Exam 2 Winter 2025 > 4) Inheritance Patterns > Flashcards

4) Inheritance Patterns Flashcards

(84 cards)

Study These Flashcards
1
Q

What is Mendelian inheritance?

A

The pattern of traits being controlled by single genes with dominant/recessive alleles
Follows Mendel’s laws of segregation and independent assortment

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

What is the law of segregation?

A

Each individual has two alleles for a gene
These separate during gamete formation so each gamete gets one allele

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

What is the law of independent assortment?

A

Alleles of different genes are inherited independently of one another during gamete formation
Applies when genes are on different chromosomes or far apart on the same one

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

What is the F1 and F2 generation?

A

F1: first filial generation, offspring produced by crossing two true-breeding individuals
F2: the offspring produced by crossing two F1 individuals

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

Define dominant.

A

An allele that is expressed in the phenotype when only one copy is present
Masks the effect of a recessive allele in a heterozygote

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

Define recessive.

A

An allele that is only expressed in the phenotype when two copies are present
Its effect is masked by a dominant allele in a heterozygote

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

Define heterozygous.

A

Having two different alleles for a gene

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

Define homozygous.

A

Having two identical alleles for a gene

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

Define gene linkage.

A

When two or more genes are located close together on the same chromosome, they tend to be inherited together rather than assorting independently

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

Define unlinked genes.

A

Genes that are on different chromosomes or far apart on the same chromosome and therefore assort independently during gamete formation

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

How would you denote two linked genes?

A

AB/ab

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

How would you denote two unlinked genes?

A

With a semicolon:
A/a; B/b

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

How would you denote genes of unknown linkage?

A

With a dot:
A/a · B/b

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

What are the four distinct eukaryotic inheritance patterns?

A

Autosomal dominant
Autosomal recessive
X-linked dominant
X-linked recessive

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

Define autosomal dominant.

A

A pattern of inheritance where only one copy of a mutated allele on a non-sex chromosome (autosome) is enough to show the trait
It appears in every generation
Males and females are affected equally

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

Give an example of an autosomal dominant condition.

A

Huntingdon’s disease
Neurofibromatosis

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

Define autosomal recessive.

A

A pattern of inheritance where two copies of a mutated allele on an autosome are needed to show the trait
Often skips generations
Males and females affected equally

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

Give an example of an autosomal recessive condition.

A

Sickle cell anaemia
Wilson’s disease
Spinal muscular atrophy

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

Define X-linked dominance.

A

A pattern of inheritance where one copy of a mutated allele on the X-chromosome is enough to express the trait
Affected fathers pass it to all daughters and no sons
Females are often more frequently affected than males

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

Give an example of an X-linked dominant condition.

A

Fragile X syndrome
X-linked hypophosphotaemia

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

Define X-linked recessive.

A

A pattern of inheritance where a mutated allele on the X-chromosome causes the trait to be expressed
Males need only one copy to be affected
Females need two copies
Therefore these conditions are usually more common in males
Affected fathers cannot pass it to sons, but all daughters will become carriers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Give an example of an X-linked recessive condition.

A

Duchenne muscular dystrophy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What type of trait is tabby coat colour in cats?

A

Autosomal
Controlled by the Tabby locus
Formed in utero via melanin bands

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What are the three patterns of tabby coat colour in cats?

A

Mackerel (TaM, dominant, leads to more dark, thinner bands via Dkk4 regulation)
Blotched (Tab, recessive)
Spotted

