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

what is tRNA

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

 what is rRNA

part of the ribosomes structure; helps catalyze peptide bonds

stages of ranslation

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

function of DNA replication

to make an exact copy of DNA before cell division

how is DNA replicated?

emzymes: helicase unzips the dna, primase lays down rna primers, dna polymerase adds new dna neucleotides 5-3, ligase seals gaps

why is dna sometimes condensed or unwound?

condensed ofr cell division

unwound to allow transcription and replication

what is a diploid cell?

a cell with two sets of chromosomes

what is tRNA?

transfer rna - one endianticodon

what is mRNA

Ribosomal RNA makes up ribosomes, catalyzes peptide bond formation 

stages of translation

initiation: mRNA binds to ribosomes

start codo: AUG RECOGNIZED

tRNA brings in methionine

ELONGATION; trna bring amino acids

peptide bonds form- ribosomes move along mRNA

TERMINATION; stop codon reached

release factors separate ribosomes, mRNA, and protein

why is nucleotide order improtant?

every 3 base=one condon=amino acid

changes protein structure and function

what is mutation?

a permanant change in the dna sequence 

what happens if the dna sequence changes?

the mRNA will carry the same change

why do cells divide?

growth, repair, replacement of old cells, reproduction

prokaryotic cell divison

binaryfission produces 2 identical daughter cells

eukaryotic cell division/mitosis

produces 2 genetically idenitcal daughter cells

ensures correct chromosome number

what happebs during interphase?

G1- cell grows, normal function, makes organelles

s phase- DNA replication

G2- final growth, prepare for mitosis

Mitosis stages

Prohase

metaphase

anaphase

telophase

cytokinesis

what happens in prophase

chromosomes condense, nuclear envelope breaks down, centrioles move to opposite poles, spindle fbers form

what happens in metaphase

chromosomes line up single file at the metaphase plate

what happens in anaphase?

sister chomatids separate, they are pulled to opposite poles of the. cell

what happens in the telophase

chromatids arrive at opposite poles, nuclear envelope reforms around each set, chromosomes begin to unwind

what happens in cytokinesis 

cytoplasm divides, produces two daughter cells 

what is the difference cytokinesis in animal and plant cells?

Animal form a cleavage furrow, the cell membrane pinches inward

plant cells form a cell plate that becomes the celll wall

does dna replication happen during mitosis

NO. it does not. it haopens during the S phase

are daughter cells identical?

YES, two daughter cells fro mitosis are genetically identical to eachother anf the parental

whats is a homologous chroosomes?

a pair of chromosomes, one form the mother and one from the father,. same gene, same order, different alleles

what is a sister chromatid?

two copies of the same chromosome produced furing DNA replication, attached at the centromere

how many rounds of cell divison?

two divisons- meiosis 1- and meiosis 2

how many dna replications?

one DNA replication before meiosis (during s phase)

does meiosis happen in body cells or sex cells?

meiosis only occurs in sex organs (testes and ovaries) to produce gametes

what happens in meiosis 1

prophase, metaphase,anaphase, telophase, and cytokinesis

what happens in (meiosis 1) prophase

chromosomes condense, homologous chromosomes pair up (synapsis) crossing over occurs(exchange of DNA)

what happens in (meiosis 1) metaphase

homologous pairs line up side by side at the metaphase plate

what happens in (meiosis 1) anaphase

homologous chromosomes separate, sister chromatids remian togther 

what happens in (meiosis 1) telophase

chromosokes reach poles, nuclear envolopes may reform

what happens in (meiosis 1) cytokinesis

divides cell → 2 haloid cells

when do homologous chromosomes separate?

in anaphase 1

when do sister chomatids separate 

in anaphase 2

what happens in (meiosis 2) prophase

nuclear envolopes break down, spindle forms again

what happens in (meiosis 2) metaphase

chromosomes line up single file

what happens in (meiosis 2) anaphase

sister chromatids separate (just like mitosis)

what happens in (meiosis 2) telophase

nuclear membranes reform around separated chromatids

what happens in (meiosis 2) cytokinesis

4 cells produced, all are haploid, all are genetically different

are gametes genetically identical?

NO, each gamete is genetically unique due to crossing over 8 independent assortment

what does haploid mean?

a cell with one set of chromosomes (N) (n23) total 46

are gametes diploid or haploid?

haploid