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Flashcards in Genetics and Brain Development Deck (161)
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1

Spinal bifida

Neural tube disorder that causes the bottom of the spinal cord to not close

2

Embryonic brain regions of the hindbrain

Mesencephalon and myelencephalon

3

Where does myelination start and where does it lead to?

Occurs in the rostral direction starting with the spinal cord, then hindbrain, midbrain, and forebrain

4

What does blue light do in optogenetics?

Activates on opsin called channelrhodopsin to allow positive ions in the neuron for firing of the neuron

5

Examples of sex-linked characteristics?

Hemophilia and color blindness

6

Characteristics of the candidate gene approach

hypothesis driven, confirmatory, systematic scanning

7

What is neurogenesis?

Formation of neurons and glia from stem cells

8

How many mutations are in the average new born?

Around 130 new mutations with most having little to no effect

9

How are genes arranged?

Linearly on chromosomes

10

Genetic disorders

Fragile-X syndrome, phenylketonuria (PKU), down syndrome

11

When does plasticity occur?

Growth and development, learning: long term potentiation and enriched environments, following injury (limited), and possibly adult neurogenesis

12

What happens with synapses in people with schizophrenia and Alzheimer's?

Too few synapses in schizophrenia and normal in Alzheimer's until older age when there are far too few

13

What is cell migration?

Cells in the cerebral cortex arrive in an inside-out fashion

14

What does retroviral gene therapy do?

A virus enters a host cell and the virus inserts its DNA into the host's DNA. The cell makes virus genes and proteins as it reads its own DNA.

15

How many genes are in the human genome?

about 23,000

16

What happens during differentiation in the dorsal-ventral axis?

Neurons are distinguished between sensory and motor

17

Where are progenitor cells found?

The ventricular zone lining the neural tube

18

What is a genotype?

A person's 23 pairs of chromosomes

19

Example of a CNV

Huntington's disease. Too many copies of a gene, specifically too many CAG repeats.

20

Abnormalities in synaptogenesis and neurocognitive disorders

Schizophrenia has less connections. Autism has a lot of immature spines

21

How do growth cones form synapses?

Growth cones approach muscle fibers, they make contact, and synaptic vesicles accumulate in axon terminal and synaptic receptors cluster at point of contact

22

What has to be taken into account when assessing heritability?

Environment

23

What does a heritability value of 0 represent?

Genes play no role in phenotypical differences. Ex - environmental toxin exposure

24

What is plasticity?

They nervous systems ability to change

25

How many pairs of autosomes?

22

26

What is histone modification?

Epigenetics. DNA may unwrap or be stopped from unwrapping from the histone

27

What is a gene?

Segment of DNA that produces a single protein

28

What are alleles?

Different versions of a gene

29

What is the mesoderm?

Middle germ layer that becomes connective tissue such as ligaments, muscles, blood vessels, and urogenital system

30

Down syndrome

Genetic disorder caused by extra chromosome

31

When is the peak amount of synapses in the visual cortex?

Around 5 months. Toys are brightly colored at this age

32

What kinds of things happen during synaptic pruning?

Late connections are killed, less efficient connections are killed, and even some neurons are killed through apoptosis

33

What does inside-out migration mean when speaking about neural migration?

Layer 6 develops first, then 5, etc. Layer 6 is the deepest and layer 1 is closest to the skull

34

What does a heritability value of 100 represent?

Genetics are completely responsible for phenotypical differences. Ex - Huntington's disease. If you have the gene, you have the disease

35

What are examples of a SNP?

Cilantro. 10% of population thinks it tastes like soap. Mutation in smell.
ApoE4. 2 copies of it have a 90% chance of Alzheimer's. Both amino acids are arginine

36

What types of studies are used in heritability?

Twin and adoption studies. Minnesota study of twin reared apart

37

What is activity dependence?

