Post on 25-Dec-2015
Genetics
Inheritance through Evolution
Essential Ideas
3.1 Every living organism inherits a blueprint for life from its parents
All members of a species have the same number of chromosomes- each with the same genes in the same gene
loci.
Understanding
A gene is a heritable factor that consists of a length of DNA and influences a specific characteristic.
The number of chromosomes
varies between species.
Understandings
A gene occupies a specific position on a chromosome.
Genes at particular loci
A gene for a specific trait occupies a corresponding place, a locus, on a chromosome.
Remember, you have two copies of each gene, one from mom and one from dad.
Understandings
The various specific forms of a gene are alleles.
Alleles differ from each other by one or only a few bases.
Review: gene lociTP53
Alleles: versions of genes
Variations of a gene
Differs by only a few base pairs
Transducin enables colour vision
Single base pair mutation at position 235 (T instead of C)
Colour vision vs. or no colour vision
Allele differences
Single nucleotide
polymorphism
Cystic Fibrosis
CFTR gene
Cystic Fibrosis
Mucous – necessary for proper fluid movement in the lungs and intestines
CFTR gene on chromosome 7
Can mutate to form excessive quantities
Autosomal recessive
Understandings
New alleles are formed by mutations.
Point mutation
Gene therapy is an experimental technique that uses genes to treat or prevent disease. In the future, this technique may allow doctors to treat a disorder by inserting a gene into a patient's
cells instead of using drugs or surgery.
Good or Bad?
Mystery of the Black Death
LRP5 gene – creates a protein receptor on immune system cell surface
Mechanism for HIV to infect cells
Missing the gene – can’t get HIV
Sickle cell disease
A base pair mutation to haemoglobin
Sickle cell disease (anemia)
Glutamic acid Valine
What differences in properties can
we deduce from the
structures?
How might this change the quaternary protein structure?
How about advantages?
Malaria and Sickle Cell Disease
Malaria
A parasitic disease
Caused by a plasmodium cell which causes cells to lyse
Carried by the Anopheles mosquito
Occurs in tropical regions
Symptoms: fever, shivering, vomiting and anemia
Death is common: kidney failure or severe anemia
Malaria
Malaria can’t infect sickled cells
Sickle cell trait (one copy of each allele)
Heterozygotes have a chemical imbalance with Potassium
Insufficient potassium cause Plasmodium to die
Understandings
The genome is the whole of the genetic information of an organism.
The entire base sequence of human genes was sequenced in the Human Genome Project.
Human Genome
The whole of the genetic information of an organism
Begun in 1990Completed in 2003
Essential Ideas
3.2 Chromosomes carry genes in a linear sequence that is shared by members of a species.
Key vocabulary
Homologous
Diploid
Haploid
Karyotypes
Sex-determination
autosome
Essential Ideas
3.3 Alleles segregate during meiosis allowing new combinations to be formed by the fusion of gametes.
Meiosis
Previously covered
Amniocentesis
Chorionic villus sampling
Essential Ideas
3.4 The inheritance of genes follows patterns.
Understandings
Mendel discovered the principles of inheritance with experiments in which large numbers of pea plants were crossed. I used the
word factor, not
gene
More Vocabulary
Genotype
Phenotype
Dominant allele
Recessive allele
Co-dominant alleles
Locus
Heterozygous
Homozygous
Carrier
Test-cross
Understanding
Gametes are haploid so contain only one allele of each gene.
The two alleles of each gene separate into different haploid daughter nuclei during meiosis.
Fusion of gametes results in diploid zygotes with two alleles of each gene that may be the same allele or different alleles.
Punnett Square
Lab Time: Monohybrid and Dihybrid Crosses with true dominance
Mendelian Genetics of Corn
Arabidopsis- Playing Mendel
Application
Inheritance of ABO blood groups
Blood Types = Multiple alleles
What are the 4 blood types in humans?
We use the letter to “I” to represent them
Time for blood lab
Understanding
Dominant alleles mask the effects of recessive alleles but co-dominant alleles have joint effects.
Many genetic diseases in humans are due to recessive alleles of autosomal genes although some genetic diseases are due to dominant or co-dominant alleles.
Some genetic disorders are sex linked. The patterns of inheritance is different with sex-linked genes.
Many genetic diseases have been identified in humans but most are very rare.
Sex-linked genes
Size of sex chromosomes
Types of traits
Colour blindness
Haemophilia
Duchene muscular dystrophy
Sample Punnett squares
Huntington’s disease
Dominant allele
Nerve damage
Co-dominant genes
Both expressed at the same time
Sample Punnett square
10.2 Understanding
Chi-squared tests are used to determine whether the difference between an observed and expected frequency distribution is statistically significant.
Bozeman Science
10.2 Application
Completion and analysis of Punnett squares
Dihybrid Crosses
Application
Pedigrees
worksheets
Understanding
Radiation and mutagenic chemicals increase the mutation rate and can cause genetic diseases and cancer.
Previously covered
Essential Ideas
3.5 Biologists have developed techniques for artificial manipulation of DNA, cells and organisms.
Understandings
Gel electrophoresis is used to separate proteins or fragments of DNA according to size.
PCR can be used to amplify small amounts of DNA.
DNA profiling involves comparison of DNA
Genetic modification is carried out by gene transfer between species.
Understandings
Clones are groups of genetically identical organisms derived from a single original parent cell.
Many plant species and some animal species have natural methods of cloning.
Animals can be cloned at the embryo stage by breaking up the embryo into more than one group of cells.
Methods have been developed for cloning adult animals using differentiated cells.
Cloning
Cutting DNA
Use restriction enzymes (endonucleases)
Recognize a set of base pairs (4 or 6)
Pasting DNA
Use DNA ligase
Recognizes sticky ends and attaches them
Copying DNA
Need a host cell
Most popular is Escherichia coli
Plasmids
Small circles of extra DNA
To copy a gene – glue it into a plasmid
How to insert in a plasmid
Plasmid removed from the host cell
Cut open with a restriction enzyme
Place copied gene into open plasmid
gene splicing
Pasted using DNA ligase
Now a RECOMBINANT PLASMID (vector)
Vector placed in bacterium
Human Insulin Production
Makes copies of gene
Express the gene
Genetically Modified Organisms (GMO)
Has an artificial genetic change
Gene transfer OR recombinant DNA
More competitive in the food market OR
Medical applications
Transgenic Plants
Flavr Savr
Delayed ripening and rotting
Some are more resistant to salt in the soil
Golden Rice
Added beta carotene
Helps with deficiency in vitamin A
Body uses beta carotene to make vitamin A
Maintains skin, teeth, aids in vision in low light
Transgenic animals
Used in medical treatment
Haemophilia – Factor IX
Natural cloning
Strawberry plants
Potato
Animal - hydra
IA idea Check out page 165
Cloning an Embryo Naturally
History of cloning
1890 – Hans Dreisch
Used sea urchins 1embryo to grow 2 identical embryos
Was not attempting to clone
kljlj
Unfertilized cell
Remove nucleus
Cultured cells
Cloning
Reproductice
Makes an entire organism
Somatic cell nuclear transfer
Therapeutic
Develop cells that have not differentiated
Ethical Issues
Start with human embryos
Skin to repair burns
New heart muscle to repair an ailing heart
New kidney tissue to rebuild a failing kidney
Previously covered
Gel electrophoresis
PCR
DNA profiling
Linkage Groups
Thomas Hunt Morgan
Early 1900’s
Worked with Drosophila melanogaster
Did not get 3:1 ratios
BGSU – Fruit fly research!
Reproduce every 2 weeks
Thousands of crosses
White eye vs. red eye
(mutants vs. wild type
Fruit fly ratios
White-eyed male x red-eyed female
3:1 (red to white)
White-eyed female x red-eyed male
2:2 (red to white)
How they discovered sex-linked genes
Understanding
Gene loci are said to be linked if on the same chromosome
Linked groups
Any two genes that are found on the same chromosome
Usually passed on to the next generation together
Can be autosomal or sex-linked
Drosophila gene map
Genotype notation
For linked genes
Skill
Identification of recombinants in crosses involving two linked genes
Gene linkage notation
Two horizontal bars symbolize homologous chromosomes and that locus of G is on the same chromosome as L
One G is on the maternal chromosome and one G is on the paternal homologue.
Read the pairs vertically; GGLL
G L____________________ G L
Example problemCross a GGLL with a ggll (G = grey, g = black; L = long-winged, l = short-winged)
G L____________________ G L
g l____________________ g l
x What will the
offspring look like?
All grey with long wings
Test cross problem
Take one of the previous offspring and mate it with a _______.
G L g l______ x ____ = g l g l
ggll
gl
GL
G L_____g l
Gl
G l_____ g l
gL
g L____g l
Gl
g l_____g l
Recombinants
Go back and look at the 2nd and 3rd possible offspring.
How do these compare to the parents?
These new combinations are known as recombinants.
Refers to both the new chromosome and resulting organism
Recombinants
Formed by
A way to increase genetic variability
Crossing over
Understanding
Variation can be discrete or continuous
The phenotypes of polygenic characteristics tend to show continuous variation
Application
Polygenic traits such as human height may also be influenced by environmental factors
Polygenic Inheritance
Involves two or more genes to control one phenotype
Continuous and discrete
Time for a video
Epigenetics: How food upsets our genes
How do you tell if a trait is continuous?
Is it either/or? (ear wax)
Is it a multiple allele? (blood type)
Displayed as bar charts
Polygenic traits
Will plot as a bell curve