Download Genetics Notes - WasmundScience

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

Point mutation wikipedia, lookup

Meiosis wikipedia, lookup

Polycomb Group Proteins and Cancer wikipedia, lookup

Karyotype wikipedia, lookup

X-inactivation wikipedia, lookup

Neocentromere wikipedia, lookup

Chromosome wikipedia, lookup

Y chromosome wikipedia, lookup

Polyploid wikipedia, lookup

Skewed X-inactivation wikipedia, lookup

Ploidy wikipedia, lookup

Genome (book) wikipedia, lookup

Microevolution wikipedia, lookup

Dominance (genetics) wikipedia, lookup

Designer baby wikipedia, lookup

Genomic imprinting wikipedia, lookup

Epigenetics of human development wikipedia, lookup

Quantitative trait locus wikipedia, lookup

Gene wikipedia, lookup

Public health genomics wikipedia, lookup

Inbreeding avoidance wikipedia, lookup

Population genetics wikipedia, lookup

History of genetic engineering wikipedia, lookup

Medical genetics wikipedia, lookup

Genetic engineering wikipedia, lookup

Human genetic variation wikipedia, lookup

Behavioural genetics wikipedia, lookup

Hardy–Weinberg principle wikipedia, lookup

Inbreeding wikipedia, lookup

Hybrid (biology) wikipedia, lookup

Genetic drift wikipedia, lookup

Transgenerational epigenetic inheritance wikipedia, lookup

NEDD9 wikipedia, lookup

Koinophilia wikipedia, lookup

Transcript
Genetics Notes
Aristotle: Greek philosopher – lived 2300 years ago
*believed traits were carried in the blood as pangenes and
transported to the reproductive organs
-expressions such as blood relative and bloodline come
from this idea
*proven wrong when the discovery was made that traits for
inheritance were found in each cell on chromosomes and
had nothing to do with the blood
Gregor Mendel – Austrian Monk
*worked on the scientific study of heredity in the late 1800’s
*unique background in math and physics
*applied mathematical background (probability) to
reproduction of pea plants
*studied 7 traits for many generations
*used probability to predict outcome of a cross
*hypothesized that each trait is controlled by something
called a “factor” – we now call these factors genes
*first to use dominant and recessive
Mendel’s Laws
1. The Law of Segregation: a pair of factors (alleles) is separated
during the formation of gametes (meiosis)
2. The Law of Dominance: One allele shows up in the phenotype
while the other is hidden
3. The Law of Independent Assortment: Factors (traits) are
distributed to gametes independently (they don’t travel
together)
P1 Generation: parental generation
F1 Generation: first filial generation – offspring from P1 generation
F2 Generation: second filial generation – offspring from F1 generation
Applied Genetics
Biotechnology is the application of biological science to solve practical
problems
*people have applied genetics to everyday use longer than they
have actually understood them
-the natives used controlled breeding to develop corn and
potatoes from wild plants
- the domestication of the dog from wild wolves
Selective Breeding: the breeding of animals and plants to produce a
desired trait by choosing which animals/plants will be bred to
which animals/plants
ex.
Sheep for wool
Cattle for beef
Inbreeding: the crossing of organisms with similar genotypes
*when you cross two closely related animals, after several
generations you will probably have homozygous alleles for the
most desired traits
*you can also have homozygous alleles for undesired traits
Inbreeding can cause problems
-may carry a recessive allele that produces harmful
traits when homozygous
ex. Deafness in dalmations
-offspring may be weak or unhealthy
ex. Royalty married royalty to keep bloodline
pure and passed on recessive trait for
hemophilia
Outbreeding: crossing of distantly related organisms
*may come from different species or more often from different
breeds within the same species
-in some cases, the cross may result in larger, healthier
offspring
ex. Mule
*when two species are crossed, offspring is almost
always sterile because chromosomes don’t match
*outbreeding is done in order to cross the best qualities of each
species
-used to improve cattle
*Brahman cattle: resistant to heat and insects
*Hereford cattle: high quality beef
Polyploidy: cells have more than two sets of chromosomes
*rare – almost always lethal in animal cells
*desired trait in plant cells
-produce double flowers and larger fruit
-can be the source of a new species of plant
-polyploidy is induced by applying a chemical called
colchicine – prevents the cell from dividing
after the chromosomes have doubled
Genetic Engineering: Modification of genes using biotechnology
*combining DNA from genes of different organisms
-called recombinant DNA
ex. Genetic engineers have transferred specific
human genes into bacteria enabling them to
