Genetics

Inheritance of Traits

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.

Questions?

BJ Shaw Panochthus frenzelianus American Museum of Natural History 2004