Complex Genetics: Multi-Gene Interaction

Question 1

Expressivity

Answer 1

Differing levels of transcription/translation change the trait (severity of disease)

Question 2

Quantitative trait loci

Answer 2

number of copies of a gene in part determine phenotype

Question 3

pleiotropy

Answer 3

A single gene determining several distinct and unseemingly unrelated characteristics. One gene influences multiple phenotypes.
Example: Aboriginal men have respiratory problems and are sterile. This is due to the defects in ONE GENE, but it AFFECTED MULTIPLE PHENOTYPES

Question 4

Sickle Cell Facts

Answer 4

Those with the sickle cell carrier are less likely to get malaria but those who ACTUALLY have sickle cell have A LOW LOW CHANCE OF SURVIVAL

Question 5

List 4 reasons why phenotypic variation for some traits can occur

Answer 5

• differences in penetrance or expressivity
• effects of modifier genes
• effects of environment
• pure chance

Question 6

How does environment affect a phenotype?

Answer 6

Because certain alleles are temperature sensitive
Example:
Siamese cats get darker when it’s colder because their colorless precursor enzyme is functional. However, it can function and thrive in hotter temperature so the cat looks lighter

Question 7

Are these environmental phenotypes heritable?

Answer 7

No, phenotypes arising from an environmental agent mimic the effects of a mutant gene. And these can be harmful or beneficial to a person

Question 8

Does environment just have to be temperature?

Answer 8

NO. Other examples include if you have a genetic predisposition to lung cancer you’re strongly affected by cigarette smoking or if you have a strong predisposition to cardiovascular disease you can be influenced by diet and exercise

Question 9

Penetrance is the percentage of a population with…

Answer 9

a particular genotype that shows the expected phenotype

Can have complete or incomplete penetrance

Question 10

Expressivity is the degree or intensity…

Answer 10

with which a particular genotype is expressed in a phenotype
Can be variable or unvarying

Question 11

Variable penetrance

Answer 11

you either have it or ya don’t have the phenotype expression. yes or no

Question 12

Variable expressivity

Answer 12

everyone has some of the trait, it’s just expressed to different extents

Question 13

Variable penetrance and expressivity

Answer 13

some people won’t have the trait, some people it’ll be very severe and others very mild

Question 14

Incomplete penetrance

Answer 14

Some individuals do not express the phenotype even though they inherit the alleles

Question 15

Discontinuous traits

Answer 15

give clear cut, ‘either-or’ phenotypic differences between alternative alleles
Example: all of the traits Mendel studied in peas were discontinuous

Question 16

Continuous traits

Answer 16

determined by segregating alleles of many genes that interact together and with the environment
Example: height, color, weight are all continuous traits

Question 17

Continuous traits are also called

Answer 17

quantitative traits

Question 18

quantitative traits

Answer 18

traits that vary over a range of time that can be measured

Question 19

Polygenic

Answer 19

controlled by multiple genes

Question 20

When the same gene is related to respiratory problems and sterility, it can be described as…

Answer 20

Pleiotropy

Question 21

If a group of individuals all had the same alleles for a specific disease but only some of those people got the disease. That trait would be…

Answer 21

incomplete penetrance