Nature Vs. Nurture

Question 1

Nature and Nurture

Answer 1

Today, there is a
consensus that almost all
human characteristics are
influenced by both
genetics (i.e., nature) and
environment (i.e.,
nurture).

• Genes and experience
  interact to produce
  unique outcomes.

Question 2

Genes

Answer 2

units of
heredity that maintain
their composition from
one generation to the
next.

Genes come in pairs
because they are aligned
on chromosomes that
also come in pairs.

Question 3

Chromosomes

Answer 3

are
double-helix strands of
deoxyribonucleic acid
(DNA).

Question 4

DNA

Answer 4

contains four
nucleotide bases:
adenine, guanine,
cytosine, and thymine.
In a double-helix strand of
a chromosome, adenine
bonds to thymine and
guanine binds to cytosine

Question 5

the genetic code

Answer 5

The sequence of
nucleotide bases

Question 6

genotype

Answer 6

The genetic makeup of
an individual

Question 7

phenotype

Answer 7

An individual’s
observable characteristics

Question 8

autosomal
chromosomes

Answer 8

22 pairs of the
chromosomes and
contain autosomal
linked genes.

Question 9

sex
chromosomes

Answer 9

are only a
pair in females.
- Sex chromosomes are
labelled X and Y.

• Females have two X
  chromosomes and males
  have a X and a Y
  chromosome.
• The X and Y
  chromosome differ in
  appearance and carry
  different genes.
• Genes located on the
  sex chromosomes are
  called sex-linked genes.

Question 10

X
chromosome

Answer 10

One example of a sexlinked gene is a gene that
codes for color vision

Question 11

homozygous

Answer 11

If you have the same
version of a gene on both
chromosomes

Question 12

heterozygous

Answer 12

If you have different versions of a
gene on both
chromosomes

Question 13

alleles

Answer 13

Different versions of the
same gene

can be dominant
or recessive (in some
cases they can be
intermediate as well).

• A dominant allele is
  expressed in either a
  homozygous or
  heterozygous condition.
• A recessive allele is only
  expressed in the
  homozygous condition.

Question 14

messenger
ribonucleic acid
(mRNA).

Answer 14

One of the strands of
DNA then serves as a
template for the
construction of a strand

RNA contains four
nucleotide bases:
adenine, guanine,
cytosine, and uracil.

Question 15

Genetic Expression

Answer 15

During genetic
expression, the partial
section of the
chromosome that
contains the gene
unravels separating
the bonds between the
nucleotide bases.

Question 16

transcription

Answer 16

The synthesis of mRNA
from DNA

Question 17

Translation

Answer 17

The ribosome uses the
strand of mRNA to
construct a protein. The
synthesis of a protein
from mRNA is called

Question 18

Proteins

Answer 18

chains of
amino acids that form
the structures of the body
and facilitate biological
functions (e.g., enzymes).

Question 19

codon

Answer 19

Three nucleotide bases
along a strand of mRNA

Question 20

transfer RNA
(tRNA)

Answer 20

• A ribosome translates
  the messenger RNA by
  moving along the RNA
  bases. At each codon, it
  signals to a molecule to deliver the
  corresponding amino
  acid. The amino acid is then attached to a
  growing chain.
• This process continues
  until the ribosome
  reaches a stop codon
  which signals that the
  protein is complete (see
  picture).

Question 21

Humans have how many genes?

Answer 21

approx.
20000 genes.

Question 22

• The expression of genes
  is controlled by sections
  of DNA called

Answer 22

enhancers
or promotor regions
- Enhancers are regulated
by proteins called
transcription factors
that bind to enhancer
regions.
- The interaction between
transcription factors and
enhancers is regulated in
part by environmental
signals

Question 23

Mutations

Answer 23

Genes can undergo
spontaneous changes
called mutations.
- Genetic mutations can
then be passed to
offspring.
- A genetic mutation
typically does not
increase the fitness of the
individual who inherits it,
however, in some rare
cases it can (e.g.,
FOXP2 gene).
Two other types of
genetic mutations are
duplications and
deletions.

Question 24

Deletions

Answer 24

occur when
part of a DNA sequence
on a chromosome is
removed.

Question 25

Duplications

Answer 25

occur when part of a DNA sequence is repeated. Most deletions or duplications are not beneficial (e.g., Williams Syndrome). An example of a disorder that is caused by a duplication in the DNA sequence is Fragile X syndrome. It affects 1 in 4000 males and 1 in 8000 females.

Question 26

Fragile X Syndrome

Answer 26

caused by a duplication in the enhancer/promoter region of the FMR1 gene (the Fragile X Mental Retardation 1 gene) located on the X chromosome. - Normally, this region contains 5 to 54 repeating CGG bases (i.e., cytosine, guanine, guanine). For example, CGGCGGCGGCGGCGGCG GCGG. The full mutation in the promoter region of the FMR1 causes the gene to become inactivated (i.e., the gene is not expressed). - Therefore, an important protein called the fragile X mental retardation protein (FMRP) is not synthesized. - Lack of the FMRP causes the symptoms associated with Fragile X syndrome.

Question 27

a FMR1 gene premutation.

Answer 27

Some people have a version of this gene that contains 55 to 200 repeats of the CGG segment.

Question 28

Epigenetics

Answer 28

The relatively new field of epigenetics explores changes in genetic expression as the result of environmental influences. These changes in genetic expression occur without changes to the underlying DNA base sequence. - Epigenetic changes provide a mechanism through which genes and experience interact.

Question 29

histone remodeling.

Answer 29

epigenetic mechanism DNA wraps around proteins called histones (think of string wrapped around a ball). - DNA wrapped around histones is called chromatin. - For a gene to be expressed, DNA must partially unwrap from the histones. - When DNA is wrapped tightly around the histones, genes are unable to be expressed. - When DNA is unwound from the histones, genes can be expressed. - Experiences (e.g., feeling socially isolated) can alter the chemical environment in a cell, which can cause histone remodeling and changes in genetic expression.

Question 30

DNA methylation

Answer 30

- DNA methylation occurs when methyl groups (CH3) bind to the promotor region of a gene. - Methylation typically causes a gene to be turned off (but not always). - Methyl groups typically bind to cytosine bases. - In fact, this is what occurs in Fragile X syndrome. The repeated CGG segment becomes hypermethylated, turning off the FMRI gene. Many types of environmental factors that can promote epigenetic changes.

Question 31

transgenerational epigenetics.

Answer 31

epigenetic changes can be passed from parents to offspring.

Question 32

Behavioral Genetics

Answer 32

the study of genetic influences on individual differences in psychological characteristics and behavior.

Question 33

Molecular genetics

Answer 33

focused on identifying the specific genes associated with psychological characteristics and behaviors (e.g., which genes are associated with psychopathy?).

Question 34

A heritability estimate

Answer 34

provides a percentage of the amount of trait variation in a population that can be accounted for by differences in genetics. - Heritability estimates range from zero to 100%. - Heritability estimates cannot be applied to specific individuals within the population that was used to calculate it. A heritability estimate can only be applied to the population that was used to calculate it because it is directly influenced by the degree of genetic and environmental variability that exists within a population.

Question 35

How do behavioral geneticists calculate heritability estimates?

Answer 35

- Twin studies compare the degree of similarity on a trait between monozygotic twins and dizygotic twins. - The higher the degree of similarity on a trait between monozygotic twins compared to dizygotic twins, the higher the heritability estimate will be. Studies of heritability estimates using Western samples have shown that differences in almost every trait and behavior in psychology has a substantial genetic influence (i.e., between 40 to 80 percent).