Organismal reproduction

Growth

Repair

Asexual (mitosis)

Sexual (fertilization after meiosis)

Daughter cells are identical copies of mother cell (clones)

Occurs in all organisms

Daughter cells are not identical copies of mother cell

Only in Eukaryotes

How prokaryotes divide

DNA is duplicated (single chromosome), 1 chromosome moved to each side of cell, cell is split into two, takes about 20 min

Unwound

Condensed

Cell growth and DNA replication

Mitosis (division of the nucleus)

Cytokinesis (division of the cell)

G₁= 1st growth phase

S= DNA duplication

G₂= 2nd growth phase

Mitosis

Cytokinesis

Seemingly most important one

If given go ahead= completes the S, G₂, and M phases and divides

If stopped= Exits the cycle into a nondividing state called the G₀ phase

Most cells in any organism are in this stage

DNA is "loose" chromatin and the nucleus is present

Prophase

Prometaphase

Metaphase

Anaphase

Telophase

DNA begins to condense

Nuclear membrane is beginning to break down

Sprindle begins to form

The chromosomes are connected to the spindle microtubules at their centromere

The nuclear membrane, ER and golgi finish breaking down

Chromosomes begin to unravel

Nuclear envelope begins to re-form

Crossing over in Prophase I

After Cytokinesis I the resulting cells are now haploid, but still have doubled chromosomes

Meiosis I (Prophase I, Prometaphase I, Metaphase I, Anaphase I, Telophase I, Cytokinesis I)

Meiosis II (Prophase II, Prometaphase II, Metaphase II, Anaphase II, Telophase II, Cytokinesis II)

Terminal chiasmata hold homologues together following crossing over

Microtubules from opposite poles attach to each homologue

Homologues are aligned at the metaphase plate side-by-side

Microtubules of the spindle shorten

Homologues are separated from each other

Sister chromatids remain attached to each other at their centromeres

Nuclear envelopes form around each set of chromosomes

Each new nucleus is now haploid

Sister chromatids are no longer identical b/c of crossing over

Generation time is too long

Parents produce relatively few offspring

Breeding experiments are unacceptable

Inheritable unit that could be passed on to offspring to determine their makeup

Genetic counterpart for the character (ex. there is a gene that determines flower color)

The heritable feature, ex. in peas, flower color is a character

Part of Phenotype (what we can see)

Variants of the character, ex. in peas, purple or white are traits for flower color

Part of Phenotype (what we can see)

Dominant

Codominant

Recessive

Dominance can only be shown if there are one or more sets of chromosomes (diploid or higher)

2 copies of a gene separate (segregate) during meiosis to form gametes

Gametes are rejoined at random during fertilization

In a dihybrid cross, the alleles of each gene assort independently

Applies only to genes on different, non-homologous chromosomes

Genes located on the same chromosome tend to be inderited together

Crossing over

Random alignment of homologues in metaphase I (independent assortment)

Random fusion of gametes

Each trait is controlled by a single gene

Each gene has only 2 alleles

There is a clear dominant-recessive relationship between the alleles

(Ex. of single gene traits- earlobe attachment, widows peak, hitch hiker's thumb0

Type of inheritance, occurs when multiple genes are involved in controlling the phenotype of a trait, the phenotype is an accumulation of contributions by multiple genes

These traits show continuous variation and are referred to as quantitative traits (ex. height and skin color)

Refers to an allele which has more than one effect on the phenotype

Can be seen in human diseases such as cystic fibrosis or sickle cell anemia (multiple symptoms can be traced back to one defective allele)

Hydrangea flowers of the same genotype range from blue-violet to pink, depending on soil acidity

Pigment production in Himalayan rabbits and Siamese cats only occurs at temperatures below 30 degrees celsius

An individual must be recessive homozygous to suffer from the disorder (ex. albinism, sickle cell anemia, cystic fibrosis)

Carriers are heterozygous (they carry the recessive allele but are phenotypically normal)

Sex linked traits

Linked genes

Genetic recombination

Chromosomal alterations (including a lack of separation during meiosis)

