1.5 DEVELOPING MAN BLOCK SUMMARY
Problem 1
Shaffer (46-58), (89-108), Berk (74-107)
CELL-NUCLEUS-CHROMOSOMES-DNA-GENES
HEREDITARY INFLUENCES ON DEVELOPMENT
Genotype: The genes that are inherited.
Phenotype: The observable traits of genes.
Chromosomes: structure made up of DNA. (23 pair of chromosomes)
DNA: long double stranded molecule that can duplicate itself (mitosis). Make up
the chromosomes. Storage of genetic information.
o Has bases. (A,T,C,G)
Genes: are segments of DNA.
o Sending assortments for protein synthesis.
o Characteristics.
Hereditary material present in human zygote: 46 chromosomes (23 from mom and
23 from dad).
Alleles: Each form of gene. (There are 2 forms of each gene, one from mom and
other from dad at the same place)
Somatic cells: body cells
Haploid (n): 23, Diploid (2n): 46
Autosomes: human chromosomes. 22 pairs.
Sex is determined by the 23rd pair. Sex chromosomes: X and Y. (XX female, XY
male)
GROWTH OF ZYGOTE AND CELL DIVISION
Mitosis
2-4-8-16 (2n)
Chromosomes duplicate themselves before division.
Result: 2 new cells which has identical pairs of
chromosomes.
Diploid (2n) =46
Somatic cells that are divided by mitosis form
muscles, bones, organs.
Continues throughout life. (healing and growing)
MEIOIS AND SEX CELLS
4 new cells, with halved number of chromosomes. Haploid (n)=23
Aside from body cells, germ cells produce gametes. (sperm, ovum) (they meet and
form zygote)
Homologous chromosome pairs: contains versions of the same gene/alleles on
the same spot for a given trait.
Independent assortment: each pair of chromosomes segregates independently of
all other chromosome pairs during meiosis.
Chromosomes duplicates itself before division.
X. Cross-over: XX (homologous chromosome). Trading sections from DNA
(exchanging genetic material). (genes)
2 new diploid cells (2n) that are unique. I.
4 new haploid cells. (n)
Crossing over is adaptive because: phenotypic changes that could change the
survival rate.
MULTIPLE BIRTHS
, Identical twins: one egg is fertilized by one sperm. Zygote divides into 2.
(monozygotic)
Fraternal twins: two eggs are fertilized by 2 sperms. Two zygotes that are
genetically different. (dizygotic)
HOW DO GENES WORK
Regulatory/modifier genes: “turn on” genes responsible for specific tasks.
SINGLE GENE INHERITANCE PATTERNS
1) Simple dominant recessive inheritance
o Many human traits are influenced by 1 pair of genes. (alleles)
o Dominant allele (brown eyes), recessive allele (blue eyes)
o AA, aa: homozygous, Aa: heterozygous.
o If each parent is Aa, they have a change to form a child with the recessive trait
(aa). %25. (both parents are carriers)
o Punnett square.
2) Codominance
o The phenotype they produce is a compromise between 2 genes.
o Ex: alleles for human blood type A and B are equally expressive, neither one is
dominant.
o AB blood type: codominance.
o Incomplete dominance: when one of two heterozygous alleles are stronger than
the other but fails to mask all the effects of the recessive allele.
3) Sex linked inheritance/X linked inheritance
o Some traits are determined by genes that are located on sex chromosomes.
o Generally: x linked recessive. (males have more problem because females have 2
sets of X chromosomes) (they can be carriers whereas males can’t)
4) Polygenic inheritance
o When a trait is influenced by many pair of alleles. (polygenic traits)
o Height, weight, intelligence, skin color.
5) Genomic imprinting
o Alleles are imprinted or chemically marked, so that one pair member is activated
regardless of its’ makeup.
HEREDITARY DISORDERS
Congenital defects: present at birth.
Chromosomal abnormalities
Abnormalities in sex chromosomes:
o When a germ cell divides during meiosis the distribution of 46 chromosomes are
sometimes uneven.
o One gamete has too many chromosomes whereas other gametes have less of a
chromosome.
o Turner’s syndrome (1/1200-4000): Underdeveloped breast, broad chest, female,
sterile, short, problems in spatial relationships, normal verbal intelligence. XO
o Superfemale (1/1000): Fertile, tall, impaired verbal intelligence, menstrual
irregularities. XXX, XXXX.
o Klinefelter’s syndrome (1/1000): Phenotypically male with some female
secondary sex characteristics. Hips and breasts. Tall. Underdeveloped testes:
infertile. Verbal deficiency.
XXY.
o Supermale: Taller than
normal. Fertile, more violent
and aggressive. XYY.
o Fragile X: mental
retardation.
Abnormalities in autosomes:
o 47 chromosomes.
,o 3 chromosomes in one spot: trisomy.
o Trisomy-21: Down syndrome: mildly or moderately intellectually impaired.
Congenital eye, ear, heart. (1/800)
Genetic abnormalities
Dominant alleles: the child will develop the disorder by inheriting the dominant
allele from either parent.
1. Huntington’s disease (1/18000-25000): uncontrolled movements does not develop
until 40 years.
Recessive alleles: sickle cell anemia, color blindness, PKU.
1. PKU (1/18000): they lack enzyme that converts a basic amino acid into byproduct.
Without enzyme, phenylalanine builds up to toxic levels that damage CNS.
