Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

BIOL 239 > 2.1 (test 1) > Flashcards

2.1 (test 1) Flashcards

1
Q

What defines dominance and recessiveness in genetics?

A

A working definition depends on the F1 hybrids from a mating between two pure-breeding lines

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What indicates complete dominance in a hybrid?

A

If the hybrid resembles one of the two pure-breeding parents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is an example of complete dominance?

A

A mating between a pure-breeding white line and a pure-breeding blue line producing white F1 hybrids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What characterizes incomplete dominance?

A

The F1 hybrid resembles neither pure-breeding parent but exhibits an intermediate phenotype

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

In snapdragons, what is the result of a cross between pure-breeding red and white flowers?

A

Hybrids with pink blossoms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the phenotypic ratio of F2 progeny from self-pollinated pink snapdragons?

A

1 red : 2 pink : 1 white

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What biochemical explanation accounts for incomplete dominance in snapdragons?

A

The A gene specifies a protein required for red pigment production

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is codominance in genetics?

A

The F1 hybrid exhibits traits of both parents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is an example of codominance in lentils?

A

A cross between pure-breeding spotted and pure-breeding dotted lentils producing heterozygotes that are both spotted and dotted

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

In humans, which alleles exhibit codominance in blood types?

A

IA and IB alleles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the possible blood types resulting from the ABO blood group gene?

A

A, B, AB, and O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the significance of blood type O in transfusions?

A

Universal donors, as they carry no surface molecules that will stimulate an antibody attack

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How many alleles can a gene have?

A

More than two alleles can exist for many traits

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the dominance relationship among the ABO blood type alleles?

A

IA and IB are dominant to i, and IA is codominant with IB

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the conclusion about alleles based on ABO blood types?

A

An allele’s dominance or recessiveness is relative to a second allele

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How many possible genotypes exist for the ABO blood group gene?

A

Six possible genotypes: IAIA, IBIB, IAIB, IAi, IBi, or ii

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the dominance series in lentil seed coat patterns?

A

A hierarchy of dominance among five alleles: spotted, dotted, clear, marbled-1, marbled-2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How do mutations contribute to the existence of multiple alleles?

A

Chance alterations in genetic material that arise spontaneously in nature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the importance of allele frequencies in genetics?

A

They allow for the calculation of the number of copies of a gene in a population

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

True or False: Mendel’s law of segregation is affected by the dominance relationships of alleles.

A

False

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Fill in the blank: The F1 hybrids in codominance exhibit ______ traits of both parents.

A

characteristics

22
Q

What happens to the alleles during gamete formation according to Mendel’s law?

A

The two alleles of a gene separate

23
Q

What do the phenotypic and genotypic ratios coincide in the case of incomplete dominance?

A

1:2:1 ratio

24
Q

What is the concept of allele frequency?

A

The percentage of a specific allele among all allele copies in a population

It reflects how common an allele is in a given population.

25
Define wild-type alleles.
Alleles present in a population at a frequency greater than 1% ## Footnote They are often designated with a superscript plus sign (+).
26
What distinguishes a mutant allele from a wild-type allele?
A mutant allele is rare in the population, while a wild-type allele is common ## Footnote Definitions can change over time as allele frequencies shift.
27
What is an example of a gene with distinguishable mutant alleles?
The agouti gene in mice ## Footnote It has 14 identified mutant alleles affecting coat color.
28
What does it mean for a gene to be monomorphic?
A gene with only one common, wild-type allele present in the population ## Footnote Example: the agouti gene in mice.
29
What defines a polymorphic gene?
A gene that has more than one common allele ## Footnote Example: the ABO blood type system with alleles IA, IB, and i.
30
What is pleiotropy?
The phenomenon where one gene contributes to multiple traits ## Footnote It occurs when a single gene influences several distinct phenotypic characteristics.
31
Give an example of pleiotropy in humans.
Maori males with respiratory issues and sterility due to a recessive allele ## Footnote The allele affects cilia and flagella function.
32
What are recessive lethal alleles?
Alleles that cause death in homozygotes before they can reproduce ## Footnote They can alter expected Mendelian ratios in offspring.
33
How can recessive lethal alleles affect Mendelian ratios?
They can skew the expected 1:2:1 genotypic and 3:1 phenotypic ratios ## Footnote This occurs if homozygotes for the lethal allele do not survive.
34
What is the phenotypic ratio when yellow mice (heterozygotes) are mated?
2 yellow mice to 1 agouti ## Footnote This is due to the presence of a recessive lethal allele.
35
What is delayed lethality?
When homozygotes survive past birth but die later due to genetic defects ## Footnote Example: Tay-Sachs disease, which leads to death by age six.
36
What is sickle-cell disease caused by?
A faulty hemoglobin molecule ## Footnote It results from mutations in the β-globin gene.
37
What are the different dominance relations observed in sickle-cell disease?
Codominance at the molecular level, complete dominance at the cellular level, and varying dominance with environmental factors ## Footnote This complexity is seen in heterozygotes under different oxygen conditions.
38
What is the significance of the HbβS allele in sickle-cell disease?
It causes sickling of red blood cells and provides resistance to malaria ## Footnote Homozygous HbβS individuals often develop severe health issues.
39
What is the impact of recessive lethal alleles in human genetics?
They often remain hidden and can be passed through heterozygous carriers ## Footnote Homozygous individuals typically do not survive to reproduce.
40
What happens to homozygotes with late-onset lethal alleles?
They can reproduce before showing severe symptoms ## Footnote Example: Friedreich ataxia, which has symptoms that appear later in life.
41
What are the two alleles discussed in relation to red blood cell shape?
HbβA and HbβS ## Footnote These alleles are involved in the genetics of sickle cell disease and malaria resistance.
42
Under normal oxygen conditions, which allele is dominant in shaping red blood cells?
HbβA is dominant to HbβS ## Footnote The majority of a heterozygote's red blood cells have a normal biconcave shape.
43
What occurs in HbβA HbβS cells when oxygen levels drop?
Sickling occurs ## Footnote This is due to the codominance of HbβA and HbβS alleles.
44
What is the effect of altitude on heterozygous carriers of HbβA and HbβS?
They experienced sickling crises ## Footnote This was observed during World War II when soldiers were airlifted.
45
In terms of malaria resistance, which allele is dominant?
HbβS is dominant to HbβA ## Footnote Infected HbβA HbβS cells are resistant to malaria.
46
What happens to infected HbβA HbβS cells in relation to malaria?
They break down before the malarial organism reproduces ## Footnote This is similar to HbβS HbβS cells.
47
Which allele is recessive to which in terms of anemia or death?
HbβS is recessive to HbβA ## Footnote HbβA is associated with better general health outcomes.
48
What is essential to define when discussing dominance relationships?
The trait under analysis ## Footnote Dominance and recessiveness are specific to each pair of alleles.
49
What explains the widespread occurrence of the HbβS allele in certain populations?
Heterozygotes are better able to survive and pass on their genes ## Footnote This is particularly true in areas where malaria is endemic.
50
What happens to HbβS HbβS individuals?
They often die of sickle-cell disease ## Footnote This highlights the risks associated with homozygosity for this allele.
51
What happens to HbβA HbβA individuals in relation to malaria?
They often die of malaria ## Footnote This illustrates the selective pressures in malaria-endemic regions.
52
What is the advantage of heterozygotes in tropical environments where malaria is found?
They are relatively immune to both sickle-cell disease and malaria ## Footnote This allows high frequencies of both alleles to persist.

BIOL 239 (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions