Chapter 5: Genetics

Question 1

how can you remove the dark pigment from a rat?

Answer 1

the agouti gene controls the distribution of black pigment so by blocking it with BPA you can halt its expression

Question 2

phenotype vs genotype

Answer 2

phenotype: gene expression converts the genetic instructions into features of a living cell
genotype: the genetic makeup of an individual containing adenine (A), guanine (G), cytosine (C), and thymine (T)

Question 3

transcription vs translation

Answer 3

transcription: DNA is transcribed into a complementary strand of RNA
translation: RNA acts as a template for ribosomes to produce amino acids sequences, which form proteins

Question 4

meiosis vs mitosis

Answer 4

meiosis: the process of gametes being formed, each containing one chromosome
mitosis: when body cells clone each other and then split

Question 5

what are the sources of genetic variability that can occur during meiosis?

Answer 5

crossing-over: where chromosomes exchange equivalent segments of DNA that results in a unique combination of genes not seen in either parent
mutations: mostly benign errors that can occur in DNA replication

Question 6

what is hemophilia?

Answer 6

a disorder that leads to excessive bleeding since blood cannot clot as easily, males are more likely to inherit this since it is X-linked, females have XX chromosomes so inheriting one X with hemophilia can be masked by the other chromosomes leading to hemophilia not developing

Question 7

what are single nucleotide polymorphisms (SNPs)?

Answer 7

when there is a DNA sequence change at one nucleotide, specific SNPs on the GABAA2 can lead to an increase in alcohol use disorder

Question 8

what are copy-number variations (CNVs)?

Answer 8

mutations resulting from duplication or deletion of sections of DNA, associated with autism spectrum disorder and schizophrenia

Question 9

how do mitochondrial DNA diseases act as a source of variability?

Answer 9

mitochondrial diseases are inherited from your mother and occur when mitochondria fail to produce enough energy for the body to function properly, this can lead to movement disorders, sensory issues, neurological problems, dementia, etc.

Question 10

what is heritability?

Answer 10

the contribution of genetics to the variation of a trait observed in a population, heritability always refers to a population, not to individuals

Question 11

what is epigenetics?

Answer 11

a reversible genetic change that does not change the DNA sequence but is influenced by environmental factors

Question 12

what are the two mechanisms of epigenetics?

Answer 12

histone modifications and DNA methylation

Question 13

how does child maltreatment of mouse pups affect their hippocampus?

Answer 13

the pups of nurturant mothers showed high levels of glucocorticoid receptors in the hippocampus regardless of whether they were handled or not handled, however, pups of non-nurturant mothers showed nearly normal levels of gene expression when handled, but reduced levels when not handled

Question 14

what does the ectoderm develop into?

Answer 14

ectoderm -> neural plate -> neural tube -> CNS

Question 15

what does the mesoderm develop into?

Answer 15

connective tissue, blood vessels, muscles, bone, urogenital system

Question 16

what does the endoderm develop into?

Answer 16

internal organs

Question 17

what are the 6 stages of the development of the nervous system?

Answer 17

1. neurogenesis
2. cell migration
3. differentiation
4. cell growth and synapse formation
5. cell death
6. synaptic pruning

Question 18

what happens during the neurogenesis step of development?

Answer 18

neurons and glia are formed from cells in the ventricular zone, progenitor cells divide by mitosis before they are specialized

Question 19

what happens during the cell migration step of development?

Answer 19

cells in cerebral cortex arrive in an inside-out fashion after they are transported by radial glia

Question 20

what happens during the differentiation step of development?

Answer 20

differentiation of the neural tube along the dorsal and ventral halves and along the rostral-caudal axis, organization of cerebral cortex affected by intrinsic and extrinsic factors

Question 21

what happens during the cell growth and synapse formation step of development?

Answer 21

axons and dendrites arise from neurites, developing axons and dendrites end in growth cones that then make contact with targets cells to form specific synapses

Question 22

what happens during the cell death step of development?

Answer 22

apoptosis takes place, access to nerve growth factors (NGFs) influence the survival of a neuron (high NGF is associated with autism)

Question 23

what happens during the synaptic pruning step of development?

Answer 23

number of functional synapses are reduced and synapses left are myelinated, PFC isn’t fully myelinated until early adulthood

Question 24

what kind of early experiences impact brain development?

Answer 24

the high plasticity of young brains makes social experiences important at a young age, the end of the myelination growth spurt reduces neural plasticity, environmental enrichment increases synaptic plasticity

Question 25

what are some disorders of the CNS?

Answer 25

spina bifida: caudal portion of the neural tube fails to close normally
fragile X: intellectual disability characterized by low set ears and a
large forehead and jaw
fetal alcohol syndrome: most preventable cause of intellectual disability

Question 26

what happens in the brain during puberty?

Answer 26

surge of gray matter development and pruning, thickening of cortex and frontal lobe, amygdala matures first which explains teen risky behavior

Question 27

what happens in the brain during adulthood?

Answer 27

the brain is fully matured by ~age 25, neurogenesis continues in the hippocampus
*Healthy aging includes brain tissue atrophy

Question 28

what is gene therapy?

Answer 28

technique that seeks to modify or manipulate the expression of a gene or to alter the biological properties of living cells for therapeutic use