Download HUMAN GENETICS Unit 1

HUMAN GENETICS BOOK NOTES/POWER POINT
*http://arizonachristian.edu/kezele_bio341
1.1- 1.4
1. Genetics: study of inherited traits and their variation (not genealogy) it is also an informational
science that is having a huge societal impact as we shall see
2. Genes are composed of segments of deoxyribonucleic acid (DNA) *tell cells how to manufacture
proteins *use 4 types of building blocks: _Gyanine, Thymine, Cytocine, Adenine (uracil-RNA)
3. Proteins: control the characteristics that create much of our individuality
4. Cells: basic units of life
5. CHART: carbs: sugars, gives energy *lipids: fats & oils, functions in membranes, hormones,
*proteins: sucrose, lipase, myosin, collagen, functions with enzymes and structure, *nucleic acids:
DNA, rRNA, tRNA, mRNA, function, genetic info protein (man.?)
6. Genome: the complete set of genetic information for an organism. *it includes all the genes
present in an organism and also DNA sequences that do not encode genes. * nearly all of our cells
contain two copies of the genome
7. Genomics: a field that analyzes and compares genomes of different species (how closely we relate
to each other and other species)
8. Bioethics: a field of study founded to address moral issues and controversies that arise in applying
medical technology
9. LEVELS OF GENETICS:
10. EPIGENOME: additional level
11. DNA: resembles a spiral staircase *double-stranded polymer consisting of a chain of nucleotides.
Back bone consists of alternating sugars, phosphates, and bases (Adenine &Guanine –purines and
Thymine & Cytosine-pyrimidines
12. RNA (deoxyribonubleic Acid) a single stranded polymer containing a phosphate, sugar (ribose),
bases (Adenine & Guanine- purines and Uracil & Cytosine- pyrimidines)
13. DIAGRAM on pg3 (figure 2): DNA uses its information in two ways. 1. DNA replication The sides of
the helix resemble eachother and attract eachother’s parts. A and T attracting and G and C
attracting. This process keeps the same info when the cell divides. 2. Transcription: DNA directs the
production of specific proteins.
14. DIAGRAM: translation_____
15. Human Genome: only 1.5% of our DNA encodes protein. –about 20.325 protein- encoding genes in
all
16. The rest of the human genome includes highly repeated sequences with increasingly unknown
functions
17. Junk DNA: noncoding DNA
18. Genes known to cause disorders or traits are cataloged in a database, the Online Mendelian
Inheritance in Man (OMIM)
19. Proteomics: the field that studies the proteins made in a particular type of cell
20. NUCLEOTIDE:
21. Alleles: are variants of genes(*genes encode proteins) *have been formed by original creation or
mutation
22. Mutation: changes in genetic sequence that distinguish allels,*mutations in sperm or egg cells
(haploid) are passed on to the next generation *mutations may be positive, negative, or neutral
23. Polymorphisms (meaning many forms) are variations in the DNA sequence that occur in at least 1%
of the population
24. Single nucleotide polymorphisms (SNPs): single base sites that differ among individuals (can cause
disease or act as genomic markers
25. Genome-wide association studies: track SNP patterns among individuals who share a particular
trait or disorder
26. Gene expression profiling: measures which genes are more or less active in particular cell types
27. Chromosomes: composed of DNA and protein found in the nucleus of the cell *Human somatic
cells have 46 chromosomes *22 pairs of autosomes (don’t differ between the sexes) *a pair of sex
chromosomes *Females have two X chromosomes, *Males have one X and a Y
28. Karyotype: a chart displaying the chromosome pairs from largest to smallest
29. Types of info in DNA sequences: *single gene: hundreds of thousands of DNA bases that encode a
protein or parts of a protein, *Genome: the entire 3.2-billion base sequence of the genetic material
in a human cell, *genome-wide association study: patterns of single-base variants (SNPs) associated
with traits or medical conditions, *Gene expression profiling: levels of mRNAs in specific cells, under
specific conditions that reflect physiology and reveal malfunction
30. Human body contains approximately 50-100 trillion cells. –all cells except RBCs contain the same
genome
31. Differentiation: causes cells to differ in appearance and function *controlled by variation in gene
expression
32. Stem cells: are less specialized and can become many different types
33. Levels of biological organization: cell> molecule>macromolecule>organelle>cell>tissue>organ>
organ system>organism
34. TISSUE TYPES:
a. Connective tissue: a variety of cell types and materials around them that protect, support, bind
to cells, and fill spaces throughout the body; include cartilage, bone, blood, and fat
b. Epithelium: tight cell layers that form lining that protect, secrete, absorb, and excrete
c. Muscle: cells that contract, provide movement
d. Nervous: neurons transmit information as electrochemical impulses that coordinate movement
and sense and respond to environmental stimuli; neuroglia are cells that support and nourish
neurons
35. The Genotype of an individual refers to the alleles they carry (underlying instruction)
36. The Phenotype is the visible trait
37. A dominant allele is expressed if the individual carries just one copy (one chromosome)
38. A recessive allele is only expressed if the individual carries two copies (two chromosomes)
39. Individuals are genetically connected into families
40. A pedigree is a diagram used to study traits in families *can be used to trace multiple genes or
genes with a large environmental component
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A population: a group of interbreeding individuals (a large collection of alleles)
The gene pool is the sum of all alleles in a population
Evolution is put forth as the changing allelic frequencies in population over time
Change and variation: *CHANGE: 1. From a very small gene pool, 2. Which increases due to
mutations & selection, 3. Until change from one kind into another kind, 4. By gain of information
*VARIATION: 1. From a very large gene pool, 2. Which divides by migration and selection, 3. Until
changes occur within a kind, 4. By loss of information
Evolution: genome comparisons among species reveals evolutionary relationships *** the more
similar the sequences are, the more recent the divergence from a common ancestor
**what is the presupposition here? Common descent rather than a common designer
Humans share genes with mice, pufferfish, fruit flies, yeast, and even bacteria -true
98% of human DNA sequences are shared with chimpanzees –untrue
Mendelian traits are determined by a single gene: their recurrence is predicted based on Mendel’s
laws
Multifactorial traits are determined by one or more genes and the environment *predicting their
recurrence is much more difficult
Most traits are multifactoral
Genetic Determinism is the idea that the expression of an inherited trait is inevitable *this may be
harmful or helpful, depending on its application: as part of a social policy, it is disastrous
Ernst Haeckle- “Politics is applied biology”- knowing genetic risk can help us make good choices
Applications of genetics: DNA profiling (dna fingerprinting) looks at SNPs and short repeated DNA
sequences *applications in forensics, history and ancestry
Forensics: indentification of victims of natural disasters or terrorist attacks *Matching the DNA of
suspects to samples left at the crime scene *helping adopted individuals locate blood relatives
DNA analysis can flesh out historical details: revealing the offspring of Thomas Jefferson and Sally
Hemmings
Ancestry: revealing the origins of the Jewish Lemba of South Africa
Pharmacogenomics a field that identifies individual drug reactions based on genetics
(Antidepressants, Chemotherapies, HIV drugs, Smoking cessation drugs, Statins (cholesterollowering drugs), Warfarin (anti-clotting)
Analysis of single gene illnesses reveals many differences from other diseases, 1. Risk can be
predicted for family members, 2. Predictive (presymptomatic) testing may be possible, 3. Different
populations may have different characteristic disease frequencies, 4. Correction of the underlying
genetic abnormality may be possible
Health Care: diseases are increasingly being described in terms of gene expression patterns.
*Tracking gene expression can reveal new information about diseases and show how diseases are
related to eachother. *This is not obvious via traditional medicine
Tests to identify about 1,200 single-gene disorders have been available for years:
a. Direct-to-consumer (DTC) genetic testing
b. The Genetic information Non-discrimination (GINA) act was passed in the US in 2008
c. Genome information is useful for developing treatment to genetic and infectious diseases
Biotechnology is the use of organisms or their parts to produce goods and services
63. Genetically-modified (GM) organisms have new genes or over- or under- express their own genes
64. Ecology: Metagenomics is the field that involves sequencing all of the DNA in a habitat: The
Sargasso Sea
65. The Human Microbiome Project:
a. The human intestinal microbiota is composed of some 10x14 microorganisms
b. 100 times as many genes as our own genome has
c. Our microbiome has significantly enriched metabolism of glycans, amino acids, xenobiotics,
methanogenesis, and biosynthesis of vitamins and isoprenoids
66. Vit B12 and Vit K: thus humans are superorganisms whose metabolism represents an amalgamation
of microbial and human attributes…evidence for intelligent design?