produce proteins
*applications of genetic engineering
-medicine
-insulin, antiviral drugs (interferon), human growth
hormone, vaccines
-gene therapy for hereditary disease
-crops, food
Ethical Issues
Human Genetics
Difficult to study patterns of inheritance
-humans have few offspring
-too many years between generations
-most of what we know about human inheritance comes from
studying families and inheritance patterns in populations
Pedigree: chart that shows how a trait and the alleles that control
that trait are inherited in a family
Karyotype: photograph that shows an individuals chromosomes
-used to determine chromosomal abnormalities
*too few or too many chromosomes
*abnormal chromosome size or shape
-chromosomes are arranged by size from biggest (#1) to
smallest (#23)
Chromosomal Disorders
*mutations can occur spontaneously – in most cases they are not
harmful and do not show up in the phenotype
-in severe cases, the fetus does not survive
-in a few cases, the mutation is able to sustain and the
child is born mentally or physically challenged
Non-disjunction: the failure of one or more chromosome pairs
to separate during meiosis
-this can result in monosomy – 1 chromosome per pair
instead of 2 or trisomy – 3 chromosomes instead of 2
Examples:
Down Syndrome: Trisomy at site #21
-mildly to severely developmentally disabled
-almond eyes and enlarged tongue
-short, stocky bodies
-muscle development and coordination poor
-prone to heart defects
Klinefelter Syndrome: Trisomy at site #23
-caused by an extra X chromosome in male XXY
-sterile
-causes feminine characteristics
-breast development, feminine body shape
-in females – XXX usually sterile and
developmentally disabled
Turner Syndrome: Monosomy at site #23
-female X instead of XX
-normal childhood – normal intelligence
-don’t go through puberty – do not reach normal
height and fail to develop sexually
-sterile
Sometimes a person is born with a normal number of chromosomes but
the chromosome structure is abnormal.
*Inversion
*Missing end
*Mutation
Cri-du-chat syndrome: disorder caused by a defective chromosome
-large deletion from chromosome #5
-cri-du-chat means cry of the cat
-babies have a cry that sounds like a cat’s meow
-extremely small head
-seriously developmentally disabled
-seldom survive more than 1-2 years
Most genetic disorders in humans are caused by single allele mutations
Recessive Genetic Disorders
*all alleles are passed on even if not expressed – these alleles
remain in the gene pool
*recessive disorders are not as common as you must have two
recessive alleles to exhibit the disorder
Tay-Sachs Disease: fatal genetic disorder that results
in the inability to break down lipids causing
an accumulation of the substance in the brain
*as lipids build up in the brain, the
individual suffers blindness and seizures
*usually causes death within the first
months of life
*most often found in Ashkenazi Jews in
in central Europe
-incidence is 100 times greater than
among non-Jews
Cystic Fibrosis: disorder that results in excessive
secretion of thick mucus from the pancreas, lungs
and other organs
*leads to blockage of digestive tract,
congestion of lungs, pneumonia, and other
infections
*if untreated, individuals die at an early age
*current treatments lead to prolonged life
*usually found in Caucasians
Dominant Allele Disorders
Huntington’s Disease: fatal disorder that involves the
deterioration of the nervous system – particularly the brain
*individuals don’t develop symptoms until late 30’s or early
40’s
*by this time, most people have passed it on to their children
Achondroplasia: Dwarfism
*never reach more than 4 ft. 4 inches
*arms and legs are disproportionately short
Other characteristics caused by dominant allele:
*polydactyly (extra fingers and toes)
*dimples, freckles, widows peaks, ability to roll tongue
**A dominant allele disorder is not always more common than a
recessive allele disorder
X-Linked Traits (sex linked)
1. Colorblindness – can’t distinguish between certain colors
2. Hemophilia – occurs almost exclusively in males
-blood can’t clot
3. Duchenne Muscular Dystrophy – progressively weakens
and destroys muscle tissue
Co-Dominant Allele Disorders
Sickle Cell Anemia: abnormal form of hemoglobin – the protein
in red blood cells that carries oxygen
*sickle cell is co-dominant to normal allele
*individuals affected by this disease contain a
mixture of normal hemoglobin and sickle cell
hemoglobin
*sickle cell attack begins when oxygen supply
becomes low – sickle cells start to stick together
and become tangled masses
*clogs capillaries and stop blood flow
*extremely painful and can cause death
*primarily found in Africans and African-Americans
*often found in areas where malaria is common –
individuals with sickle cell have an increased
resistance to malaria