1. Genetics

2. Genes
Gene – is a heritable factor that consist of a length of DNA and influences a specific characteristic
Heritable means passed on from parent to offspring
Characteristic – refers to genetic traits
Eyes, hair color
Locus – a specific place on a chromosome where a specific trait occupies

3. Genes

4. Alleles Variations or versions of a gene
An allele is one specific form of a gene
Alleles differ from each other by one or only a few bases
If one or more bases (A,C,G, or T) is misplaced or substituted for a different base the result can be dramatic

5. Mutation A random rare change in genetic material
One type of mutation involves a change of the sequences of bases in DNA
When this happens the corresponding bases along the mRNA are altered during transcription
Thus changing the polypeptide
Changing the protein

6. Mutation
A mutation that provides an individual or a species a better chance for survival is considered to be a beneficial mutation.
Good chance that it is passed on to the next generation
Mutations that cause disease or death are detrimental mutations and are less likely to be passed on to future generations
Less likely to pass on because organism will not survive long enough to procreate
There are mutations that have no effect
When a mutation is successfully passed on from one generation to the next it becomes a new allele

7. Mutation
Base Substitution – the replacement of one base or nucleotide with another
Usually causes no change to the protein
But sometimes change results in a change that affects protein function
Sometime drastically
Because several amino acids have more than one codon it makes it possible that a mutation have no effect on a protein

8. Mutation - Base Substitution
Sickle – Cell Disease (AKA – Sickle Cell Anemia)
A mutation in the gene that codes for hemoglobin in red blood cells
Gives a different shape to the red blood cell
Cell takes on a crescent shape like a sickle

9. Mutation - Base Substitution
Sickle Cell
In this case one base is substituted for another so the 6th codon in this sequence of hemoglobin GAG becomes GTG
The result the amino acid glutamic acid is now valine instead
Valine has a different shape causing hemoglobin to take a different shape
Symptoms:
Weakness, fatigue, and shortness of breath
Oxygen cannot be carried efficiently by the irregularly shaped red blood cell
Hemoglobin tends to crystallize as well becoming less flexible
Red blood cells can get stuck in the capillaries causing blood clots

10. Mutation - Base Substitution
Sickle Cell
Although debilitating those who have sickle cell are resistant to malaria
Demographically sickle cell is found in those originating in West Africa or the Mediterranean

11. Genome / Histones Genome – the complete set of genetic
materials of an organism, as
defined by the order of bases in the
DNA
Our maps of human chromosomes are still far from complete.
There are many sequences we do not know what they do.
Complete genomes of some organisms have been worked out:
Fruit Fly Drosophila melanogaster
The bacteria Escherichia coli
Both have been genetically experimented for years

13. The Human Genome Project
Began in the 1990’s (government funded) International cooperation
Challenge was to sequence the human genome
Was completed in 2003
DNA sequences are entered into a data base and are available to researchers all over the world
Scientist are now working on deciphering the code
Which genes do what???

14. The Human Genome Project
Sequences are used by scientists:
Identify embryonic development
Evolutionary relationships with other species
For human health; aid in diagnosing, treating, and possibly preventing many ailments
allergies
diabetes
Cancer
Production of new medicines

15. Chromosomes
Prokaryotes have one chromosomes consisting of a circular DNA molecule
Prokaryotes can reproduce using binary fission (dividing) where as organisms like planta and animals more frequently use sexual reproduction
Involving a male and a female
Prokaryotes only have one parent SO ONE CHROMOSOME

16. Prokaryotes Chromosomes
Plasmids – small loops of DNA that are extra copies of the genetic material of the organism
Not connected to the main bacterial chromosome
Plasmid replicate independently of the chromosomal DNA
Help the cell adapt to unusual circumstances
Can also be found in Archaea
Not found in Eukaryotes
Can be used for Genetically Modified Organisms (GMO)