67. Human Genome: 3.100 Mbp (6.2 billion bases), Chimp: 3,500 Mbp (7 billion bases) -11.5%
difference
UNIT 2.1
(read up to 1.1 chap 2 slideshow
1. Our bodies include more than 260 cell types
a. Somatic (body) cells have two copies of the genome and are said to be diploid
b. Sperm and egg cells have one copy of the genome and are haploid
c. Stem cells can both replicate themselves and give rise to differentiated cells
2. Two main groups of cells:
a. Prokaryotic cells: lack nuclear membranes (no distinct organelles)
b. Eukaryotic cells: possess defined nuclei and other organelles
3. Domains of life: biologists recognize three broad categories of organisms in three Domains
a. Archaea: unicellular prokaryotes, no peptidoglycans, several RNA Polymerases, Antibiotics
don’t kill *because of those reasons
b. Bacteria: unicellular prokaryotes, peptidoglycans; one kind RNA polymerase, antibiotics can
kill
c. Eukarya: includes both unicellular and multicellular eukaryotes *exp: algae
4. ADD CHART HERE
5. Cell: surrounded by the plasma membrane, contains: Cytoplasm organelles divides labor by
partitioning areas or serving specific functions
6. The Nucleus: the largest structure in a cell; surrounded by double bi-layered nuclear envelope;
contains (made of proteins):
a. Nuclear pores that allow movement of some molecules in and out
b. Chromosomes composed of DNA and proteins
c. Nucleolus, which is the site of ribosome production (difference in appearance but not
completely separate from other structures) *produces ribosomal RNA
7. >>>slide #9 CANNOT READ PRINt
8. 4 types of carv
9. The NOR contains genes for 5.8S, 18S, and 28S rRNA (three designations): Nucleolar Organizing
Regions are regions of chromosomes around which the nucleolus forms the particular part of
a chromosome that is associated with a nucleolus after the nucleus divides and reforms.
10. (RE: NOR) The region contains several tandem copies of ribosomal RNA genes, clustered on
the short arms of chromosome 13, 14, 15, 21, and 22 (the acrocentric *short arms*
chromosomes
a. Three types of NOR: metacentric, subcentric, acrocentric
11. S refers to Svedberg units, a measure of the rate of sedimentation, which correlates with size of
the molecules. *suspended solid to settle out, measures inflammation of blood- larger sizes
settle down faster which = the larger #s
12. These are the large and small subunits of the ribosomes, with the associated proteins
13. Secretion: illustrates how organelles function together to coordinate the basic functions of life
14. Endoplasmic Reticulum (ER): interconnected membranous tubules and sacs; winds from the
nuclear envelope to the plasma membrane
15. Rough ER: contains ribosomes and is involved in protein synthesis
16. Smooth ER: does not contain ribosomes and is important in lipid synthesis
17. Golgi Apparatus: stack of flat membrane-enclosed sacs; processing center that adds sugars
forming glycoproteins and glycolipids; site of final protein folding; products are released into
vesicles that bud off to the plasma membrane (folding occurs)
18. Lysosomes: membrane-bound sacs containing >40 types of digestive enzymes, break down
bacteria, cellular debris, and nutrients. (garbage compactor/ destroyer/ deals with recycled
pieces *WBC are coated with lysosomes
19. Tay-Sachs: is an inherited lysosomal storage disorder *lysosomes are not breaking down
properly, excess storage (found in Jewish culture)- takes 3-6 m.o. to show up (6 yrs max of life)
20. Perioxisomes: are sacs with outer membranes studded with several types of enzymes, break
down lipid, rare biochemicals; synthesize bile acids; detoxify compounds from free radicals; are
abundant in liver and kidney cells *outer membrane gets rid of free oxygen radicals
21. Mitochondria: surrounded by two membranes; site of ATP (energy) production, Contains their
own circular DNA; human mitochondrial DNA is inherited only from the mother (power plant of
the cell)
22. Ribosome: two associated globular subunits of RNA and protein; scaffold and catalyst for
protein synthesis
23. Plasma Membrane: forms a selective barrier; a phospholipid bilayer; a phosphate end
(hydrophilic) ; & Fatty acid chains (hydrophobic) *contains proteins, glycoproteins, and
glycolipids:
a. Important to cell function and interactions
b. May be receptors, cell markers
c. Form channels for ions and larger molecules
24. Faulty ion channels cause inherited diseases:
a. Sodium channels: mutations lead to absence of or extreme pain (impulses axons and
neuron)
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b. Potassium channels: mutations lead to impaired heart function, deafness (dec contraction
of heart muscle leads to congenitive heart failure)
c. Chloride channels: mutations lead to cystic fibrosis (deposition of salt- salty tasting skin
