36
Q

Huntington disease is caused by a __ __ allele

A

dominant lethal

37
Q

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

A

die in utero

38
Q

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

A

develop normally; get disease later in live

39
Q

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

A

phenotypically normal

40
Q

Define pleiotropy

A

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

41
Q

What are three reasons pleiotropy occurs?

A

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

42
Q

What is an example of pleiotropy?

A

sickle cell anemia

43
Q

Sickle cell anemia is a __ __ disorder

A

autosomal recessive

44
Q

What are the two alleles affected in Sickle Cell Anemia?

A

Hb(A)
Hb(S)

45
Q

Sickle cell anemia results from a defect in the?

A

mutation in the gene for the beta chain of hemoglobin

46
Q

What are the two major productions of sickle cell anemia?

A

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

47
Q

Define overdominance

A

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

48
Q

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

A

Disease resistance
homodimer formation
variation in functional activity

49
Q

What is an example of overdominance?

A

Sickle cell anemia + malaria

50
Q

Discuss the overdominance pattern of sickle cell

A

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

Genetics (9 decks)

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