DNA and GENETICS

DNA Structure Draw and label a diagram of a DNA molecule from memory.

Did you include… Sugar Phosphate Nitrogen base Complementary base pairing (A-T and G-C) Double stranded Double helix

Draw one nucleotide from memory.

Function and Structure Made of repeating nucleotides (subunit of nucleic acids) Sugar-phosphate backbone with hydrogen bonds weakly attaching nitrogen bases (ACTG) Sequence of nucleotides is the blueprint for you Changes in sequence of base pairs (mutations) can be good, bad, or neutral and are the ultimate source of evolution

Complementary Base Pairing Write the complementary strand: ACTTAACCGGATTCCATG

ACTTAACCGGATTCCATG TGAATTGGCCTAAGGTAC

Chargaff’s Rule %A = %T and %G = %C Why? If a DNA sample has 30% A and 20%G, how much %T and %C? --------------------------------------------------------------------- G=15% C= T= A=

DNA REPLICATION DNA strands are separated and unwind Original strands serve as template Free floating nucleotides attach to complementary base pairs Enzymes involved “Semi-conservative” model: each resulting DNA molecule has one original/parent strand and one new/daughter strand http://www.youtube.com/watch?v=zdDkiRw1PdU

Central Dogma DNARNAProtein

RNA RNA Ribonucleic acid Always single stranded Has ribose as sugar instead of deoxyribose Always single stranded Uracil (U) instead of Thymine (T) C=G A=U Three types of RNA mRNA – messenger RNA tRNA – transfer RNA rRNA – ribosomal RNA

DNA vs RNA--Quiz yourself: DNA, RNA, or Both? Single stranded Double stranded Uracil Can leave nucleus Replication Coded instructions Nitrogen base, sugar, and phosphate group Transcription Translation Smaller

Transcription Transcription – the process of making mRNA from DNA A.K.A. RNA synthesis Takes place in the nucleus of cells Enzymes, splicing (introns and exons) mRNA leaves nucleus http://www.youtube.com/watch?v=WgvnFYyJGZQ

Practice DNA = TAC - CCG - TAA - CTA - GCT - TTA

Transcription Practice DNA = TAC - CCG - TAA - CTA - GCT - TTA RNA = AUG - GGC - AUU - GAU - CGA - AAU

Codons Every 3 bases of mRNA codes for a specific amino acid Amino acids are bonded together to make proteins

RNA= UCG 

RNA= UCG  Serine

GUG CCC

RNA  PROTEINS Translation - The act of making proteins from the nucleic acid code found in mRNA; location: ribosomes tRNA – transfer RNA – translates the 3 letter codons into proteins tRNA has an anti-codon – a 3 letter sequence complementary to the mRNA codons Each anti-codon corresponds to a certain amino acid

Amino acids bond together and protein is released.

Translation http://www.youtube.com/watch?v=_6Rrymt6XwI

Cell organelles involved in protein synthesis and processing Nucleus—genetic code Ribosome—protein factory Endoplasmic Reticulum—transport system (“shipping and receiving”) Golgi Apparatus—modify, package, & transport (“post office” or “Amazon warehouse”) Proteins can be packaged in vesicles and shipped out or used within the cell Mnemonic: N R E G V

Practice: Transcribe and Translate! DNA: TGG CGA GGA RNA: Amino Acids:

Practice: Transcribe and Translate! DNA: TGG CGA GGA RNA: ACC GCU CCU Amino Acids: Threonine-Alanine-Proline

Check your vocabulary: hydrogen bond mutation nucleotide nucleus phenotype phosphate group polypeptides proteins ribonucleic acids - RNA ribosomes thymine transcription translation uracil adenine amino acids chromosomes codon complimentary strand cytosine deoxyribonucleic acid DNA replication double helix endoplasmic reticulum enzymes genes golgi apparatus guanine

Mutations Mutations can delete, substitute, invert, or insert one or more nitrogen bases to a gene. Parts or entire chromosomes can be copied, deleted, or altered. Effects can be positive, negative, or neutral. Mutations in gametes may be inherited in offspring generations. Mutations can be induced in biotechnology experiments—like oil-eating bacteria

Mutations Types Gene Missense—alters an amino acid Nonsense—makes stop codon Frameshift (Deletion, Insertion)—affects all subsequent amino acids

Nature vs Nurture You are a product of both your genes and your environment. Genes are segments of DNA that code for proteins: DNARNAProteins Many environmental influences affect gene expression (ex.—height is determined by both genes and nutrition) A phenotype is how a gene is expressed (ex.—height, brown hair, sickle cells)

Genetics Complete a Punnett Square for the following: An alien homozygous recessive for green skin mates with another alien who is heterozygous for red skin. Follow simple dominance rules. Predict the % of offspring with green skin and then with red skin.

PUNNETT SQUARES Diagrams used for: Example: Flipping Coins Predicting the result of a cross. Determining the probability of a certain result. PROBABILITY – the likelihood that something will happen (it is not definite) Example: Flipping Coins What is the probability of HEADS? 1/2 What is the probability of TAILS? What is the probability of 2 HEADS in a row 1/2 x 1/2 = 1/4 Each flip is an independent event Previous outcomes DON’T affect future outcomes

GENETICS – the study of heredity. HEREDITY – the transmission of genes from parents to offspring. GREGOR MENDEL – the father of genetics.

Vocabulary: A. Small section of DNA coding for a protein B. Genetic makeup; ex. Tt C. Gene that is masked by another; represented by a lower case letter; ex. t D. Gene that covers up or masks another gene; represented by a capital letter; ex T E. Two identical forms of a gene: ex TT or tt F. Two different forms of a gene: Tt G. Physical appearance of expression of a gene; ex. Brown eyes H. Different forms of a gene; ex red or white flowers Phenotype Genotype Heterozygous Homozygous Dominant Recessive Gene Allele

MENDEL’S CONCLUSIONS from pea plant experiments: Traits are controlled by genes GENE – small segment of DNA on a chromosome that codes for a trait.

