Genetics and The Development of the Human Brain

Question 1

Our personal set of genetic instructions

Answer 1

Genotype

Question 2

Genotype interacts
with environmental influences to produce _______, your observable characteristics

Answer 2

Phenotype

Question 3

Your genotype
consists of _________ matched pairs of chromosomes.

Answer 3

23

Question 4

________ occurs when these genetic instructions are converted into a feature of a living cell.

Answer 4

Gene expression

Question 5

All mitochondrial DNA (mDNA) originates from the ______

Answer 5

Mother

Question 6

If a person has two identical alleles at a given site, the individual is
considered to be ________ for that gene.

Answer 6

Homozygous

Question 7

If a person has two
different alleles, such as a gene for Type A blood and a gene for
Type O, he or she will be considered _________ for that gene.

Answer 7

Heterozygous

Question 8

A __________ allele will produce its phenotype only when it occurs in
a homozygous pair.

Answer 8

Recessive

Question 9

A _________ allele produces a phenotypical trait regardless of
whether its pair is homozygous or heterozygous.

Answer 9

Dominant

Question 10

Approximately ______ of mammals’ genes are _________, which
means that only one allele is expressed. The identity of the
expressed gene depends on which parent supplied the allele.

Answer 10

1 percent, imprinted

Question 11

Egg and sperm cells are formed through the process of _______

Answer 11

Meiosis

Question 12

_________ may occur in segments of DNA that do not appear to influence
phenotypical traits, or a _______ may result in a recessive allele.

Answer 12

Mutations

Question 13

_____ result from genes on the X chromosome that are not duplicated on the Y chromosome.

Answer 13

Sex-linked characteristics

Question 13

Extreme _______ is more common among mothers who had given birth to gay sons (13%) than among mothers of heterosexual sons (4%).

Answer 13

Skewing

Question 13

Rosa Hoekstra and her
colleagues reported that “individual differences in endorsement on autistic
traits show substantial heritability _______

Answer 13

57%

Question 14

__________ cannot be assessed without taking the environment into account

Answer 14

Heritability

Question 15

It is the complete set of an organism’s genetic
material, including all of its genes and non-coding
sequences of DNA.

It contains all the information necessary for the structure, function, and regulation of an organism’s
cells.

Answer 15

Genome

Question 16

It is a permanent change in the DNA sequence of a
gene or a chromosome.

It can be caused by various factors and can result in genetic variations that may affect an organism’s traits

Answer 16

Mutation

Question 17

It is a specific sequence of DNA that contains
instructions for producing a particular protein or set of
proteins.

These are the basic units of heredity and determine various traits and characteristics of an organism.

Answer 17

Gene

Question 18

It is a type of cell division that occurs in sexually
reproducing organisms, resulting in the formation of haploid cells (gametes, such as sperm and egg cells) from diploid cells.

It reduces the chromosome number by half and introduces genetic diversity.

Answer 18

Meiosis

Question 19

It refers to the complete set of proteins expressed by an organism, tissue, or cell at a specific point in time.

It encompasses the entire range of proteins encoded by the genome.

Answer 19

Proteome

Question 20

It refers to the genetic makeup of an individual organism.

It includes all the genes and genetic variations an organism possesses, whether they are expressed (observable) or not.

Answer 20

Genotype

Question 21

It is a long, thread-like structure made of DNA and associated proteins (histones) found
in the cell’s nucleus.

It may carry genetic information and are organized into pairs in most organisms.

Answer 21

Chromosome

Question 22

It refers to the observable characteristics or traits of an organism, which result from the interaction between its
genotype and the environment.

It includes physical features, behaviors, and other attributes.

Answer 22

Phenotype

Question 23

It is a variant or a different version of a gene that can occupy a specific location (locus) on a chromosome.

It may result in variations in a particular trait.

Answer 23

Allele

Question 24

The cell formed by the merger of egg and sperm is known as a _______

Answer 24

Zygote

Question 25

From two to eight weeks following conception, the
developing individual is known as an ________

Answer 25

Embryo

Question 26

After the eighth week until birth, the individual is a _________

Answer 26

Fetus

Question 27

A week after conception, the human zygote has already formed
three differentiated bands of cells known as _________

Answer 27

Germ layers

Question 28

The outer layer is the __________, which will develop into the
nervous system, skin, and hair.

Answer 28

Ectoderm

Question 29

The middle layer is the ________, which forms connective tissue,
muscles, blood vessels, bone, and the urogenital systems.

Answer 29

Mesoderm

Question 30

The final layer is the __________, which will develop many of the
internal organs, including the stomach and intestines.

Answer 30

Endoderm

Question 31

During the course of development, large numbers of cells die in the process known as __________, or programmed cell death.

Answer 31

Apoptosis

Question 32

The term apoptosis comes from the Greek word for ______

Answer 32

“Falling leaves”

Question 33

Apoptosis during development was first described by ___________, who observed that nearly half of the spinal
motor neurons produced by chick embryos died before the birds
hatched.