*instisated mucous, thick mucous–cystic fibrosis *chromosome 7 CFTR), results in plugged
airways. TX: phy pounding, vests
Cytoskeleton: meshwork or protein rods and tubules; includes three major types of proteins:
microtubules, microfilaments, intermediate filaments
a. Functions: maintain cell shape, connect cells to each other, transport organelles and small
molecules, provide cell motility (some cell types), move chromosomes in cell division,
compose cilia
b. Microtubules: transport (surface area & minimal value (RBC) for O2 absorbtion
Cell division and death: normal growth and development require an intricate interplay between
the rates of two processes
c. Mitosis: Cell division *produces two somatic cells from one
d. Apoptosis- cell death * precise genetically-programmed sequence to cause cell death
Programmed cell death is part of normal development. *Mitosis and apotosis work together to
form a functional body. Cancer can result from too much mitosis, too little apotosis
Cell cycle: the sequence of events associated with cell division
e. G phase: gap for growth (metabolism- normal cell function)
f. S phase: DNA synthesis (laying the groundwork)
g. M phase: mitosis (nuclear division)
h. Cytokinesis: cell division
Stages of the cell cycle:
i. Interphase: prepares for cell division. (uncondensed) Replicates DNA and subcellular
structures. Composed of G1, S, and G2, Cells may exit the cell cycle at G1 or enter G0, a
quiescent phase
j. G0: not going to replicate in the future- most nerve cells
k. Mitosis: division of the nucleus (physical division of the cells), unwound to replicate
l. Cytokinesis: division of the cytoplasm (cyto: cell, kinesis-motion)
Replication of Chromosomes: Chromosomes are replicated during S phase prior to mitosis. The
result is two sister chromatids (copies not separate chromosomes-46) held together at the
centromere
Mitosis: used for growth, repair, and replacement, consists of a single division that produces
two identical daughter cells, A continuous process divided into 4 phases: prophase, metaphase,
anaphase, and telophase
Prophase: replicated chromosomes condense, microtubules organize into a spindle, nuclear
envelope and nucleolus break down
Metaphase: chromosomes line up on the cell’s equator, spindle microtubules are attached to
centromeres of chromosomes, cytokinesis is done *microtubial diameter: 25 microns,
*microfilaments: 18 microns- separates (furrows), intermediate 10-12 microns.
Anaphase: centromeres divide, chromatids separate and become independent chromosomes,
they move to opposite ends of the cell
35. Telophase: chromosomes uncoil, spindle disassembles, nuclear envelope reforms
36. Cytokinesis: cytoplasmic division occurs after nuclear division is complete. Organelles and
macromolecules are distributed between the two daughter cells. Microfilament band contracts,
separating the to cells
37. Cell Cycle control: checkpoints ensure that mitotic events occur in the correct sequence.
Internal and external factors are involved. Many types of cancer result from faulty checkpoints.
*Protein surviving- apoptosis checkpoint after G2
38. 3 check points: DNA damage checkpoint, Apoptosis checkpoint, Spindle checkpoint
39. Telomeres: located at the ends of the chromosomes. Contain hundreds to thousands of repeats
of 6-base DNA sequence. Most cells lose 50-200 endmost bases after each cell division. After
about 50 divisions, shortend telomeres signal the cell to stop dividing. Sperm, eggs, bone
marrow, and cancer cells produce telomerase that prevent shortening of telomeres (fluorescent
dots on the picture) *after 50 divisions cannot divide
40. Sequence contains: 4 G’s & 2 T’s –base sequence, repeated a zillion times (at end provide
barrier)
41. Apoptosis: begins when a cell receives a “death signal”. Killer enzymes, caspases, are activated,
destroy cellular components. Phagocytes digest the remains. Dying cell forms bulges called blebs
42. ****Exp: “deathstar” from star wars, mission impossible tv series: gets assignment on cassette
and self destructs, dead cell blebs are destroyed by macrophages
43. Cell-to-cell interactions: make multicellular life possible. Two broad types: 1)signal transduction,
2) cellular adhesion *Defects cause certain inherited disorders
44. Signal Trasduction: the process of transmitting a signal from the environment to a cell. Exp: air
duct: conveys things that channel from which things can be moved. *relay electrical signals
Receptor binds to “first messanger”. Interaction with regulator causes enzyme to produce “2nd
messanger”. Cellular response is elicited which is typically enzyme activation. Amplification due
to cascades ***EXAMPLES: light, chemical gradients, temp change, toxin, hormone, growth