17. Chromosomes The DNA of eukaryotic cells occur as chromosomes
Chromatin – strands of DNA, not visible, and proteins called histones
This is the form chromosome takes when not dividing
Nucleosome – beads that consists of 2 molecules each of four different histones
DNA wraps twice around these eight protein molecules
DNA is attracted to the histone because DNA is negatively charged and the histones are negatively charged.
Between the nucleosomes is a single strand of DNA
Usually a 5th type of histone attached to the linking string of DNA near each nucleosome
Further wrapping the DNA molecule making it highly condensed

18. Chromosomes
The wrapping or packaging of DNA regulates the transcription process
This allows only certain areas of the DNA molecule to be involved in protein synthesis

19. Multiple Chromosomes
Eukaryotic cells have multiple pairs of chromosomes
Each have a set of instructions for the cell
So in eukaryote species there are different chromosomes that carry different genes

20. Multiple Chromosomes
Homologous Chromosomes – two chromosomes that carry the same genes
Two chromosomes is that one came from the father and the other from the mother
Homologous chromosomes carry the same sequence of genes but not necessarily the same alleles of those genes

21. Diploid and Haploid Cells
Diploid- describes a nucleus that has chromosomes organized into pairs of homologous chromosomes
Most humans cells are diploid cells
A set of 23 chromosomes
23 from mother
23 from father
Haploid – only have a single chromosome from each pair
Gametes
Human have 23 chromosome
The majority of sexual reproducing animal cells are Diploid
Exceptions are Male Bee, Wasp, and Ant cells
These are haploid

22. Diploid and Haploid Cells
n represents the haploid number and refers to the number of sets of chromosomes that a nucleus can have
Human egg have n = 23
Human sperm have n = 23
Zygote – is formed and the two haploid nuclei fuse together matching up their chromosome pairs
Humans have 2n = 46

23. Chromosome Number
Generally speaking the number of chromosomes is a feature of particular organisms within a species.

24. Karyograms and Karyotypes
Karyogram – shows the chromosomes of an organism in homologous pairs of decreasing length.
Shape depends on position of the centromere
Used to show a persons karyotype
Karyotype – the specific number and appearance of the chromosomes in his or her cells

25. Karyograms and Karyotypes
How is it obtained?
Cells are obtained and grown in a culture
The cells are stained and prepared on a glass slide, to see their chromosomes under a light microscope
Photomicrograph images are obtained of the chromosomes during a specific phase of cell division called mitotic metaphase.
The images are cut out and separated, a process that can be done using scissors or a computer
The images of each pair of chromosomes are placed in order by size and the position of their centromeres.
Except for the 23 chromosome which can be of different sizes.

26. Sex Determination 23 pair of chromosomes is the sex chromosome
Determines sex
The X chromosome is much larger than the Y
X has many more genes
Human Females have XX
Female eggs produce only X chromosomes
Human Males XY
Male sperm have either an X or a Y
Autosomes – chromosomes that do not determine sex
Human have 22 pairs of autosomal chromosomes

27. Autoradiography
A technique in which radiation from a substance is captured on photographic film or camera sensor
Autoradiograms are exposed to radioactive particles being given off by the substance itself
Used in genetics to measure the length of DNA strands

28. Autoradiography
Cairns’ techniques involves injecting radioactive materials into the DNA samples that will expose the film faster.
Called radio markers
For measuring DNA strands the DNA forming during replication is given a radioactive form of a molecule called Thymidine.
Thymidine is a component of a DNA nucleotide
Thymine (T) with the pentose sugar (nucleotide)
³H-thymidine (³H radioactive isotope)
The radioactive ³H molecule is used as a radio marker to keep track of where those thymidine molecules are
Leaves traces of its presence on photographic film

29. Autoradiography John Cairns used this technique in 1962
Showed a bacterium chromosome is made up of a single circle of DNA
Replicated by being unzipped
According to Wikipedia he’s still alive