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What is X-linked inactivation?
A process in females where one X chromosome is silenced in each cell A random choice Leads to mosaic expression of X-linked genes Ensures gene dosage balance with males
26
What is the XXY karyotype?
Klinefelter syndrome Males with an extra X chromosome Can cause reduced fertility, tall stature, and some learning or hormonal differences
27
What are chimeras?
Organisms composed of cells from two different zygotes Can have mixed genotypes in different tissues Rare in humans but more common in animals that carry large litters
28
How are male individuals represented in human pedigrees?
Square
29
How are female individuals represented in human pedigrees?
Circle
30
How are non-binary/gender diverse individuals represented in human pedigrees?
Star/diagonal square
31
How do you indicate that an organism is a carrier in a human pedigree?
A vertical strikethrough
32
What is Huntingdon's disease?
An autosomal dominant neurodegenerative condition Leads to formation of plaques in the brain Results in early dementia and death Onset of symptoms is late so sufferers often have children before developing symptoms
33
What is Sickle cell anaemia?
An autosomal recessive disorder causing malformations of red blood cells Means they're prone to sticking in capillaries Causes anaemia
34
Why does sickle cell trait protect against malaria?
Plasmodium falciparum (the malaria parasite) infects RBCs Sickling kills RBCs faster So the parasite has less time to multiply
35
How do heterozygous and homozygous Sickle cell anaemia symptoms differ?
Homozygous (sickle cell disease): anaemia, pain crises, organ damage, fatigue, risk of infections Heterozygous (sickle cell trait): milder/no symptoms, may experience problems in extreme conditions (low oxygen, dehydration), often protected against severe malaria
36
What is a Barr body?
The inactivated X chromosome in female cells Appears as a dense, dark-staining spot in the nucleus
37
What is fragile X syndrome?
An X-linked dominant genetic disorder Caused by CGG repeat expansion in the FMR1 gene on the X-chromosome Leads to intellectual disability, learning difficulties, sometimes characteristic physical features (long face, large ears) Males usually more severely affected than females
38
What is complete dominance?
Where one allele fully masks the effect of the other in a heterozygote The heterozygous phenotype is identical to the homozygous dominant phenotype
39
What is haplosufficiency?
When one functional copy of a gene is enough to produce a normal phenotype Loss of the second copy does not cause disease
40
What is haploinsufficiency?
When one functional copy of a gene is not enough to produce a normal phenotype Loss of one allele causes a disease or abnormal trait
41
What does dominant negative mean?
A mutant allele produces a protein that interferes with the normal protein from the other allele Even in a heterozygote, the mutant protein will disrupt function, causing a disease phenotype In a heterozygote, roughly 3/4 of dimers will be non-functional because of this
42
What is a lethal allele?
A gene variant that causes death when present in homozygous or sometimes heterozygous individuals Affects genotype ratio in offspring 2:1 instead of 1:2:1 Lethality can sometimes vary depending on environment (conditional mutations)
43
What is an allelic series?
A set of different alleles at a single locus that produces a range of phenotypes Shows varying dominance relationships
44
What is epistasis?
When the expression of one gene is masked by the expression of another gene E.g. masking gene B is said to be epistatic to A, and A is hypostatic to B
45
What is recessive epistasis?
When the homozygous recessive genotype of one gene masks the expression of another E.g. coat colour in Labradors - two recessive alleles at the E locus prevent deposition of pigment, masking the B locus (black/brown colour)
46
What is dominant epistasis?
Occurs when a single dominant allele of one gene masks the expression of another gene E.g. fruit colour in squash, a dominant allele at the W locus prevents pigment formation, masking the second locus
47
What is duplicate gene action?
When two different genes produce the same effect A dominant allele at either gene gives the same phenotype Only the double homozygous recessive genotype would show a different phenotype A form of genetic redundancy Also known as duplicative dominant epistasis
48
What is complementary gene action?
When two different genes must both have at least one dominant allele to produce a particular phenotype If either gene is homozygous recessive, the phenotype is not expressed Also known as duplicative recessive epistasis
49
What is the complementation test?
A genetic test to determine if two mutations causing the same phenotype are in the same gene or in different genes Cross the two mutants Normal offspring means the mutations are in different genes (complement each other) Mutant offspring means the mutations are on the same gene (no complementation)
50
What is codominance?
When a heterozygote expresses both alleles fully and equally Neither allele masks the other E.g. AB blood group
51
List the allelic interactions.
Complete and incomplete dominance Codominance Haplosufficiency/insufficiency Dominant negative Lethality
52
List the non-allelic interactions.
Recessive epistasis Dominant epistasis Duplicate gene action Complementary gene action Modifiers Suppressors
53
Which two loci determine human blood type?
ABO (encodes A/B enzymes) H (produces H antigen)
54
What are the alleles at the ABO locus?
A B O (recessive)
55
What are the alleles at the H locus?
H (functional) h (non-functional)
56
Explain complete dominance, codominance, and incomplete dominance in blood groups.
Complete dominance = A/B is dominant over O Codominance = AB expresses both A and B antigens equally Incomplete dominance = heterozygote shows intermediate phenotype
