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Praxis (5236) - Biology > 3A6 Non-Mendelian Genetics > Flashcards

3A6 Non-Mendelian Genetics Flashcards

Identify and describe patterns of non-Mendelian inheritance and the impact of the environment on genetic variation.

1
Q

What is an inheritance pattern where both dominant genes are expressed in heterozygous individuals rather than blending?

A

Codominance

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2
Q

What is a pattern of inheritance where hetrozygous individuals will display a blend of traits?

A

Incomplete dominance

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3
Q

What are sex-linked traits?

A

Traits found on the X chromosome.

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4
Q

Why are males more likely to be affected by sex-linked conditions like color-blindness?

A

Males have only one X chromosome, so a single copy of the color-blind allele will determine their phenotype.

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5
Q

What is the advantage of having two X chromosomes in females regarding sex-linked traits?

A

Disadvantageous recessive phenotypes can be masked in a heterozygote.

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6
Q

What is a sex-limited trait and where are they usually found?

A

A trait that is only expressed in one of the sexes. Typically found on an autosome, although they are just expressed in one sex.

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7
Q

What is true of genes that are said to be linked?

A

The genes are found on the same chromosome.

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8
Q

What are multiple alleles?

A

Three or more variations of a gene.

Traits controlled by multiple alleles include:

  • Blood type in humans
  • Fur color in animals
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9
Q

What happens when a person inherits one IA allele and one IB allele for blood type?

A

They have blood type AB.

When both IA and IB alleles are present, they are co-dominant, resulting in blood type AB.

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10
Q

How is the i allele different from IA and IB alleles for blood type?

A

It is recessive towards both IA and IB alleles.

The i allele is recessive, meaning it is not expressed when IA or IB alleles are present.

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11
Q

What are monogenic traits?

A

Traits that are controlled by a single gene.

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12
Q

What is a polygenic trait?

A

A trait in which the phenotype is controlled by more than one gene.

Examples of polygenic traits in humans:

  • Eye color
  • Skin color
  • Height
  • Hypertension
  • Diabetes
  • Schizophrenia
  • Asthma
  • Cancer
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13
Q

What is polygenic inheritance?

A

It is an inheritance where one characteristic is controlled by two or more genes.

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14
Q

Define the characteristics of polygenic traits.

A

Quantitative, multifactorial, controlled by multiple genes or environment.

Quantitative: Having continuous variation.

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15
Q

What does it mean when polygenic traits are considered multifactorial?

A

Multiple genes and/or the environment influence the phenotype.

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16
Q

How do polygenic traits contribute to natural selection?

A

They create a wide variety of phenotypes in a species, increasing the likelihood of a good fit for the environment.

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17
Q

What makes polygenic traits different from Mendelian traits?

A
  • Polygenic traits are controlled by multiple genes.
  • Mendelian traits are inherited at a single gene with two alleles.
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18
Q

What is co-dominant inheritance?

A

Both alleles are expressed together in the heterozygous organism.

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19
Q

What is epistasis?

A

The phenomenon of one gene suppress or interfere with the physical expression of another gene.

Polygenic traits that require the presence of an epistatic gene:

  • Hair color
  • Eye color
  • Skin color
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20
Q

What are the types of epistasis?

A
  • Recessive epistasis
  • Dominant epistasis
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21
Q

When does dominant epistasis occur?

A

When there is complete dominance of one gene.

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22
Q

What is recessive epistasis?

A

Occurs when recessive alleles on one gene interrupt or mask the expression of another gene.

Example: Albinism

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23
Q

What are the causes of epistasis?

A
  • Mutagens or physical or chemical influences which can cause a gene to mutate and be broken.
  • Recombination during meiosis.
  • Nondisjunction during meiosis.
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24
Q

How can epistasis be a factor in disease?

A

It can worsen the severity of diseases, such as Alzheimer’s, by interacting with other genes to exacerbate the condition.