factor
45. Toxin: interferes with messaging from 1st neuron to second neuron (exp: phosphate poisoning
kills insects
46. CAMP: second messenger (widespread)
47. Cascade: signal that can cause millions of molecules to be produced
48. Cellular Adhesion: a precise sequence of interactions among proteins that connect cells.
Example of inflammation: three types of cellular adhesion molecules (CAMs), help guide WBCs
to the injured area. *inflammation results in undesired cell adhesion Examples: Selectins,
integrins, and adhesion receptor proteins *creates a water tight layer of cells- cellular
maintainence *
49. Stem Cells: a stem cell divides by mitosis, producing some daughter cells that retain the ability
to divide and some that specialize. Progenitor cells (before generating) do not have the capacity
of self-renewal
m. All cells in the human body descend from stem cells via mitosis and differentiation
n. Cells differentiate down cell lineages by differential gene expression
o. Stem cells are present throughout life and provide growth and repair
p. Stem cells and progenitor cells are described in terms of their developmental potential
q. Totipotent: can give rise to every cell type
r. Pluripotent: have fewer possible fates
s. Multipotent: have only a few fates
50. Stem cells in health care: there are 3 general sources of human stem cells
t. Embryonic stem cells: created in lab dish using the inner cell mass (ICM) of an embryo
u. Induced pluripotent stem (iPS) cells- somatic cell reprogrammed to differentiate into any of
several cell types
v. Adult stem cells- Tissue-specific or somatic stem cells
51. Stem Cell Applications: stem cells are being used in four basic ways: 1) discovery and
development of drugs, 2) observing the earliest sign of disease, 3) treatment of disease via
implants and transplants, 4) stimulating stem cells in the body via the introduction of
reprogramming proteins
52. Stopped here Monday 8/27
Meiosis and Development
1. Stages of the Human Life Cycle
a. Genes orchestrate our physiology after conception through adulthood. Development is the
process of forming an adult from a single-celled embryo.
b. In humans, new individuals form from the union of sex cells or gametes *sperm from the
male and oocyte from the female from a zygote
2. The male reproductive system
a. sperm cells are made in the seminiferous tubules of the testes. The prostate gland, seminal
vesicles, and bulbourethral glands add secretions to form the seminal fluid.
b. Sperm mature and are stored in the epididymis (epi- upon, di-two). They leave through the
ductus deferens and then the urethra
3. The female reproductive system
w. Oocytes mature in the ovaries. Each month, an ovary releases an oocyte into the uterine
tube (also called phylopian) *if the oocyte is fertilized, it continues to the uterus where it
divides and develops. If it is not fertilized, the body expels it, along with the uterine-lining
via the menstrual flow *alternate egg release
x. Egg released to space between the fibria (fringe) and fallopian tube (sometimes it ends
outside and results in an atopic pregnancy
y. Hormones control the cycle of oocyte development (hormones: Estrogen, FSH-from anterior
pituitary gland
4. Meiosis
z. The cell division that produces gametes (aka sex cells) with half the number of
chromosomes
aa. Occurs in special cells called germline cells
bb. Maintains the chromosome number of a species over generations
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cc. Ensures genetic variability via the processes of independent assortment and crossing over
of chromosomes
dd. New term for natural selection: programmed filing (from wide variety of genes)
ee. Consists in two divisions: Meiosis I= the reduction division: reduces the number of
chromosomes from 46 to 23, Meiosis II: the equational division- produces four cells from
the two produced in Meiosis I
ff. Note: each division contains a prophase, a metaphase, an anaphase and a telophase
(cytokinesis- cell motion/ending the phase after telophase)
Prophase 1
a. Homologus pair- up and undergo crossing over (exchange/switching of portions of the
chromosomes)
b. Chromosomes condense
c. Spindle forms
d. Nuclear envelope breaks down
Metaphase 1
gg. Homologous pairs align along the equator of the cell
hh. The random alignment pattern determines the combination of maternal and paternal
chromosomes in the gametes
Anaphase 1
ii. Homologs separate and move to opposite poles of the cell
jj. Sister chromatids remain attached at their centromeres
Telophase: nuclear envelope reforms. Spindle disappears. Cytokinesis divides cell into two
Interkinesis: a short interphase between the two meiotic divisions. Chromosomes unfold into
very thin threads. Proteins are manufactured. However, DNA is NOT replicated a second time
Prophase 2- chromosomes are again condensed and visible. Spindle forms nuclear envelope
fragments
Metaphase 2: chromosomes align along the equator of the cell
Anaphase 2: centromeres divide, sister chromatids separate to opposite cell poles
Telophase 2: nuclear envelope reforms, chromosomes uncoil, spindle disappears
Results of Meiosis
kk. Four haploid cells containing a single copy of the genome