The more it is active, the more it used. Use it or lose it

38

Gene x environment interaction with BPA and the agouti phenotype

Rats with a high BPA diet expressed the agouti phenotype. They were much larger and lightly colored

39

Embryonic brain region of the midbrain

Mesencephalon

40

Genetic modification approaches

Knock in or transgenic models, knock out deletion, optogenetics, CRISPR-CAS9 gene editing, retroviral gene therapy

41

What type of unplanned genetic diversity is sickle cell anemia?

Mutation

42

How are genes expressed?

Transcription to translation to amino acids combining to form completed proteins

43

What are dizygotic twins?

Fraternal

44

How does histone modification work?

A methyl group (CH3) or other molecules bind to the tails of histones, either blocking them from opening or allowing the to open for transcription

45

Example of a critical period

Learning a language

46

How does optogenetics work?

Insert specific channels from algae. Light opens and closes these channels.

47

How is epigenetics involved in mRNA modification?

mRNA translation may be blocked or enabled. ncRNA binds to mRNA preventing translation

48

What is concordance?

A match, or agreement, of a trait. Both twins have it

49

When is the prefrontal cortex completely myelinated?

Early adulthood around 21-25

50

Brain structures of the telencephalon

Cerebrum (includes cerebral cortex, white matter, basal nuclei)

51

What does heritability refer to?

A population, not an individual

52

Where are most human trait values of heritability?

30%-60%

53

Environmental toxins causing disorders of brain development

Fetal alcohol syndrome and prenatal exposure to other drugs

54

What studies are used to study behavioral genetics through family linkage?

Family studies, twin studies, adoption studies, and sibling studies

55

When does myelination occur?

23 gestational weeks. Burst around birth. It occurs in bursts and is less gradual than most processes

56

What does synaptic pruning do?

Reduces the number of functional synapses. Efficiency process that focuses on the connections that matter

57

How does neurogenesis happen?

Progenitor cells divide by mitosis. They can become a lot of different things

58

Where does neurogenesis originate from?

Cells in the ventricular zone

59

What might relate to critical periods?

Myelin bursts and neurotrophins available in large or small amounts

60

What happens in apoptosis?

Cells dies through programmed cell death

61

What influenced synaptic pruning?

Neurotrophins and functionality of the synapse

62

What do genome wide association studies do?

Look at patient DNA and non-patient DNA to compare differences to discover SNPs associated with diseases

63

Example of higher heritability

Schizophrenia

64

What does synaptic density reach adult levels?

18 years

65

What are filopodia?

Long, fingerlike extensions from growth cones of neurities. They detect chemicals from other cells

66

How does the body know which parts are part of which segment during differentiation?

Hox genes

67

What is an example of what SNPs can do?

SNPs in the APOE gene can predict risk for Alzheimers disease

68

Where are the motor neurons in the spinal cord?

Ventral half. Ventral root in spinal cord.

69

Examples of planned genetic diversity

Crossing-over, meiosis, sexual reproduction

70

Where are the sensory neurons in the spinal cord?

Dorsal half. Dorsal root in the spinal cord

71

What is a phenotype?

Observable characteristics

72

What is the control referred to in knock-in and knock-out studies?

wild type

73

How does epigenetics explain differences in identical twin DNA?

As they get older, the twins will act different from each other but still have the same DNA

74

What is the ectoderm?

Outer germ layer that becomes skin and neural tissue

75

What happens during differentiation in the rostral-caudal axis?

The parts of the nervous system are segmented. Spinal cord, myelencephalon, mesencephalon, diencephalon, and telencephalon

76

Six stages of neural development

1.) neurogenesis
2.) migration
3.) differentiation
4.) circuit formation
5.) neuron death (apoptosis)
6.) pruning and rearrangement of connections

77

Examples of unplanned genetic diversity

Mutations, sing nucleotide polymorphisms (SNPs), copy-number variations (CNVs)

78

What are single-nucleotide polymorphisms (SNPs)?

DNA sequence change at one nucleotide

79

What do progenitor cells do?

