GENETIS - 3rd Year 1st Sem Midterm Reviewer

DNA REPLICATION

DNA contains information needed to carry out cell activities, it is the genetic material. So, when cells divide, they must make an exact copy of the DNA to pass along to the next cell.

Semi-conservative Replication.

New strands of DNA are made from old strands and new nucleotides. This is called ____________ _______

Enzymes

act as biological catalysts, which means they speed up chemical reactions in the body.

Hypothesis 1: Conservative Model

The parent double helix remains intact: all new copies are made.

Hypothesis 2: Semiconservative Model

Two strands of parental double helix separate and each functions as the template for a new half.

Hypothesis 3: Dispersive Model

Each strand made is composed of a mixture of new and old material.

e. coli

Bacteria:

DEOXYRIBONUCLEIC ACID

Nucleic Acids are made from repeating units of nucleotides.

Phosphate group

Deoxyribose sugar

Nitrogenous Base

DNA nucleotides are composed of

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

What are the 4 Nitrogenous Base?

The DNA Ladder

The sides (uprights) of the ladder are made of alternating phosphate groups of one nucleotide and the sugar of the next nucleotide.

The DNA Ladder

The rings of the ladder are made up of paired complementary nitrogen bases. (A-T, C-G)

hydrogen bonds.

These nitrogen bases are held together by ______ ____

The DNA Ladder

These nitrogen bases are held together by hydrogen bonds.

5' and 3'

Each strand ends with either the phosphate (__) or the sugar (__) making them anti parallel.

anti parallel

Each strand ends with either the phosphate (5') or the sugar (3') making them ____ ______

Double Helix

The ladder is twisted to form a helix shape (Watson & Crick).

Double Helix

In eukaryotic cells, we have multiple strands of DNA molecules organized with proteins into chromosomes.

Double Helix

DNA is wrapped up around proteins such as histones to make chromosomes.

Double Helix

DNA stores an organism's genetic information and controls the production of proteins and is thus responsible for the biochemistry of an organism.

Double Helix

DNA is found primarily in the nucleus of a cell in strands of genetic material called chromosomes.

Double Helix

Each chromosome is a single piece of double stranded DNA; specific areas of the chromosomes that are responsible for particular body functions are called genes.

Double Helix

The actual genetic coding is due to the sequence based on the DNA strand.

CCT = proline, GAG = glutamate, GTG = valine

Every amino acid in every protein is coded by sequence of 3 bases (DNA triplet) ___=_______, ___=_______, ___=_______

Ribonucleic Acid (RNA).

The instructions coded by the 3-base sequences are actually carried to the areas in the cells where the protein manufacture occurs by _______ ____

Double Helix

The structure (shape) and functions of the thousands of organisms is controlled by the order of the amino acids in the protein, and therefore is ultimately controlled by the sequence of bases of the DNA.

FIRST STEP: Initiation

SECOND STEP: Elongation

THIRD STEP: Termination

What are he 3 Steps in DNA Replication

FIRST STEP: Initiation

The first step is to unwind the double helix structure of the DNA molecule, and "unzip" the strands. The separated strands will act as templates for making the new DNA.

SECOND STEP: Elongation

The two strands are replicated in different ways, because they run in opposite directions to each other.

THIRD STEP: Termination

A DNA polymerase proofreads the new strands to make sure there are no mistakes in the new DNA sequence.

FIRST STEP: Initiation

This is carried out by an enzyme called helicase, which breaks the hydrogen bonds holding the base pairs of the 2 strands together.

SECOND STEP: Elongation

One is oriented in the 3' to 5' direction towards the replication fork. This is the leading strand.

THIRD STEP: Termination

Finally, an enzyme called DNA ligase seals the DNA back into two continuous double strands. The DNA automatically winds itself back into a double helix.

FIRST STEP: Initiation

Separating the strands creates a "Y" shape called a "replication fork".

SECOND STEP: Elongation

The other is oriented away from the replication fork. This is the lagging strand.

THIRD STEP: Termination

The result is 2 DNA molecules that each consist of one new and one old strand of DNA. This is why DNA replication is described as semi-conservative - half of the chain is part of the original DNA molecule, and half is brand new.

STEP 1: Initiation

Helicase: an enzyme that unwinds and unzips DNA double helix by breaking hydrogen bonds together.

Replication Forks: the sites where nucleotides are exposed.

Single Strand Binding Proteins (SSB's): holds each strand apart.

Topoisomerase: to help relax the unwided DNA strands.

STEP 2 & 3: Elongation & Termination

DNA Polymerase: the enzyme that helps derive synthesis of DNA.

It brings in free complementary nucleotides that are linked together (phosphate groups to sugars).

RNA Primer: produced by Primase that guides DNA polymerase to initiate the start of binding.

DNA Ligase: enzymes that seal the fragments into a continuous strand.

Leading Strand: construction of the new strand works off the template of the old strand. 5' to 3' (downwards) continuous construction.

Lagging Strand: 3' to 5' (upwards) discontinuous construction where the strand is made in short fragments also known as "Ozaki Fragments".

Helicase

an enzyme that unwinds and unzips DNA double helix by breaking hydrogen bonds together.

Replication Forks

the sites where nucleotides are exposed.

Single Strand Binding Proteins (SSB's)

holds each strand apart.

Topoisomerase

to help relax the unwided DNA strands.

DNA Polymerase

the enzyme that helps derive synthesis of DNA.

