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 – round or wrinkledSeed Color – yellow or greenSeed Coat – gray or whitePod Shape – smooth or constrictedPod Color – green or yellowFlower Position – axial or terminalFlower Color – purple or whitePlant Height – tall or short

1. Gregor Mendel Monk - studied pea plants in the 1800’s

a) True breeding = _____________

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) Crosses – for each trait Mendel crosses true breeding plants and makes observations of the offspringex: P Tall Pea Plant x Short Pea Plant F1 All tall pea plants

Only 1 characteristic showed in the F1 generationWhy not a blend of the parent plants?_________ – cross between parents with different traits

All tall plants

e) Conclusions

1. biological inheritance is determined by factors that are

passed from one generation to the next

____________

____________ = different forms of genes

2. _____________________ – some alleles are dominant over recessive alleles. The recessive trait will only show if the dominant trait is not present.

f) Segregation

What about the F2 generation?

What happens next?

Were the recessive alleles still present in the pea plant?

Cross - F1 x F1

Ex: Hybrid Tall Pea Plant x Hybrid Tall Pea Plant

F2 – Mostly Tall; some Short; Short trait reappeared

Some how the short trait _________ from the tall trait

1. __________________________________________ When gametes are formed during meiosis there is asegregation/separation of alleles on homologouschromosomes.

As a result of fertilization, __________________________.

As a consequence, _____________________ are likely to be produced.

Short separated from tall

2. Probability and Inheritancea) ________ = genetic make up / two alleles of an individual

___________________ = same alleles (TT or tt)__________________ = different alleles (Tt) = Hybrid

b) _______________ = physical characteristic (Tall or Short)Usually determined by the genotype – sometimes the ___________ can affect the

phenotype.

Can two organisms have the same phenotype but different genotypes?

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

3. Write the gametes on the outside of the box

4. Combine the parents gametes

Remember only 1 gamete from each parents

T T t t

T T

t

t

T t T t

T t T t

All the offspring are genotype Tt – heterozygousThe genotype tells the phenotype – Tt TallIn the heterozygous the recessive allele is hidden

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 10,000s of pea plants Mendel always had this ratio in the phenotypes.

T t x T t

d) _________________________________ If the genes for two different traits are located on different Chromosomes (____________________ chromosomes), they segregate randomly during meiosis and, therefore, may be _________________________ of each other.

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?

ex: Dihybrid Cross

the organisms are heterozygous for two traits. (Use letters that are easy to tell the difference)

T R T r t R t r

T R

t R

T r

t r

T T R R T T R r T t R R T t R r

T T R r T t R r

T t R rT t R R

T t R r T t r r t t R r t t r r

T t r r

t t R rt t R R

T T r r

Phenotype Ratio:

9 Tall Round

3 Tall Wrinkled

3 Short Round

1 Short Wrinkled

3. Other Patterns of InheritanceNot all genes come with dominant and recessive alleles

a) Incomplete Dominance – neither allele is dominantheterozygous results in a mix of characteristicsex: Flower Color in Snap DragonsR = red; W = white

Red Flower x White Flower

R R

W

W

Genotype Ratio:

Phenotype Ratio:

b) Codominance

both alleles show in the phenotype

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 more than two allelesthe individual only has 2 alleles, but more than two exist in the population

ex: Blood TypesIA = type A; IB = type B; i = type O IA & IB are codominant but both are dominant over i

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?

Bill is the father

d) Polygenic Traits traits produced by the interaction of many genesShow a wide range of phenotypes

Ex: Skin color, Eye Color, Height

e) _________________________ 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

Ex: Color Blindness

A normal man and a woman that is a carrier for

colorblindness have children.

X Y x X Xn

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?

Watch for the wording of the question

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

recessive allelelack pigment in skin, hair, eyes

2) ____________________ recessive alleleexcess mucus in lungs;

increases susceptibility to infections; death in childhood unless treated

3) _____________________ (PKU) recessive alleleaccumulation of phenylalanine

(amino acid) in tissuebody can not break down the

amino acidmental retardation if they eat

phenylalanine

4) ________________ Disease recessive allelehigher 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) ________________________ codominant allelered blood cells have a crescent shape misshapen hemoglobincan not carry O2 as well

7) Polydactyl dominant alleleextra toes and fingersnot always expressed

8) ____________________ chromosomal disorderextra 21st chromosome cause by nondisjunction

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!

DNA = molecule that stores and transmits genetic information

3. Watson and Crick – 1950’s Used Rosalind Franklin’s x-ray pattern of DNA to build its 3-D structure Double helix with complimentary base pairs

a) DNA Structure Nucleotides A = _______________ B = _______________ C = _______________

__________________________ ________________From the human to the DNA – PBS Flash

DNA STRUCTURE

MOVIE

4. DNA Replication a) Occurs inside the ______ during S phase of cell cycle b) DNA molecules separate into ___ strands, then produces two new complimentary strands following the rules of base pairing c) Each original strand serves as a __________ for 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) _________ = Ribo Nucleic Acid

single stranded nucleic acid

contains Ribose as the sugar not __________ as in DNA

has the base _______ instead of _________ as in DNA

Types of RNA _______ = messenger RNA carries gene out of the nucleus _______ = ribosomal RNA makes up ribosome _______ = transfer RNA brings in amino acid

b) Transcription

1st step of protein synthesis; similar to replication

DNA ______________

Occurs in the ______________

“Unzip” DNA – uses 1 side of DNA as a template

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 synthesismRNA ______ __________ ___________occurs in the ______________ at the _______________Ribosome reads ___________ on mRNAMatches the codon to an anticodon on tRNA

Ribosome reads next codon and brings in next tRNA with matching anticodonSince tRNA is attached to Amino Acids – two amino acids are located next to each otherThis 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

___________ in the _________ sequence

Some are ____________

Some are ____________

Most are _____________

Mutations are only passed to the next generation if they occur in _________

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 nucleotidesubstitution = 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) __________________ Mutationsinsertion or deletion of a single nucleotidechanges the codons read by the ribosomeusually affects _________ 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) Deletion

2) Addition / Duplication

3) Inversion – rearrange the genes

4) Translocation – move a piece of a chromosome to a non homologous chromosome

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 choosing specific traits in organisms, mating the organisms, and hoping some of the offspring have the combinations of the traits

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 cut DNA with restriction enzymes 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