lecture 8

Question 1

what are the two postulates for the basic principle of gene expression?

Answer 1

genes are present on homologous chromosomes, and chromosomes segregate and assort independently

Question 2

is dominance and recessiveness always the rule?

Answer 2

no

Question 3

what are mutations?

Answer 3

the ultimate source of alleles

Question 4

how do new phenotypes arise?

Answer 4

the result of changes in functional activity of gene product

Question 5

examples of how mutations arise

Answer 5

eliminating enzyme function, changing relative enzyme efficiency, changing overall enzyme function

Question 6

loss-of-function mutation

Answer 6

causes loss of WT function

Question 7

gain-of-function mutations

Answer 7

mutation enhances function of WT and increases the quantity of gene product

Question 8

neutral mutations

Answer 8

no change to the phenotype of tho the evolutionary fitness of the organism

Question 9

what does a loss of function mutation cause?

Answer 9

the gene being partilally or fully inactivated

Question 10

what is complete loss of function result in in a loss of function mutation?

Answer 10

a null allele

Question 11

are loss of function mutations usually dominant or recessive?

Answer 11

recessive

Question 12

what are gain of function mutations often called?

Answer 12

activating mutations

Question 13

what are loss of function mutations often called?

Answer 13

inactivating mutations

Question 14

what do gain of function mutations usually do?

Answer 14

enhances activation of the gene or its products

Question 15

are gain of function mutations usually dominant or recessive?

Answer 15

dominant

Question 16

what are dominate-negative mutations?

Answer 16

the mutant allele acts antagonistically to the WT allele

Question 17

what are dominant negative mutations also called?

Answer 17

antimorphic mutations

Question 18

what are dominant negative mutations often implicated in?

Answer 18

cancer

Question 19

neutral mutations

Answer 19

have no selective benefit or negative effect

Question 20

what is an example of a neutral mutation?

Answer 20

a silent mutation (they can’t be seen)

Question 21

what are the new gene notation rules?

Answer 21

there is no dominance/ recessive interaction, superscripts are used on an italic uppercase letter

Question 22

incomplete or partial dominance

Answer 22

results in an intermediate phenotype

Question 23

incomplete dominance example:

Answer 23

a red and a white snapdragon will produce pink offspring

Question 24

tay sachs disease

Answer 24

human biochemical disorder from incomplete dominance: homozygous recessive results in death, heterozygous results in 1/2 enzyme activity as compared to WT homozygous individuals

Question 25

codominance

Answer 25

two alleles of a single gene are both expressed in heterozygotes

Question 26

example of codominance:

Answer 26

a pure red and pure white cow produce a roan cow which is red with white spots

Question 27

codominance in humans

Answer 27

MN blood groups in humans; characterized by antigen glycoprotein which is found on the surface of red blood cells.

Question 28

codominant inheritance

Answer 28

distinct expression of gene products of both alleles

Question 29

multiple allele

Answer 29

three or more alleles of the same genes which result in a mode of unique inheritance

Question 30

example of multiple inheritance in humans

Answer 30

ABO blood groups

Question 31

does the i allele produce antigen?

Answer 31

no

Question 32

essential genes

Answer 32

genes that are absolutely required for survival, but mutations can be tolerated if heterozygous

Question 33

what would happen if someone was homozygous recessive for an essential gene?

Answer 33

they would not survive

Question 34

what makes a gene considered essential?

Answer 34

when the los of its function compromises the viability or fitness of the organism

Question 35

lethal alleles

Answer 35

are of essential genes

Question 36

recessive lethal alleles

Answer 36

result in homozygous recessive individuals and do not survive

Question 37

dominant lethal alleles

Answer 37

presence of one copy of allele results in death

Question 38

huntingtons disease

Answer 38

dominant autosomal allele, onset of disease in heterozygotes are delayed until adulthood. characterized by the degeneration of nervous system, demetica, and early death

Question 39

homozygous lethal alleles

Answer 39

some may result in a distinctive mutant phenotype

Question 40

lethal alleles in mice

Answer 40

mutant alleles behave dominantly to normal alleles to control coat color, behaves as homozygous recessive lethal allele