RNA Primer

produced by Primase that guides DNA polymerase to initiate the start of binding.

DNA Ligase

enzymes that seal the fragments into a continuous strand.

Leading Strand

construction of the new strand works off the template of the old strand. 5' to 3' (downwards) continuous construction.

Lagging Strand

3' to 5' (upwards) discontinuous construction where the strand is made in short fragments also known as "Ozaki Fragments".

DNA REPAIR

DNA polymerases, DNA ligases and other enzymes repair altered DNA ladders by comparing the strand to the complement strand.

DNA REPAIR

___ _____ happens if they find a pair of bases that are not complementary. They will excise one and replace it with a complement to fix the DNA sequence.

DNA repair

The part that gets replaced can have a probability of acquiring DNA mutations.

POLYMERASE CHAIN REACTION

DNA Replication is necessary in a cell to perpetuate genetic information. Researchers use DNA replication conducted outside cells in a biotechnology called DNA amplification.

POLYMERASE CHAIN REACTION

First and best-known DNA amplification technique. It uses DNA polymerase to rapidly replicate a specific DNA sequence in a test tube.

RIBONUCLEIC ACID

A single strand nucleic acid made from also repeating units of nucleotides.

Coding RNA

carries genetic information to make proteins.

Non Coding RNA

Performs regulatory or structural roles (not used to make proteins).

e.g., tRNA, rNA, miRNA, siRNA, snRNA etc.

Messenger RNA (mRNA)

Carries genetic instructions from DNA in the nucleus to the ribosomes in the cytoplasm, where proteins are made.

Transfer RNA (tRNA)

Brings amino acids to the ribosome to help build proteins.

Ribosomal RNA (rRNA)

Forms part of the ribosome, the structure where proteins are synthesized.

Small Nuclear RNA (snRNA)

Helps in RNA splicing - removes introns from pre-mRNA to make mature mRNA.

Small Interfering RNA (siRNA)

Silences or "turns off" specific genes by degrading mRNA after transcription.

Micro RNA (miRNA)

Regulates gene expression by blocking translation or destabilizing mRNA.

GENETIC CODE

In each DNA ladder, the blueprint for a protein is depicted in the sequence of nucleotides.

GENETIC CODE

Three DNA nucleotides, "DNA triplet" represents one amino acid (the building blocks of protein).

GENETIC CODE

The genetic code is converted to a sequence of amino acids called a polypeptide chain through the process of protein synthesis as depicted by the central dogma of molecular biology.

Codons

found on the mRNA

Anti Codons

found on the tRNA

one

Each tRNA can carry only ___ amino acid.

64 and 20

There are ___ different codons, but only __ amino acids.

Degeneracy/Degenerate Code

means multiple codons code for the same amino acid.

e.g., Leucine (Leu) is coded by six codons: UUA, UUG, CUU, CUC, CUA, CUG

Redundancy

refers to the actual repetition or overlaps. Different codons specify the same amino acid.

e.g., UUA and CUG both specify Leucine

Starting Codon

AUG = mETHIONE

Initiating the start of translation.

Stop Codon

UAA, UAG, UGA

Instructing the ribosome to end the translation by releasing the polypeptide chain.

POINT MUTATIONS

A point mutation is a small change in a single nucleotide DNA base pair that can alter a single amino acid or stop protein synthesis - sometimes harmless, sometimes disease-causing.

Base Substitution

One nucleotide is swapped for another

e.g., A → G

Base Insertion

One extra base is added.

e.g., AUG → AUUG (an extra U is added)

Base Deletion

One base is removed.

e.g., AUG → AG (U deleted)

Silent Mutation

Missense Mutation

Nonsense Mutation

What are he 3 type of Base Substitutions?

Silent Mutation

Changes one base, but the new codon still codes for the same amino acid. No changes will occur.

Missense Mutation

Changes one base, but the new codon still codes for the same amino acid. Changing the shape will change the function of the protein.

Nonsense Mutation

Changes one base, turning a codon into a premature stop codon.

Frameshift Mutation

Occurs when one or more nucleotides are added or deleted (not in multiples of 3). This shifts the reading frame, changing how the codons are read from that point onward.

Proteins

_____ make up all living materials.

Proteins

_____ are composed of amino acids - there are 20 different amino acids.

20 amino acids

Different proteins are made by combining these __ _____ ____ in different combinations.

ribosomes.

Proteins are manufactured (made) by the ______

FUNCTION OF PROTEINS

1. Help fight disease

2. Build new body tissue

3. Enzymes used for digestion and other chemical reactions are proteins (Enzymes speed up the rate of a reaction).

4. Component of all cell membranes.

PROTEIN SYNTHESIS

DNA contains the genetic code for the production of proteins.

Central Dogma for Molecular Biology

describes the flow of genetic information from DNA to RNA to protein.

RIBOSOMES

Known as the site of protein synthesis.

RIBOSOMES

It is composed of proteins and rRNA.

RIBOSOMES

Divided into two subunits: Large and small ribosome subunits.

RIBOSOMES

It is the location for translation.

Transcription

Function: The process of copying genetic information from DNA to mRNA.

Location: Nucleus

Main Enzyme: Rna Polymerase

Starting Material: DNA

End Product: mRNA

Translation

Function: The process of reading mRNA to assemble amino acids into a protein

Location: Cytoplasm

Main Enzyme: Ribosome

Starting Material: mRNA

End Product: Protein