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25
What is **pleiotropy**?
One gene affecting **multiple traits**. ## Footnote Examples: TBX5 gene codes for T-box 5 protein, affecting upper limbs and heart.
26
What is the **difference** between pleiotropy and polygenic inheritance?
* **Pleiotropy**: one gene affects multiple traits. * **Polygenic inheritance:** many genes influence one trait.
27
What is **antagonistic pleiotropy**?
When a trait that increases fitness in one area decreases fitness in another.
28
What is **senescence**?
The deterioration associated with **aging**.
29
How does antagonistic pleiotropy relate to senescence?
Competing effects of a gene causing traits that enhance fitness earlier in life but lead to age-related disorders and decreased lifespan.
30
What is the **difference** between antagonistic pleiotropy and normal pleiotropy?
* **Antagonistic** pleiotropy involves traits with competing effects. * **Normal** pleiotropy involves a single gene affecting multiple traits.
31
Provide examples of pleiotropic diseases.
* Sickle cell anemia * Phenylketonuria (PKU) ## Footnote Sickle cell anemia alters the shape of red blood cells so that they are sickle shaped, and can no longer adequately transport oxygen. Phenylketonuria prevents the breakdown of phenylalanine into tyrosine.
32
What is **cytoplasmic inheritance**?
Inheritance of genes in the cytoplasm of a cell not within the nucleus. ## Footnote Also known as extranuclear inheritance.
33
What is the distinct feature of cytoplasmic inheritance?
* The female is generally the only contributor toward the inheritance of specific DNA. * Patterns of phenotypes do not appear as expected in Mendelian laws of inheritance.
34
What is **mitochondrial inheritance**?
Inheritance of genes from mitochondrial DNA, mainly maternal.
35
What is **mitochondrial DNA** also known as?
mtDNA
36
What organelles contain their own copies of DNA similar to mitochondria?
**Chloroplasts** found in plant cells.
37
How does the inheritance pattern of **mitochondria** and **chloroplasts** differ from nuclear DNA?
They follow the inheritance pattern of cytoplasmic inheritance, not Mendelian genetics.
38
What are the **three types** of cytoplasmic inheritance?
* Vegetative segregation * Uniparental inheritance * Biparental inheritance
39
What is **vegetative segregation**?
Random replication and separation of organelles in the cytoplasm during cell division, producing daughter cells with a random sampling of parental cytoplasmic organelles.
40
When does **uniparental inheritance** occur?
When offspring inherit extranuclear genetic information from a single parent.
41
When does **biparental inheritance** occur?
When extranuclear genetic information is inherited from both parents. ## Footnote Very rare and can only occur in some species.
42
What is **epigenetics**?
The study of how **environmental factors** influence heritable traits. ## Footnote Does not involve changes to the underlying DNA sequence.
43
Why are humans considered **poor model organisms** for the study of genetics?
* Long generation times. * Inability to make controlled crosses. * Limited number of offspring. * Restrictions on genetic manipulation.
44
What do human geneticists study **in the absence** of controlled crosses and genetic manipulation?
* Human genome in its natural context. * Naturally occurring mutations. * Family pedigrees.
45
What is a **pedigree**?
Charts of family histories that show **phenotypes** and **family relationships** of individuals.
46
What can be determined by **analyzing pedigrees** in the study of human genetics?
* Whether a genetic condition is dominant or recessive. * Whether a condition is caused by a gene on the X chromosome or an autosome.
47
How are **males** and **females** represented in a pedigree?
* Male represented by a **square**. * Female represented by a **circle**.
48
What does an **open shape** in a pedigree represent?
Individual **does not** exhibit the trait of interest.
49
What does a **filled-in shape** in a pedigree represent?
Individual **exhibits** the trait of interest.
50
What is a proband in a pedigree?
The first affected family member seeking medical attention. ## Footnote Marked with an angled arrow labeled with a capital P pointing to the filled in shape.
51
How are family relationships represented in a pedigree?
* **Marriage line** connecting shapes of partners. * **Vertical line** for children. * **Divorce** is represented by a break in the relationship line that connects the couple.
52
How are **twins** represented in a pedigree?
By a **bifurcated vertical** line. ## Footnote Monozygotic twins are represented by connecting the split line with a horizontal line.
53
How is **death** indicated in a pedigree?
By placing a **diagonal line over the symbol** of the deceased individual.
54
How are miscarriages and abortions shown on a pedigree chart?
* **Miscarriage**: Triangle shape attached with a shorter vertical line. * **Filled-in triangle** indicates the fetus was *affected*. * A **diagonal line over the triangle** if pregnancy was *terminated*.
55
What is the **difference** between autosomal and sex-linked conditions?
* **Autosomal** conditions are caused by genes on chromosomes 1-22. * **Sex-linked** conditions are caused by genes on the X chromosome.
56
Why are complex diseases more challenging to study than simple autosomal conditions?
They have contributions from **multiple gene loci** and non-genetic factors, making them more difficult to understand.
57
What method do human geneticists use to study complex diseases due to their multifactorial nature?
Population genetics
58
How do geneticists try to minimize the impact of non-genetic factors when studying complex diseases?
Match the non-genetic factors of affected and unaffected individuals.
59
What type of condition is caused by a **gene on an autosome**?
Autosomal condition ## Footnote Examples: * Huntington's disease * Polycystic kidney disease * Cystic Fibrosis
60
What is the inheritance pattern for autosomal **dominant** traits?
An individual will develop the condition if they get **a copy of the gene** from either one of their parents.
61
What is a **carrier** in genetics?
Someone who has one copy of the gene for a genetic condition but also has another gene that keeps them from developing the condition.
62
How are carriers identified in a **pedigree for autosomal recessive traits**?
*If two unaffected parents have offspring that are affected*, then the pedigree is showing an autosomal recessive trait.
63
Explain the difficulty in identifying autosomal recessive conditions in pedigrees.
Most of the recessive alleles remain hidden in unaffected carriers and only become apparent in a small number of family members, often separated by generations.
64
How are carriers identified in a pedigree for **sex-linked traits**?
If there are *affected male children, unaffected female children, and unaffected parents*, then it is most likely a sex-linked trait and the **mother is a carrier**.
65
Describe the **inheritance pattern** of sex-linked traits.
Sex-linked traits often follow a **crisscross** pattern of inheritance. ## Footnote Affected males pass a sex-linked recessive gene to their daughters, who become carriers of the trait. These carrier females then pass the affected allele to half of their sons and daughters.

Praxis (5236) - Biology (39 decks)

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