ll. Each cell is unique- carries a new assortment of genes and chromosomes
Comparison of Mitosis and Meiosis
c. Mitosis: one division, two daughter cells per cycle, chromosome number of daughter cells
same as that of parent cell (2n), occurs in somatic cells, occurs throughout life cycle, used
for growth, repair, and asexual reproduction
d. Meiosis: two divisions, four daughter cells per cycle, daughter cells genetically different,
chromosomes number of daughter cells half that of parent cell (1n), occurs in germline cells,
in humans, completes after sexual maturity, used for sexual reproduction, producing new
gene combinations
16. Spermatogenesis: A diploid spermatogonium (refers to the germline of the cell) , Spermatid
(immature sperm) , speratazoa (animal seed) divides by mitosis to produce a stem cell and
another cell that specializes into a primary spermatocyte
a. In meiosis 1, the primary spermatocyte produces two haploids secondary spermatocytes
b. In meiosis 2, each secondary spermatocyte produces two haploid spermatids
c. Spermatids then mature into a tad-pole shaped spermatids
d. –ium: singular, -ia: plural
ENDED CLASS HERE 8/29
17. Oogenesis: a diploid oogonium divides by mitosis to produce a stem cell an another cell that
specializes into a primary oocyte
mm. In meiosis I, the primary oocyte divides unequally forming a small polar body and a
large secondary oocyte
nn. In meiosis II, the secondary oocyte divides to from another polar body and a mature haploid
ovum
oo. Unlike spermatogenesis oogenesis is a discontinuous process
pp. A female begins meiosis when she is a fetus *****N2K**********
1) Oocytes arrest at prophase I until puberty (FHS and LH)
2) After puberty, meiosis I continues in one or several oocytes each month but halts again
at metaphase II
3) Meiosis is only completed if the ovum is fertilized
4) Ovulation-release of the egg
5) Eptopic: out of place
6) Fertilization occurs in distal portion of fallopian tubes
18. Fertilization
qq. Union of sperm and ovum. In the female, sperm are capacitated (chemical interaction:
chemicals in vagina which enable the sperm to do what it needs to do) and drawn to the
secondary oocyte
rr. Acrosomal enzymes aid sperm penetration. (through the zona…?) Chemical and electrical
changesin the oocyte surface block entry of more sperm (otherwise trisomy would take
place)
ss. The two sets of chromosomes fuse into one nucleus, forming the zygote
tt. Second polar body develops from division
19. Cleavage: a period of frequent mitotic divisions- resulting cells are called blastomeres. (mere:
segments) Developing embryo becomes a solid ball of 16+ cells called a morula.(morula latin for
blackberry) The ball of cells hollows out to form a blastocyst (blast that which gives rise to the
beginning of an organism, aka germ) and fills with fluid
20. Blastocyst: consists of two main parts: Inner cell mass (ICM) which develops into the embryo
21. a. Trophoblast,(troph: means feeding-trough) which develops into the placenta
uu. Implantation in the uterus occurs around day 6 (sperm implants the “eagle has landed”)
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vv. The syncytiotrophoblast (syn-with fuze) secretes human chorionic gonadotropin (hCG)
*positive pregnancy test
Gastrulation: theprimary germ layers form in the second week after fertilization: (example:
pushed in basketball)
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Ectoderm (outermost layer) skin, nervous tissue, lens of eyes, pituituary gland, adrenal
medula
xx. Mesoderm (middle layer) muscle, contective tissue…
yy. Endoderm (innermost layer) GI, liver and pancreas (lining connected to outside)
zz. This Three-layered structure is the gastrula (future GI tract)
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Cells in each germ layer begin to form specific organs
Supportive structures: structures that support and protect the embryo include: Chorionic villi
(portion of a placenta), amniotic sac, umbilical vesicle (not yoke sac)-1st site of blood formation,
Allantois, Umbilical cord (life line)- formed from mesoderm (gets nutrients from diffusion) *By
10 weeks the placenta is fully formed
Table 3.2 REVIEW
Multiple births:
A. Dizygotic twins (fraternal) arise from two fertilized ova, same genetic relationship as any
two siblings (two sperm, and two eggs)
B. Monozygotic twins (identical) *arise from a single fertilized ovum, embryo spits early
during development, twins may share supportive structures (one egg and one sperm)
The Embryo Develops
A. Organogenesis: is the transformation of the simple three germ layers into distinct organs
1) During week 3, a band alled the primitive streak appears along the back of the embryo
(the nerve system develops here)
2) This is followed rapidly by the notochord, neural tube, heart, central nervous system,
limbs, digits, and other organ rudiments
3) By week 8, all the organs that will be present in the newborn have begun to develop,
the prenatal human is now called a fetus *fetus means little one (week 10 all organs are
in place)
4) The fetus grows: during the fetal period, structures grow, specialize and begin to
interact. Bone replaces cartilage in the skeleton. Body growth catches up with the head.
