genes and cellular function chapter

DNA

long thread like molecule with uniform diameter, varied length

DNA structure

a sugar, phosphate group, nitrogenous base

DNA bases

Adenine, thymine, cytosine, guanine

purines 

adenine and guanine 

pyrimidines

cytosine and thymine

adenine to thymine bonds

2 H-bonds

cytosine to guanine bonds

3 H-bonds

gene

segment of DNA coding for synthesis of a specific protein

chromatin

DNA + protein, fine filamentous DNA material complexed with proteins called histones

histones

proteins around which DNA winds, cluster in groups of 8 molecules, creates granule called core protein 

kinetochores

protein plaques on each side of centromere, plays a role in cell division

RNA bases

adenine, uracil, guanine, cytosine

RNA

single nucleotide chain, functions mainly in the cytoplasm

genetic code

system that enables the 4 nucleotides to code for the amino acid sequences of all proteins

mRNA

serves as a code for a particular protein

codon

3 base sequence, DNA and mRNA

start codon

AUG

stop codons

UAG, UGA, UAA

transcription location

nucleus

transcription enzyme

RNA polymerase

transcription

DNA to RNA, copying genetic instructions from DNA to mRNA, reads base from one strand of DNA to build a complementary strand of mRNA, enzyme within the nucleus removes introns from RNA and splice exons together 

Translation location

cytoplasm

translation

RNA to protein, nucleotide converted into amino acids, a ribosome leads the mRNA code and forms a protein

mRNA, translation

carries code from nucleus to cytoplasm

tRNA, translation

delivers a single amino acid to the ribosome, contains an anticodon, complementary to the mRNA codon 

ribosomes, translation

reads the message and build the peptide chain, contains large and small subunit, free in cytosol, on rough ER, and nuclear envelope

Initiation, first step of translation

ribosomes assembles with mRNA in cytosol, tRNA brings first amino acid

elongation, second step of translation

ribosome creates peptide bond between first and second amino acid, ribosome moves down mRNA and growing peptide is now attached to tRNA

termination, third step of translation

ribosome reaches stop codon, A site binds to a release factor, ribosome disassembles and dissociates from mRNA

DNA replication first step

unwinding the helix from the histones

DNA replication second step

DNA helicase unzips small portion of helix, separates the strands 

DNA replication third step

DNA polymerase moves along each strand, reads the exposed bases, and synthesizes he complementary strands 

what enzyme connects the segments

DNA ligase

semiconservative replication

each new DNA molecule contains old and new DNA

DNA replication fourth step

new histones synthesized are used to organize new DNA strands into nucleosomes

G1, first gap phase

cell carries out normal tasks and synthesizes proteins and material for next phase

S, synthesis phase

cell replicates all nuclear DNA and duplicate centrioles

G2, second gap phase

cell repairs DNA replication errors, grows and synthesizes enzymes that control cell division 

prophase

condenses into compact chromosomes, nuclear envelope disintegrates

metaphase

chromosomes align on the equator, mitotic spindles form

anaphase

daughter chromosomes migrate to opposite sides

telophase

chromosomes cluster on each side of the cell, nuclear enveloped redevelops

cytokinesis

division of cytoplasm into two cells