2. Sickle cell anemia (1/500): sickle shaped blood cells, contain less oxygen.
3. Color-blindness.
Mutation: changes in the chemical structure of a strand of DNA. Some mutations
could be beneficial: sickle cell anemia prevents people from malaria.
PRENATAL DEVELOPMENT
After conception: In fallopian tube the sperm enters to the ovum = zygote
(contains biochemical material from mom and dad to form a single cell to a
developed human being).
1) Zygote (conception through implantation to uterus) (0-14 days) Geminal.
o Divides by mitosis a lot of cells: blastocyst: 60-80 cells within 4 days after
conception. (cell differentiation)
o Inner layer of blastocyst: forms embryo (embryonic disk), outer layers forms:
tissues that protect and nourish the embryo.
o Implantation: Blastocyst reaches the uterine wall and tendrils burrow inward. (7 th
to 9th day) Blood starts to grow a house for the baby.
o Development of support systems:
Amnion: Watertight sac, has amniotic fluid. Cushion the developing organism
against movements, regulate temperature.
Yolk sac: produces blood cells until the embryo is capable to produce. (liver and
bone marrow)
Chorion: surrounds the amnion, has blood vessels that becomes the lining of
placenta.
Placenta: Is fed by blood vessels from pregnant woman.
Barrier that prevents the blood of mom and baby from mixing.
Semipermeable. O2, CO2, salt, sugar and proteins can pass, blood cells can’t.
Waste products such as CO2 will travel through umbilical cord to mother where it
will be absorbed to mother’s bloodstream and thrown out.
Allantois: forms the umbilical cord (connects embryo to the placenta)
2) Embryo (beginning of the 3rd week/implantation - end of 8th) Embryonic.
the embryonic disk differentiates into 3 layers.
Ectoderm: Nervous system, skin and hair.
Mesoderm: Muscles, bones and circulatory system and internal organs.
Endoderm: Digestive system, urinary tract, lungs and glands.
o A portion of ectoderm folds into neural tube to become brain and spinal cord.
o All the major organs are formed including heart and liver (blood production) (no
need to yolk sac)
o Production of neurons. Glial cells develop. Synapses increase.
o Face, eyes, nose, mouth begin to form.
o Sense of touch emerges.
o MOST RAPID GROWTH EVER. MOST SENSITIVE PERIOD.
o 7-8 weeks: Sexual development of baby. (undifferentiated gonads)
, 3) Fetus (9th week - baby is born) Fetal.
o All major organ systems begin to function.
o Coordination between systems. (NS, organs, muscles)
o Sexual development: testosterone: testes. No testosterone: ovaries.
o By the end of 3rd month, the sex of the baby can be detected.
o Visual and auditory senses are functional.
7th through 9th month (third trimester)
o Age of viability: Survival outside of uterus is possible.
o Sleep wake routines. Motor activities.
o Finishing phase.
o Layer of fat is added: temperature regulation.
o Baby receives antibodies from mother’s immune system against illnesses till their
own immune system starts to work.
TRIMESTER SHOWS TIME, STAGES SHOWS THE DEVELOPMENT OF
STRUCTURES.
POTENTIAL PROBLEMS IN PRENATAL DEVELOPMENT
Teratogens: Any disease, drug or agent that can harm a developing embryo or
fetus by causing physical deformities, retarded growth, blindness, brain damage.
Additive effect of different teratogens.
The effects of teratogens are worst during the sensitive period. (most rapid
growth)
o Sensitive period: Each major organ system or body part has a sensitive period,
when it is most susceptible to teratogens.
o Zygote: before implantation. Rarely have some impacts.
o Embryonic: effects are most likely to occur.
o Fetus: lower effects. brain, ears, eyes genitals can be strongly affected.
Individual differences: Susceptibility to teratogen: determined by mother’s
genetic makeup
Dosage principle: Longer the exposure to teratogen more damage it can cause.
Age of the mother: menopause, aging of reproductive organs.
Sleeper-effect principle: Some teratogens are not appeared until later.
Quality of the post and prenatal environment.
Alcohol: Compromising the functions of placenta. (indirect) Stays in the
circulation of fetus for a long time. Reuptake of amniotic fluid. SMOOTHER
BRAIN SURFACE. UNDERDEVELEOPED BRAIN.
Fetal alcohol syndrome (FAS): microcephaly (small head), indistinct philtrum,
thin upper lip. Malformation of heart and liver. Direct: language, learning,
attention problems.
FAE (fetal alcohol effect): small exposure to alcohol: poor motor and attention
skills. (five or more drinks) Can affect male reproductive system: low motility of
sperms, abnormally formed sperm.
Tobacco: oxygen displaces with CO, damages CNS, impairs placenta and material
exchange with fetus (constricts blood vessels and lessens blood flow to uterus).
LOW BIRTH WEIGHT. Miscarriage. Sudden infant death syndrome. Childhood
obesity. Passive smoking. Asthma, cancer. ADHD.
Antidepressants: heart defects, respiratory diseases, prematurity.
Thalidomide: Limbs are missing.
Caffeine: Miscarriage. Low birth weight. 200 ml. 3 cups of coffee.
Illicit drugs: cognitive, behavioral defects.
o They born drug addictive: strong withdrawal symptoms. Trouble sleeping.
Marijuana: Emotion and attention problems. Amygdala deformation. Problems
persist when the children are 10 years old. Thicker cerebral cortex. Problem
solving, judgment, memory problems.
Cocaine: Premature. Miscarriage. Hampering the flow of nutrients to placenta
(Constricts blood vessels). Lower IQ, lower spatial abilities.