Sex organs become more distinct. In the final trimester, the fetus moves and grows
rapidly, and fat fills out the skin. The digestive and respiratory systems mature last
Birth Defects: the time when a particular structure is sensitive to damage is called its critical
period. Birth defects can result from a faulty gene or environmental insult. (critical period first
6 weeks)
A. Most birth defects develop during the embryonic period
B. These are more severe than those that arise during the fetal period, why??
Teratogens: chemical or other agents that cause birth defects:
A. Examples: Thalidomide, Cocaine, Cigarettes, Alcohol, Some microbes, Some nutrients,
cytalomegalo virus (TORCHES)
B. Phocomila (thalidomide)
C. Vit A (spontaneous ab, heart, neural defects), Inc Vit C (scurvy), folic acid dec (neural tube
defects), Vit B6 (clubfoot, cleft lip and palate), thiamine (heart defects affecting rhythm and
size), Minerals
29. Aging: Genes may impact health throughout life. Single-gene disorders that strike in childhood
tend to be recessive. Adult- onset single-gene traits are often dominant. Interaction between
genes and inviornmental factors. *EXP: Malnutrition before birth***
A. Genes control aging both passively and actively. A few single-gene disorders can speed the
signs of aging
B. Segmented progeroid syndromes- Hutchinson-Guilford syndrome
C. Progeria: super premature aging
30. Is longevity inherited? Aging reflects genetic activity plus a lifetime of environmental influences.
Human chromosome 4 houses longevity genes
A. Genome-wide screens of 100 year olds are identifying others. Adoption studies compare the
effects of genes vs. the environment on aging
CHAPTER 4
A tale of two families
A. Modes of inheritance are the patterns in which single-gene traits and disorders occur in
families
B. Huntington disease is autosomal dominant- affects both sexes and typically appears every
generation (if that allele is there it is going to show up)
C. Cystic fibrosis is autosomal recessive- affects both sexes and can skip generations through
carriers
Gregor Mendel
A. A priest who performed research in planting breeding, without knowledge of DNA, cells, or
chromosomes. He described the units of inheritance and how they pass from generation to
generation. He was not recognized during his lifetime and was Charles Darwin’s contemporary
(it was not published) *1859 orgin of species
B. Experiment from 1857-1863 on traits in 24,034 plants. He developed the laws of inheritance and
used:
1. Controlled plant breeding
2. Careful record keeping
3. Large numbers
4. Statistics (in other words, observational science)- not presuppositional science
*oppotational verifiable ,testable repeatable, falsifiable,
5. HistoricalL past, based on assumption wich is predisposed to what you believe,
C. Observational science ***see above
D. Historical science
True-Breeding plants
A. Offspring have the same trait as parents (the offspring are going to have the same genes)
B. Examples:
1. Round-seeded parents produce all round-seeded offspring
2. Yellow-seeded parents produce all yellow-seeded offspring
3. Shorter parents produce all short offspring
C. Monohybrid Cross: True-breeding plants with two forms of a single trait are crossed.(one set of
allels that have different traits- one locus) Progeny (the first generation after) show only one
form of the trait. *phenotype: appearace vs genotype: actual genetic traits… The observed trait
is dominant. The masked trait is recessive.
1. In these experiments, Mendel confirmed that hybrids hide one expression of a trait, which
appears when hybrids are crossed
2. Mendel speculated that gametes contained particular units or “elementen” (plural form in
german- elements)
3. These are now allels. Versions of the same gene. Arise from: Differ in DNA sequence at one
or more sites.
Mendel’s First Law- Segregation
A. Each plant possesses two units (alleles) for each trait. (one from each parent) How? Alleles
separate in the formation of gametes
B. Gametes contain ONE allele for each trait. At fertilization, gametes sort and combine randomly
C. NOTE: Mendel was really observing the events of meiosis and fertilization
Terms
A. Genotype: the alleles present in an individual
1. Homozygous carry same alleles (TT or tt)
2. Heterozygous carry different allels (Tt)
B. Phenotype: the trait observed (tall or short)-pheno- phantom (Ghost-what you don’t see)
C. Wild Type: most common phenotype**
D. Mutant phenotype: a product of a change in the DNA (mutation loss of information)
Punnett Square: represents particular genes in gametes and how they may combine in offspring
Test Cross:
A. A monohybrid cross yields:
1. 1 TT: 2 Tt: 1 tt (genotypic ratio), and
2. 3 tall: 1 short (phenotypic ratio)
B. Mendel distinguishes the TT from the Tt tall plants with a test-cross, which is the –cross an
individual of unknown genotype with a homozygous recessive individual
Eye Color:
A.
wild-type human eye color is brown, blue and green eyes stemmed from mutations or SNPs
(single nucleotide polymorphisms (different shape, more than one allel)- mutions in one base of
the DNA) that persisted.
