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Revision Examination Tests
“Come all for this greatness”
...100% Correct Ans...
PSYCHOLOGY 101NOTES 2024/2025 - DISTINCTION GUARANTEED
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Behavior genetics is a branch of psychology that examines the genetic
base of behavior and personality differences among people. An
understanding of genetics begins with the following basic concepts:
A vast number of cells make up the human body. Each cell has forty-six
chromosomes, which come in twenty-three pairs. The only exceptions
are sex cells.
Sex cells are sperm in males and eggs in females. Each sex cell has
only twenty-three chromosomes.
Chromosomes are made up of thin strands of deoxyribonucleic acid
(DNA). Each chromosome pair contains thousands of genes.
Genes are segments of DNA that function as hereditary units. Genes are
carried on chromosomes.
DNA is made up of units called nucleotides. There are only four different
nucleotides, labeled A, C, G, and T. Long strings of nucleotides make up
genes.
Genes get translated into proteins, which carry out various functions in
our bodies. For instance, some proteins serve as the building blocks of
cells. Other proteins function as enzymes or hormones.
Who Shares Genes?
No two people share the exact combination of genes unless they are
identical twins. However, all family members share some genes with one
another. The closer the biological relationship between individuals, the
more genes they share. The chart below shows the percentage of genes
any person shares with his or her close relatives:
Percentage of Shared Genes
Identical twin 100 percent
Parent 50 percent
, Brother or sister 50 percent
Nonidentical twin 50 percent
Grandparent 25 percent
Monogenic and Polygenic Traits
Some characteristics or traits are controlled by a single gene, which
means they are monogenic. A single gene, for example, can be part of
what brings about alcoholism or schizophrenia.
Most traits are controlled by the actions of several genes, which means
they are polygenic. For example, a person’s intelligence is linked to the
combination of several genes.
The environment also shapes traits, and later in this chapter we will
discuss how genes interact with the environment to produce
psychological traits.
Heritability
In a group of people, a particular psychological trait, such as intelligence,
usually varies a lot. Differences in groups may be due to genes or the
environment, and researchers use a statistic called heritability to see
which has the largest influence. Heritability is a mathematical estimate
that indicates how much of a trait’s variation can be attributed to genes.
There are three important principles of heritability:
Heritability estimates don’t reveal anything about how much genes
influence a person’s traits. These figures tell us only to what extent trait
differences between people can be attributed to genes.
Heritability depends on the similarity of the environment for a group of
people. In a group of people who share similar environments, heritability
of a particular trait may be high. However, that same trait may have low
heritability in a group of people who operate in different environments.
Even if a trait is highly heritable, it can still be influenced by
environmental factors.
Example: Imagine that ten people live in identical environments.
Somehow, they experienced identical prenatal environments while in
their mothers’ wombs, were raised in identical homes by parents who
were identical in every way, and had all the same childhood and
adulthood experiences. Suppose that these ten people turn out to be
different with respect to one trait, such as the rate at which they can
wiggle their ears. Since both genes and environment can influence traits,
these differences would have to be genetic, since they could not be due
to differences in environment. In such a case, heritability of the ear-
wiggling trait would be close to 100 percent. Now suppose some of
Revision Examination Tests
“Come all for this greatness”
...100% Correct Ans...
PSYCHOLOGY 101NOTES 2024/2025 - DISTINCTION GUARANTEED
100%
Behavior genetics is a branch of psychology that examines the genetic
base of behavior and personality differences among people. An
understanding of genetics begins with the following basic concepts:
A vast number of cells make up the human body. Each cell has forty-six
chromosomes, which come in twenty-three pairs. The only exceptions
are sex cells.
Sex cells are sperm in males and eggs in females. Each sex cell has
only twenty-three chromosomes.
Chromosomes are made up of thin strands of deoxyribonucleic acid
(DNA). Each chromosome pair contains thousands of genes.
Genes are segments of DNA that function as hereditary units. Genes are
carried on chromosomes.
DNA is made up of units called nucleotides. There are only four different
nucleotides, labeled A, C, G, and T. Long strings of nucleotides make up
genes.
Genes get translated into proteins, which carry out various functions in
our bodies. For instance, some proteins serve as the building blocks of
cells. Other proteins function as enzymes or hormones.
Who Shares Genes?
No two people share the exact combination of genes unless they are
identical twins. However, all family members share some genes with one
another. The closer the biological relationship between individuals, the
more genes they share. The chart below shows the percentage of genes
any person shares with his or her close relatives:
Percentage of Shared Genes
Identical twin 100 percent
Parent 50 percent
, Brother or sister 50 percent
Nonidentical twin 50 percent
Grandparent 25 percent
Monogenic and Polygenic Traits
Some characteristics or traits are controlled by a single gene, which
means they are monogenic. A single gene, for example, can be part of
what brings about alcoholism or schizophrenia.
Most traits are controlled by the actions of several genes, which means
they are polygenic. For example, a person’s intelligence is linked to the
combination of several genes.
The environment also shapes traits, and later in this chapter we will
discuss how genes interact with the environment to produce
psychological traits.
Heritability
In a group of people, a particular psychological trait, such as intelligence,
usually varies a lot. Differences in groups may be due to genes or the
environment, and researchers use a statistic called heritability to see
which has the largest influence. Heritability is a mathematical estimate
that indicates how much of a trait’s variation can be attributed to genes.
There are three important principles of heritability:
Heritability estimates don’t reveal anything about how much genes
influence a person’s traits. These figures tell us only to what extent trait
differences between people can be attributed to genes.
Heritability depends on the similarity of the environment for a group of
people. In a group of people who share similar environments, heritability
of a particular trait may be high. However, that same trait may have low
heritability in a group of people who operate in different environments.
Even if a trait is highly heritable, it can still be influenced by
environmental factors.
Example: Imagine that ten people live in identical environments.
Somehow, they experienced identical prenatal environments while in
their mothers’ wombs, were raised in identical homes by parents who
were identical in every way, and had all the same childhood and
adulthood experiences. Suppose that these ten people turn out to be
different with respect to one trait, such as the rate at which they can
wiggle their ears. Since both genes and environment can influence traits,
these differences would have to be genetic, since they could not be due
to differences in environment. In such a case, heritability of the ear-
wiggling trait would be close to 100 percent. Now suppose some of
