40 Questions
What is the main factor that contributes to the development of disorders like attention-deficit/hyperactivity disorder?
Interaction between inherited predisposition and environmental factors
What is the primary reason why identical twins, despite having the same genetic code, look and act slightly different?
Epigenetic variation
What is the term used to describe the study of biochemical modifications of genetic expression that do not alter DNA sequence?
Epigenetics
What are the chemical molecules that affect the way a cell reads a gene's DNA?
Tags
What is the function of the chemical tags in epigenesis?
To differentiate various types of body cells
What can cause epigenetic changes, according to the text?
Environmental factors
What are some common ailments that epigenetic changes can contribute to?
Cancer, diabetes, and heart disease
What is the phenomenon where certain genes are turned off or on as they are needed by the developing body or triggered by the environment?
Epigenesis
What type of correlation occurs when a child's genetic makeup influences their environment?
Reactive correlation
What is the term for the tendency of certain genetic and environmental influences to reinforce each other?
Genotype-environment correlation
In which scenario does a passive correlation occur?
When a child is living with a biologically related parent
What is the result of reactive correlation in the example of a child who shows interest and ability in music?
The child's genetic inclination toward music is strengthened
What is the term for the study of the genetic and environmental factors that influence behavior?
Behavioral genetics
What type of correlation occurs when a child's environment is influenced by their biological parents, but the child does not control it?
Passive correlation
What percentage of inheritance is associated with certain rare physical disorders?
100%
What is the main goal of the science of behavioral genetics?
To measure the relative influence of heredity and environment on traits
What is heritability?
A statistical estimate of the contribution of heredity to individual differences in a specific trait
What is the concept used to study the influence of heredity and environment on traits?
Behavioral genetics
Why is it important to study the influence of heredity and environment on traits?
To understand the complex array of hereditary and environmental forces that influence traits
What is the relationship between heredity and environment in shaping traits?
Heredity and environment have a complex interaction that influences traits
How is heritability measured?
By looking at groups of people with known genetic relationships and assessing concordance
What is the limitation of heritability?
It cannot be measured directly
What is the primary reason why defects transmitted by recessive genes tend to be lethal at an earlier age?
Because recessive genes can be transmitted by heterozygous carriers who do not themselves have the disorder
What is the result of the presence of a dominant/recessive gene pair in a person's genome?
The full expression of the dominant gene and the masking of the recessive gene
What is the primary characteristic of alpha thalassemia?
Severe anemia that reduces the ability of the blood to carry oxygen
Which genetic disorder is most commonly found in males and is marked by muscle weakness and minor intellectual disability?
Duchenne muscular dystrophy
What is the typical outcome for infants with anencephaly?
They are usually stillborn or die soon after birth
What is the primary treatment for hemophilia?
Frequent transfusions of blood with clotting factors
What is the characteristic of spina bifida?
Incompletely closed spinal canal
Which genetic disorder is typically found in families of Mediterranean descent?
Beta thalassemia
What is the typical outcome for people with cystic fibrosis?
They typically have a short life span
Why can recessive genes be transmitted to the next generation?
Because recessive genes can be transmitted by heterozygous carriers who do not themselves have the disorder
What is the main reason why highly canalized traits tend to be predictable and reliable?
They are critical for survival and natural selection has designed them to develop in a predictable way
What is the characteristic of highly canalized traits in terms of their expression?
They are strongly programmed by genes and have little opportunity for variance in their expression
What is the purpose of natural selection in designing highly canalized traits?
To make traits more predictable and reliable for survival
What is an example of a highly canalized trait in humans?
Motor development sequence
Why are highly canalized traits less susceptible to environmental influences?
Because they are deeply influenced by genetics and have a strong channel
What is the role of genetics in the development of highly canalized traits?
Genetics strongly programs the development of these traits
What is the consequence of a highly canalized trait being influenced by an extreme change in environment?
The trait will change dramatically
What is the main difference between highly canalized traits and other traits?
Highly canalized traits are strongly influenced by genetics and have little opportunity for variance in their expression
Study Notes
Epigenetic Influences on Gene Expression
- Epigenetic variation can explain why identical twins, who share 100% of their genetic code, look and act slightly different.
- Epigenetic influences involve biochemical modifications of genetic expression "above the genome" without altering DNA sequence.
- Epigenesis works via chemical molecules, or "tags," attached to a gene that affect the way a cell "reads" the gene's DNA.
- Environmental factors, such as nutrition, smoking, sleep habits, stress, and physical activity, can cause epigenetic changes.
Inheritance and Genetic Disorders
- Many disorders arise from the interaction between an inherited predisposition (an abnormal variant of a normal gene) and an environmental factor.
- Recessive genes are not expressed if the parent is heterozygous for that trait, and may not be apparent that a child is at risk for receiving two alleles of a recessive gene.
- Defects transmitted by recessive genes tend to be lethal at an earlier age, in contrast to those transmitted by dominant genes.
- Examples of genetic disorders include:
- Alpha thalassemia: severe anemia, primarily affects families of Malaysian, African, and Southeast Asian descent.
- Beta thalassemia (Cooley's anemia): severe anemia, primarily affects families of Mediterranean descent.
- Cystic fibrosis: overproduction of mucus, affects 1 in 2,000 White births.
- Duchenne muscular dystrophy: fatal disease, usually found in males, marked by muscle weakness and minor intellectual disability.
- Hemophilia: excessive bleeding, usually affects males, affects 1 in 10,000 families with a history of hemophilia.
- Anencephaly: absence of brain tissues, affects 1 in 1,000 births.
- Spina bifida: incompletely closed spinal canal, affects 1 in 1,000 births.
Correlation between Genotype and Environment
- Genotype-environment correlation: the tendency of certain genetic and environmental influences to reinforce each other.
- Passive correlations: correlations between genotype and environment that are beyond the child's control, applicable to young children.
- Reactive correlations: correlations between genotype and environment where children evoke different reactions from others based on their genetic makeup.
Behavioral Genetics
- Behavioral genetics: the study of the relative influences of heredity and environment on behavior.
- Heritability: a statistical estimate of the contribution of heredity to individual differences in a specific trait within a given population.
- Heritability cannot be measured directly, but can be estimated by studying groups of people with known genetic relationships.
- Canalized traits: traits that are strongly programmed by genes and have little opportunity for variance in their expression, such as those necessary for survival.
Explore the relationship between inherited predispositions, environmental factors, and epigenetic variations. Learn how identical twins with the same genetic code can exhibit differences.
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