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Unit VII: Genetics
Understanding our genes and the ways they are passed to the next generation.
Basic Genetics Modern Genetics
A. Basic Genetics
Genetics = study of heredity
understanding of how characteristics get passed from parent to offspring, generation to generation
b) Traits = specific characteristicSeed Shape – ________________Seed Color – _________________Seed Coat – __________________Pod Shape – _________________Pod Color – __________________Flower Position – ______________Flower Color – ________________Plant Height – ________________
1. Gregor Mendel Monk - studied pea plants in the 1800’s
a) True breeding = purebred
Trait Allele = ________________
c) Generations
P = parent generation – original plants
F1 = first filial generation = offspring of the original plants
F2 = second filial generation = offspring of F1
d) ___________ – for each trait Mendel crosses true breeding plants and makes observations of the offspringex: P ____________________________ F1 ________________________
Only 1 characteristic showed in the F1 generationWhy not a blend of the parent plants?_________ – __________________________________________________________
All tall plants
e) Conclusions
1. biological inheritance is determined by factors that are
passed from one generation to the next
________________
________________________
2. ____________________ – _______ _______________________________________________________________________________________________________________________________.
f) Segregation
What about the F2 generation?
What happens next?
Were the recessive alleles still present in the pea plant?
Cross - ________________
Ex: ________________________________________
F2 – Mostly Tall; some Short; Short trait reappeared
Some how the short trait separated from the tall trait
1. ________________________________________
___________________________________________________________________________________________________________________________________.
As a result of fertilization, _________________________.
As a consequence, _____________________ are likely to be produced.
Short separated from tall
2. Probability and Inheritancea) ________ = ____________________________________
_____________ = same alleles (TT or tt)_____________ = different alleles (Tt) = Hybrid
b) ___________ = ____________________ (Tall or Short)Usually determined by the genotype –
_____________ ____________________________________________.
Can two organisms have the same phenotype but different genotypes?
Phenotype = Tall ____________________
How could the genotype be determined?_______________________________________
c) Punnett Square
representation of parental gametes and
the different allelic combinations of the offspring
ex: Cross: True breeding Tall x True breeding Short
1. Determine the genotypes of the parents
2. Determines the possible gametes of the parents (segregation)
3. Write the gametes on the outside of the box
4. Combine the parents gametes (recombination)
Remember only 1 gamete from each parents
______________________________________________________________________________________________________________________________
ex: Cross: Heterozygous Tall x Heterozygous Tall
What is the genotype ratio?
What is the phenotype ratio?
Through his knowledge of math and detailed record keeping, with thousands of pea plants Mendel always had this ratio in the phenotypes.
d) ____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________.
Not only did Mendel look at single traits, he observed the probability of the inheritance of multiple traits at the same time.
What if the plants are tall with round seeds and short with wrinkled seeds what allelic combinations will occur in successive generations?
What if the genes are on the same chromosome?- _________________
ex: Dihybrid Cross
the organisms are heterozygous for two traits. (Use letters that are easy to tell the difference)
Phenotype Ratio:
______________
______________
______________
______________
3. Other Patterns of InheritanceNot all genes come with dominant and recessive alleles
a) _____________________ – neither allele is dominant___________________________________________ex: Flower Color in Snap DragonsR = red; W = white
Red Flower x White Flower
Genotype Ratio:
Phenotype Ratio:
b) Codominance
________________________________
some cells produce one allele other cells produce the other
ex: Roan Colored Cattle
R = red coat; W = white coat
RW = Roan = Some red hair some white hair in the coat
What is the probability that the offspring of two roan colored cattle would be roan colored?
c) Multiple Alleles genes that have __________________________the individual only has 2 alleles, but more than two exist in the population
ex: Blood Types__________________________________________________________________________________
Who is the Daddy?
A woman with type A blood has a child with type O blood, but she is unsure of the father. Bob has type AB blood and Bill has type A blood.
