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Genetics > Human and Animal Development > Flashcards

Human and Animal Development Flashcards

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Biology 101 flashcards
1
Q

fertilised Zygote

A

——-> Cleavage (Embryonic Stem Cells)

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2
Q

After 32 cells

A

Cells multiply
and differentiate
(specialise)

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3
Q

Inner Cells

A

forms embryo

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4
Q

outer cells

A

forms placenta

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5
Q

3 1/2 days in MICE ——> 4 days

A

ENDODERM FORMS

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6
Q

IMPLANTATION IN WALL OF UTERUS

A

4.5 DAYS IN MICE
9 DAYS IN HUMANS

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7
Q

PRIMITIVE STREAK

A

6 days in mice
15 days in humans

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8
Q

Gastrulation

A

7 ½ days in mice
3 weeks in humans

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9
Q

Hind lib bud

A

9 days in mice
5 weeks in humans

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10
Q

Neurulation

A

Formation of spinal cord and brain (occurs after
gastrulation)

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11
Q

Organogenesis

A

Formation of organs

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12
Q

Spina bifida occulta

A

Common
No noticeable effects

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13
Q

Spina bifida cystica

A

Serious effects

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14
Q

Cranium bifida

A

Malformation of skull
Often stillborn

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15
Q

Epigenetics

A

*Cells are directed to specialise in different ways
*Controlled by genes being switched on and off
in different ways in different cells
*Professor Conrad Hal
Waddington (1905-1975)
*Proposed the term in 1940
*Professor Sir Adrian Bird (1947 - )
*Discovered the molecular basis
of epigenetics

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16
Q

continued

A

*Genetic changes not associated with changes in
the DNA sequence
*Genes permanently switched on/off
*determines cell type

17
Q

Genetics versus the environment

A

“nature – nurture debate”
*Clear genetic influences
* E.g. Haemophilia – presence of the defective
alleles causes the phenotype

18
Q

continued

A

Clear environmental influences
* E.g. Ricketts – vitamin D deficiency causes
phenotype

19
Q

continued

A

Example of both - Rhesus blood group and pregnancy
* Blood groups Rh+ and Rh-
Rh-Rh+ Blood
Transfusion
Generates
antibodies
against RH+
leading to severe
reaction

20
Q

continued

A
  • Problems during pregnancy
  • Rh- mother with Rh+ foetus
    Rh-
    1st RH+ child – no
    problems
    Mother
    generates
    antibodies
    against RH+
    Rh+ 2nd RH+ child – mother
    mounts an immune
    response against
    foetus - miscarriage
21
Q

continued

A

Example – temperature sensitive genes
* Siamese cat
* Growth in a cooler environment
produces a darker colour in
extremities – the pigmentation
gene is “switched on” in a cooler
environment

22
Q

Measuring the effects of Genetics
versus the environment

A

*Keep the environment constant
* E.g. plant genetics
*Keep the genetics constant (more difficult)
*Need for genetically identical individuals
* Inbred lines (e.g. laboratory mice)
* Cloning (e.g. “Dolly” the sheep)
* Twins

23
Q

Twin Studies

A

Heredity Environment
Identical twins
reared apart
Identical twins
reared together
Fraternal twins
reared together
Fraternal twins
reared apart
Identical Different
Identical Identical
Different Identical
Different Different

24
Q

Heritability

A
  • Probability that shared phenotypes are NOT explained by
    the environment or by chance
  • Gives an approximation of the contribution of genetics to
    a phenotype
  • For example, a heritability score of 80% means that there
    is probably a significant genetic effect
  • Can be determined by comparing phenotypes in
    monozygotic (MZ) and dizygotic (DZ) twins
25
Q

: Genetics of
Schizophrenia

A
  • Specific clinically defined category of neurodiversity
  • Long-term condition that involves psychosis
  • Difficulty in distinguishing own thoughts from reality
  • Long term debate about whether this is genetically
    inherited (nature) or induced by the environment
    (nurture)
    Case study: Genetics of
    Schizophrenia
  • Historically, (up to 1970s) – thought to be related to
    upbringing of children
  • Early studies in 1950s -1970s identified that it ran in families
  • a possible genetic influence?
  • Twin studies demonstrated a high degree of heritability
    Case study: Genetics of
    Schizophrenia
  • Historically, (up to 1970s) – thought to be related to
    upbringing of children
  • Early studies in 1950s -1970s identified that it ran in
    families - a possible genetic influence?
  • Twin studies demonstrated a high degree of heritability
  • Concept of “genetic susceptibility”
  • Other factors affect it, but only individuals that are
    genetically susceptible
    Case study: Genetics of
    Schizophrenia
  • 2017 Danish twins study (Hilker et al 2017)
  • Danish Twin register – started in 1954 and includes twins born
    from 1870 onwards
  • Complete records for all Danish-born twins born from 1968
  • Danish Psychiatric Central Research Register – all pyschiatric
    admissions since 1969
  • 31,524 twin pairs
    But other factors are involved…
  • Includes upbringing…but only if genetically susceptible
  • More schizophrenic individuals born in winter rather than
    summer….linked to influenza epidemics
  • Infectious agents – the parasite Toxoplasma gondii
  • Development errors in the brain of the brain (non-genetic)
  • Dietary…deficiency of essential fatty acids
  • So both nature and nurture contribute…and its com
26
Q

Genetics of intelligence

A
  • Need a Standardised measure of intelligence
  • Intelligence Quotient (IQ)
  • But does not measure all forms of intelligence
  • However, a strong correlation between IQ and success at
    school
    Case study: Genetics of intelligence
  • Twin studies show a heritability of around 50%
  • Moderate influence of genetics
    Case study: Genetics of intelligence
  • Twin studies show a heritability of around 50%
  • Moderate influence of genetics
  • 25% comes from the shared environment for the twins
  • 25% from their unique environment
    Case study: Genetics of intelligence
  • Twin studies show a heritability of around 50%
  • Moderate influence of genetics
  • 25% comes from the shared environment for the twins
  • 25% from their unique environment
  • Heritability increases with age (less than 40% at age 9 but as
    high as 80% beyond age 20)
  • Suggests that the environmental effects are more significant
    earlier in life
    Case study: Genetics of intelligence
  • Twin studies show a heritability of around 50%
  • Moderate influence of genetics
  • 25% comes from the shared environment for the twins
  • 25% from their unique environment
  • Heritability increases with age (less than 40% at age 9 but as
    high as 80% beyond age 20)
  • Suggests that the environmental effects are more significant
    earlier in life
  • So both nature and nurture contribute…and its
    complex
27
Q
A

Genetics (8 decks)

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