DNA transcription and translation

where us DNA stored?

in the nucleus

parts of a nucleotide

sugar, phosphate group, nitrogen base

DNA molecule construction

double helix - two strands running antiparallel

direction of strands 

opposite directions - one 5’→3’: the other 3’→5’

sugars and phosphates

form the backbone with phosphodiester bonds 

purines and pyrimidines

purines: A, G (2 Rings)

Pyrimidines: T, C (1 Ring)

base paring

A-T, G-C ( in RNA, A-U)

Hydrogen bonds

hold base pairs togtether ( A-T has 2: G-C has 3)

DNA vs RNA 

DNA- double strand, has thymine, deoxyribose.

RNA- single stranded, has urcail, ribose

central dogma

DNA→RNA→protein

Gene

segment of DNA that codes for a protein

transcription steps:

intiation: RNA polymerase binds to promoter

Elongation: mRNA strand made

Termination: RNA polymersse stops at the end of the gene

where transcription happens

in the nucleus

RNA polymerase finds starts by

binding to promoter region on DNA

template vs. non-template strand

template = used to make mRNA

non-template = coding strand (same as mRNA expect T→U)

complementary base paring in transcription 

RNA bases pair with DNA: A–U, T–A, G–C, C–G.

mRNA modifications

• 5’ Cap → protects RNA, helps ribosome bind.

• 3’ Poly-A tail → protects RNA from degradation.

• Introns → removed (noncoding).

• Exons → kept (coding).

where mRNA goes after modification

leave nucleus → goes to ribosome in cytoplasm

where does translation happen?

in thr cytoplasm

what ribosome does

read mRNA and assembles amino acids into protein

codon

3-base sequence on mRNA that codes for animo acid

anti codon

3-base sequence on tRNA that pairs with mRNA codon 

condon code for

an animo acid or stop signal

tRNA

carries amino acid to ribosome; anticodon on one end, amino acid on the other.

rRNA

part of the ribosomes structure; helps catalyze peptide bonds

translation steps

initiation:ribosome binds to mRNA start codon

elongation:amino acids linked together

termination: stp codon reached→ protein released

mutation

a change in the DNA sequence

effect of mutation of mRNA/protein

changes mRNA codon→ may change amino acid → can alter protein