Neurogenesis through mitosis. Neural or glial

80

Changes in gene expression or phenotype that don't involve changes to the DNA sequence. Changes how DNA is used based on experience

Epigenetics

81

What happens during puberty?

A period of cortical thickening followed by thinning

82

Where was adult neurogenesis first discovered?

In rodent hippocampus and olfactory bulbs

83

Brain structures of the diencephalon

Thalamus, hypothalamus, epithalamus

84

What are axons?

Coding sequences

85

What is the human genome?

set of instructions for constructing a human being

86

When is the brain fully mature and when does it start to decrease in weight?

25 and 45

87

Are sex-linked characteristics more common in males or females?

Males

88

Which genotype is riskiest when contributing to the serotonin transporter gene?

The short/short genotype bc it is the gene and the environment playing a role in emotional problems related to stressful life events

89

What happens during neuronal maturation and circuit formation?

Growth cones move out to form neural connections

90

What are copy-number variations (CNVs)?

Variable numbers of genes or gene series

91

When does the highest number of synapses occur?

Childhood

92

Wide spread vs specific mutations

Depends on how many genes are impacted

93

The three stages of prenatal development

Zygote to embryo to fetus

94

What are critical periods?

Time when particular experience is influential and after which experience has little or no effect

95

How do genetic mutations occur?

Can occur spontaneously or in response to radiation, chemicals, or other mutagens

96

What is discordance?

A non-match, or disagreement, of a trait. One twin has it and the other doesn't.

97

What does a heritability value of X=X% represent?

X% of the population variation we see in a trait can be accounted for by genetic differences.

98

How many pairs of sex chromosomes?

1

99

What is heritability?

The contribution of genetics to the variation of a trait observed in a population

100

What are monozygotic twins?

Identical

101

What is PKU?

Phenylketonuria. Genetic disorder that causes an inability to process the amino acid phenylalanine

102

When is the peak amount of synapses in the prefrontal cortex?

Around ages 1-5. Elementary school and learning how to raise hand, ask to go to the bathroom, etc.

103

Where do neurons move from and where do they move to in neural migration?

Move from ventricular zone of fetal tube to their final location. They start in the center and move out. They move with the help of radial glia

104

Why do teens often feel like everything is against them?

Their amygdala is developing

105

What are the two ways epigenetics work?

Blocks gene to stop transcription, expression.
Unlocks gene to allow transcription, expression.

106

What proteins are associated with motor neurons?

Sonic hedgehog protein

107

What does CRISPR-CAS9 gene editing do?

Guide RNA carries a guide sequence of DNA to a cell along with the Cas9 protein. The guide RNA attaches the DNA strand with it to the target DNA and the Cas9 protein cuts the guide RNA out and they leave. The DNA is swapped into the place of the old DNA and the resulting DNA is edited

108

How is the neural tube closed?

Neural plate to neural groove to the neural tube. Neural plate on ectoderm that folds in creating the neural groove that digs in the mesoderm and closes off to form the neural tube inside the mesoderm below the ectoderm.

109

Stages of apoptosis

Cell death genes to activate caspases to breakup DNA and proteins to cell death

110

What does transcription do?

DNA partially unwinds and a strand of complementary RNA is made. It makes RNA

111

What does translation do?

RNA instructs ribosomes to produce amino acids. RNA to amino acids

112

Why do teens exhibit risky behavior?

Immature connections between the limbic system, prefrontal cortex, and amygdala

113

What does yellow light do in optogenetics?

Activates off opsin called halorhodopsin to allow negatively charged ions in the neuron to stop the neuron from firing

114

Signs of early differentiation in prenatal development

Germ layers, neural plate, neural groove, neural tube, prosencephalon, mesencephalon, and rhombencephalon

115

How many cells are made a minute in neurogenesis?

Up to 250,000

116

Dominant, codominant, and and recessive alleles

Dominant - always expressed
Codominant - expressed sometimes
Recessive - both expressed

117

What proteins are associated with sensory neurons?

