Biology test TOMORROW

Centrosomes

an organelle near the nucleus of a cell that contains the centrioles (in animal cells) and from which the spindle fibers develop in cell division.

anchorage dependent inhibition

A mechanism that controls cell growth in which cells can only divide when they are anchored to a surface; i.e. inside a culture jar or extracellular matrix of a tissue

growth factors

stimulate the growth and division of cells

C+G

pyrimidines

Centromere

Area where the chromatids of a chromosome are attached , holds to sister chromatids together

somatic cells

Any cells in the body other than reproductive cells

Gametes

reproductive cells

benign

harmless

malignant

(adj.) deadly, extremely harmful, evil; spiteful, malicious

checkpoint

A control point in the cell cycle where stop and go-ahead signals can regulate the cycle.

Metasis

The spread of cancer cells beyond their original site

density-dependent inhibition

crowded cells stop dividing

Interphase (Mitosis)

G1, S, G2

G1 phase

stage of interphase in which cell grows and performs its normal functions

binary fission

A form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size

A+G

purines

A+T

2 hydrogen bonds

C+G

3 hydrogen bonds

Diploid

2 sets of chromosomes

Haploid

having a single set of unpaired chromosomes

Chromatin

Substance found in eukaryotic chromosomes that consists of DNA tightly coiled around histones, complexes of DNA and its proteins

Chromosomes

threadlike structures made of DNA molecules that contain the genes

Kinetochores

The structures on sister chromatids where microtubules attach

Synthesis Phase

DNA replication

G2 phase

Cell grows and creates proteins, contains a checkpoint

Prophase (mitosis)

chromosomes condense and spindle apparatus begins to form

Prometaphase (Mitosis)

The nuclear membrane disintegrates. Spindle microtubules attach to chromatids.

Metaphase

Chromosomes line up in the middle of the cell

Anaphase

Phase of mitosis in which the chromosomes separate and move to opposite ends of the cell

Telophase/Cytokinesis (Mitosis)

Nucleus reforms (telophase) and cell is divided in two (cytokinesis)

2 sister chromatids

1 kinetochore or 1 chromosome

locus

Location of a gene on a chromosome

Telomeres

Repeated DNA sequences at the ends of eukaryotic chromosomes.

asexual reproduction

Process by which a single parent reproduces by itself, identical genetic copies

clone

Group of genetically identical individuals

Karyotype

A display of the chromosome pairs of a cell arranged by size and shape.

cells not produced by mitosis

gametes, specialized cells, and germ cells

Prophase 1 of meiosis

Chromosomes become visible; nuclear envelope breaks down; crossing-over occurs.

Metaphase 1 of meiosis

Paired homologous chromosomes line up across the center of the cell

Anaphase 1 of meiosis

homologous pairs separate

Telophase/Cytokinesis I meiosis

2 haploid cells form, each chromosome still has 2 sister chromatids

Prophase II meiosis

A new spindle forms around the chromosomes

Metaphase II Meiosis

chromosomes line up on metaphase plate (not identical)

Anaphase II Meiosis

Sister chromatids split and head toward opposite poles

telekinesis/cytokinesis II Meiosis

nuclear envelope develops and cytoplasm divides

aster

A radial array of short microtubules that extends from each centrosome toward the plasma membrane in an animal cell undergoing mitosis.

crossing over

Process in which homologous chromosomes exchange portions of their chromatids during meiosis.

Synaptomeal complex

mediates and maintains synapsis along the full length of each pair of homologous chromosomes.

