The Beginning
of Life:
Conception and
Genetics
PSY103
DEVELOPMENTAL PSYCHOLOGY
Hello, Love,
Goodbye.
• The Heroine: Ovum •
Corona radiata
Nucleus
Cytoplasm
Zona pellucida
Source: https://www.altrui.co.uk/resources /the-human-egg
-cell-explained/
• Bata, Bata… Kailan Ka Ginawa? •
Less fertile
(unlikely to
conceive)
25
24
23
26
27 28 1
2
3
Menstruation
(least fertile stage)
4
5
6
22
7
21
8
20
19
18
17
16 15 14 13
Possible to
conceive
12
9
10
11
Possible to conceive
Most fertile
• The Basics
A
B
C
Genetics
- the scientific study of genes and heredity
Heredity
- the sum of all biological processes by which particular
characteristics are passed on from parents to their offspring
Biological Psychology
- the study of the biological mechanisms of behavior and
mental processes
• Mechanisms of Heredity •
Requisite 1: CHROMOSOMES
- threadlike structures of nucleic
acid and protein found in the
nucleus of each cell
v
v
Autosomes
v
Sex chromosomes
• Mechanisms of Heredity •
v
Requisite 2:
DEOXYRIBONUCLEIC ACID
(DNA)
v
Genome
Source: https://nigms.nih.gov/education/factsheets/Pages/genetics.aspx#:~:text=%E2%80%8B%E2%80%8B%E2%80%8BWhat%20is,that
%20help%20the%20body%20work.
v
Requisite 3: CHEMICAL BASES
v
v
v
v
Adenine
Thymine
Guanine
Cytosine
Source: Pinel & Barnes, 2018
• Mechanisms of Heredity •
• Mechanisms of Heredity •
v
Requisite 4: GENE
- the sequence of bases in a portion of a DNA molecule that
carries instructions needed to assemble a protein
Source: https://www.genome.gov/geneticsglossary/acgt#:~:text=A%20DNA%20molecule%20consists%20of,needed%20to%20assemble%20a%20protein.
Chromosome
Base Pairs
Genes
Chromosome
Base Pairs
Genes
1
249 M
3000
13
110 M
800
2
240 M
2500
14
100 M
1200
3
200 M
1900
15
100 M
1200
4
190 M
1600
16
90 M
1300
5
180 M
1700
17
80 M
1600
6
170 M
1900
18
70 M
600
7
150 M
1800
19
60 M
1700
8
140 M
1400
20
60 M
900
9
130 M
1400
21
40 M
400
10
130 M
1400
22
40 M
800
11
130 M
2000
X
150 M
1400
12
130 M
1600
Y
50 M
200
• Gene Expression •
• Gene Expression •
1)
2)
3)
4)
5)
The genetic code stored in the DNA is copied to a similar molecule called
RNA (ribonucleic acid) in the cell of the nucleus (TRANSCRIPTION).
- Thymine is replaced by Uracil in the RNA
The messenger RNA (mRNA) carries the information from the DNA out of
the nucleus into the cytoplasm.
The mRNA interacts with a specialized molecular machine called a
ribosome, which reads the sequence of mRNA nucleotides (TRANSLATION).
- Each sequence of three nucleotides, called a codon (e.g., ATT, CTT,
TGT, GAT), usually codes for one particular amino acid (i.e., building
blocks of protein).
The transfer RNA (tRNA) assembles the protein using one amino acid at a
time.
Protein assembly continues until the ribosome encounters a “stop” codon.
Amino Acids
DNA Codons
Amino Acids
DNA Codons
Isoleucine (I)
ATT, ATC, ATA
Tyrosine (Y)
TAT, TAC
Leucine (L)
CTT, CTC, CTA, CTG,
TTA, TTG
Tryptophan (W)
TGG
Valine (V)
GTT, GTC, GTA, GTG
Glutamine (Q)
CAA, CAG
Phenylalanine (F)
TTT, TTC
Asparagine (N)
AAT, AAC
Methionine (M)
ATG
Histidine (H)
CAT, CAC
Cysteine (C)
TGT, TGC
Glutamic Acid (E)
GAA, GAG
Alanine (A)
GCT, GCC, GCA, GCG
Aspartic Acid (D)
GAT, GAC
Glycine (G)
GGT, GGC, GGA, GGG
Lysine (K)
AAA, AAG
Proline (P)
CCT, CCC, CCA, CCG
Arginine (R)
CGT, CGC, CGA, CGG,
AGA, AGG
Threonine (T)
ACT, ACC, ACA, ACG
Stop Codons (Stop)
TAA, TAG, TGA
Serine (S)
TCT, TCC, TCA, TCG,
AGT, AGC
Trait
Genes
Protein
Eye color
OCA2 (Chromosome 15)
P protein (controls melanin)
HERC2, ASIP, IRF4, SLC24A4, TYR
Black hair
MC1R
Melanocortin 1 receptor (produces
eumelanin)
ASIP, DTNBP1, GPR143, HPS3, MITF
Nose shape
GLI3
Zinc finger protein (controls the
breadth of nostrils)
PAX1
Paired-box protein Pax 1 (affects
the width and pointiness of the
nose)
Hair thickness
TCCH
Trichohyalin (found in hair follicles)
Athletic performance
ACTN3
Alpha actinin-3 (influence strength
and endurance of muscles)
Self-discipline
KATNAL2
Katanin Catalytic Subunit A1 Like 2
Sociability
PCDH15
Protocadherin Related 15
How Do Genes Influence
Development?
