1. information

2. replication

3. transmission

4. variation

nucleotides are the building blocks

a strand of DNA or RNA

two strands form a double helix

--> chromosomes ---> genome 

phosphate group

pentose sugar

nitrogenous base

Pentose sugar: deoxyribose

nitrogenous bases: 

purines: adenine and guanine

pyrimidines: cytosine and thymine

pentose sugar: ribose

nitrogenous bases: 

purines: adenine and guanine

pyrimidines: cytosine and uracil

the sugar carbons are from 1' to 5'

the base is attached to 1'

the phosphate is attached to 5'

covalently

(the phosphodiester bond is the link between two sugars held together by phosphate groups) 

phosphates and sugars form the backbone; bases project from the backbone

the directionality is from 5' to 3'

5' -TACG - 3'

there is the most of the adenine-thymine and then less of the guanine-cytosine

also, the amount of thymine and adenine are similar. then the amount of cytosine and guanine are similar. 

its double stranded

its helical

its got the sugar phosphate backbone with the bases on the inside

its stabilized by hydrogen bonding 

the base pairs are specifically bonded to each other

A pairs with T

G pairs with C

--> the widths are kept constant, and there are 10 base pairs per turn

two of the strands are complementary 

– 5’–GCGGATTT–3’

– 3’–CGCCTAAA–5’

two of the strands are antiparallel: one strand goes 5' to 3' and the other strand goes 3' to 5'

the space filling model shows grooves

the major groove is where proteins bind and affect gene expression

then there is also the minor groove

during replication, 2 parental strands separate and serve as template strands

then new nucleotides must obey the AT/GC rule

the end result is 2 new double helices with the same base sequence as the original

what does origin of replication mean? 

how do bacteria and eukaryotes differ? 

its the site of the start point for replication

bacteria have a single origin

eukaryotes require multiple origins

covalently links nucleotides

so... the incoming deoxynuceloside triphosphates go through the DNA polymerase, and then at the DNA polymerase catalytic site they are binded together and out comes the template strand (exits in the same direction that the deoxynucleoside triphosphates come in)

they are free nucleotides with 3 phosphate groups

there is the breaking of covalent bond to release pyrophosphate (2 phosphate groups) provides the energy to connect adjacent nucleotides 

1. DNA polymerase is unable to begin DNA synthesis on a bare template strand

-DNA primase must make a short RNA primer that will be removed and replaced with DNA later

2. DNA polymerase can only work 5' to 3' 

1. conserves energy

2. ensure genes expressed in appropriate cell type and at the correct stage in development

when lactose ecomes present, the B-galactos-i-dase breaks down lactose, and it (lactose) can be transported into the cell via lactose permease

due to gene regulation, the bacterium produces more lactose permease and B-galactosidase

the bactertia uses the lactose until it is gone and the proteins incolved with lactose are degraded

at the level of transcription!

also can control the rate that mRNA is translated or the protein/post-translation level

repressors: inhibit transcription

activators: increase the rate of transcription

a. a site where protein binds to DNA

b. a site for small effector molecules

transcribed as polycistronic mRNA

allows for regulation of a group of genes with a common function

in G1: 46 chromosomes

in G2: have 46 pairs of sister chromatids, or 96 chromatids 

external: environmental conditions, signaling molecules 

internal: cell cycle control molecules, checkpoints

cyclin dependent kinases (remember, amount of cyclin is what varies throughout cycle); kinases must be bound to cyclin to be active 

cyclin:

myotic cyclin active at G2/M check point, is degraded through mitosis

G1 cyclin is present during mid G1 / S restriction point- is degraded after cell enters S phase 

male bees are haploid, female bees are diploid

plants exhibit polyploidy (agriculture example of wheat) 

statistics with aneuploidy

About ?% of all fertilized human eggs 

result in an embryo with an abnormality in 

chromosome number 

• Approximately ?% of all spontaneous 

abortions are due to alterations in 

chromosome number 

5-10%

50%

Downs- trisomy 21- 1/800

Edward- trisomy 18- 1/6,000

Patau- trisomy 13- 1/15,000

what is the name for each of the following sex chromosomal conditions

XXY

XYY

XXX

XO

XXY: Kleinfelter (male) 

XYY: Jacobs (male)

XXX: Triple X (females)

XO: Turner (females) 

genes

2 genes for a character (one on each chromosome) 

Particulate Model:

• Offspring are a combination of both parents
• The characteristics of both parents are passed on to the next generation as separate entities
• Variation is maintained over time^[3]

genotype: genetic composition of individual 

phenotype: characteristics that are the result of gene expression 

• Possible patterns 

–2 genes linked so that variants found together 

in parents are always inherited as a unit 

–2 genes are independent and randomly 

distributed

Dihybrid offspring

offspring are hybrids 

with respect to both traits 

Law of Independent Assortment

Alleles of different genes assort independently 

of each other during gamete formation

At meiosis, one member of each chromosome 

pair segregates into one daughter nucleus and...

its homologue segregates into the other 

daughter nucleus. During the formation of 

haploid cells, the members of different 

chromosome pairs segregate independently of 

each other. 

what leads to the independent 

assortment of alleles found on different 

chromosomes

Random alignment of chromosome pairs 

during meiosis I

caused by recessive X linked gene, encodes defective clotting pattern; 

females only can be carriers if father is not infected, but if mother is a carrier, the son will be infected. 

