Unit 2: Beyond Mendelian Genetics

Question 1

Lethal Allele Combinations

A genotype (allele combination) that causes death is, by strict definition _____.

Death from genetic disease can occur at any stage of development or life.

Answer 1

Lethal

Question 2

Lethal Allele Combinations

Tay-Sachs disease is lethal by age ____ or ___

Answer 2

3 or 4

Question 3

Lethal Allele Combinations

Huntington
disease may not be lethal until ________.

Answer 3

late middle age

Question 4

Lethal Allele Combinations

In a population and evolutionary sense, a lethal genotype has a more specific meaning—it causes death before the individual can reproduce, which prevents passage
of mutations to the next generation

BASAHIN LANG

Question 5

An example of a lethal genotype in humans is ______________ dwarfism, which has
the distinct phenotype of a long trunk, short limbs, and a large head bearing a flatvface. It is an autosomal dominant trait, but is most often the result of a spontaneousv(new) mutation.

Answer 5

achondroplastic dwarfism

Question 6

Different Dominance Relationships

■ type of relationship between alleles, with a
heterozygote phenotype intermediate
between the two homozygote phenotypes

Answer 6

Incomplete Dominance

When F1 generation (all pink flowers) is self
pollinated, the F2 generation is 1:2:1
red, pink, white

Question 7

___________ in which a threshold level is necessary for health illustrate both complete and incomplete dominance.

Answer 7

Enzyme deficiencies

Question 8

_________ (FH) is an example of incomplete dominance that can be observed in carriers on both the molecular and whole-body levels

Answer 8

Familial hypercholesterolemia

Question 9

A person with two disease-causing alleles does not have receptors on liver cells that take up the ___________ (LDL) form of cholesterol from the bloodstream, so it builds up.

Ex. The phenotypes parallel the number of receptors—individuals with two mutant alleles die
in childhood of heart attacks

Answer 9

low-density lipoprotein

Question 10

A person with one disease-causing allele has half the ______ number of receptors.

those with one mutant allele may suffer heart attacks in
young adulthood,

Answer 10

normal

Question 11

Someone with two wild type alleles has the ______ number of receptors

those with two wild type alleles do not develop this inherited form of
heart disease.

Answer 11

normal

Question 12

Different alleles that are both expressed in a heterozygote are codominant.

The ABO blood group system is based on the
expression of codominant alleles.

Answer 12

Co-dominance

Question 13

Codominant traits

Genotype: AA and AO
Phenotype: ______

Answer 13

A

Question 14

Codominant traits

Genotype: BB and BO
Phenotype: ______

Answer 14

B

Question 15

Codominant traits

Genotype: AB
Phenotype: ______

Answer 15

AB

Question 16

Codominant traits

Genotype: OO
Phenotype: ______

Answer 16

O

Question 17

Blood type: A
Antigen: A
Genotype:_________

Answer 17

A / A / Ai

Question 18

Blood type: AB
Antigen: AB
Genotype:_________

Answer 18

B / B / Bi

Question 19

Blood type: AB (rare)
Antigen: A and B
Genotype:_________

Answer 19

A / B

Question 20

Blood type: O
Antigen: neither
Genotype:_________

Answer 20

ii

Question 21

Mendel’s laws can appear not to operate when one gene masks or otherwise affects the phenotype of another

It refers to interaction between different genes, not
between the alleles of the same gene.

Answer 21

Epistasis

Question 22

Epistasis

A gene that affects
expression of another is called a ________.

Answer 22

modifier gene

Question 23

A familiar epistatic interaction is
____, in which one gene blocks the action of genes that confer color.
______ is seen in many species.

In epistasis, the blocked gene is expressed (transcribed into RNA normally, but the protein product of the modifier gene inactivates it removes a structure needed for it to contribute to the phenotype, or otherwise counteracts its effects.

Answer 23

albinism

Question 24

A blood type called the __________ phenotype also illustrates epistasis.

It results from an interaction between a gene called H and the I gene tha confers ABO blood type. The H gene controls the placement of a molecul to which antigens A and B attach on red blood cell surfaces.

Answer 24

Bombay

Question 25

WHen was Bombay first discovered? | It is present in 0.004% population ## Footnote Can receive blood only from Bombay blood group people

Answer 25

1952

Question 26

Bombay was named by whom?

