Chapter 4a: Modification of Mendelian Ratios

Question 1

what are Mendel’s 4 postulates?

Answer 1

1. unit factors exist in pairs
2. dominance/ recessiveness
3. paired unit factors segregate
4. independent assortment

Question 2

2 things that describe a loss-of-function mutation

Answer 2

1. premature stop codon

2. misshapen active site

Question 3

2 things that describe a gain-of-function mutation

Answer 3

1. better enzymatic performance

2. gene duplications lead to gene family proliferation

Question 4

a neutral mutation is AKA

Answer 4

a synonymous mutation

Question 5

when no dominance exists between alleles that is known as

Answer 5

variation

Question 6

an intermediate phenotype is?

Answer 6

one that results from a cross between parents with contrasting traits

Question 7

give an example of an intermediate phenotype

Answer 7

R1R2 gives a pink color

Question 8

what type of dominance describes a trait where neither allele is dominant?

Answer 8

incomplete or partial dominance

Question 9

codominance describes

Answer 9

-influence of both alleles that is clearly evident

Question 10

what are the two forms of glycoproteins that exist

Answer 10

M and N

Question 11

mating between two heterozygous individuals can produce

Answer 11

children with all 3 blood types (A, B, AB)

Question 12

inadequate substrate for enzyme that causes h substance to be incompletely formed is due to a rare mutation in the _____ gene.

Answer 12

FUT1

Question 13

lethal genes represent…

Answer 13

essential genes

Question 14

essential genes are

Answer 14

• absolutely required for survival

- tolerated if heterozygous

Question 15

what type of mutations result in homozygous recessive individuals that do not survive?

Answer 15

recessive lethal alleles

Question 16

lethal alleles are inherited in a

Answer 16

recessive manner

Question 17

the presence of one copy of this type of allele results in death

Answer 17

dominant lethal allele

Question 18

Huntington’s disease is an example of a

Answer 18

dominant lethal allele

Question 19

combining modes of inheritance modifies the 9:3:3:1 ratio because of

Answer 19

product law

Question 20

epigenesis is defined as

Answer 20

a progression in the complexity of a phenotype as development increases

Question 21

complex phenotypes come from…

Answer 21

undifferentiated cells

Question 22

epistasis is when the…

Answer 22

expression of one gene masks/modifies effect of another gene pair

Question 23

in epistasis a gene masks the

Answer 23

phenotypic effects of another gene

Question 24

effects of epistasis can be inferred if

Answer 24

• inheritance is discontinuous
• genes are not linked
• complete dominance exists
• all P1 crosses involving homozygotes/ F1 are heterozygous
• F2 is focus of analysis

Question 25

complementation analyses allows one to determine if

Answer 25

two mutations with a similar phenotype are different alleles of the same locus

Question 26

two characteristics of complementation analysis

Answer 26

1. screens number of individual mutations resulting in the same phenotype
2. can predict the total number of genes determining a trait

Question 27

a complementation group shows..

Answer 27

all mutations present in any single gene

Question 28

complementation analyses is what type of genetic study?

Answer 28

a special form of test cross

Question 29

define pleiotropy…

Answer 29

the expression of a single gene that has multiple phenotypic effects

Question 30

give an example of pleiotropy

Answer 30

marfan syndrome

-affects eyes, aorta, bones, and other tissues that use fibrillin