• Protein •
Type
Function
Example
Antibody
Binds to specific foreign particles (e.g., viruses &
bacteria) to help protect the body
Immunoglobuli
n (lgG)
Enzyme
Carry out almost all of the chemical reactions that
take place in cells; assist with the formation of new
molecules by reading the genetic information
stored in DNA
Phenylalanine
hydroxylase
Messenger
Transmit signals to coordinate biological processes
between different cells, tissues, and organs
Growth
hormone
Structural
Component
Provide structure and support for cells; allow the
body to move
Actin
Transport/Storage
Binds and carry atoms and small molecules within
cells and throughout the body
Ferritin
• Genes •
Genotype
the set of genes that
make up a person’s
heredity
Phenotype
an individual’s
observable physical,
behavioral, and
psychological traits
• Allele •
Homozygous genotype
Having inherited the same version or allele of
a gene from each biological parent
Heterozygous genotype Having inherited different versions or alleles
of a gene from each biological parent
Rules that govern the way genotypes
influence phenotypes
1. Dominant-recessive
pattern
a pattern of inheritance in which
a single dominant allele is enough
to influence a phenotype
(complete dominance), but two
recessive alleles are necessary to
produce an associated trait
Dominant allele
variation of a gene that will
produce a phenotype even if
only one copy of it is inherited
Recessive allele
variation of a gene that will
produce a phenotype only if
it is inherited from both
parents
Rules that govern the way genotypes
influence phenotypes
2. Codominance
3. Incomplete dominance
a pattern of
inheritance in which
two alleles of the
same gene are both
expressed in an
individual
a pattern of
inheritance in which
the dominant allele
is only partially
expressed
4. Polygenic inheritance
a pattern of
inheritance in which
many genes
combine to form a
phenotype
Rules that govern the way genotypes
influence phenotypes
5. Mitochondrial inheritance
a pattern of inheritance in which
the genes that produce a
phenotype are carried in the
mitochondria
Rules that govern the way genotypes
influence phenotypes
6. Multifactorial inheritance
A pattern in which
heredity (genotype) and
environment interact to
bring about a phenotype
The environment
can affect genetic
expression
Genes can influence
the kind of
environment to which
a person is exposed
- niche-picking
Environmental influences
typically make children
within a family different
Gene Variant
What is a gene variant?
How can gene variants affect
health and development?
How do gene variants
occur?
Do all gene variants
affect health and
development?
What kinds of gene variants are possible?
Missense
variant
(substitution)
What kinds of gene variants are possible?
Nonsense
variant
(substitution)
What kinds of gene variants are possible?
Insertion
What kinds of gene variants are possible?
Deletion
What kinds of gene variants are possible?
Duplication
What kinds of gene variants are possible?
Repeat
expansion
Genetic Disorders/Conditions
Autosomal dominant disorder
●
One altered copy of the
gene in each cell is
sufficient for a person to
exhibit a genetic condition.
Genetic Disorders/Conditions
Autosomal Dominant Disorder
Disorder
Description
Causes
Huntington
disease
Progressive brain disorder that
causes uncontrolled movements,
emotional problems, and loss of
thinking ability
Mutations in the HTT gene
produce the CAG trinucleotide
repeat for 40 to 120 times.
Blue-yellow
color vision/
defects
Problems with differentiating shades
of blue and green and cause difficulty
distinguishing dark blue from black
Altered OPN1SW gene leads to
the premature destruction of the
S cones
Familial
hemiplegic
migraine
Involves severe migraine headaches
and episodes of fever, seizures,
prolonged weakness, coma, memory
loss, difficulty with speech, confusion,
and drowsiness.
Mutations in the CACNA1A,
ATP1A2, SCN1A, and PRRT2 genes
affect the nerve cells and
neurotransmitters.