B. The surface of the back of the iris contributes to the intensity of the eye color ***One gene is
turned on by another gene (other genes control the outcome): ( epistasis (upon, on top,
standing)**
C. Magic and fuzzy words (fig 4.6) “anchient” hypothesis, arose, would have increased
Autosomal Inheritance:
A. Human autosomal traits are located on non-sex chromosomes (#s 1-22)
B. They may be inherited as: autosomal dominant or Autosomal recessive
Autosomal Dominant Traits:
A.
B.
C.
D.
E.
Males and females can be affected. Male-to-male transmission can occur.
Males and females transmit the trait with equal frequency.
Successive generations are affected
Transmission stops after a generation in which no one is affected
For many autosomal dominant traits, affected individuals are heterozygous (Aa)- the
homozygous dominant phenotype (AA) is either lethal or very rare
Autosomal Recessive Traits (table 4.3)
*just one gene have trait, both the disease
*Consanguinity (with blood) really close relative
Leviticus 17
Solving Genetic Problems:
1.
2.
3.
4.
5.
List all genotypes and phenotypes for the trait
Determine all genotypes of the parents
Derive possible gametes (possible combinations)
Untie gametes in all combinations to reveal all possible genotypes ***
Repeat for successive generations
On the Meaning of Dominance and Recessivness
1. Whether an allele is dominant or recessive is important in determining risk and critical in
medical genetics:
2. Reflect the characteristics or abundance of a protein
3. Recessive traits have “loss of function”
4. Dominant traits have “gain of function”
5. Recessive disorders tend to be more severe, Why? (don’t make it too long)
END OF NOTES 9/5
Mendel’s Second Law- Independent assortment
1. Considers two genes on different chromosomes
2. The inheritance of one does not influence the chance of inheriting the other
3. Independent assortment results from the random alignment of chromosome pairs during
metaphase 1 or meiosis
4. Determines which chromosome lines up on each side of the equator
Probability: The likelihood that an event will occur. Two applications of probability theory are useful in
solving genetics problems 1) Product rule & 2) sum rule
Product Rule: the probability of simultaneous independent events equals the product of their individual
probabilities.
a. Example: If both parents are dihybrid (RrYy), what is the probability of having an offspring that is
homozygous recessive for both traits? (…do the reasoning for one gene at a time, then multiply
the results)
b. ¼ for one gene, ¼ for another: ¼ x ¼ equals 1/16
c. (Methalene blue exp –pee blue)
Sum Rule: the probability of mutually exclusive events equals the sum of the individual
probabilities…example:
A. Parents are heterozygous for a trait, R.
B. What is the chance that that their child carries at least one dominant R allele? –probability of
child being RR=1/4, -probability of a child being Rr=1/2, -Probability of child being R_=1/4 + 1/2=
¾
Pedigree Analysis
A. For researchers, families are tools; the bigger the family, the easier it is to discern modes of
inheritance
B. Pedigrees are symbolic representations of family relationships and the transmission of inherited
traits *KNOW THE SYMBOLS (SA-spontaneous abortion, terminated pregnancy -abortion)
C. An inconclusive pedigree: this pedigree can account for either an autosomal dominant or an
autosomal recessive trait
D. An unusual pedigree: a partial pedigree of Egypt’s Ptolemy Dynasty showing: Genealogy, not
traits. Extensive inbreeding
E. The flood was _4,360_years ago (year Methusala dies*when he dies it 1659- genealogies in
chapter 5 in Genesis)
Conditional Probability:
A. pedigrees and Punnett squares apply Mendel’s laws to predict the recurrence risks of inherited
conditions
B. Example: Taneesha’s brother Deshawn has sickle cell anemia, an autosomal recessive disease.
What is the probability that Taneesha’s child inherits the sickle cell anemia allele from her? (SEE
EXAMPLE IN NOTES
Consangunity mating with *burden of mutations, adding mutation, 2nd law of thermodynamics genomic
analysis (1,000)