DNA Structure

DNA STRUCTUREBlueprint of Life Standard 5a-c

5a. DNA & RNA DNA is a double helix made of a

sugar-phosphate backbone with complimentary bases paired in middle

Nucleotide (sugar, phosphate, & base)

A pairs with T C pairs with G

RNA vs. DNA Difference DNA RNA# of Strands Double SingleBases thymine uracilSugar Deoxyribose Ribose

Questions 1. The monomers that are put together

to make nucleic acids are called: A) Nucleotide B) Phosphate C) Base D) Sugar

A. Nucleotides

C. Nucleic Acids2. DNA & RNA are made up of which type of macromolecule?

A) CarbohydrateB) LipidsC) Nucleic AcidsD) Proteins

DNA RNA

-________ stranded - ______ stranded- ____________ (sugar) - _______ (sugar)- thymine (nitrogenous base) - _____ (nitrogenous base)

1. DNA or RNA?2. Identify the bases in strand B

GTGACC

5b. DNA Replication DNA Replication makes a

copy of DNA before cell division (mitosis or meiosis)

DNA replication is semi-conservative Each parent strand is a

template for new daughter strand.

DNA has anti-parallel strands They run in opposite directions

Enzymes carry out replication 1) Helicase – unzips DNA 2) Primase – starts

replication 3) Polymerase – matches A-

T, C-G to make new strands 4) Ligase – glues lagging

strand fragments together

Question What does semi-conservative mean?

A) Strands are anti-parallel. B) The old strands serve as templates for

the new DNA. C) The old strands are lost.

What enzyme matches DNA base pairs (A-T, C-G)?

A) HelicaseB) PrimaseC) PolymeraseD) Ligase

B. Old strand is conserved

C. Polymerase

5c. Genetic Engineering Recombinant DNA contains DNA

from 2+ organisms. Restriction enzymes cut out gene

from DNA Vectors (bacteria & viruses) can be

used to insert new gene into cell. Uses:

1) Make medicines Ex: insulin, human growth hormone

2) Food Crops Ex: pest-resistant, larger fruits/veggies

PROTEIN SYNTHESISDNA > mRNA > ribosome > proteinStandard 4a & b

4a. Protein SynthesisProtein Synthesis = making

proteins 1. Transcription = DNA >

mRNA DNA is transcribed

(copied) into messenger RNA (mRNA) to leave the nucleus

DNA is too big, it does not leave the nucleus

mRNA carries the info in DNA out of the nucleus to the ribosomes in the cytoplasm

4a. Protein Synthesis 2. Translation = mRNA > protein mRNA is translated into a protein

by a ribosome

Codon = 3 letter “words” on mRNA Ex. U G G U C A A U C

Transfer RNA (tRNA) matches each codon and transfers the correct amino acids

Amino acids add together to make a polypeptide chain, which becomes a protein

4b. Build a Protein 1. Transcription DNA > mRNA

Base Pairing Rules DNA: A-T C-G mRNA: A-U C-G

Transcribe the DNA template strand into mRNA

DNA : C T G T A C G G A template strandmRNA: G A C A U G C C U

A base sequence of DNA is shown below.

ACAGTGC How would the base sequence be

coded on mRNA? A) TGTCACG B) GUGACAU C) UGUCACG D) CACUGUA

4b. Build a Protein 2. Translation:

mRNA > protein

Use the codon tableCodon Amino

AcidAUGUGUACGGACUAA, UAG, UGA

MUTATIONS & PROTEINSChanges in DNA std. 4c-e

4c. Mutations Mutation = permanent change in the DNA

base sequence Mutations can be good, neutral, or bad

1.Single base change – may or may not have an effect (ex: A C)What would happen if GGG changed to GGC?

both= Gly so nothing…What would happen if UAC changed to UAG?

stops protein production so effect could be major…

2. An insertion or deletion changes the reading “frame” The fat cat ate the rat The atc ata tet her at Major effects!

Mutations occurs in sperm or egg – passed to offspring = disease Tay Sachs disease, sickle-cell anemia, muscular dystrophy

Mutations occurs in regular body cells they may cause cancer

4d. Cell Specialization All cells in your body have the

SAME DNA Only genes need by that cell are

expressed.

Each cell only expresses the portion of the DNA containing the genetic information for the proteins required by that cell at that time.

The remainder of the DNA is not expressed

Example: The cells of in your skin have the

DNA that codes for your eye color protein. They just don’t use it

4e. Proteins 20 amino acids make up all proteins. Your body creates many different proteins by

changing the number and sequence of amino acids

Proteins vary from about 50 to 3,000 amino acids in length.

The types, sequences, and numbers of amino acids used determine the type of protein produced.

Hemoglobin – 574 aa Insulin – 51aa

One human disease is caused by a change in one codon in a gene from GAA to GUA. This disease is the result of:

A a mutation.B a meiosis error.C crossing-over.D polyploidy.

Although there are a limited number of amino acids, many different types of proteins exist because the

A. size of a given amino acid can vary. B. chemical composition of a given amino acid can vary. C. sequence and number of amino acids is different. D. same amino acid can have many different properties.

Mutations within a DNA sequence are:

A. natural processes that produce genetic diversity.

B. natural processes that always affect the phenotype.

C. unnatural processes that always affect the phenotype.

D. unnatural processes that are harmful to genetic diversity.

CHROMOSOMESWound up DNA Standard 2e-f

2e. Chromosomes Write really small!!! Chromosome -

wound-up DNA containing genes

Sister chromatids are identical copies held together by a centromere

Draw & label a chromosome on the right margin.

