genetics inheritance of traits. gregor mendel 1822 – 1884 born to peasant parents ordained a...
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Gregor Mendel
1822 – 1884 Born to peasant
parents Ordained a priest in
1847 Studied physics and
natural science 1851-1853
1857(?) began pea experiments
http://www.jic.ac.uk/germplas/pisum/zgs4f1.gif
Inheritance
Children resemble their parents because they directly inherit traits from them
Parts of DNA are expressed, and these are called genes (note that geneticists also refer to sequences not expressed as genes)
Genes are not always identical – and each is referred to as an allele
One gene may have many alleles – or variations of that gene’s ultimate function
Mendel’s Peas
Began with plants that only produced each of these – only spherical or dented seeds, only yellow or green seeds, only purple or white flowers (etc.)
http://mac122.icu.ac.jp/gen-ed/mendel-gifs/03-mendel-characters2.JPG
Mendel’s Peas
Crossed a wrinkled with a spherical seed plant
Crossed a yellow with a green seed plant
Results? Dominant and
recessive genes
http://www.wwnorton.com/college/anthro/evolve4/ch/02/2_1.jpg
Punnett Squares
Remember during meiosis that 1 cell replicates DNA, the pairs separate, then the original and copy of DNA separates to 4 cells
The Punnett reflects a single mother and single father germ cell’s possibilities
http://www.biologie.uni-hamburg.de/b-online/library/onlinebio/mono2.gif
Punnett Squres
Help to determine chance of inheriting a specific allele
Genes are randomly assorted
http://courses.bio.psu.edu/fall2005/biol110/tutorials/tutorial4_files/fig_14_8.gif
Human Genetic Conditions
Use of Mendelian genetics can determine the likelihood of inheriting or carrying a dangerous allele – like Huntington's disease
http://www.daviddarling.info/images/autosomal_dominant.jpg
Genetic Disorders – Single Gene Cystic Fibrosis
defective gene 7 protein produced normally
helps salt (sodium chloride) move in and out of cells
if protein doesn't work correctly movement is blocked and an abnormally thick sticky mucous is produced on the outside of the cell
cells most seriously affected by this are the lung cells
mucous clogs the airways in the lungs, and increases the risk of infection by bacteria
http://www.sjsu.edu/faculty/gerstman/StatPrimer/autorecessive.jpg
Genetic Disorders – Single Gene Sickle Cell Anemia
single nucleotide substitution 11 prevents oxygen from
reaching the spleen, liver, kidneys, lungs, heart, or other organs, causing a lot of damage
Without oxygen, the cells that make up these organs will begin to die
As a result, these patients often experience frequent infections
Many others
http://library.thinkquest.org/06aug/00440/images/sicklecell.jpg
Genetic Disorders - Chromosomal Down Syndrome Turner Syndrome Klinefelter Syndrome Cri du chat Syndrome Williams Syndrome Many others
Down Syndrome triploidy 21 Distinctive features:
flat face small broad nose abnormally shaped ears large tongue upward slanting eyes with small
folds of skin in the corners respiratory infections gastrointestinal tract
obstruction (blocked digestive tract)
Leukemia heart defects hearing loss hypothyroidism various eye abnormalities moderate to severe mental
retardation
http://www.ucl.ac.uk/~ucbhjow/bmsi/lec7_images/47_xx_21.gifhttp://www.faqs.org/health/images/uchr_07_img0706.jpg
Turner Syndrome missing X Distinctive features:
shorter than normal may fail to start puberty when
they should because ovaries (which produce eggs, as well as the sex hormones estrogen and progesterone) fail to develop properly.
