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BIO207 > Extensions to Mendel's Laws > Flashcards

Extensions to Mendel's Laws Flashcards

1
Q

What is complete dominance?

A

The hybrid resembles one of the two parents

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2
Q

What is incomplete dominance?

A

Hybrid is intermediate phenotype of both parents

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3
Q

What is codominance?

A

Hybrid shows traits from both parents.

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4
Q

What are the genotypic and phenotypic ratios of F2 progeny from F1 parents with incomplete dominance?

A

1:2:1

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5
Q

What traits do F1 hybrids have in codominance?

A

Display traits of both parents

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6
Q

What are the F2 progeny ratios in codominance?

A

1:2:1 for both phenotype and genotype

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7
Q

What three alleles determine ABO blood types in humans?

A

I^A = A type sugar
I^B = B type sugar
i = no sugar

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8
Q

When are successful blood transfusion made and why?

A

Only with matching blood types because antibodies are made against type A and type B sugars.

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9
Q

Who are universal blood recipients?

A

Type AB

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10
Q

Who are universal blood donors?

A

Type O

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11
Q

What is an extreme example of multiple alleles?

A

Histocompatibility antigens

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12
Q

What are histocompatibility antigens?

A

Cells surface molecules on all cells except for RBCs and sperm that facilitate proper immune response to foreign antigens.

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13
Q

Why does everyone have a distinct histocompatibility phenotype?

A

Three major genes encode the antigens, each gene has 400-1200 codominant alleles

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14
Q

What are mutations?

A

Chance alterations of genetic material that arise spontaneously

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15
Q

When can mutations be transmitted to offspring?

A

If the occur in gamete-producing cells

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16
Q

What is the frequency of gametes with mutations?

A

10^-4 to 10^-6

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17
Q

How can mutations be used to follow gene transmission?

A

Mutations that result in phenotypic variants

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18
Q

What is allele frequency?

A

Percentage of the total number of gene copies for one allele in a population

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19
Q

What is the wild-type (+) allele

A

The most common allele in a population

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20
Q

What is a mutant allele?

A

An allele that is rare in a population

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21
Q

What does it mean for a gene to be monomorphic?

A

Gene has only one common wild-type allele

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22
Q

What does it mean for a gene to be polymorphic?

A

Gene has more than one common allele

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23
Q

What are common variants?

A

High-frequency alleles of polymorphic genes

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24
Q

What is pleiotropy?

A

The phenomenon of a single gene determining several distinct and seemingly unrelated characteristics

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25
Q

Give an example of pleiotropy

A

Many aboriginal Maori men have respiratory problems and are sterile.
Defects due to mutations in a gene required for function of cilia and flagella

26
Q

What does a 2:1 F1 ratio indicate?

A

A recessive lethal allele; synthetic lethality

27
Q

What is epistasis?

A

An allele at one gene masks the effects of another gene

28
Q

What is an epistatic gene? Hypostatic?

A

Epistatic = gene that does the masking
Hypostatic = gene that is masked

29
Q

Describe the two genes that determine coat colour in labs.

A

B alleles determine black and brown colour.
ee of gene E is epistatic to B and determines yellow

30
Q

What is an additive gene interaction?

A

Four distinct F2 phenotypes

31
Q

What is the biochemical explanation for coat colour in labs?

A

Protein E helps generate eumelanin, protein B deposits it.
B- deposits eumelanin densely (black)
bb deposits eumelanin less densely (brown)
ee animals cannot make eumelanin (yellow)

32
Q

How does recessive epistasis lead to a rare blood type in humans?

A

Individual appears to have type O blood but can pass A or B to their children.
Gene for substance H is epistatic to the ABO gene.
Without H substance, there is nothing for A or B sugar to attach to.
All type A, AB, B, O people are H-
People with hh will appear to be type O

33
Q

What are redundant genes?

A

Genes where only one dominant allele needs to be preset

34
Q

What is the ratio of redundant genes?

A

15;1

35
Q

What is the F2 phenotypic ratio for additive gene interactions?

A

9:3:3:1

36
Q

What is the F2 phenotypic ratio of recessive epistasis?

A

9:3:4

37
Q

What is the F2 phenotypic ratio of reciprocal recessive epistasis?

A

9 to 7

38
Q

What is reciprocal recessive epistasis?

A

When homozygous, recessive allele of each gene masks the dominant allele of the other gene.

39
Q

What is dominant epistasis I?

A

Dominant allele of one gene hinders effects of both alleles of the other gene

40
Q

What is the ratio of dominant epistasis I?

A

12 to 3 to 1

41
Q

What is dominant epistasis II?

A

Dominant allele of one gene hides effects of dominant allele of other gene

42
Q

What is the F2 phenotypic ratio of dominant epistasis II?

A

13 to 3

43
Q

What are heterogeneous traits?

A

Traits with the same phenotype but caused by different mutations in different genes.

44
Q

What is an example of a heterogeneous trait in humans?

A

Deafness

45
Q

What is complementation testing?

A

Used to determine if a particular phenotype arises from mutations in the same or separate genes.

46
Q

What phenotypes can complementation testing be applied to?

A

Recessive

47
Q

What can cause phenotypic variation (3)?

A

Effects of modifier genes
Effects of environment
Pure chance

48
Q

What is pentrance?

A

The % of individuals with a particular genotype that show the expected phenotype

49
Q

What is expressivity?

A

The degree or intensity with which a particular genotype is expressed in a phenotype.

50
Q

What are modifier genes?

A

Genes that alter the phenotypes produced by alleles of other genes,

51
Q

Describe an example of modifier genes.

A

T locus of mice
Mutant T allele causes abnormally short tail
Tails can be 75% of normal length or 10%
Different inbred strains carry alternative alleles of a gene that modifies T phenotype.

52
Q

How does temperature affect coat colour in siamese cats?

A

Extremities are darker than body because of a temperature sensitive allele.

53
Q

How does temperature affect survivability of a Drosophila mutant?

A

Shibire mutants develop normally at <29C but are inviable at temperatures higher than that.

54
Q

What are conditional lethal mutations?

A

Mutations that are lethal only under some conditions.

55
Q

What is phenocopy?

A

Phenotype arising from an environmental agent that mimics the effect of a mutant gene.

56
Q

Is phenocopy heritable?

A

No

57
Q

Give examples of phenocopy in humans.

A

Thalidomide ingestion by pregnant women produced a phenocopy of phocomelia, a rare dominant trait.
Children with heritable PKU can receive a protective diet.
Genetic predisposition to cardiovascular disease can be influenced by diet and exercise.
Genetic predisposition to lung cancer is strongly affected by cigarette smoking.

58
Q

What are discontinuous traits?

A

Traits with either-or phenotypic differences between alternative alleles

59
Q

How are discontinuous traits determined?

A

By segregating alleles of many genes that interact together and with the environment

60
Q

What is a common feature of continuous traits? WHat does it mean?

A

Usually polygenic - controlled by multiple genes

61
Q

What is another term for continuous traits?

A

Quantitative traits.

62
Q

What are examples of continuous traits in humans?

A

Height and skin colour

BIO207 (9 decks)

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