biology - DNA, transcription, translation

chromosomes are made of

long coiled molecules of DNA wrapped around histones

DNA molecule contains four different bases

cytosine

adenine

thymine

guanine

base pairings for DNA

A-T

C-G

wrong bases paired together can lead to

apoptosis

programmed cell death

what does DNA control

production of proteins

what is DNA

the genetic material found in all living organisms

types of nucleic acid

DNA and RNA

where is DNA found in which cell

nucleus of eukaryotes

and plasmids of prokaryotes

where can DNA also be found

mitochondria

chloroplasts of plant cells

RNA is found in what forms

transfer RNA

messenger RNA

ribosomal RNA

genetic material of some viruses

what does DNA and RNA consist of

units called nucleotides

what does a nucleotide consist of

sugar, phosphate and one of the 4 bases

what does the nucleotide base component do

compromise the genetic code

condensation polymerisation

joining nucleotides together

how are nucleotides joined together

covalent bonds between the phosphate group of one nucleotide and the third carbon atom of the pentose sugar in the next nucleotide.

what does condensation polymerisation produce

an alternating backbone of sugar-phosphate-sugar along the polynucleotide chain.

DNA structure

double stranded (double helix)

sugar and phosphate on outside (backbone)

nitrogenous bases created "rungs" (held together by hydrogen bonds)

the two strands of helix run in opposite directions (anti parallel orientation)

hydrogen bonds are

VERY STRONG

the more bonds means

the larger the molecule

DNA strand

double

RNA strand

single

DNA sugar

deoxyribose

RNA sugar

ribose

bases for RNA

guanine

cytosine

uracil

adenine

role of DNA

storing and transferring genetic information

role of RNA

to directly code for amino acids and act as a messenger between DNA and ribosomes to make proteins.

nucleotide structure in more depth

nitrogenous base (A,T,C,G) or (A,U,C,G)

pentose sugar (will have 5 sides)

1 or more phosphate groups

carbon residues in the pentose are numbered 1′ through 5′

the base is attached to the ribose's 1′ position, and the phosphate is attached to the 5′ position.

the 'prime' distinguishes

these residues from those in the base

the T base is replaced with what mRNA base

uracil

transcription definition

transcription involves the production of a piece of messenger RNA (mRNA) using the DNA template. Happens in the nucleus of cells.

transcription pairs with

mRNA

first step of transcription

initiation:

RNA polymerase binds with transcription factors within the promoter region. This signal weakens the hydrogen bonds in DNA to break it - unwind or unzip it. This allows RNA polymerase to start transcribing.

initiation of transcription (different answer)

RNA polymerase attaches to the promoter region on the DNA and begins to unzip the DNA into two strands.

second step of transcription

elongation:

RNA polymerase moves along the strand and brings "free" complementary RNA nucleotides. Producing a new single strand of pre-mRNA.

elongation of transcription (different answer)

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

termination of transcription (different answer)

DNA zips up and mRNA leaves the nucleus

third step of transcription

termination:

transcription ends when RNA polymerase detaches, releasing the pre-mRNA - this allows the DNA to reform its original double helix (the pre-mRNA becomes mRNA).

steps of transcription

initiation, elongation, termination

RNA polymerase

an enzyme that builds RNA by reading the DNA

how to tell if its a copy

pairs are A-U not T

summarisation of transcription

-DNA unwinds/unzips

-RNA polymerase catalyses transcription

-nucleotides are joined by RNA polymerase

-transcription of DNA template strand to pre-mRNA

-pre-mRNA is complementary to DNA template strand

-in the pre-mRNA 'A' pairs with 'U' not 'T'

why can't DNA leave the nucleus

it is too big

sections of a gene

promoter, coding sequence, terminator

first section of a gene

promoter region (TATA box)

second section of a gene

coding sequence (transcribed gene) (transcription)

last section of a gene

terminator

the terminator sequence

post-transcriptional process means

after transcription has occurred

exons (simple)

the coding regions

introns (simple)

sequences that do not code for the protein

in eukaryotic cells a piece of what is produced as a result of transcription

pre-mRNA

what needs to be modified before translation

the piece of pre-mRNA

what does the piece of RNA produced contain

introns and exons

what is removed to leave only the part of mRNA that will be expressed

introns

what are the three processes that pre-mRNA will undergo before becoming mRNA and functional outside of the nucleus

addition of a methyl cap (5' capping)

addition of a poly A tail (3' polyadenylation)

RNA splicing (removing introns)

what happens at the end of post transcription

there is a piece of mRNA that can be translated into a protein

what does the three processes do

completes the molecule

coming out with nice ends

summarised post transcriptional process

pre-mRNA

remove excess info

3 processes

becomes mRNA

introns definition

introns in the DNA are long sequences of codons that have no protein-coding function.

introns may be remnants of now unused ancient genes

codons

a three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code.

what happens when the introns are removed

it leaves only the part of mRNA that will be expressed

what does the methyl cap and poly A tail do for the pre-mRNA

THESE PROTECT THE RNA FROM DEGRADATION

degradation

a decline to a lower condition, quality, or level

translation definition

translation is the process of building a polypeptide chain from amino acids, guided by the sequence of codons on the mRNA.

structures involved in translation

messenger RNA, transfer RNA, ribosomes, amino acids

messenger RNA in translation

delivery service

molecules (mRNA) carries the code for the DNA that will be translated into an amino acid sequence

transfer RNA in translation

deliver truck - gets it to the right location

molecules (tRNA) transport amino acids to their correct position on the mRNA strand

ribosomes in translation

storage shed/facility

provide the environment for tRNA attachment and amino acid linkage

amino acids in translation

from which the polypeptides are constructed

what fits into the grooves of the ribosomes

mRNA strand and polypeptide chain

what is the ribosomal subunits constructed up of

protein and ribosomal RNA (rRNA)

when are the ribosomal subunits form a functional unit only

when they attach to a mRNA molecule

the job of the ribosome

sending information out

when they see a need they will act on it

like firefighters

tRNA molecule

anticodon

the site of the 3-base sequence that 'recognises' and matches up with the codon on the mRNA molecule

mRNA molecule

mRNA

anti

opposite to the codon

nuclear pore

in which the mRNA passes into the cytoplasm

exit point of the nucleus

anticodon

group of three bases on a tRNA molecule that are complementary to an mRNA codon

DNA polymerase

An enzyme that catalyzes the formation of the DNA molecule.

helicase

An enzyme that untwists the double helix at the replication forks, separating the two parental strands and making them available as template strands.

gene expression

process by which a gene produces its product and the product carries out its function

differential gene expression

The expression of different sets of genes by cells with the same genome.

direction of transcription

5' to 3' direction

initiation of transcription

RNA polymerase attaches to the promoter region on the DNA and begins to unzip the DNA into two strands.

elongation of transcription

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

structural gene

genes that code for polypeptides

regulatory gene

A gene that codes for a protein, such as a repressor, that controls the transcription of another gene or group of genes.

homeotic genes

Genes that determine basic features of where a body part is.

transcription factors

a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence.

sense strand

original

antisense strand

opposite

moves from 3' to 5' (opposite direction)

adenine base

thymine base

guanine base

cytosine base

anti parallel

run in opposite directions

also paired with opposite pairs

dissociation

split in hydrogen bonds between bases in double helix

helpful in dna replication

polysome

assembly of ribosomes translating a piece of mRNA

genetic code

all living things on earth use the same code to turn DNA or RNA information into protein amino acid sequences.

degenerate

multiple things can code for the same amino acid