Chapter 2- Heredity, Environment, and the Brain Flashcards
1
Q
DNA
A
deoxyribonucleic acid
2
Q
Chromosomes
A
Structures that store and transmit genetic information in the nucleus of the cell, and mitochondria
3
Q
Gene
A
Segment of DNA along the length of a chromosome, codes for traits like eye color, enzyme production. There are two types of genes: protein-coding genes and regulator genes.
4
Q
How many pairs/total chromosomes are there?
A
23 pairs, 46 total chromosomes.
5
Q
What are the structural units of chromosomes called?
A
Nucleosomes
6
Q
Genotype
A
Genetic code
7
Q
Phenotype
A
Observable characteristics
8
Q
Protein-coding genes
A
Directly affect the body’s characteristics
9
Q
Regulator genes
A
Modify instructions given by protein-coding genes (control how other genes behave-> power to turn on or off protein-coding genes)
10
Q
DNA is wrapped around _________ protein structures, loosely or tightly.
A
Histone protein structures.
11
Q
What is the difference between loosely/tightly wrapped DNA?
A
Loosely wrapped- DNA is transcribed.
Tightly wrapped- DNA is methylated, cannot be transcribed, virtually inactive.
12
Q
What is the epigenome ?
A
The control panel for genes, using chemical tags such as methylation in response to the environment.
13
Q
Loosely wrapped DNA
A
Genes are accessible and can be read to make proteins.
14
Q
Tightly wrapped DNA
A
Genes are hidden and inactive.
15
Q
What happens to the structure of chromosomes in epigenetics as a response to inputs/environmental factors?
A
It changes. This regulates gene expression.
16
Q
Does every cell have the same DNA?
A
Yes, every somatic cell except for gametes has the same DNA/genes, but different genes are active, have been active, might become active, to produce tissue differentiation and maintenance.
17
Q
How do all somatic cells have the same DNA/genes but contribute to different functions?
A
Different genes are active; this produces tissue differentiation and maintenance. For example, skill cells activate genes for producing keratin, etc.
18
Q
What happens when chromatin is tightly compacted?
A
Genes in the compacted area cannot be transcribed or expressed. Genes cannot be transcribed into RNA, which is the first step in making proteins.
19
Q
Somatic cells are (haploid/diploid)
A
Diploid. 23 pairs, 46 strands of chromosomes.
20
Q
Gametes
A
Sex cells (sperm and ovum) created by meiosis of primordial cells in the gonads (testes and ovaries)
21
Q
Meiosis
A
Cell division process that halves the number of chromosomes normally present in body cells
- Gametes are haploid
- Crossing over in meiosis produces genetic variability, which is adaptive
- Meiosis begins with puberty for males and continues
- Occurs (mostly) prenatally for females, with maturation beginning in puberty; maturation stops in midlife
- Epigenetic marks need to be removed in production of gametes
22
Q
Zygote
A
Cell formed when sperm and ovum unite at conception. Contains 46 chromosomes.
23
Q
Crossing over in meiosis produces genetic variability, which is adaptive. Why is it adaptive?
A
Increases a population’s chances of surviving environmental changes.
24
Q
Gametes are… and have ….. chromosomes
A
Gametes are sperm cells and ova (cell cells) and have 23 single strand chromosomes, which eventually form a diploid zygote with 46 total chromosomes (23 pairs).
25
Human sex is determined by which pair of chromosomes?
The 23rd pair (last pair).
26
How many autosomes are in the genetic code?
22 matching pairs of chromosomes.
27
Which chromosomes are the sex chromosomes?
The 23rd pair of chromosomes.
28
Sex chromosomes: What are they for male/female, what is the size, what are possible ambiguities.
XX in females
XY in males
The X chromosome is relatively long; Y chromosome is short and carries little genetic material. Existence of people with intersex traits is redefining sex as a spectrum; there are multiple known and suspected causes. Babies may be born with ambiguous genitals, or genitals that are inconsistent with genetic sex.
29
Intersex
Babies may be born with ambiguous genitals or genitals that are inconsistent with genetic sex.
30
An early embro has 46 chromosomes, this is its karyotype (chromosomes arranged after staining). The embryo is?
Options:
One long strand (X) and one short strand (Y)= male.
Two long strands (XX)= female
Ambiguities in intersex?
31
Monozygotic twins
- What is their genetic material like?
Monozygotic= identical twins.
A single fertilized egg splits into two embryos (share 100% of their genetic material).
Monozygotic twins are genetically identical, share 100% of DNA.
32
Dizygotic twins
- What is their genetic material like?
Dizygotic= fraternal twins. Two separate eggs fertilized by two separate sperm cells.
Dizygotic twins share 50% of their genes, just like regular siblings.
33
Where there are 3 or more fetuses in one pregnancy,
Two or more may be identical.
Triplets can be a combination of identical twins and a fraternal sibling, or all could be identical.
The specific genetic relationship depends on how the embryos formed (whether one egg split into multiple embryos or if multiple eggs were fertilized).