BMP protein

118

Homozygous vs heterozygous alleles

Homozygous - copies are the same
Heterozygous - copies are different

119

Microcephaly and anencephaly

Neural tube defect that causes part of or all of the cortex to not develop

120

What is the endoderm?

Inner germ layer that becomes many internal organs

121

Brain structures of the mesencephalon

Midbrain (part of the brainstem)

122

When is the peak number of synapses in the brain?

It is different for different areas of the brain

123

What happens during synaptic rearrangement?

Synapses are rearranged from a diffuse pattern to a more focused pattern

124

What are sex-linked characteristics?

Recessive genes on one X chromosome that are not duplicated on the Y chromosome will be expressed in male offspring

125

Characteristics of genome wide association study

Data-drive, exploratory, relies on mutation map

126

Gene x environment interaction with the serotonin transporter gene, stress, and depression

Does not show complete dominance, two alleles (short and long), emotional problems in response to stressful life events or frequent bullying

127

What happens with synapses in people with autism?

They have too many synapses

128

The three germ layers and what will they become?

Ectoderm, mesoderm, and endoderm. They will grow into something else

129

How does cell migration occur?

Cells are guided by radial glia

130

Negative effects of sickle cell

Poor oxygen capacity. Bad on mountain top

131

How is epigenetics involved in DNA modification?

Transcription of DNA in mRNA may be enabled or blocked. It is blocked by methyl groups binding to CG base pairs to block transcription

132

Embryonic brain regions of the forebrain

Telencephalon and diencephalon

133

How are positive, neutral, and negative effects of mutations determined?

Depends on content of the environment

134

What do mice in complex environments show in their neurons?

More branches and spines

135

What are CNVs associated with?

Huntington's disease and Down syndrome

136

Example of lower heritability

Anxiety

137

What are lamellipodia?

Flat, sheet like extensions from core of growth cones

138

When is concordance used?

Twin studies

139

Brain structures of the myelencephalon

Medulla oblongata (part of the brainstem)

140

Why do teens need more sleep than older adults?

Higher myelination levels lead to increased need for sleep

141

Positive effects of sickle cell

Protection against malaria. Good in jungles

142

What do decreased levels of dopamine and serotonin lead to?

Mood swings, sensation seeking, and emotional regulation problems

143

What is fasiculation?

When neurons bundle to follow the same path. They like to do this

144

Increased amounts of what can affect the limbic system?

Estrogen and testosterone

145

What are mutations?

Errors in DNA replication

146

Brain structures of the mesencephalon

Pons (part of the brainstem) and cerebellum

147

What do amino acids do in gene expression?

Combine to form completed proteins

148

What are neurotrophins?

Help neurons to grow and thrive

149

How does fetal alcohol syndrome occur?

Binge drinking in the second and third trimester

150

What are the two parts of a growth cone?

Filopodia and lamellipodia

151

What type of process is epigenetic?

Dynamic. It is constantly changing and happening

152

Imprinted allele

Genes are expressed in a parent of origin manner

153

What does the knock-out approach do?

Take genetic info and cut it out to see what happens

154

What are introns?

Noncoding sequence found between axons (regulatory genes). Not tied to protein but often regulatory

155

Brain changes related to healthy aging

Medial temporal lobe areas involved with memory and executive pathways connecting basal ganglia and frontal lobes

156

What do growth cones do?

They test which way the neuron should expand

157

What roles might neurogenesis play?

Adult learning and memory, cognitive decline in decline of neurogenesis, multiple reserves help resist loss of function

158

What does the knock-in approach do?

Take genetic info from other species and add it to a different species. Humanizing a mouse

159

How do neurotrophins impact apoptosis?

Cells compete for a finite amount of resources and if they can't get enough neruotrophins, they die due to enzymes

160

How many nucleotides in the haploid and diploid human genome?

3 billion haploid and 6 billion diploid

161

What is epigenetics?

Heritable changes in gene activity and expression