final exam prep for bio

i hate this class i hate this class i hate this class

DNA contains the ____ ____ of every cell

DNA contains the ____ ____ of every cell

molecular blueprint

proteins are the ____ ____ of the cell

construction workers

proteins control

cell shape

function

reproduction

synthesis of biomolecules

there is a flow of information from ____ to _____

DNA; protein

DNA in eukaryotes is kept in the

nucleus

Protein synthesis occurs at ____ in ____

ribosomes; cytoplasm

DNA infor is carried by ____ from the nucleus to the cytoplasm

RNA

RNA differs from DNA

single-stranded

uses sugar ribose

base uracil

messenger RNA

carries DNA gene information to the ribosome

single-stranded "intermediate copy" of DNA

mRNA

transfer RNA

carries amino acids to the ribosomes for addition to the growing protein

have a "cloverlead" shape

tRNA

ribosomal RNA

part of the structure of ribosomes

each ribosome consists of two subunits - one small and one large

rRNA

genetic information is transcribed into ____ and then translated into ____

RNA; protein

information in a DNA gene is copied into mRNA in the process of

transcription

mRNA, tRNAs carrying amino acids, and a ribosome, synthesizes a protein in the process of

translation

genetic code

translates the nucleotide sequence into amino acids in proteins

bases in mRNA are read by the ribosome in triplets called

codons

individuals who cracked genetic code

nirenberg and matthaei

nirenberg and matthaei's experiment

created artificial mRNAs of known sequence and observed what proteins they produced

mRNA start codon

AUG

three stop codons

UAA, UAG, UGA

transcription of a DNA gene into RNA has three stages

1. initiation

2. elongation

3. termination

transcription initiation stage 1

RNA polymerase binds to the promoter region at the beginning of a gene

transcription initiation stage 2

the DNA molecule is unwound and strands are separated at the beginning of the gene sequence (this creates single strand regions of the DNA)

transcription elongation

• generates a growing strand of RNA

• knows what to make since it "reads" the DNA template strand

• the bases in the newly synthesized RNA strand are complementary to the DNA template strand

• as the RNA strand leaves the DNA strands, the helix re-forms

transcription termination

• transcription stops when the RNA polymerase reaches the termination signal

• RNA polymerase then detaches from the DNA

• a mRNA sequence has been fully generated

messenger RNA synthesis differs between ____ and ____

prokaryotes and eukaryotes

genome is small, one circular chromosome

prokaryote

have no nuclear membrane, translation and transcription are not separated in space or time

prokaryote

all genes are "back-to-back" with no spacers

prokaryote

entire genome is transcribed into mRNA, and then translated

prokaryote

dna is in the nucleus and the ribosomes are in the cytoplasm

eukaryote

genes are spaced out over long distances

eukaryote

regions that code for a protein are called

exons

spacer regions between genes are called

introns

enzymes in the nucleus cut out the introns and splice together the exons to make

mature mRNA

more nucleotides are added at the beginning and end of the mRNA molecule, forming a "cap" and "tail"

eukaryote

the mRNA exits the nucleus through a membrane pore and associates with a ribosome

eukaryote

during translation, mRNA, tRNA and ribosomes cooperate to ____ ____

synthesize proteins

translation has three steps

1. initiation

2. elongation

3. termination

translation initiation step 1

a pre-initiation complex forms, consisting of the small ribosomal subunit and a methionine tRNA

translation initiation step 2

the UAC anticodon of the methionine tRNA binds the mRNA molecule by base-pairing with the AUG start codon at the beginning of the mRNA

translation initiation step 3

the two ribosomal subunits attach together, holding the mRNA between them ("threading the needle")

a second tRNA anticodon base-pairs with the second codon on the mRNA

translation elongation

a peptide bond is formed between methionine and the amino acid attached to the second tRNA

translation elongation

the "empty" tRNA is released and the ribosome moves down the mRNA one codon

translation elongation

a third tRNA, with an anticodon complementary to the third codon of the mRNA base-pairs with mRNA

translation elongation

this tRNA attaches its amino acid to the previous one using a peptide bond

translation elongation

translation termination

when the ribosome reaches a stop codon in the mRNA molecule, releasing factors cause it to release

translation termination

the completed peptide chain, mRNA and ribosomal subunits no longer associate together

translation termination

there is no amino acid associated with the tRNA reaching the stop codon

translation termination

a sequence of amino acids (protein) is the resulting product

each DNA gene codes for

a single protein

____ produces an mRNA strand complementary to the DNA template strand

transcription

the mRNA leaves the ____ and associates with a ____ in the ____

nucleus; ribosome; cytoplasm

transfer RNAs in the cytoplasm are loaded with their appropriate ____ ____

amino acids

the ribosome selects the ____ on the basis of the base-pairing of the anticodon with the exposed mRNA codon

tRNAs

the ____ contains a stop codon to define where protein synthesis ends

mRNA

changes in the base sequence of DNA caused by mistakes during replication or by various environmental factors

mutations

mutations fall into five categories

1. inversions

2. translocations

3. deletions

4. insertions

5. substitutions

occur when pieces of DNA are broken apart and re-attached, within a single chromosome or to a different chromosome

inversions and translocations

may be relatively benign if entire genes are merely moved from one place to another

inversions and translocations

if a gene is split in two in inversion or translocation mutations

it will no longer code for a complete, functional protein

occurs when one or more nucleotides are removed from the gene sequence

deletion

occurs when one or more nucleotides are added to the gene sequence

insertion

do not alter the amino acid specified

silent (neutral) mutations

introduce a STOP codon

nonsense mutations

replace one amino acid with another

missense mutations

result from the insertion or deletion of nucleotides within the coding sequence in non-multiples of 3

frameshift mutations

may/may not change amino acid sequences of the proteins

nucleotide substitutions (point mutations)

alter the reading frame of the mRNA that is translated into amino acids

frameshift mutations

the human genome has

20,000 to 25,000 genes

in eukaryotic cells, transcriptional regulation occurs on at least three levels

1. the individual gene

2. regions of chromosomes

3. entire chromosomes

biotechnology

modification of organisms, cells, or molecules to produce food, drugs, or other goods

more modern uses modify the genes directly through

genetic engineering

recombinant DNA

DNA that has been altered to contain genes or portions of genes from different organisms

transgenic/genetically modified organisms

plants and animals that express DNA that has been modified or derived from other species

bacteria pick up pieces of DNA from the environment in

transformation