Lecture 2: DNA, RNA, protein Flashcards
Deoxyribonucleic acid (DNA) does what
Stores genetic information in its sequence
Ribonucleic acid (RNA) does what
Decodes genetic information into instructions for building proteins
DNA is
DNA is a polymer
Repetition of a monomer
Nucleotides are building blocks
Polynucleotide chains
Nucleotides are determined by
Phosphate group
Sugar
Nitrogenous base
Four types of nucleotides in DNA
Four types of nucleotides depending on the nitrogenous base linked to the sugar
A- adenine
C-cytosine
G- guanine
T- thymine
DNA structure is
Double helix
Alternating sugar and phosphate groups form the sides
Sugar – phosphate backbone
Phosphate of one nucleotide links to the sugar of the adjacent nucleotide
Base pairing of nucleotides in DNA
A pairs with T
C pairs with G
Pairing produces weak attractive forces between opposite bases
Holds polynucleotide chains together
Hydrogen bonds
Base pairing occurs when the two polynucleotide chains are lined up in opposite directions
Anti-parallel
Packaging of DNA includes
DNA associates with proteins to form chromosomes
DNA double helix coils around histone proteins – called nucleosome
Further folded into a thicker fiber
Additional packaging achieves chromosome structure for mitosis and meiosis
Supercoiling
DNA replication is
Prior to cell division, DNA must be copied in order to provide each daughter cell with the entire genome
Requires extensive and accurate DNA replication
Key resides in complementary base pairing
Strands separate
Each strand acts as a template to produce a complementary strand
Semi-conservative replication
What happens by DNA replication
Two new molecules identical to the first are produced
Each has 1 strand from the original molecule
Each has one newly made strand
Central dogma is
DNA → RNA → Protein
Transcription is
Coded information within DNA is copied into a complementary RNA sequence
Translation is
RNA associates with ribosomes
The synthesis of the encoded protein molecule
Information transfer is located in
The DNA and the site of protein synthesis are physically separated
DNA is located in the nucleus
The information carrier is nucleus
Information transfer can cause
Protein synthesis occurs at ribosomes within the cytoplasm
Most genes contain the information for the production of a specific protein
Directly or indirectly leads to the expression of a particular phenotype
Purpose of genetic material is to encode the production of proteins in the correct cell, at the correct time, and in the correct amount
RNA characteristics
RNA is a polymer of nucleotides
The sugar is ribose
Bases are A,G,C and U
Uracil replaces thymine
Uracil is similar to thymine and can pair with A
RNA is usually found in the single strand form
RNA is usually much shorter in sequence
RNA transcription
RNA is produced in a manner similar to DNA replication
DNA template strand used for synthesis of a complementary mRNA strand
mRNA does what
The information carrier from DNA to ribosome
The mRNA nucleotide sequence represents the instructions for assembly of a precise amino acid sequence
Acts as an intermediate gene expression product
Proteins are and determined by
Proteins are polymers of amino acid chains
Twenty different amino acids are found within proteins
Each different protein has a specific amino acid sequence
Polypeptide is
A single chain of amino acids
Protein shape
a functional unit composed of one or more polypeptides in a 3-D shape
4 levels of protein structures and what they are
Primary – amino acid sequence
Secondary – bending or twisting of polypeptide into repeating patterns
Tertiary – 3-D shape determined by amino acid interactions and surrounding environment
Quantiary – 2 or more polypeptides bind to form a functional protein
How does a gene become a protein
A gene comprises a linear sequence of nucleotide pairs
A protein is a linear sequence of amino acids
The nucleotide sequence determines, and correlates with, the amino acid sequence
Each consecutive three nucleotide set specifies a single amino acid of the encoded protein
3 nucleotides code 1 amino acid
The genetic code is
Genetic code specifies the relationship between the nucleotide sequence and the amino acid sequence
Each triplet of nucleotides codes for a specific amino acid
Known as a codon
The code is degenerate – amino acids are represented by more than one codon
Translation on producing proteins
Translation involves converting the mRNA message into a polypeptide chain
Mutation is
The flow of information from DNA to protein needs to be highly efficient and accurate
Mutation = change in genetic material
Mutations can be neutral, beneficial or detrimental
A mutation can occur in any cell of the body at any time
Mutation is determined by
Timing and location of mutation is critical to the severity of the effect and to whether the mutation can be passed to offspring
Mutations in cells that give rise to gametes (germ-line cells) can be passed to offspring
Mutations in somatic cells are not passed to offspring
Mutation can be repaired by
Several dozen different enzymes exist to detect and repair structural alterations to DNA
Excise damaged or mismatched nucleotides
Fill the gap with the correct nucleotides
Reseal the gap
No system is error free
Why can mutation not be fixed
Changes can escape detection and repair
DNA may have errors
Message in mRNA may be faulty
Protein product may be changed
Spontaneous mutations result from
result from abnormalities of biological processe
Induced mutations caused by
caused by environmental agents that enter cell
Mutagens are
chemical substances or physical agents that cause mutations
Types of mutation changes and what happens
Mutations can cause 2 types of changes to a gene
Base sequence is changed
May be no amino acid change, one amino acid change, or shortened polypeptide
One or more nucleotides are added or removed
Results in a frameshift
Completely different amino acid sequence is produced
Cancer is caused by
Cancer is a disease characterized by uncontrolled cell division
Cancer is usually an acquired condition that occurs later in life
Carcinogens are
Carcinogens are agents that increase the likelihood of developing cancer
Promote changes in DNA of somatic cells
DNA alterations that affect cell division can lead to cancer