34
Alleles
Two forms of a gene, one inherited from each parent
35
Homozygous
Alleles from both parents are alike
36
Heterozygous
Alleles differ
37
Dominant-recessive inheritance
Also called Mendelian inheritance.
- Only the dominant allele affects child's characteristics
- Heterozygous individuals can be carriers
- Homozygous inheritance of some recessive alleles can cause serious disabilities and diseases, such as PKU
38
Incomplete-dominance pattern
Both alleles are expressed in the phenotype, resulting in a combined trait or intermediate phenotype; example: wavy hair, hazel eye color
39
X-linked pattern
Harmful allele carried on X chromosome, so males are more likely to suffer from X-linked diseases.
40
Which sex is affected the most by X-linked disorders? Provide example
X-linked disorders affect males more severely than females.
Example:
Fragile X is caused by a change in the FMR-1 gene on the X chromosome. Fragile X affects around 1 in 4,000 males and between 1 in 5,000 and 1 in 8,000 females.
In the FMR-1 gene, the triplet word 'CGG' can be repeated too many times.
Production of FMRP is disrupted. FMRP is found primarily in neurons in the hippocampus and cerebellum.
41
Genes active or inactive in neural stem cells can influence all aspects of brain development. What are neural stem cells?
Precursor cells that give rise to all types of neurons + glial cells (support cells) in the brain.
42
Misregulation of genes in neural stem cells can lead to?
Developmental disorders, cognitive impairments, etc
43
Genomic imprinting
Epigenetic marking (imprinting) of alleles within the ovum or sperm; leads to parental-origin-specific expression of a small subset of genes in mammals.
Affects whether a gene will be active or silenced.
- One pair member is silenced, the other is expressed regardless of its makeup
Maternal imprinting: Maternal allele is silenced
Paternal imprinting: Paternal allele is silenced
Example: Prader-Willi syndrome; paternal chromosome 15 absent or silenced; mutation in meiosis or very early development
44
Genomic imprinting is an exception to the typical way in which gene copies are expressed. Why?
Either the maternal or paternal allele is silenced (turned off) of does not exist, and the other allele is expressed.
45
Maternal imprinting
Maternal allele is silenced, paternal allele is expressed.
46
Paternal imprinting
Paternal allele is silenced, maternal allele is expressed.
47
Mutation
Sudden, permanent change in segment of DNA. Can happen naturally or induced by environmental factors.
48
Germline mutation
A mutation occuring in cells that give rise to gametes (sperm/egg). Passed on.
49
Somatic mutation
A mutation occuring in normal body cells (non-germ cells). Not passed to offspring but can affect the individual where the mutation occurred, such as cancer.
50
Are germline mutations inherited?
Yes. In cells that give rise to gametes.
51
Are somatic mutations inherited?
No. Are body cells, not sex cells.
52
Polygenic inheritance
Many genes affect a characteristic, such as height, weight, intelligence, personality. Many factors (environment).
53
Aneuploidy
Wrong number of chromosomes
54
What is the most common case of aneuploidy (chromosomal disorder)?
Down syndrome, or Trisomy 21. An individual has an extra copy of chromsome 21 (3).
- Most common chromosomal disorder
- In 95% of cases, results from failure of 21st pair of chromosomes to separate during meiosis (non-disjunction)
- Consequences include intellectual disability, memory and speech problems, limited vocabulary, slow motor development
55
What can people do when concerned about genetic disorders?
- Pre-marital genetic testing
- Pre-pregnancy genetic testing
- IVF pre-implantation genetic testing
- Screening during pregnancy
- Use of donor sperm or ova
- Adoption
56
What are some environmental contexts that interact with biology/epigenetics?
- Family- particularly caretaking in infancy and toddler years
- Socioeconomic status
- Family functioning
- Affluence
- Poverty
- Neighborhoods and schools
- Cultural context
57
How does the environment affect development? Example of mouse in impoverished cage vs. enriched cage
Appearance of nerve cell in impoverished mouse cerebrum: Nerve cells in cerebrum are responsible for higher cognitive functions like learning and memory. Neve cell is less developed, more simplified. Fewer synapses, fewer branches. Appearance is poor. The brain's ability to form new connections/strengthen existing ones is limited due to environmental stimulation.
Appearance of nerve cell in enriched cage mouse cerebrum:
More complex nerve cell with more dendritic branches. Neuroplasticity enhanced (brain is more capable of adapting and forming new connections)
58
Experience-expectant plasticity
These experiences are expected during development for normal brain functioning. This form of development is not "genetically wired" but rather the genetic program for development needs to be triggered by experience; if the appropriate experience is not encountered, development does not proceed normally (language acquisition etc).
During early development, the brain forms neural connections in anticipation of certain sensory experiences, social interactions, and environmental stimuli. The brain expects visual input to form connections in the visual cortex. The brain expects auditory input for the development of language/auditory processing regions.
59
Experience-dependent plasticity
In this domain, plasticity continues throughout the course of the lifespan. No critical period (learning instrument, skill etc).
60
Experience expectant vs experience dependent plasticity- main difference
Experience expectant plasticity- has critical period (infancy/childhood/adolescence).
