UNITS 5 + 6 (Except RNA Modification After Transcription)

G0 Phase

Normal cell activities

S Phase

DNA Replication, Ploidy stays the same

Ploidy

The number of sets of chromosomes in a cell or an organism

G2

Ensures the formtion of haploid gamete cells in sexually reproducing diploid organisms.

• Results in daughter cells with half the number of chromosomes as the parent cell and generic diversity from parents and each other.

Diploid

(2n) Two full sets of chromosomes

Ex. Body cells

Haploid

(n) One set of chromosomes

Ex. Sex cells

Meiosis I

Reduction division, homologous pairs seperate, there is a reduction in the chromosome number

Meiosis I Phases

Prophase I, Metaphase I, Anaphase I, Telophase I

Prophase I

Nuclear envelope disappears, fibers form, DNA coils into duplicated chromosome (sister chromatids), pairing of homologous chromosomes, synapsis and crossing over occurs (recombinant chromosomes), genetic information

Metaphase I

Homologous chromosomes ine up in the middle of the cell, independent assortment occurs

Anaphase I

Each double chromosomes migrates to opposite sides of the cell

Homologous chromosomes becomes sister chromatids (splitting apart)

Telophase I

Nuclear envelope begins to reappear, cytokinesis occurs, each nucleous only contrains one diploid chromosomes from each homologous pair

Differences from Mitosis (Meiosis I)

Reduction division, genetically diverse (ploidy halved), genetically diverse daughter cells, 4 daughter cells and 2 rounds of division

Meiosis II

Division which sister chromatids seperate, maintains the chromosome number but reduces the amound of DNA in each chromosome (cells go from diploi to haploid

Prophase II

Nuclear envelop begins to disappear, fibers form, sister chromatids are there, chromatids get bigger

Metaphase II

Single diploid chromosome are aligned at the center of the cell

Anaphase II

Sister chromatids are seperated, haploid chromosomes are migrating to the sides fo the cell

Telophase II

Nuclear enevelope begins to appear again, cytokinesis occurs, nucleous contrain single chormosomes (chromatids)

4 genetically DIVERSE daughter cells

Differences between Mitosis (Meiosis II)

EQUATION DIVISION (ploidy is the same, amount of genetic material inside chromosomes decrease.

Genetically Diverse

4 Daughter cells

2 Rounds of division

Crossing Over

Increases the genetic diversity among gametes, occurs during Prophase I, homologous chromosomes exchange genetic information

Nondisjunction

Error in Meiosis that resuts in incorrect ploidy

Nondisjunction in Meiosis I

Homologous chromosomes fail to seperate, causese all 4 cells to have abnormal ploidy

Nondisjunction in Meiosis II

Double chromosomes fail to seperate into single chromosomes leads to alteration of the ploidies to be 2 cells with (n), 1 cell with (n+1), 1 cell with (n-1)

Indeoendent Assortment

The order of homologous pairs during Metaphase I,affects which chromosomes end up in each gamete. Genes are independently inherited from one another

Fertilization

Genetic information from each parent is contributed to a fertilized egg (zygote later on), doubles the amount of chromomes present

Gene

Unit of heredity coding for a trait, can be transferred from one generation to the next

Trait

Genetically determined the characteristics of an organism

Allele

Specific variation of the gene inherited from parents.

Dominant

Expressed in phenotype

Recessive

Overpowered by the dominant allele

Genotype

The combination of inherited alleles

Homozygous

2 of the same alleles

Heterozygous

2 different alleles

Phenotypw

Expression of the genotype

Karyotype

Display of the chromosome pairs of a cell arranged by size and shape

Law of Segregation

When gametes are formed, each allele of one parent segregates randomly into the gametes, such that half of the parent's gametes carry each allele.

Law of Independent Assortment

The alleles of 2 (or more) different genes get sorted into gametes independently of one another. In other words, the allele a gamete receives for one gene does not influence the allele received for another gene.

Law of Complete Dominance

The dominant allele covers the expression of the recessive allele

Punnett Square

Used to visulize results of a test cross

Epistasis

Expression of one gene controlled by another gene

Incomplete Dominance

Alleles blend

Codominance

Both alleles show in the offspring

Multiple Alleles

Multiple alleles exist for a trait (ex. human blood)

Sex Linkage

Alleles present on the X chromosome (ex. color blindness)

Gene-Linkage

Alleles located on the same chromosome travel together during crossing over.

Pattern Seen: Large numbers of a certain trait in an offspring

Closely linked genes lead sto less recombination and crossing over

Organelle Dependent Traits

Affected mother produces ALL affected children, traits found on the mitochondira are only inherited from the maternal parent, NON NUCLEAR DNA

Recombination Frequency

The percentage of recombinant frequency also represents the distance between alleles on a chromsome in map units

Recombinant offspring/progenyare children that have a different allele combination to their parents.