[image]

pattern that occurs when the heterozygote expresses both alleles simultaneously; blood type example; carrying A and B alleles results in the expression of both A and B antigens on the blood

pattern that occurs when an allele is dominant in one sex and recessive in another, such as pattern balding in humans

this is because sex hormones affect the molecular expression of genes, which can have an impact on the phenotype  

the mutants were missing one of the three enzymes required to linearly process precursor molecule into argenine. if you gave the mutant the molecule that ought to have been produced by the enzyme that it was missing, it makes all the other enzymes and so then can create argenine

results suggested that each mutation caused a defect in only one enzyme in a metabolic pathway.

usually, one polynucleotide strand

the sugar is ribose

contains uricil instead of thymine (uricil has a hydrogen where the thymine has a methyl)

"the adapter molecule"- that can bind amino acids and recognize a nucleotide sequence

adapter molecules contain anticodons complementary to the codons in mRNA

initiation

elongation

termination

About 10 base pairs at a time

Reads in the 3' to 5' direction (because creates in the 5' to 3' direction. because can only add on to the 3' end)

what specifies to the RNA polymerase that termination ought to occur?

how might termination occur?

a specific DNA base sequence

it varies- for some genes, the transcript falls away from the DNA template and RNA polymerase- for others, a helper protein helps to pull it away

promoter

start codon

exon 1

intron 1

exon 2

stop codon

terminator

In genetics, a promoter is a region of DNA that facilitates the transcription of a particular gene. Promoters are located near the genes they regulate, on the same strand and typically upstream (towards the 5' region of the sense strand).

In order for the transcription to take place, the enzyme that synthesizes RNA, known as RNA polymerase, must attach to the DNA near a gene. Promoters contain specific DNA sequences and response elements which provide a secure initial binding site for RNA polymerase and for proteins called transcription factors that recruit RNA polymerase. These transcription factors have specific activator or repressor sequences of corresponding nucleotides that attach to specific promoters and regulate gene expressions.

nucleic acid hybridization

(target DNA is denatured and then incubated with a probe- a nucleic acid strand from another source. if the probe has a complementary sequence, then base pairing forms a hybrid

there will be portions matched (exon matched with probe) and non matched loops (introns)

domains

(introns interrupt but don't scramble the DNA sequence encoding a polypeptide)

G cap (modified guanosine triphosphate) is added at the 5' end, facilitates mRNA binding to ribosome and protects mRNA from being digested by ribonucleases

poly A tail (AAUAAA) sequence after last codon is a signal for an enzyme to cut the pre-mRNA, then another enzyme adds 100-300 adenines to the tail- may assist in export from the nucleus & is important for stability of RNA

the AAUAAA is part of the pre mRNA before modification (was created from DNA by RNA polymerase)

consensus sequences

snRNPs bind at consensus sequences and near the 3' end

with eneergy from ATP, proteins are added to form an RNA-protein complex, the spliceosome- the complex cuts pre-mRNA, releases introns, and splices togther exons to make mature mRNA

snRNPs are bound to consensus sequences, come together to form spliceosome and chop off introns (on side, then loose side bonds to other end of intron)

transcription and translation occurence:

prokaryotes vs. eukaryotes

prokaryotes: at the same time in the cytoplasm

eukaryotes: transcription in the nucleus then translation in the cytoplasm

gene structure:

prokaryotes vs. eukaryotes

prokaryotes: DNA sequence is read in the same order as the amino acid sequence

eukaryotes- noncoding introns within coding sequence

prokaryotes- none

eukaryotes: introns spliced out, 5' cap and 3' poly A tail added

start codon: AUG- initiation signal for translation

stop codons: UAA, UAG, UGA- stop translation and polypeptide is released

describe the structure of tRNA

attachment site and how?

opposite that?

what is unique about each?

the 3' end is the amino acid attachment site- binds covalently

at the midpoint of the tRNA is the anticodon which is the site of base pairing with mRNA

the anticodon of each tRNA is unique

specificty for the base at the 3' end of the codon is not always observed

allows cells to produce fewer tRNA species but does not allow the genetic code to be ambigous

what is the "second genetic code"

the process of tRNA charging

this is because each aminoacyl tRNA synthetases is highly specific for one amino acid and its corresponding tRNA

a specific amino acid

a specific tRNA

ATP

large subunit: 3 molecules of rRNA and 49 different proteins in a precise pattern

small subunit: one molecule of rRNA and 33 different proteins

A (amino acid site)

P (polypeptide site)

E (exit site)

on the large subunit

binds with anticodon of charged tRNA