57
How are RBC antigens produced?
The H enzyme produces the O antigen ABO enzymes produce A/B antigens (requiring functional H)
58
What is the Bombay blood group?
A rare variant (hh genotype) No functional H antigen is produced No A/B/O antigens are expressed
59
Why can a child of apparent O parents be A/B if one parent is Bombay phenotype?
The parent carries unexpressed A or B alleles which are not visible due to the hh genotype
60
What is genetic determinism?
An incorrect view that genes alone are the sole determinant of a characteristic
61
How is the colourpoint locus in cats influenced by the environment?
Colourpoint locus encodes enzyme for coat pigmentation Specific alleles produce proteins that are only active at lower body temperatures So body parts where temperature is lower will have more pigment and vice versa
62
What is penetrance?
The proportion of individuals with a specific genotype who actually show the expected phenotype If all individuals express the trait, this is complete penetrance
63
What is incomplete penetrance?
When some individuals with the genotype do not show the phenotype E.g. a person carries a dominant allele for a disease but do not develop symptoms E.g. epilepsy
64
What is expressivity?
The degree of gene expression Could be influenced by the environment as well as genotype
65
How do penetrance and expressivity disprove genetic determinism?
By showing that having a mutation is a risk factor but not a guarantee of affecting phenotype The environment plays a role and phenotypes can vary massively
66
What is eugenics?
Practices to limit reproduction of certain groups to create a 'fitter' population Operates under the flawed assumption that all human characteristics (e.g. poverty) are controlled by genetics
67
What are complex traits?
Traits that are polygenic and often environmental factors
68
What is quantitative genetics?
The study of traits that vary continuously and are influenced by multiple genes and environmental factors
69
What is additive gene action?
When each allele contributes a small, cumulative effect to the phenotype Common in polygenic traits like height or skin colour
70
What is non-additive gene action?
When the effects of alleles are not simply summed Instead, interactions between alleles or genes affect the phenotype (e.g. dominance, epistasis)
71
What is broad sense heritability?
The proportion of total phenotypic variation in a population that is due to genetic variation Includes all genetic effects
72
What is the equation for broad sense heritability?
H^2 = R/S R = response differential (the difference between means of the offspring and the base population) S = selection differential (the difference between means of the selected group and the base population)
73
What is narrow sense heritability?
The proportion of phenotypic variation due to additive genetic effects only Important for predicting response to selection in breeding or evolution If heritability is zero, no control can be exercised If heritability is one, full control can be exercised by careful crossing and selection In reality, most values lie between the extremes
74
What are QTLs?
Quantitative trait loci Regions of the genome that contribute to variation in a complex trait Can contain one or more genes affecting the trait Identified using genetic mapping and statistical analysis
75
What is QTL mapping?
A method to identify QTLs that influence a complex trait Involves crossing individuals with different trait values Genotyping offspring at many markers, then statistically associating markers with trait variation
76
What is GWAS?
Genome-wide association study A method used to scan the entire genome for genetic variants associated with a trait or disease Involves genotyping many individuals at thousands/millions of markers Statistically testing each marker for association with the phenotype
77
What is linkage disequilibrium?
Non-random associations of alleles at different loci in a population Occurs when certain combinations of alleles are inherited together more often than expected by chance
78
What is pleiotropy?
When a single gene affects multiple, seemingly unrelated traits E.g. Marfan syndrome (mutations in FBN1 affect the skeleton, eyes, and cardiovascular system)
79
What is the relationship between SNPs in each APOE variant?
There is linkage disequilibrium They tend to be inherited together as they are close on the gene
80
What is Alzheimer's disease?
A complex disease caused by multiple factors Is discrete, not continuous (you either get it or you don't) Population risk is 10-15% Heritability is around 70%
81
What are the APOE gene variants and which contribute to risk of AD?
APOE2: reduced risk of AD APOE3: neutral APOE4: increased risk *Additive effect: two copies of APOE4 leads to higher risk than having one copy
82
Compare clinical and direct-to-consumer genetic testing.
Clinical: Ordered by doctors for relevant tests Full sequencing is possible Interpretation considers all variants Direct-to-consumer: Often only sequences well-known variants (cheaper and faster) Skewed towards variants common in white Europeans Often potentially harmful mutations may be missed Data sold to third parties compromises genetic privacy
83
What are modifiers?
Mutations or alleles of specific genes that can modify (NOT MASK) the expression of different genes E.g. transcription factors
84
What are suppressors?
When a second mutation reverses the effect of another Restores a wild-type phenotype Can be intragenic or intergenic Intergenic suppressors often work by altering a pathway to restore function, while intragenic suppressors work within the same gene
Exam 2 Winter 2025
flashcards
Decks in class (9)
# Cards
Brainscape helps you reach your goals faster, through stronger study habits.
© 2026 Bold Learning Solutions. Terms and Conditions