Chapter 4:

Question 1

Two postulates that are the possible of gene transmission

Answer 1

1. Genes are present on homologous chromosomes
2. Chromosomes segregate and assort independently

Question 2

Gene interaction

Answer 2

Single phenotype is affected by more than one set of genes

Question 3

X-Linkage

Answer 3

genes that are present in the X chromosome

Question 4

Alleles

Answer 4

alternative forms of a gene

Question 5

Mutation

Answer 5

Ultimate source of alleles
Note: new phenotype result from changes in functional activity if gene product
-Elimination enzyme function
-Changing relative enzyme efficiency
-Changing overall enzyme function

Question 6

Wild-type alleles

Answer 6

Occurs most frequently in nature and is usually (not always) dominant

Due to natural selection

Question 7

Loss of function Mutations

Answer 7

-New phenotype results from change in activity
-Mutation causes loss of wild-type function

Question 8

Gan-of function mutations

Answer 8

-Mutation enhances function of will type
-Quantity of gene product increases

Question 9

Neutral mutations

Answer 9

-No change to the phenotype
-No change to the evolutionary fitness of the organism

Question 10

DO MORE RESEARCH ON THIS: Adding or moving the amino acid is dangerous

Question 11

Dominant alleles are indicated by

Answer 11

-an italoc uppercase letter of uppercase case

Question 12

Recessive alleles are indicated by

Answer 12

an italic lowercase letter, or an italic letter or group of letters

Question 13

Mutant alleles are indicated by

Answer 13

an italic letter

Question 14

Wild type alleles are indicated by

Answer 14

italic letter plus superscript + (e^+)

Question 15

Incomplete or partial dominance

Answer 15

Intermediate phenotype
Niether alle is dominant

Question 16

Example of dominance in snapdragon

Answer 16

Red snapdragon is crossed with whote snapdragon

F1 offspring: pink flowers
F2 generation: 1/4 red, 1/2 pink, 1/4 white
-Phenotypic and genotypic ratios are the same
Each genotype has its own phenotype

Question 17

Incomplete dominance in humans example

Answer 17

Tay-Sachs disease

Question 18

Threshold Effect

Answer 18

Normal phenotypic expression results
Certain level (usually 50% or less) of gene product is attained
In Tay-Sach’s disease, less than a 50 percent threshold

Question 19

Codominance

Answer 19

-No dominance or recessiveness
-No incomplete or blending
-Joint expression of both alleles in a heterozygote

Question 20

Multiple alleles

Answer 20

-Three or more alleles of the same gene
-resulting mode of inheritance unique
-Can only be studied in populations

Question 21

Example of Multiple alleles

Answer 21

Human ABO blood groups
-example of muliple alleles
-A and B antigens present on surface of red blood cells
-Three alleles of a single gene responsible for ABO phenotypes

Question 22

A and B antigens

Answer 22

CArbohydrate groups bound to lipid groups on red blood cells

Question 23

H substance

Answer 23

-One or two terminal sugars are added
-O blood types (ii) only have the H substance protruding from the red blood cells

Question 24

Essential genes

Answer 24

Absolutely required for survival
-Mustations can be tolerated if heterozygous

Question 25

Why can mutations (if heterozygous) of essential genes be tolerated?

Answer 25

One type of allele is sufficient for survivial
Homozygous recessive will not survive

Question 26

Recessive lethal allele

Answer 26

Mutaion of essential genes behaves as a recessive lethal alleleq

Question 27

Lethal Allele

Answer 27

Has the potential to cause death of organism
-alleles are a result of mitations in essential genes
-inherited in a recessive manner
-

Question 28

Dominant lethal allele + provide an example

Answer 28

-Presence of one copy of allele results in death
Ex. Huntigton’s disease

Question 29

Huntigton’s disease

Answer 29

Dominant autosomal allele H
Onset of disease in heterozygous delayed until adulthood
Characterized by progressive degeneration o f nervous system, dementia, and early death

Question 30

Agouti gene in mice (coat color)

Answer 30

Agouti allele A
Mutant yellow allele A^y

Question 31

Mutant Allele (A^y)

Answer 31

Behvaes dominantly to normal allele to control coat color
Behaves as homozygous recessive lethal allele

Question 32

Pleiotropy

Answer 32

Expression of single gene has multiple phenotypic effects

Example Marfan syndrome
Porphyria Variegata

Question 33

Sex-limited inheritance

Answer 33

Expression of specific phenotype is limited to one sex

Question 34

Sex-influenced inheritance

Answer 34

Sex of individual influences expression of the phenotype

Not limited to one sex or the other

Question 35

Penetrance

Answer 35

Percentage of expression of the mutant genotype in a population

Question 36

Expressivity

Answer 36

-Range of expression of mutant phenotype
-REsult of genetic background differences or environmental effects

Question 37

Genetic background: Position effect

Answer 37

-The physical location of gene influences expression
-Translocation or inversion events modify the expression
-Gene relocated to condensed or genetically inert chromosome (called heterochromatin)

Question 38

Conditional Mutations

Answer 38

Ideal temperatures for animals

Example: Darker fur on cooler areas of body (tail, feet, ears)
enzymes loose catalytic function at higher temps

Question 39

Nutritional mutations in genetics

Answer 39

prevent ssynthesis of nutrient molecules in microbes
Phenotype may be expressed depending on diet

Example Phenylketonuria: loss of an enzyme to metabolize amino acid called phenylalanine, severe issues unless low Phe diet