Extensions to Mendel's Rules (Lec 6 & 7)

Question 1

What is it called when the phenotype of the heterozygote is the same as the phenotype of one of the homozygotes

Answer 1

dominance

Question 2

True or False?

Cystic Fibrosis is considered to be a recessive disease.

Answer 2

true

Question 3

In cystic Fibrosis mutated form of CFTR causes channels to remain closed and this ion remains within cells

Answer 3

Cl-

Question 4

In regards to Cystic Fibrosis, heterozygotes produce both normal and mutated CFTR at the cellular level, this can be considered what? At the phenotypic level it can be considered what?

Answer 4

co-dominance; normal

Question 5

What is it called when the phenotype of the heterozygote is intermediate between the phenotypes of the two homozygotes?

Answer 5

incomplete dominance

Question 6

What is it called when the phenotype of the heterozygote includes the phenotypes of both the homozygotes?

Answer 6

co-dominance

Question 7

What is penetrance?

Answer 7

percentage of individuals having a specific genotype that express the expected phenotype

Question 8

What is expressitivity?

Answer 8

the degree to which a character is expressed

Question 9

Type O blood carriers are called what? Type AB?

Answer 9

Type O - universal donor

Type AB - universal recipient

Question 10

The masking of one gene by another gene at a different locus is called what?

Answer 10

epistasis

Question 11

The epistatic gene is the gene that does what?

Answer 11

masks the other gene

Question 12

The hypostatic gene is the gene that does what?

Answer 12

gets masked

Question 13

What is dominant epistasis?

Answer 13

homozygous dominant or heterozygous genotypes mask the effects of the hypostatic gene

Question 14

What is recessive epistasis?

Answer 14

presence of either of two homozygous recessive genotypes will mask the hypostatic gene

Question 15

What does a 9:3:4 phenotypic ratio indicate?

Answer 15

recessive epistasis

Question 16

what does a 12:3:1 phenotypic ratio indicate?

Answer 16

dominant epistasis

Question 17

What does a 9:7 phenotypic ratio indicate

Answer 17

duplicative recessive epistasis

Question 18

What does a 15:1 phenotypic ratio indicate?

Answer 18

duplicative dominant epistasis

Question 19

When does complementation occur?

Answer 19

when an individual organism possessing two recessive mutations has a wild-type phenotype

Question 20

What are sex-infuenced characteristics determined by?

Answer 20

autosomal genes

Question 21

How much penetrance do sex-limited characteristics (also determined by autosomes) have in the opposite sex?

Answer 21

zero

Question 22

What are some characteristics of cytoplasmically inherited traits?

Answer 22

present in males and females, usually inherited from one parent (usually the maternal parent), reciprocal crosses give different results, exhibit extensive phenotypic variation

Question 23

What is the genetic maternal effect?

Answer 23

phenotype of the offspring is determined by the genotype of the mother

Question 24

Differential expression depending on whether it is inherited from the male or the female parent is called what?

Answer 24

genomic imprinting

note: due to DNA methylation differences in sperm and eggs

Question 25

What are characteristics of Prader-Willi Syndrome?

Answer 25

small hands and feet, short stature, poor sexual development, mental retardation, voracious appetites, mutation is always inherited from father

Question 26

What are characteristics of Angelman Syndrome?

Answer 26

exhibit frequent laughter, uncontrolled muscle movement, large mouth, unusual seizures, mutation is always inherited from mother

Question 27

The phenotype of a sex-linked characteristic is determined by what?

Answer 27

genes located on the sex chromosome

Question 28

What are discontinous characteristics?

Answer 28

characteristics with only a few easily distinguishable phenotypes

ex: tall pea plant vs short pea plant

Question 29

What are continuous characteristics?

Answer 29

characteristics characterized by a continuous distribution of phenotypes; often polygenic

ex: human height/weight

Question 30

Characteristics encoded by genes at multiple loci are called what?

Answer 30

polygenic characteristics

ex: kernel color in wheat

Question 31

Characteristics that are polygenic and also influenced by environmental factors are called what?

Answer 31

multifactorial characteristics

ex: human intelligence

Question 32

Define pleiotropy

Answer 32

one gene affects multiple characteristics

ex: lethal allele for yellow coat color in mice

Question 33

What is the phenomenon in which a genetic trait becomes more strongly expressed and/or is expressed at an earlier age in succeeding generations?

Answer 33

anticipation

ex: huntington’s disease, fragile-x syndrome