Diploid= female

Haploid= male

There is more of a chance for crossing over to occur

The recombination frequency is higher

Genetic map of a chromosome based on recombination frequencies

The distances between genes are shown as map units (one map unit = 1% recombination frequency)

Non-disjunction

Direct alteration of chromosome structure

Pairs of homologous chromosome do not separate during meiosis

One gamete receives two of the same type of chromosome and the other receives no copy

Ex. Down syndrome (Trisomy 21)

• XXY- male but abnormally small testes and sterile (may have mental retardation)
• XYY- male, no effect
• XXX- female, no effect
• X- female, but will not undergo puberty without hormone treatment, sterile 

Having 3 or more sets of chromosomes

Rare in animals, more common in plants, more normal in appearance than aneuploids [Ex. Triploidy (3n), Tetraploidy (4n)]

Deletion

Duplication

Inversion

Translocation

Chromosomal alteration, Removes a part of chromosome structure

Ex. "Cry of the Cat" syndrome

Messes up chromosome structure

Non-homologous chromosomes have crossing over occur between them

Ex. Certain cancers- Chronic myelogenous leukemia (CML)

1953- proposed structure for DNA

1962- awarded Nobel prize

• Hershey and Chase- nucleotides contain "programming" information
• Chargaff- nucleotide composition
• Rosalind Franklin- X-ray crystalography 

He analyzed the nucleotide base composition of a variety of organisms

He found a relationship between Adenine and Thymine (A-T), and Guanine and Cytosine (G-C)

He found that ratios were diverse among organisms

She is credited with providing the eveidence for the symmetry of DNA

She died in 1958 from cancer

Matthew Meselson and Franklin Stahl in 1958

They radioactively labeled DNA and followed it in E. coli

Complementary (A with T, G with C)

Anti-parallel (funs from 5' to 3', read and synthesized only in this direction)

Parental Strand- Template strand

Daughter Strand- the new strand

• Single-strand binding proteins (stabilization)
• Primase (synthesizes RNA primer)
• Helicase (unwinds DNA)
• "Sliding clamp"
• DNA polymerase III (adds nucleotides) 

It can only add nucleotides to an existing strand (can't initiate a strand)

It can only add nucleotides in one direction (5' to 3' - new strand)

A leading strand and a lagging strand are formed

Forces the new strand to be made in small chunks, and then connected

The chunks are called Okazaki fragments

Mistakes during replication

Mutagens- chemical, physical or radiation based agents

Specific

Non-specific

Base-pair substitutions

Base-pair insertions or deletions

Silent mutations

Missense mutations

Nonsense mutations

A base-pair subsitution

Still code for an amino acid, may be the wrong one

Additions or losses of nucleotide pairs in a gene (often cause more damaging effects on the protein than substitutions do)

Can cause a frameshift mutation (changes that alter the reading frame for reading codons to code for amino acids)

DNA is in the nucleus

The mRNA is created and processed (parts are removed or changed)

The mRNA travels to the cytosol

A ribosome binds to the mRNA to translate it into a protein

The specific set of 3 nucleotides that translates for a specific amino acid

Discovered by Francis Crick and Sydney Brenner

The transfer of information from the DNA strand to the messenger RNA strand

Carried out by RNA polymerase (5' to 3')

Nucleotides are matched with their corresponding bases, DNA to RNA (A to U, T to A, C to G, G to C)

• DNA- double stranded, Deoxyribose as sugar, uses T-A
• RNA- single stranded, Ribose as sugar, uses U-A 

Initiation

Elongation

Termination

It happens in the nucleus befor it travels to the cytoplasm

Both ends are usually altered

Some interior parts of the molecule are cut out, and the remaining parts are spliced together

They seem to facilitate the export of mRNA

They protect mRNA from hydrolytic enzymes so none of the important coding section is taken off

They help ribosomes attach to the 5' end

Carries a specific amino acid on one end

Has an anticodon on the other end (has a complementary base-pairs with a codon on mRNA)

A (amino) site

P (peptide) site

E (exit) site

Initiation

Elongation

Termination

Small ribosome subunit binds to mRNA

Initiator tRNA binds to mRNA

Large ribosome subunit binds to tRNA

This requires GTP

Codon recognition

Peptide bond formation

Translocation