2e. Homologous Chromosomes Homologous chromosomes – have the

SAME genes at the SAME locations One came from mom, one from dad

2f. Sex-determination Karyotype – chart shows all the

homologous pairs Autosomes - pairs 1-22 Sex chromosomes - 23rd pair determines

sex XX = girl XY = boy

Questions True or False: 1) Humans have 46 chromosomes 2) Humans have 23 pairs of

chromosomes 3) Pairs 1-23 are autosomes 4) XX is male 5) XY is male 6) Sister chromatids are copies of each

other. 7) Homologous chromosomes are

identical.

MEIOSISMaking Sex Cells std. 2a-d, 2g

2a. Chromosome Number

1. Chromosome Number Diploid (2n) – somatic (body) cells

with 2 sets of homologous chromosomes Humans = 46 chromosomes (23

pairs)

Haploid (n) – gamete sex cells that have 1 set of chromosomes Humans = 23 single chromosomes

Divide Box 2a into 2 columns (5 concepts to write, 3 in left column, 2 in right)

Questions1) A bug has a haploid number n=5. What is the diploid number (2n)?2) A crocodile has a diploid number 2n=50. What is the haploid number (n)?

meiosismeiosis

Haploid gamete

Diploid

Haploid gamete

2n

n n

2a. Meiosis Overview2. Meiosis vs. Mitosis Meiosis – cell division specific to sexual

reproduction that results in 4, genetically different, haploid gamete (sex) cells

Mitosis – asexual cell division that results in 2, genetically identical, diploid cells

Zygote46

2323

First cell of a new organism

Questions A = Mitosis B = Meiosis C = Both 1) Type of cell division. 2) Produces 2 cells 3) Produces 4 cells 4) Sexual reproduction 5) Asexual reproduction 6) Resulting cells are genetically different 7) Diploid to haploid 8) Resulting cells are genetically identical 9) Diploid to Diploid

1)C2)A3)B4)B5)A6)B7)B8)A9)B

2a. Steps of Meiosis3. Steps of Meiosis Steps are mostly the same as Mitosis, but

diploid cell divides twice Meiosis I separates the homologous pairs Meiosis II separates sister chromatids

Steps of Meiosis

2a. Crossing Over4. Crossing Over Homologous chromosomes

pair up and randomly trade piece of DNA during Prophase I

This creates genetic variation (new gene combinations that never existed before)

Draw Crossing Over (middle step in diagram)

2a. Independent Assortment5. Independent Assortment Genes for different traits sort

independently into gametes Genes on different chromosomes are not

connected

Ex: The gene for eye color is not connected to the gene for hair color.

Questions What accounts for so many possible

combinations of genes in gametes? A) Crossing-over B) Independent Assortment C) Both of these

C. Both

True or False: Meiosis 1 separates homologous pairs,

while Meiosis II separates sister chromatids. True!

2b. Meiosis in Humans Only gonads undergo meiosis

MALES = the testis produces 4 sperm (gametes)

FEMALES = the ovaries produces 1 large egg (gamete) and 3 polar bodies

2c. Random SegregationLaw of Segregation It is random whether the gamete gets

the maternal or paternal version of each trait

Each gamete only gets one alleleDraw the diagram:Ex: If a pea plant is tall (Tt), half the gametes will have T and the other half will have t.

After fertilization, the offspring will have 2 alleles, one from mom & one from dad

If a corn plant has a genotype of Ttyy, what are the possible genetic combinations that could be present in a single grain of pollen from this plant?

A. Ty, ty B. TY, ty C. TY, Ty, ty D. Ty, ty, tY, TY

2d. Fertilization Fertilization: Sperm + egg = zygote

(23) (23) (46) haploid + haploid = diploid

n + n = 2n

2g. Predicting Offspring Alleles - different

versions of a trait Ex: Blue or brown eyes

Knowing the alleles of the parents allows you to predict the possible traits of the offspring.

Use a Punnett Square

Questions True or False? 1) Segregation occurs when genes

separate into gametes. 2) Females produce 4 eggs. 3) Males produce 4 sperm. 4) Fertilization occurs when diploid eggs

and sperm make a zygote. 5) Human zygotes have 23 chromosomes. 6) Alleles are different versions of a trait.

PUNNETT SQUARESPredicting InheritanceStandard 3a & b

3a. Punnett Squares Vocabulary to know: Genotype = genes (TT, Tt, tt) Phenotype = appearance (Tall or short) Homozygous/Purebred = 2 of the same

allele (TT or tt) Heterozygous/Hybrid = 2 different alleles

(Tt)

Types of Inheritance1. Autosomal – genes on

regular body chromosomes (#1-22)

Dominant covers up recessive ex: Bb The protein created by

the dominant gene functions better or is darker/stronger than the recessive protein

2. Incomplete & Codominance Incomplete dominance =

show mix/blend between two alleles Ex: Red + White = pink

Codominance = show both traits at once Ex: Red + White = red &

white stripes

3. Sex-linked – genes on X-chromosome Because men have

only 1 X (XY) they don’t have a “backup” X like women (XX) to hide the trait

If the X is bad, men have the disease Colorblindness,

hemophilia

3b. Mendel’s Laws (see 2a & c) Mendel’s Law of Segregations – see 2c Mendel’s Law of Independent

Assortment – see 2a5