Biology RNA Polymerase & Mitosis Phases Study Guide

Nucleus houses

the nuclear DNA, along with the nucleolus and cytoplasm

Nucleic acid is formed by

repeating monomers called nucleotides

Nucleotides

building blocks of nucleic acids

DNA is composed of

deoxyribonucleotides

which include five-carbon sugar deoxyribose, a phosphate, and one of the four nitrogenous bases (A, C, G, T)

Phosphodiester Bonds

bonds between phosphate group and pentose sugar in nucleic acids.

Complementary Base Pairing

DNA, T pairs with A; G pairs with C

RNA, U pairs with A and G pairs with C

Histones

protein molecules around which DNA is tightly coiled in chromatin

helps package DNA molecules within the nucleus

Nuclesome

repeating subunit of chromatin fibers, consisting of DNA coiled around histones

Chromatin

substance found in eukaryotic chromosomes that consists of DNA tightly coiled around histones

our genetic DNA is typically present in our cells as chromatin

Chromosomes

threadlike structures made of DNA molecules that contain the genes

needed to prevent DNA from becoming tangled during cell division

Genes

DNA segments that serve as the key functional units in hereditary transmission

provide instructions for the synthesis of very specific proteins

each gene has a promoter (start signal) and terminal (stop signal) for transcription, or copying, of a gene into an RNA molecule

Transcription

the process happens in the nucleus, where the RNA polymerase enzyme creates an RNA molecule from ribonucleotides using DNA as a guide

Translation

occurs within the cytoplasm by ribosomes, is the formation of a specific protein from amino acids as directed by the RNA molecule

Transcription Required Structures

DNA, ribonucleotides, RNA polymerase

In Transcription DNA is required because

a specific segment of DNA serves as the template to form an RNA molecule

In Transcription Ribonucleotides are required because

these are the monomers that will be used to synthesize the newly formed RNA polymer

Ribonucleotides Types One Nitrogenous Base

Adenine, Thymine, Cytosine, Guanine, Uracil

In Transcription RNA Polymerase

is the enzyme that facilitates the placement of ribonucleotides with the bases of the DNA template as an RNA molecule is synthesized

RNA Polymerase assembles the ribonucleotides by

complementary-pairing nitrogenous bases of the ribonucleotides with nitrogenous bases of DNA

DNA, RNA Polymerase, and Ribonucleotides are located in the

nucleus

Three Functional Types of RNA are produced during transcription

mRNA, tRNA, rRNA

mRNA

messenger RNA, type of RNA that carries instructions from DNA in the nucleus to the ribosome

tRNA

transfer RNA, type of RNA that carries amino acids to the ribosome

rRNA

ribosomal RNA, type of RNA that makes up part of the ribosome

The process of transcription to form mRNA includes three major events

inititation, elongation, termination

Template Strand

the strand of DNA that specifies the complementary mRNA molecule

Coding Strand

The strand of DNA that is not used as a template during transcription, also called the sense strand

Transcription Initiation

RNA polymerase attaches to the promoter region of DNA strand, and synthesis begins

Transcription Elongation

mRNA is assembled by adding nucleotides complementary to DNA template strand - DNA rewinds once read

Transcription Termination

when the terminal region at the end of the gene is attached, RNA polymerase is released from the DNA as hydrogen bonds are broken between the DNA strand and newly formed mRNA

the newly formed mRNA strand is a recipe copied from DNA for synthesizing a specific protein (e.g insulin)

Modifications to mRNA

5'methyl cap and 3' poly A tail

splicing results in a mature mRNA, which can be used to make a protein

pre-mRNA

form of mRNA that contains both introns and exons

Introns

sequence of DNA that is not involved in coding for a protein

Exons

coding segments of eukaryotic DNA

Splicing

the process of removing introns and reconnecting exons in a pre-mRNA

Capping

unique bonding of a ribonucleotide containing guanine to the lead end of the mRNA

increases stability of an mRNA strand, helping to prevent its digestion by nucleic acid digesting enzymes (in cytosol)

polyA tail

tail is a stretch of adenine nucleotides added to the 3' end of a messenger RNA (mRNA) molecule.

helps stabilize the mRNA, protects it from degradation, and aids in the export of the mRNA from the nucleus to the cytoplasm for translation

Translation Required Structures

ribosomes, mRNA, tRNA, amino acids

Translation Product

protein

Translation Ribosomes

composed up of a large subunit and a small subunit synthesized by the nucleolus

large subunits - A (aminoacyl) site, P (peptidyl) site, E (exit) site

A (aminoacyl) site is where

new amino acids are added

P (peptidyl) site holds the

newly forming polypeptide (protein)

E (exit) site is

where tRNA sits before being released from the ribosome

Protein

an organic compound that is made of one or more chains of amino acids and that is a principal component of all cells

Codon

three-nucleotide sequence on messenger RNA that codes for a single amino acid

Translation Start Codon

signals the start of translation and the amino acid methionine

AUG

Translation End Codon

serve as the point where the reading of mRNA ends

UAA, UAG, UGA

Translation Anticodon

pairs with complementary mRNA codon

tRNA Acceptor End

provides an attachment site for a specific amino acid

tRNA Anticodon

serve as an adapter site, complementary to mRNA codon

first sequence (e.g UAC) determines the specific amino acid to which a given tRNA attaches

Translation Steps

initiation, elongation, termination

Translation Initiation

small subunit attaches to mRNA upstream of start codon (AUG), the large subunit joins complex and the tRNA in now in the P site

Translation Elongation

a charged tRNA with a complementary anticodon base-pairs with the codon of the mRNA in the A site bringing it with a specific amino acid

a peptide bond is formed between the amino acid in the P site and the amino acid in the A site (bond of amino acid to tRNA in P site breaks)

the ribosome then moves three nucleotides positions (same as codon) down the start codon on the mRNA

repeats until the entire mRNA sequence has been translated

Translation Termination

is when a stop codon (UAA, UAG, or UGA) enters the A site to end translation

release factor enters the A site

ribosome hits release factor bound to mRNA start codon, two subunits of the ribosome are separated from mRNA and new synthesized protein is released

Polyribosome

string of ribosomes simultaneously synthesizing same protein

Why is DNA considered the cell's control center?

DNA is responsible for directing the synthesis of the proteins that carry out body functions

indirectly responsible for other metabolic changes that occur within a cell,

including synthesis of steroids and other lipids, and the enzymatic pathway of glucose oxidation

Mitosis occurs in

somatic (body) cells

Meiosis occurs in

germ (sex) cells

Somatic Cell Division

occurs when one cell divides to produce two genetically identical cells

Cell Cycle Phases

G1, S, G2, mitosis, cytokinesis

Explain Cell Cycle

the cell cycle is a series of stages that a cell goes through to grow and divide

G1 phase

cell growth and preparation for DNA replication

S phase

DNA replication

G2 phase

growth and preparation for divison of DNA

Cytokinesis

division of the cytoplasm to form two separate daughter cells

Mitosis Phases

prophase, metaphase, anaphase, telophase

Mitosis Prophase

chromosomes condense become visible, the nuclear envelope begins to break down

Mitosis Metaphse

chromosomes align at the cell's equator

Mitosis Anaphase

sister chromatids are pulled apart to opposite poles of the cell

Mitosis Telophase

chromosomes gather on each side of the now separating cell

DNA replication

the process of making a copy of DNA

Apoptosis

process of programmed cell death

Apoptosis Process

destruction of DNA polymerase

digestion of the DNA into small fragments

digestion of cytoskeleton, cell shrinks

formation of blebs on plasma membrane surface

condensation of cytosol and destruction of organelles

release of proteins