Chapter 4 Gen

Question 1

Wild-type alleles

Answer 1

Prevalent alleles in a population

Question 2

Polymorphism

Answer 2

More than one wild-type allele may occur in large populations, a phenomenon

Question 3

Mutant alleles

Answer 3

Alleles that have been altered by a mutation

Question 4

Incomplete Dominance

Answer 4

heterozygote exhibits a phenotype that is intermediate between the corresponding homozygotes

Question 5

Codominance

Answer 5

both alleles are expressed in a heterozygous individual

Question 6

Incomplete Dominance Example

Answer 6

If a red and white flower mix and makes a pink flower

Question 7

Codominance example

Answer 7

In an AB blood type both the antigens for A and B are expressed

Question 8

Incomplete Dominance for Mendel round peas

Answer 8

On a surface level the Round Peas showed the traits for the dominant allele, either homozygote or heterozygote
BUT
In a closer look, we could see that the heterozygotes were actually less starchy than the homozygotes making it incomplete

Question 9

Over-Dominance

Answer 9

-phenomenon where a heterozygote has greater reproductive success compared to both of the corresponding homozygotes (heterozygote advantage)

Question 10

over-dominance in respect to sickle cell

Answer 10

HbAHbS individuals (heterozygotes) have an “advantage”:
* over HbSHbS, because they do not suffer from sickle cell
disease
* over HbAHbA, because they are more resistant to malaria

Question 11

Describe various mechanisms that might make a heterozygote more fit than
either homozygote. Given an example be able to identify over-dominance.

Question 12

A blood Type

Answer 12

Antigen: A
Antibody:B

Question 13

B blood type

Answer 13

Antigen: b
Antibody: A

Question 14

AB Blood Type

Answer 14

Antigen: A and B
Antibody: Neither A nor B

Question 15

O Blood Type

Answer 15

Antigen: Neither A nor B
Antibody: Both A and B

Question 16

What is the molecular basis for the production of the A and B antigens, and
what happens if an individual possesses only the i allele.

Question 17

Given a case of disputed paternity, ascertain if a particular blood group for
the parents is theoretically possible.

Question 18

What is a complete H antigen? What happens to a person who has the
Bombay blood group (hh, homozygous recessive)? Which of the three
antigens does he normally produce A, B, H? Which of the antibodies does he
naturally produce Anti-A, Anti-B, anti-H? When tested using standard tests
that usually test for A and B antigens only but not the H antigen, individuals
with Bombay blood group (hh) show up as O blood group. Therefore, if they
receive transfusion from an O individual explain why it would be dangerous.

Question 19

Lethal allele

Answer 19

allele that may lead to the death of an organism

Question 20

essential gene

Question 21

recessive lethal allele

Question 22

dominant lethal allele

Question 23

Why do recessive lethal alleles such as in the case of Manx cats, give a ratio of
2:1 (phenotype: normal) for a second trait (eg defective spine and tail) that
the allele may be associated when heterozygotes are crossed to one another?
(the first trait is lethality). For this second trait the allele behaves in a
dominant manner

Answer 23

Dominant homozygotes die an embryonic death so they are left out of the ratio of offspring.

Question 24

conditional lethal alleles

Answer 24

lethal allele that may be the death of an organism if all the conditions are met

Question 25

example of conditional lethal allele

Answer 25

G6PD deficiency results from a deficiency of an enzyme that is especially important for protecting red blood cells from harmful oxidizing agents. People with G6PD deficiency can live healthy lives but can die from severe destruction of red blood cells after eating fava beans. Fava beans have multiple oxidizing agents that can endanger the red blood cells in these patients.

Question 26

semi-lethal alleles

Answer 26

lethal allele that does not kill every single organism that has this allele

Question 27

Be able to explain the dominant lethal nature of the Huntington allele (Look
at the dominant allele in heterozygote and does it lead to death due to the
neurodegenerative disease). In this case of heterozygote, the individual is
able to be born and enter adulthood, however thereafter he or she begins to
develop neurodegeneration that is 100% fatal by 65 years and therefore it is
categorized as a lethal allele). What is the nature of the mutation carried in
the disease allele and what is the consequence on the Huntingtin protein?
Be able to explain how this lethal mutation continues to be maintained in the
human population

Question 28

pleitropy

Answer 28

expression of one gene at different stages of development

expression of one gene that affects cell function in more than one way

expression of one gene in different cell types

Question 29

gene interaction

Answer 29

pattern where allelic variants of two different genes affect a single trait

Question 30

complementation

Question 31

epistasis

Question 32

epistasis example

Answer 32

For summer squash, the dominant allele for one gene leads to yellow color while the recessive allele for this gene leads to green color. When the genotype of a second gene is either homozygous dominant or heterozygous, neither color is produced and the squash is white.

Question 33

gene modifier effect

Question 34

gene redundancy

Question 35

Which ratio is modified due to gene interaction between the alleles of two
genes lying on two non-homologous chromosomes?

Question 36

Do epistasis and other observations of gene interactions results suggest the
violation of Mendel’s laws of segregation and independent assortment?
Justify your answer

Question 37

sex-limited inheritance

Answer 37

occurs in only one of the two sexes

Question 38

sex-influenced inheritance

Answer 38

-autosomal
-Traits where an allele is dominant in one sex but recessive in
the opposite sex
* Sex influence is a phenomenon of heterozygotes

Question 39

sex-influenced inheritance example

Answer 39

Scurs (hornlike growth) in cattle
* Caused by an autosomal gene
* Allele Sc is dominant in males, but recessive in females

Question 40

scur example

Answer 40

The growth of scurs, small horn-like growths on the faces of cattle, is inherited with the sex-influenced alleles Sc and sc. The trait is dominant in males and recessive in females. Suppose a male with no scurs is mated to a female with scurs. What is the pattern expected for their offspring?

Question 41

sex-linked inheritance

Answer 41

found on one of the two types of
sex chromosomes, but not both