Genetic Disorders/Conditions
Autosomal recessive disorder
●
Two copies of the gene
variant is needed for an
offspring to develop a
disorder
Autosomal Recessive Disorder
Disorder
Description
Causes
Phenylketonuria Characterized by harmful
(PKU)
levels of phenylalanine,
leading to brain damage,
intellectual disability,
seizures, delayed
development, behavioral
problems, and psychiatric
disorders
Variations in the PAH gene
produce altered versions of
phenylalanine hydroxylase
(enzyme), resulting in the buildup of toxic levels in the blood and
other tissues
Cystic fibrosis
Mutations in the CFTR gene
produce mucus that is unusually
thick and sticky which clogs the
airways and various ducts of the
lungs, pancreas, and other organs
Progressive damage to the
respiratory system (chronic
coughing, wheezing,
inflammation) and chronic
digestive problems
- multifactorial inheritance
Autosomal Recessive Disorder
Disorder
Sickle cell
disease
* sickle-cell
trait
Description
Characteristic features include
a low number of red blood cells
or anemia, repeated infections,
yellowing of the eyes and skin,
and periodic episodes of pain
Causes
Mutations in the HBB gene produce
atypical hemoglobin molecules in
red blood cells, hence negatively
affecting the delivery of oxygen to
cells throughout the body
- multifactorial inheritance
Tay-Sachs
disease
Characterized by neurological
problems, muscles used for
movements are weak,
involuntary muscle twitches,
seizures, difficulty swallowing,
vision and hearing loss,
intellectual disability
Variants in the HEXA gene affect the
ability of the beta-hexosaminidase A
enzyme to breakdown a fatty
substance (GM2 ganglioside), leading
to the dysfunction of neurons in the
central nervous system
Sickle Cell Disease
Genetic Disorders/Conditions
X-linked dominant
disorder
●
A disorder
caused by a
variant in one
copy of the gene
on the X
chromosome
X-Linked Dominant Disorder
Disorder
Description
Causes
Fragile X
syndrome
The characteristic features
include learning disabilities
(delayed speech by age 2),
cognitive impairment, anxiety,
hyperactive behavior, a long and
narrow face, large ears, flat feet,
and enlarged testicles after
puberty
Mutations in the FMR1 gene
result in a CCG triplet repeat
for 55 to 500 times which turns
off the FMR1 gene, leading to
disruptions in the nervous
system functions
X-linked
chondrodysplasia
punctata 2
Characterized by spots near the
end of bones, shortening of the
bones in the upper arms and
thighs, dry, scaly patches of skin,
and eye abnormalities (cataracts,
small eyes, small cornea)
Alterations in the EBP gene
prevent cells from producing
enough cholesterol needed for
normal embryonic
development and the
development of hormones and
digestive acids
Genetic Disorders/Conditions
X-linked recessive
disorder
●
A disorder
caused by a
variant in one
copy of the gene
on the X
chromosome for
males, but two
copies of the
mutated gene
for females
X-Linked Recessive Disorder
Disorder
Description
Causes
Hemophilia
A bleeding disorder that
slows the blood clotting
process
Variants in the F8 or F9 gene lead to
the production of an abnormal version
of the protein called coagulation factor
VIII or IX, as a result, blood clots
cannot form properly
Red-green
color
blindness
Have trouble distinguishing Mutations in the OPN1LW or OPN1MW
between some shades of
lead to an absence of L or M cones or to
red, yellow, and green
the production of abnormal opsin
pigments in these cones that affect
red-green color vision
Genetic Disorders/Conditions
Y-linked disorder
●
A disorder
caused by an
altered gene
located on the Y
chromosome
Y-Linked Disorder
Disorder
Y chromosome
infertility
Description
Difficulty in fathering
children; may produce no
mature sperm cells
(azoospermia), fewer than
the usual number of
sperm cells
(oligospermia), or sperm
cells that are abnormally
shaped or that do not
move properly
Causes
Deletions of genes in the
azoospermia factor regions of the Y
chromosome, which prevent the
production of one or more proteins
needed for normal sperm
development
Genetic Disorders/Conditions
Mitochondrial
disorder
●
A disorder
caused by
variants in
mitochondrial
DNA
Mitochondrial Disorder
Disorder
Description
Causes
Leber
hereditary optic
neuropathy
(LHON)
Characterized by
blurring and clouding of
vision, which may lead to
severe loss of visual
acuity and color vision
Mutations in the MT-ND1, MT-ND4,
MT-ND4L, or MT-ND6 gene in the
mitochondria disrupt the making
of proteins involved in normal
mitochondrial function (i.e.,
converting oxygen, fats, and simple
sugars to energy
Chromosomal Error
A disorder characterized by an
extra or a missing chromosome
May occur during the
formation of gametes, in
early fetal development, or in
any cell after birth
Trisomy 21 (Down Syndrome)
A disorder associated
with intellectual
disability, a distinct
facial appearance, weak
muscle tone (in infancy),
small ears, a short neck,
small hands and feet,
and an increased risk of
developing several
medical conditions
Turner Syndrome (XO)
Ø
Affects females
Ø
One copy of the X chromosome is
missing or altered
(translocations, deletions,
duplications)
Ø
Features include a short stature,
reduced functioning of the
ovaries, egg cells die
prematurely, absence of puberty
Klinefelter Syndrome (47, XXY)
Ø
Affects males
Ø
Characterized by small testes,
reduced amount of testosterone,
delayed or incomplete puberty,
breast enlargement, decreased
muscle mass and bone density, a
reduced amount of facial and body
hair, and infertility
Triploidy