Answer 26

Dr. Bhande and others

Question 27

# Pleiotropy A single-gene disease with many symptoms, or a gene that controls several functions or has more than one effect, is termed __________. ## Footnote Such conditions can be difficult to trace through families because people with different subsets of symptoms may appear to have different diseases.

Answer 27

pleiotropic

Question 28

# Pleiotropy The most common form of this autosomal dominant condition is a defect in an elastic connective tissue protein called **fibrillin.** ## Footnote The protein is abundant in the lens of the eye, in the aorta (the largest artery in the body, leading from the heart), and in bones of the limbs, fingers, and ribs. The symptoms are lens dislocation, long limbs, spindly fingers, and a caved-in chest. The most serious symptom is a weakening in the aorta, which can suddenly burst. If the weakening is detected early, a synthetic graft can replace the section of artery wall and save the person’s life.

Answer 28

Marfan syndrome

Question 29

Mutations in different genes that produce the same phenotype lie behind ___________ ## Footnote It can occur when genes encode enzymes or other proteins that are part of the same biochemical pathway, or when proteins affect the same body part

Answer 29

genetic heterogeneity

Question 30

# genetic heterogeneity Consider ____________, in which abnormal collagen causes fragile bones. ## Footnote Before a second causative gene was discovered, some parents of children who were brought to the hospital with frequent fractures and who did not have a mutation in the one known gene were accused of child abuse. Today eight genetically distinct forms of the disease are recognized.

Answer 30

osteogenesis imperfecta

Question 31

# Phenocopies An environmentally caused trait that appears to be inherited is a _________. ## Footnote Such a trait can either produce symptoms that resemble those of a known single-gene disease or mimic inheritance patterns by affecting certain relatives. For example, the *limb birth defect caused by the drug thalidomide* ***is a phenocopy of the rare inherited illness phocomelia. ***

Answer 31

phenocopy ## Footnote Physicians recognized the environmental disaster when they began seeing many children born with what looked like phocomelia. A birth defect **caused by exposure to a widely used teratogen** was more likely than a sudden increase in incidence of a rare inherited disease.

Question 32

Regulate organ development a. Homeotic b. Homeobox c. Hox Genes

Answer 32

a

Question 33

Code for transcription factors a. Homeotic b. Homeobox c. Hox Genes

Answer 33

b

Question 34

Determine the identifies of each body segement. a. Homeotic b. Homeobox c. Hox Genes

Answer 34

c

Question 35

# Homeobox genes in humans: Vitamin __ can affect homeobox genes

Answer 35

Vitamin A

Question 36

# Homeobox genes in humans: Drug ________ affected 1 or more homeobox genes

Answer 36

Thalidomide

Question 37

# Homebox genes in humans The most dramatic examples of homology are in the ***______*** genes, as well.

Answer 37

***Hox genes***

Question 38

Drug that was meanr as a sleeping aid but prescribed to pregnant women to treat anxiety and nausea ## Footnote - Caused serious birth abnormalities for hundreds of children - This sdrug led to stricter tests to determine a drug''s impact on a fetus

Answer 38

Thalidomide

Question 39

# On Phenotypic Expression - Penetrance and Expressivity refers to the *percentage of individuals* ***who have a particular genotype*** who have the associated phenotype. ## Footnote An allele combination that produces a phenotype in everyone who inherits it is completely penetrant. Huntington disease is nearly completely penetrant. Almost all people who inherit the mutant allele will develop symptoms if they live long enough. Complete ______ is rare.

Answer 39

Penetrance

Question 40

# On Phenotypic Expression - Penetrance and Expressivity refers to variability in *severity of a phenotype*, or the ***extent to which the gene is expressed.*

Answer 40

Expressivity

Question 41

This refers to the inheritance of a trait *governed by more than one genes. *Generally, ***three or more genes*** govern the inheritance of _________ traits. Multipl independent genes have an additive or similar effect on a single quantitative trait. ## Footnote Ex. Human Height, Weight, Skin color

Answer 41

Polygenic traits

Question 42

This is another example of polygenic disorder with multiple genes located on different chromosomes contributing to it susceptibility. Analysis of the genetic factors is further complicated by the fact that numerous environmental factors interact with genes to produce the disorder.

Answer 42

Type 2 diabetes