Experience dependent plasticity- skills learned etc, not required for healthy and normal development of brain.
61
Prenatal inputs to development from the environment
- Hormones
- Substances consumed by mother
- Mother's illnesses
- Late gestation (sounds, tastes and light)
62
Gene/Environment interactions influence phenotypes (physical, physiological, behavioral). Explain
Genotype is what is coded- but does not always translate to the phenotype. Phenotype is the expression.
The environment influences how genetic information is expressed and whether it is expressed.
63
How could environmental influence affect gene expression for height and weight?
Nutrient Availability-> height and weight can be influenced by nutrition during childhood, even if genetic potential for height is predetermined by genotype.
64
Do epigenetic changes change DNA sequences?
NO.
Experiences induce epigenetic changes. Nutrition induces epigenetic changes. Prenatal and early developmental epigenetic changes have long lasting effects.
But they are PHENOTYPIC variation (what is expressed), not what is present in the gene.
65
Individuals exposed to famine during pregnancy had babies with ________
LBW (low birth weight).
This indicates that prenatal nutrition is a key factor in shaping lifelong health, and early exposure to malnutrition can lead to epigenetic changes that have lasting effects on disease susceptibility.
66
Which trimester can epigenetics play the most SEVERE role?
1st trimester- fetus impacted the most severely by events such as chronic stress, famine etc.
67
Does normal variation in parental/maternal behavior have any impact on development? Is the mechanism epigenetic?
Most likely, yes. Higher observable from 1st trimester.
68
Effects of LG-ABN?
Licking, grooming, and arched back nursing.
-> Alters the expression of genes related to stress response in key brain regions (hippocampus, amygdala)
69
What is the difference between high and low LG-ABN on pups?
High LG-ABN: Increased GABA and central benzodiazepine receptor density, increased ability to handle stress. Larger receptor density correlates with less stressed response.
70
What is the effect of maternal care on the body's system for responding to stress (there is a name for this system)?
Maternal care changes the HPA axis, which is the body's system for responding to stress, including density of glucocorticoid receptors in Hpc.
Good care changes gene expression in a positive direction, lowers corticosterone levels. Lowers anxiety levels and is transmitted to the next generation.
71
Paternal care-> Epigenetic changes?
Yes.
Slowed the rate of aging in both males and females, but significantly more in males. Males who received paternal care are more likely to show "alloparenting," meaning they help care for pups. Early paternal interaction teaches males nurturing behaviors that they pass on.
72
Epigenetic transmission of maternal stress to children?
Exposure to extreme adversity increases methylation of the GR gene, integral in stress-hormone regulation.
73
Life history theory
Posits that early experience (both prenatally and in infancy) prepares/programs the individual for the type of world they will be living in.
74
What are the two components of life history theory?
Fast short life strategy and slow longer life strategy.
Fast short life strategy- be vigilant, anxious, mate early and often- the world is harsh
Slow longer life strategy- be relaxed, invest in development, mate later, producing fewer healthier offspring- the world is benevolent.
Either or can be adaptive if the early environment predicts the later environment.
75
What are the parallel phenomena to LG-ABN for humans?
- Sensitive and responsive care in the first years of life
- Attachment between infant and caretakers, secure attachment
76
Behavioral Genetics
- How is it studied
Seeks to answer the question: How do differences in behavior relate to differences in genetics?
- Family studies, twin studies (to observe prenatal and postnatal epigenetic changes)
77
What type of studies do behavioral geneticists use?
Family studies (particularly twin studies). Use correlational studies to estimate the heritability of various traits
78
Heritability
Estimate of proportion of variance in a phenotype within a population associated with genetic variance in that population. If heritability is 70%, genetics account for 70% of the variation in that population, with the rest due to environment or chance
79
Gene-environment correlation
Genes influence environments to which individuals are exposed
80
Passive correlation
Parents provide environments to which children respond (Parents are athletic, encourage sports, kids excel at sports bc genes)
81
Evocative correlation
Children evoke responses influenced by their heredity, which strengthen original behavior pattern. Natural traits (like outgoing or shy) cause others to react in certain ways, which can reinforce the child's behavior (such as a talkative child getting attention, making them talk more)
82
Active correlation
Children engage in niche-picking, actively seeking environments that complement their heredity (Children pick environments that fit their own interests/natural abilities. Such as a child who loves reading having the inclination to seek out libraries.)
83
Do psychological traits and disorders have a genetic component?
Yes. This affects risk, but does not determine health outcomes.
84
Study on children of schizophrenic parents-findings
Children adopted by well functioning families had no increased risk of developing schizophrenia.
Children adopted by poorly functioning families had greatly increased risk of developing schizophrenia.
85
Early brain development
Neurogenesis (the process by which new neurons are generated from neural stem cells) and migration along radial glia.
Circuits begin to form as axons and dendrites extend.
Spontaneous neural activity is essential for neurons to survive and connect to other neurons.
86
What factor is a major threat to development?
Childhood poverty
- Homelessness, housing insecurity, food insecurity, physical and psychological safety