have a stocky appearance arms that turn out slightly at the
elbow receding lower jaw short webbed neck low hairline at the back of the
neck lymphedema (swelling of hands
and feet) heart and/or kidney defects high blood pressure infertility
https://images1.clinicaltools.com/images/gene/karyotypes/turnersyndromexnoy.jpghttp://learn.genetics.utah.edu/content/disorders/whataregd/turner/images/turner_person.jpg
Klinefelter Syndrome - XXY Distinctive features:
develop as males often tall don't develop secondary
sex characteristics, such as facial hair or underarm and pubic hair
extra X chromosome primarily affects the testes, which produce sperm and the male hormone testosterone
http://images2.clinicaltools.com/images/gene/trisomyxxy.jpghttp://learn.genetics.utah.edu/content/disorders/whataregd/klinefelter/images/kleinfelter_person.jpg
Cri du chat Syndrome deletion 5 Distinctive features:
small head (microcephaly)
an unusually round face a small chin widely set eyes folds of skin over their
eyes a small bridge of the
nose. heart defects muscular or skeletal
problems hearing or sight problems
http://www.biology.iupui.edu/biocourses/N100/2K2humancsomaldisorders.htmlhttp://www.findhealer.com/glossary/images/criduchat.gif
Williams Syndrome missing part 7 Distinctive features:
mental retardation heart defects unusual facial features (small
upturned nose, wide mouth, full lips, small chin, widely spaced teeth)
low birth weight failure to gain weight
appropriately kidney abnormalities, and low
muscle tone behaviors, such as
hypersensitivity to loud noises and an overly outgoing personality.
http://medgen.genetics.utah.edu/photographs/diseases/high/williams_syndrome_original1.gif
Multifactoral Genetic Disorders Alzheimer’s Disease
People who have the disorder slowly lose their ability to think clearly. At first, they may forget words or names, or have trouble finding things. As the disorder worsens, they may forget how to do simple tasks (such as walking to a friend's house or brushing their hair). Some people with Alzheimer's also feel nervous or sad
http://2.bp.blogspot.com/_kQrramY7bs4/RvB6HmEZFCI/AAAAAAAACQU/b6sysujyPKU/S420/alzheimer.normal.brain.jpg
More Mendel
Besides dominance/recessive, there is: incomplete dominance co-dominance multiple alleles polygenic inheritance pleiotrophy
Definitions
Phenotype – the expression of the genes – what the organism looks like and how it functions
Genotype – genes inherited – the alleles of the genes whether expressed or not
For example, if an organism inherits both the dominant and recessive alleles, it would have the phenotype of the dominant allele, but the genotype would be both dominant and recessive
Incomplete Dominance
Organism receives both alleles, in this case, red flower and white flower. The phenotype is intermediate to red and white - pink
http://dwb4.unl.edu/Chem/CHEM869N/CHEM869NLinks/www.rrz.uni-hamburg.de/biologie/b_online/ge08/01.gif
Co-dominance
When alleles share fully in the expression of the gene. For example, our blood types A, B, AB and O.
http://www.agen.ufl.edu/~chyn/age2062/lect/lect_10/bloodtyp.gif
Multiple Alleles
Follows same “rules” as other inheritance
Frequency of the allele can change with the population
http://static.icr.org/i/articles/imp/imp-3647-Allele%20freq.jpghttp://1.bp.blogspot.com/_DZH2cmCoois/Rdyly-4z72I/AAAAAAAABAg/Z8LaotoW8s4/s400/ABO_antigens.jpg
Polygenic Inheritance
But we don’t inherit one gene… Estimates range from
20,000 to 40,000 coding genes
http://porpax.bio.miami.edu/~cmallery/150/mendel/c8.14x13.polygenic.jpghttp://www.diversitycourses.co.uk/diversity3.jpg
Pleiotrophy
Hemophilia – single gene influence multiple phenotypic traits Lacking protein in blood Excessive bruising Pain and swelling in the
joints Vision loss Anemia Fatigue Neurological problems if
bleeding occurs in brain
http://www.friesian.com/history/impfamil.jpghttp://upload.wikimedia.org/wikipedia/commons/a/a3/XlinkRecessive.jpg
Gender
Is it a boy or girl? Mom always has XX Dad has XY Dad’s sperm cells – two
X and two Y (remember, DNA replicates first)
Mom’s egg cells – four X cells
http://www.csupomona.edu/~biology/bio110/inherit/fig10.gif
Not true for all species
Some species, the female has different chromosomes and the male has the identical chromosomes. In this system, the chromosomes are referred to as W and Z
Some species gender is determined by temperature Some species can change from male to female or vice
versa Some species, only queens and drones reproduce Some species are both male and female –
hermaphrodite The term "hermaphrodite" derives from Hermaphroditus, the son of
Hermes and Aphrodite, who fused with the nymph Salmacis, and thus possessing physical traits of both sexes.