2. Genes have alternative forms. ALLELE – alternative forms of a gene Every individual has 2 alleles for each trait One from mom One from dad Example: Purple flowers = P (from mom) White flowers = p (from dad) Genotype of offspring = Pp

3. Alleles can be dominant or recessive Dominant alleles are always expressed Recessive alleles can be masked by Dominant ones. Recessive alleles are expressed only when there are two copies EXAMPLES: T- tall TT - tall t – short Tt – tall tt – short

4. An individual is said to be Homozygous if both of its alleles are the same. TT or tt DD or dd An individual is said to be Heterozygous if its alleles are different. Aa Tt Bb Dd

6. LAW OF SEGREGATION - alleles are separated during the formation of gametes. A gamete can only have ONE allele or THE OTHER T = Tall t = short If a plant has Tt, gametes can either have a T or t in them If a plant has TT, gametes can only have T in them If a plant is tt, gametes can only have a t in them **Remember—letters represent forms of a gene!

LAW OF INDEPENDENT ASSORTMENT - alleles for different characteristics are distributed to gametes independently. EXAMPLE: Just because you have one dominant trait (Ex: Brown eyes), does not mean that you have ALL dominant traits.

Incomplete Dominance and Co-Dominance

Incomplete Dominance Neither allele is dominant over the other. Heterozygous individuals have a phenotype that is in between the homozygous individuals Understand the inheritance pattern—symbols may differ (caps, lower case, ‘) and be able to read keys.

Snapdragons In snapdragons, flower color can be red, pink, or white. The heterozygous condition results in pink flowers WW RW RR

Incomplete Dominance Cross Key: R= Red r= White F1 Phenotype: 100% pink F1 Genotype: 100% heterozygous Rr

F1 Cross Key: R= Red r= White Phenotype: 1:2:1 25% Red 25% White 50% Pink Genotype: 1:2:1 25% homozygous RR 25% homozygous rr 50% heterozygous Rr

Co-dominance Both alleles are expressed equally Neither allele is recessive Both expressed as if they are a mixed dominance--patterns Erminette chickens Roan Cows/Horses

Co-Dominance Erminette Chicken Key: B =Black B1 = White B B B1 B B1 B B1 B1 B B1 B B1 P generation Black chicken X White chicken F1 generation = erminette (checkered patterned) Phenotype: 4:0 or 100% erminette Genotype: 4:0 or 100% heterozygous

Multiple Alleles So far every trait has had only 2 variations Some characters have more than two  ex. Blood types Individuals still have only 2 alleles Examples: Coat color in rabbits

Multiple Alleles C= full color  Dominant to all other alleles cch = Chinchilla  recessive to C dominant to c ch = Himalayan  recessive to both C and cch. Dominant to c allele c= albino, no color  recessive to all other alleles. Inherit C  cch  ch  c Dominant Recessive (Continuum of dominance)

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What’s your type? Multiple Alleles AND Codominance

Blood Type Percentages Data from CDC 2002

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Blood Type Inheritance (Understand PATTERN, read keys.)

Incomplete and Codominance

Incomplete Dominance When one trait does not completely take over the other trait. Based on the above definition what do you think would happen when a homozygous black cat (BB) crosses with a homozygous white cat (WW)? BB x WW

BB x WW (Incomplete Dominance) BW BB- black WW- white BW- grey 4/4 grey kittens

Codominance When one trait is neither dominant or recessive, therefore both are expressed. Based on the above definition what do you think would happen when a homozygous black cat (BB) would cross with a homozygous white cat (WW)?

BB x WW (Codominance) B W BW BB- black 4/4 striped WW- white BW- black and white striped 4/4 striped

Karyotypes Charts or pictures that show chromosomes; help to determine chromosomal disorders and gender Can see extra or missing chromosomes (whole or part)

Pedigree Charts that show how traits are inherited through generations; can help determine mode of inheritance Circles=female Squares=male Read KEY! Different colors/shading show people expressing trait (Sometimes half of a colored/shaded symbol show carriers)

has 47 total chromosomes in his body cells 1. Turner’s Syndrome A Male who has an extra X chromosome; he has 47 total chromosomes in his body cells 2. Klinefelter’s Syndrome B Female who is missing an X chromosome—only has one copy (45 total chromosomes in body cells) 3. Down Syndrome/Trisomy 21 C Dominant gene mutation; usually begins in midlife; brain damage begins and person loses control over his/her body; 50% chance of giving this disease/gene to offspring 4. Hemophilia D Bleeding disease; more males than females (sex-linked); lack of clotting factor in blood—lots of external and internal bleeding when blood vessels broken 5. Sickle cell anemia E Extra copy of the 21st chromosome; short stature, slanted eyes, lower intelligence 6. Color blindness F Cannot see all colors; sex-linked inheritance pattern or head trauma 7. Huntington’s Disease G Red blood cells are not shaped properly; can cause tiredness from not carrying enough oxygen; displays codominance 8. PKU H. Lack enzyme to break down a certain amino acid; can cause severe mental retardation

Vocabulary recessive sex-linked test cross biotechnology cloning DNA fingerprinting DNA sequencing electrophoresis gene therapy genetic engineering genetically modified organisms recombinant DNA selective breeding stem cell transgenic organism alleles chromosomes codominance dominant DNA genes genetics genotype heterozygous/hybrid homozygous/pure incomplete dominance multiple alleles pedigree phenotype polygenic Punnett square