Test Cross

Crossing of an individual of unknown genotype with a homozygous recessive individual to determine the unknown gene m

Monohybrid Cross

Only one gene (ex. hair color)

Dihybrid Cross

Two genes (ex. hair color and eye color)

Multiplication Rule

2^n = number of combinations

n = number of differnet alleles

Homozygous Dominant x Homozygous Recessive

Results in heterozygous offspring 4:1 (D:R)

Homozygous Dominant x Heterozygous

Results in 2 heterozygous and 2 homozygous dominant while all express the dominant trait 4:0 (D:R)

Homozygous Recessive x Heterozygous

Results in the 2 homozygous recessive and 2 heterozygous dominant 2:2 (D:R)

Heterozygous x Heterozygous

Results in 1 homozygous dominant, 2 heterozygous, 1 homozygous recessive 3:1 (D:R)

Dihybrid Cross

2 Dihybrid Individuals crossed, 9:3:3:1 (DD:DR:RD:RR)

Dihybrid Test Cross

Dihybrid Individual x Homozygous Recessive Individual 1:1:1:1

Dominant

Present in all generations, if parents have it there is a high change offsprings will have it as well

Recessive

Trait can be hidden, 2 unaffected parents have an affected child

Sex-Linked Dominant

Mother unaffected ALL SONS unaffected

Father affected ALL DAUGHTERS affected

Sex-Linked Recessive

Mother affected ALL SONS affected

Father unaffected ALL DAUGHTERS unaffected (Daughter are carriers)

Many males found with these traits

Epigenetics

Genes may not be activated due to environmental factors, genes may be activated, but proteins may not be folded or formed correctly for gene expression due to environmental factors

DNA AND RNA

Polymerase containing nucleotides

Chain like molecules

Base pairing rules

Purine + Pyrimidine:

• Purine has 2 rings (bigger):

  • Adenine and Guanine

• Pyrimidine has 1 rings (smaller):

  • Cytosine, Thymine, Uracil

DNA

Has thymine, double starnded, no oxygen, 5’3’, anti-parallel, negative charge due to the phosphate group present

RNA

Contains oxygen, single stranded, has uracil, RNA Is used to help gene expression in humans

Phosphate, nitrogenous base, and 5-carbon sugar ribose'

Molecules are used to facilitate protein synthesis using DNA information , ribosomes contain RNA and assembles proteins

mRNA

Make proteins in the cytoplasm

tRNA

Transfer amino acids to ribosomes

snRNA

Components of the snRNP spliceosomes that catalyze the splicing of pre-mRNA

rRNA

Ribosomal DNA

Prokaryotic Organisms

Circular chromosomes, smaller genomes, plasmids found in the cytosol

Euakryotic Organisms

Multiple, linear chromosomes, plasmids are found in the nucleus

Prokaryotic AND Eukaryotic

Both contrain plasmids

Plasmids

Small extrachromosomsal, double stranded, circular DNA molecules.

Griffith (1928)

Mice experiment, discovered transformation

Avery, MacLeod, Macarty (1944)

Enzymes were used, proved DNA is genetic material

Erwin Chargaff (1944)

Paper chromatography, DNA is assembled in a paired structure

Hershey, Chase (1952)

Centrifuged DNA, genetic material is composed of phosphorus

Rosalin and Maurice Williams (1953)

X-ray, nitrogenous bases are paired in a purine pyrimadine paired structured

Watson and Crick (1953)

Proved DNA is a double helix structure (STOLE THAT SHIT)

Measelson and Stahl (1958)

N-14 and N-15 for DNA Replication, DNA is a semi-conservative model

Replication

Happens during S Phase and M Phase in the Cell Cycle

Helicase

Unzips DNA into 2 strands and breaks the HYDROGEN bonds between the bases

Topoisomerase

Releases the tension of the DNA and prevents supercouiling as unzippign is going on

Single Stranded Binding Protein

Keep Strands Seperated

Leading Strand

DNA Replication from 5’ to 3’ end

• Nucleotides can only be added to the 3’ end

Lagging Strand

Replicated OPPOSITE to the direction of DNA unzipping

RNA Primers

Placed on both strands by DNA primase to initiate DNA building

DNA Polymerase III

Synthesize DNA in leading strand, synthesizes DNA in Okazagi Fragments for the lagging strand

DNA Polymerase I

Removes primers on strands

DNA Ligase

FIlls the gap betwen the Okazagi Fragments

Central Dogma of Genetics

DNA → RNA → Protein

Transcription

Process in which an enzyme directs the formation of mRNA molecule

Transcrition Steps

One strand of the DNA is used as a template for RNA synthesis

• Called the ANTISENSE strand

The other one is called SENSE strand

RNA Polymerase synthesizes RNA with the ANTISENSE (5’ to 3’ direction)

Initiation:

• Start the process, transcription factors open DNA at the promoter sequence

Elongation:

• RNA Polymerase reads from 5’ to 3’ to synthesize RNA strand

Termination:

• Stop the synthesis of RNA, releases the DNA and pre-mRNA trascript

mRNA

Messagner RNA, carries genetic information from DNA to ribosomes.

• Information is used to direct protein synthesis at the ribosome site

Codon

3 base sequence foundon the mRNA

tRNA

Transfer RNA, Gives amino acids to ribosomes to help create the especific polypeptide directed by the mRNA

• Anticodons is a 3 base sequence on the tRNA

rRNA

Ribosome RNA, Functional units of ribosomes responsible for protein assembly, base pairing of anti-codons occur in the ribosomes, creates primary polypeptides as tRNA releases amino acids