Molecular Biology and Cell Division

DNA

- found in nucleus of cell

- only molecule that can replicate itself

- codes for characteristics

- regulates production of proteins

deoxyribonucleic acid

DNA

Universal code

Describes the fact that the code used to convert DNA sequences into protein sequences is the same in all organisms on Earth.

Griffith

Experimented with mice and strains of bacteria to discover transforming factor

Transforming factor

Refers to DNA's ability to transform

Hammerling

Experimented with large unicellular algae to prove that hereditary material is stored in the nucleus

Hereditary material

the information which is passed from one cellular generation to the next

- DNA

Franklin

- took pictures of DNA using X-ray diffraction

- used shadows to discover shape of DNA

- Discovered double helix shape

Chargaff

- looked at % of each nitrogenous base

- discovered that A-T and C-G

- discovered base pairs

Watson & Crick

- used discoveries of Franklin and Chargaff to build structural model of DNA

- shows double helix

- shows complementary base pairs

Complementary base pairing

In DNA, T pairs with A and G pairs with C

In RNA, U pairs with A and G pairs with C

Nitrogenous base

Adenine, Thymine, Cytosine, Guanine

Sugar phosphate backbone

The alternating chain of sugar and phosphate to which nitrogenous bases are attached

Deoxyribose

sugar found in DNA

Nucleotide

monomer of nucleic acids made up of a deoxyribose, phosphate and nitrogenous base

nucleic acids

DNA and RNA

5' end

Attached to phosphate

- "ph" five

3' end

Attached to sugar

Antiparallel

The opposite arrangement of the sugar-phosphate backbones in a DNA double helix

- "DNA is 69ing"

Direction enzymes read

3' -> 5'

Direction enzymes build

5' -> 3'

DNA replication

The process in which DNA makes a duplicate copy of itself

- single strand of DNA acts as template for formation of complementary strand

(1) Helicase

Enzyme that "unzips" DNA

- separates DNA into two strands

(2) Binding proteins

Proteins that bind to newly exposed DNA strands to prevent the hydrogen bonds from reforming

(3) Primase

Enzyme that ads RNA primer to strand for polymerase III to "hook" onto

(4) DNA polymerase III

synthesizes new DNA only in the 5' to 3' direction

- adds complementary nucleotides to existing DNA strand

Leading strand

synthesized continuously because it is configured in a 3'-5' direction

- DNA polymerase can build in 5'-3' direction

Lagging strand

DNA strand formed in short fragments starting at RNA primer

- due to 5'-3' direction so DNA must be read "backwards" towards replication fork

Okazaki fragments

Short fragments of DNA that are a result of the synthesis of the lagging strand during DNA replication

(5) DNA polymerase I

Removes RNA primer from newly formed DNA and replaces it with appropriate nucleotides

- small gaps are left where RNA is removed

(6) Proofreading

DNA polymerase "reads" newly formed DNA, cuts out incorrectly paired nucleotides and adds correct nucleotide

(7) DNA Ligase

an enzyme that eventually joins the sugar-phosphate backbones of the Okazaki fragments

- fills "gap" in DNA left by P1 removing RNA primer

Gene expression

conversion of the information encoded in a gene first into messenger RNA and then to a protein

ribonucleic acid

RNA

RNA

- 3 types

- single stranded

- ribose (instead of deoxyribose)

- Uracil base (U) instead of Thymine (T)

mRNA

RNA that transports information from DNA in the nucleus to the cell's cytoplasm, contains codon

tRNA

RNA that carries amino acids to the ribosome, contains anti-codon

rRNA

RNA that makes up part of ribosomes, helps tRNA build polypeptide chain

Central dogma

DNA-> transcription-> RNA-> translation-> protein

Transcription

Transcribe DNA into mRNA

3 Steps:

- initiation

- elongation

- termination

Initiation

RNA polymerase binds to promoter (TATTA box), DNA unwound exposing template strand

Elongation

Make a "long" sequence of RNA

Termination

RNA polymerase reaches a terminator sequence and detaches from the template

Translation

mRNA moves from nucleus to cytoplasm, is read by a ribosome and used to make polypeptide chain

Codon

A specific sequence of three adjacent bases on a strand of DNA or RNA that provides genetic code information for a particular amino acid

restriction enzyme

Enzyme that cuts DNA at a specific sequence of nucleotides

transformation (DNA)

taking DNA from the outside of the cell and bringing it on the inside

EcoR1

restriction enzyme that recognizes the DNA sequence GAATTC and will always cut between G/AATTC

Recombinant DNA

DNA produced by combining DNA from different sources

Seminconservative

DNA replication is...