Recombinanat Chromosomes

individual chromosomes that carry DNA from 2 different parents

Watson, Crick, and Franklin

Developed the double helix model of DNA.

phages (bacteriophages)

viruses that infect bacteria

Hershey and Chase

concluded that the genetic material of the bacteriophage was DNA, not protein., T2, enters an E,coli cell

Chargraff

A=T and G=C

Telomerase

An enzyme that catalyzes the lengthening of telomeres in eukaryotic germ cells.

bacterial chromosome

circular thread of DNA that contains the cell's genetic information

Histones

protein molecules around which DNA is tightly coiled in chromatin

Nucleosome

repeating subunit of chromatin fibers, consisting of DNA coiled around histones

semiconservative model

Type of DNA replication in which the replicated double helix consists of one old strand, derived from the old molecule, and one newly made strand.

DNA groups

Phosphate, nitrogenous and sugar group

antiparallel

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

dispersive model

each strand of both daughter molecules contains a mixture of old and newly synthesized DNA

purine + pyrimidine

width consistent with X-ray data

origins of replication

Site where the replication of a DNA molecule begins, consisting of a specific sequence of nucleotides.

replication fork

A Y-shaped region on a replicating DNA molecule where new strands are growing.

Helicases

enzymes that untwist the double helix at the replication forks

single stranded DNA binding proteins

- bind to the unraveled strand preventing the re-association of the DNA strands & degradation of DNA by nucleases

-Unpaired strands of DNA are very "sticky" so proteins are required to hold the 2 strands apart

Topoisomerase

Enzyme that breaks, swivels and rejoins the parental DNA and functions in DNA replication, helping to relieve strain in the double helix ahead of the replication fork.

primer

A short segment of DNA that acts as the starting point for a new strand

Primase

An enzyme that joins RNA nucleotides to make the primer.

DNA pol I

Removes RNA nucleotides of primer from 5' end and replaces them with DNA nucleotides

DNA polymerase III

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

leading strand

The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' to 3' direction.

lagging strand

A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5' to 3' direction away from the replication fork.

DNA ligase

A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3' end of a new DNA fragment to the 5' end of a growing chain.

Nucleic Hybridization

formation of a stable double-stranded nucleic acid molecules from complimentary single-stranded molecules

Plasmids

small circular DNA molecules that replicate separately from the bacterial chromosome

gene cloning

The production of multiple copies of a gene.

cloning vector

a DNA molecule that can carry foreign DNA into a host cell and replicate there

restriction enzymes

an enzyme produced chiefly by certain bacteria, having the property of cleaving DNA molecules at or near a specific sequence of bases.

Transcription

(genetics) the organic process whereby the DNA sequence in a gene is copied into mRNA

Translation

Process by which mRNA is decoded and a protein is produced

initiation of transcription

Attachment of RNA polymerase to the promoter

RNA polymerase binds to a promoter start (start!)

elongation (transcription)

RNA polymerase unzips the DNA and assembles RNA nucleotides using one strand of DNA as a template.

termination of transcription

RNA polymerase reaches a terminator sequence (Stop codon) and detaches from the template

Promoters

regions of DNA that have specific base sequences

Transcritpion factors

mediates the binding of RNA polymerase and the ignition of transcription

transcription initiation complex

The completed assembly of transcription factors and RNA polymerase bound to a promoter.

TATA box

A promoter DNA sequence crucial in forming the transcription initiation complex.

Transcription is more complex in....

Eukaryotes

Capping

-Modified guanosine attached to 5' end

-Needed for mRNA to exit nucleus and bind ribosome

poly-A tail

Modified end of the 3' end of an mRNA molecule consisting of the addition of some 50 to 250 adenine nucleotides.

Exons

Coding segments of eukaryotic DNA.

Introns

Noncoding segments of nucleic acid that lie between coding sequences.

alternative splicing

regulated process during gene expression that results in a single gene coding for multiple proteins

initiation of translation

mRNA is attached to a subunit of the ribosome, the first codon is always AUG

elongation (translation)

codon recognition, peptide bond formation, translocation

termination of translation

occurs when a stop codon in the mRNA reaches the A site of the ribosome

amino acids

Amine, carboxylic acid, functional groups and a side chain specific to each amino acid

common amino acid #

20

Codons

The three-base sequence of nucleotides in mRNA