Who is the baby’s daddy?
d) Polygenic Traits traits produced by the interaction of many genesShow a wide range of phenotypes
Ex: Skin color, Eye Color, Height
e) Sex Linked Traits genes that occur on the sex chromosomesX and Y chromosomes XX = female; XY = maleX chromosome is larger and carries more genes
Since males only have 1 X chromosome, what ever allele is on the chromosome shows up in the phenotype
Females have two alleles for the geneex: color blindness and hemophilia
eye color in drosophila
Ex: Color Blindness
A normal man and a woman that is a carrier for
colorblindness have children.
a) What is the chance they will
have a colorblind child?
b) If they are having a girl what is the chance she will becolorblind? A boy?
a) Pedigree a diagram of family relationships that uses symbols to represent people and lines to represent genetic relationships. easier to visualize relationships within familiesPedigrees are often used to determine the mode of inheritance (dominant, recessive, etc.) of genetic diseases.
4. Human Inheritance
b) Karyotype and Amniocentesis
picture of chromosomes
22 pairs of autosomes, 1 pair of sex chromosomes
Used to determine gender
and chromosomal disorders
c) Human Genetic Diseases / Disorders1) Albinism
_________________lack pigment in skin, hair,
eyes
2) Cystic Fibrosis _________________excess mucus in lungs;
increases susceptibility to infections; death in childhood unless treated
3) Phenylketonuria (PKU) _________________accumulation of
phenylalanine (amino acid) in tissue
body can not break down the amino acid
mental retardation if they eat phenylalanine
4) Tay-Sachs Disease ____________________higher occurrence (1/100 vs 1/100,000) in Jewish families of eastern European ancestrylipid accumulation in brain cells, nervous system break down death in early childhood
5) Achondroplasia Dwarfism dominant allelebones fuse and stop growth
6) Sickle Cell Anemia ____________________red blood cells have a crescent shape misshapen hemoglobincan not carry O2 as well
7) Polydactyl dominant alleleextra toes and fingersnot always expressed
8) Down Syndrome chromosomal disorderextra 21st chromosome cause by _____________________
9) Huntington’s Disease______________________Usually ___________ of symptoms______________, loss of coordination
10) Duchenne muscular dystrophy___________________Muscle degeneration that causes usually death
B. Modern Genetics
1. Griffiths’ Experiments – 1920s
2 Strains of bacteria
One strain is deadly
Even when killed, the deadly strain can pass something to the non-deadly strain to make it a killer!
2. Avery’s Experiments – 1940sRepeats Griffith’s experiments but adds enzymes that break down different compounds in the cells
Not until he destroys DNA that the mice live!
3. Watson and Crick – 1950’s Used Rosalind Franklin’s x-ray pattern of DNA to build its 3-D structure _____________________________ _____________________________
a) DNA Structure Nucleotides A = _________________ B = _________________ C = _________________
Nucleotide Gene Chromosome ______________________________________________________________________________________________
From the human to the DNA – PBS Flash
DNA STRUCTURE MOVIE
4. DNA Replication a) Occurs inside _________ during S phase of cell cycle b) DNA molecules ____________________, then produces two _______________________ following the rules of base pairing c) Each original strand serves as ______________ the new strand
T A C C G G A C C C G T A G G C A A T A GA T G G C C T G G G C A T C C G T T A T C
Original DNA DNA “Unzips”
T A C C G G A C C C G T A G G C A A T A G
A T G G C C T G G G C A T C C G T T A T C
Enzymes fill in nucleotides
Check out this site on your own for a more detailed explantation
More Complicated but explains the process really well.