Mutation

Permanent, inheritable changes in the genetic material

- messed up DNA leads to messed up cells

Somatic mutations

Mutations that occur in body cells

Germ line mutations

occur in gametes and are inherited

Silent mutation

A mutation that changes a single nucleotide, but does not change the amino acid created

- no noticeable change

Deletion mutation

a change in the base sequence of a gene that results from the loss of one or more base pairs in the DNA

- caused nucleotides or (if whole codon deleted) amino acids to shift down

Insertion mutation

a mutation in which one or more nucleotides are added to a gene

- cause nucleotides to shift over

Hemophilia

Absence of a certain protein that is required for blood clotting

- traced to single defective gene

Cystic fibrosis

Deletion of 7th, 8th and 9th nitrogen bases that leads to respiratory issues

Sickle cell anemia

GAG codon has been replaced with GTG which causes sickle shaped blood cells

DNA clock

- inferring relationships through # mutations

- more time between = more mutations = more difference in DNA

Mitochondrial DNA

- passed through mother

- closer this type of DNA to another person, the closer the relationship

Chromosome

- contains DNA and proteins

- condensed or uncondensed

- can be duplicated or unduplicated

- 46/cell in humans

duplicated chromosome

2 sister chromatids attached by a centromere

Unduplicated chromosome

Single strand of uncopied DNA

Chromatid

one half of a duplicated chromosome

Chromatin

Clusters of DNA, RNA, and proteins in the nucleus of a cell

Centromere

Area where the chromatids of a chromosome are attached

Cell cycle

series of events that cells go through as they grow and divide

- healing, growth, development from zygote

Interphase

- 90% of cell cycle

- cell "doing its job"

- growth of organelles and DNA replication

- nucleus is PRESENT and chromosomes are UNCONDENSED

Mitosis

Division of cell into two identical daughter cells

Prophase

- nucleus disappears

- chromosomes condense

- centrioles separate and form spindles

Metaphase

- chromosomes meet in the middle

- nucleus NOT present

Anaphase

- chromosomes are pulled apart

- nucleus NOT present

Telophase

- new nucleus forms

- cell begins splitting

Cytokinesis

division of the cytoplasm to form two separate daughter cells

Cell clock

- cells can only divide a certain number of times

- more specialized a cell is, the less likely it will divide by mitosis

Cancer

Cells undergoing uncontrolled cell growth

- divide indefinitely

- "speeding through cell cycle" and not doing its job during interphase

Cloning

the production of identical offspring by asexual reproduction

MtDNA

mitochondrial DNA

Identical twins

twins who develop from a single fertilized egg that splits in two, creating two genetically identical organisms

Fraternal twins

- twins who come from two different eggs fertilized by two different sperm

- genetically no closer than normal brothers/sisters

Meiosis

- form sex cells (gametes)

- 2 stages in cell division

- results in cells with half the number of chromosomes (haploid)

Spermatogenesis

Formation of sperm through meiosis

Oogenesis

Formation of eggs through meiosis

independent assortment

the random distribution of the pairs of genes on different chromosomes to the gametes, creates genetic diversity

Crossing over

Process in which homologous chromosomes exchange portions of their chromatids during meiosis, creates genetic diversity

Fertilization

Process in sexual reproduction in which male and female reproductive cells join to form a new cell, creates genetic diversity

Meiosis stages

Interphase -> meiosis I -> cytokinesis -> meiosis II -> cytokinesis

Haploid

A cell with one set of chromosomes

Diploid

A cell with two sets of chromosomes

Homologous chromosomes

Chromosomes that have the same sequence of genes, that have the same structure, and that pair during meiosis

- "they are the same"

Karotype

A picture of all the chromosomes in a cell arranged in pairs

Y chromosome

the sex chromosome found only in males

Gamete

sex cell

Synapsis

the fusion of chromosome pairs at the start of meiosis

Allele

Different forms of a gene

Polyploidy

condition in which an organism has extra sets of chromosomes

N

One set of chromosomes

2n

diploid, two sets of chromosomes

Trisomy

3 copies of the same chromosome

- 3 chromosomes where there is supposed to be a set of two