Answer 33

Viktor Hamburger (1975)

Question 34

Neurotrophins influence the survival of a neuron by interrupting
cellular suicide programs that culminate in apoptosis. All cells
appear to contain _________

Answer 34

Cell death genes

Question 35

When activated by cell death genes, enzymes known as __________
break up DNA and proteins, which quickly leads to cell death.

Answer 35

Caspases

Question 36

Just as the brain initially overproduces neurons, followed by a
refinement in their numbers, we experience a burst of synaptic
growth followed by a period of _________, in which the
number of functional synapses is reduced.

Answer 36

Synaptic pruning

Question 37

_________ suggested that pruning might eliminate up to ________ of all synapses in the human visual cortex after the
first year of life.

Answer 37

Huttenlocher (1994), 42%

Question 38

Structurally, ________ occurs in a rostral direction starting in the spinal cord, followed by successive
myelination of the hindbrain, midbrain, and forebrain.

Answer 38

Myelination

Question 39

Functionally, the sensory parts of the cortex appear to be myelinated at an ________ than the motor parts of the cortex.

Answer 39

Earlier time

Question 40

The last area to be myelinated is the _________, which is responsible for some of our most sophisticated cognitive functions. The
________ is not completely myelinated until early adulthood

Answer 40

Prefrontal cortex

Question 41

Without this flexibility, or _________, it is unlikely that we would be
able to learn and store new memories.

Answer 41

Plasticity

Question 42

In some cases, the time
frame of plasticity is limited, in which case we refer to the window
of time in which change can occur as a ___________. In other
cases, it appears as though change can occur indefinitely.

Answer 42

Critical period

Question 43

______ described the phenomenon of
imprinting in several species of birds.

Answer 43

Konrad Lorenz (1952)

Question 44

_______ followed the development of Romanian orphans adopted by Canadian parents. Children adopted prior to 6 months of age appear to have recovered from their earlier deprivation.

Children adopted later in life improved but did not make as good a recovery as the children adopted earlier. These findings suggest that human intellectual development is also subject to critical periods.

Answer 44

Elenor Ames (1997)

Question 45

Several hypotheses have been proposed to account for the closing of critical periods of development. Growth spurts in myelin have been observed in parts
of the brain involved with ____________ between the ages of 6 and 13 years.

Answer 45

Language and spatial relations

Question 46

It is a severe congenital birth defect where the neural tube, which eventually forms the brain and spinal cord,
fails to close completely during early fetal
development.

This results in the absence of a major portion of the brain, skull, and scalp.

Babies born with this disorder typically do not survive long after birth, and the condition is often incompatible
with life.

Answer 46

Anencephaly

Question 47

It is a genetic disorder that affects cognitive function and behavior.

It is caused by a mutation in the FMR1 gene on the X chromosome.

Individuals with this disorder may exhibit intellectual disabilities, social and communication difficulties,
hyperactivity, and repetitive behaviors.

It is the most common inherited cause of intellectual
disability.

Answer 47

Fragile X syndrome

Question 48

It is a neural tube defect that occurs when the neural tube does not close properly during early fetal development.

It can lead to a range of physical and neurological
problems.

The severity of this disorder varies, with some individuals
having relatively mild symptoms, while others may experience significant disability.

It often involves damage to the spinal cord and may result in paralysis, bladder and bowel issues, and other
complications.

Answer 48

Spina bifida

Question 49

It is also known as trisomy 21, is a genetic disorder caused by the presence of an extra copy of chromosome 21.

It leads to physical and intellectual disabilities of
varying degrees.

Individuals with this disorder typically have distinct facial features, developmental delays, and may experience a range of health issues, including heart
problems, vision and hearing impairments, and cognitive challenges.

Answer 49

Down syndrome

Question 50

It is a condition characterized by an abnormal accumulation of cerebrospinal fluid (CSF) in the brain’s ventricles, leading to
increased intracranial pressure.

This condition can result from a variety of causes, including congenital factors, infections, or blockages in the flow of CSF. Symptoms may include headaches, nausea, balance
problems, and, in infants, an enlarging head circumference.

Treatment often involves surgical procedures to drain excess CSF

Answer 50

Hydrocephalus

Question 51

The first suggestion that more extensive neurogenesis might occur in mature
animals came from __________, who discovered that songbirds produced new neurons when they learned new songs.

Answer 51

Barnea and Nottebohm (1994)

Question 52

Adult neurogenesis might also protect the mature brain from the
effects of ______

Answer 52

Stress

Question 53

Similar findings in the human brain and in mice have been reported by _________. The new neurons did not migrate to primary visual cortex. As we discovered previously, visual organization appears to possess a critical period
that closes in childhood. We would be surprised, therefore, to find new neurons
migrating to the visual cortex.

Answer 53

Gage (2000)