http://207.207.4.198/pub/flash/24/menu.swf
Easy Version of DNA Replication
5. Protein Synthesis
a) RNA = ____________________
single stranded nucleic acid
contains Ribose as the sugar not __________ as in DNA
has the base Uracil instead of _________ as in DNA
Types of RNA
b) Transcription
1st step of protein synthesis; similar to replication
DNA mRNA
Occurs in the ______________
“Unzip” DNA – uses ______________________________
RNA polymerase fills in complimentary RNA bases
mRNA detaches from DNA
mRNA leaves nucleus
Simple Trasncription Animation
Just another Trancription animation
T A C C G G A C C C G T A G G C A A T A G
A T G G C C T G G G C A T C C G T T A T C
Original DNADNA “Unzips”
A U G G C C U G G G C A U C C G U U A U C
Enzymes fill in RNA nucleotidesRNA breaks from DNADNA reconnects
The groups of 3 bases on the mRNA is called a CODON
The codon codes for specific amino acids when making a protein
c) Translation2nd step of protein synthesis______ ______ _____ ______occurs in the ______________ at the _______________Ribosome reads __________ on mRNAMatches the _______ to an ____________ on tRNA
Ribosome reads next codon and brings in next tRNA with matching anticodonSince tRNA is attached to Amino Acids – __________ ___________________________________This proximity allows the _______________Makes a peptideRepeats until mRNA says stop
More than 1 ribosome can attach to the mRNA at a time
Makes multiple peptides
Translation Animation
d) Protein Synthesis Overview
e) Genes code for peptides generally a protein is the combination of more than 1 peptide
To see it in some more detail check out the following website on protein synthesis
http://learn.genetics.utah.edu/content/begin/dna/
Try this website as an interactive for replication and protein synthesis
http://www.pbs.org/wgbh/aso/tryit/dna/shockwave.html
6. Mutations
Changes in the DNA sequence
Some are good
Some are bad
Most are neutral
Mutations are only passed to the next generation if they occur in gametes
Mutations in somatic cells are not passed – acquired characteristics are not passed
a) Gene Mutationschanges in a single gene
1) Point Mutations – involve just one nucleotide______________ = change one nucleotide for anotherex:
T A C G C G A C C C G A
becomesT A C G C C A C C C G A
the change may or may not change the amino acid
2) _________________________________________________ of a single nucleotidechanges _____________________________________usually affects all amino acids after the mutationex: DNA: T A C C G G A C C C G A
mRNA: A U G G C C U G G G C UAmino A: Met Ala Try Cys
InsertionDNA: T A C G C G G A C C C G
A mRNA: A U G C G C C U G G G C
UAmino A: Met Arg Leu Gly
The order of amino acids changed changes protein (big time)
Ex:
delete 1 letter
THE FAT CAT ATE THE RAT THE FTC ATA TET HER AT ????
Completely change everything after the deletion
No longer makes sense The same thing happens with the protein
The order of the letter (amino acids) determines the structure of the words and sentence (protein)
One little mistake can completely change the meaning
b) Chromosomal Mutations
changes the structure of a chromosome
rearrange the genes on a chromosome
1) _________________
2) _________________
3) _______________________________
4) _______________________________
______________________________________
Chromosomal Mutations
c) Mutagenic Agents factors that cause mutations 1) Radiation –
X-rays ultraviolet radioactive substances, and cosmic rays
2) Chemicals – formaldehyde, benzene, asbestos fibers THC
nicotine
7. DNA Technology ways in which the knowledge of DNA can help benefit society
a) Selective Breeding _______________________________________________________________________________________________________________
ex: dogs, cattle, crops selective breedinghas been occurring for 1000s of years
b) Genetic Engineering recombinant DNA; transfer DNA from one organism to anotherisolate gene ________________________________ combine DNA of organisms place recombinant DNA in a new organism*restriction enzymes = cut DNA at very specific sequences
can be used to make a variety of products
bacteria that can make: Insulin, Human Growth Hormone
crops that resistant to disease and insects
livestock with extra copies of growth hormone gene
c) Cloning
making an exact genetic copy
Remove the nucleus of an egg cellUse the nucleus of a body cell Insert the nucleus into the egg cell Grow the egg cell Identical genetic copy of the body cell
organism
Click and Clone
d) Gel Electrophoresismaking “DNA Fingerprints”
use restriction enzyme to cut DNA into fragments
place DNA into a porous gel electrify gel and DNA fragments
move small pieces move the farthest
DNA banding pattern = finger print
Gel Electrophoresis - Learning Center
Gel Electrophoresis Virtual Lab
e) Human Genome Project sequence all human DNAmap and locate all thehuman genes about3,000,000,000 base pairs inorder
help to find and cure diseases
Gene Therapy find defective gene andreplace it with a healthy gene