unit 6 - molecular genetics

Nitrogenous Base

Nitrogenous Base

A molecule that contains nitrogen and has the chemical properties of a base. The binding of these base pairs forms the structure of DNA .

Adenine

A chemical compound that is used to make one of the building blocks of DNA. Bonds with thymine or uracil.

Guanine

A chemical compound that is used to make one of the building blocks of DNA and RNA. Bonds with cytosine.

Cytosine

A chemical compound that is used to make one of the building blocks of DNA and RNA. Bonds with Guanine.

Thymine

A chemical compound that is used to make one of the building blocks of DNA and RNA. Bonds with adenine.

Uracil

A chemical compound that is used to make one of the building blocks of DNA and RNA. Bonds with adenine.

Double helix

A term used to describe the physical structure of DNA.

Sugar-phosphate backbone

Forms the structural framework of nucleic acids, including DNA and RNA. This is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.

Carbon labeling (primes)

the numbering of ring carbons then continues in a direction (clockwise or counter-clockwise)

DNA

The molecule inside cells that contains the genetic information responsible for the development and function of an organism. Double Helix

RNA

a single-stranded molecule which has a shorter chain of nucleotides

Complementary base pairs

Hydrogen bonds hold the two strands of the molecule together. These pair up with each other in a consistent way,

Chargaff’s Rule

states that in the DNA of any species and any organism, the amount of guanine should be equal to the amount of cytosine and the amount of adenine should be equal to the amount of thymine.

Antiparallel

A term used to describe the opposite orientations of the two strands of a DNA double helix; the 5' end of one strand aligns with the 3' end of the other strand.

Nucleotide bonding (5’ to 3’ or vice versa)

to the orientation of nucleotides of a single strand of DNA or RNA. specifically refer to the 5th and 3rd carbon atoms in the deoxyribose/ribose sugar ring.

Histone

A type of protein found in chromosomes. These bind to DNA, help give chromosomes their shape, and help control the activity of genes. Enlarge. Structure of DNA.

Nucleosome

a section of DNA that is wrapped around a core of proteins

Semiconservative replication

the two strands of DNA unwind from each other, and each acts as a template for synthesis of a new, complementary strand. This results in two DNA molecules with one original strand and one new strand.

Helicase

enzyme that separates double-stranded DNA into single strands allowing each strand to be copied.

DNA Polymerase

enzymes that create DNA molecules by assembling nucleotides, the building blocks of DNA.

Primase

enzyme that creates a primer on a DNA strand by adding RNA nucleotides to the strand according to the DNA template sequence.

Primer

a short nucleic acid sequence that provides a starting point for DNA synthesis.

Ligase

for sealing any breaks in the sugar-phosphate backbone of the strand, sealing Okazaki fragments (the glue)

Okazaki Fragments

short sections of DNA formed at the time of discontinuous synthesis of the lagging strand during replication of DNA, need to be sealed by ligase

Leading Strand

a single DNA strand that, during DNA replication, is replicated in the 3' – 5' direction (same direction as the replication fork). DNA is added to this continuously, one complementary base at a time.

Lagging Strand

a single DNA strand that, during DNA replication, is replicated in the 5′ – 3′ direction (opposite direction to the replication fork). DNA is added to this in discontinuous chunks called 'okazaki fragments'.

Telomerase

progressive synthesis of telomeric DNA repeats (TTAGGG) at the 3′ ends of linear chromosomes, thereby reversing the loss of DNA from each round of replication.

mRNA

Role is to carry protein information from the DNA in a cell's nucleus to the cell's cytoplasm (watery interior), where the protein-making machinery reads it’s sequence and translates each three-base codon into its corresponding amino acid in a growing protein chain. (messenger)

tRNA

type of RNA that carries amino acids to the ribosome. serves as a link (or adaptor) between the mRNA molecule and the growing chain of amino acids that make up a protein

rRNA

a major constituent of ribosomes. It ensures the proper alignment of the mRNA and the ribosomes during protein synthesis and catalyzes the formation of the peptide bonds between two aligned amino acids during protein synthesis. (ribosomal)

Transcription

the process by which a cell makes an RNA copy of a piece of DNA. This RNA copy, called messenger RNA (mRNA), carries the genetic information needed to make proteins in a cell.

Translation

the process by which a cell makes proteins using the genetic information carried in messenger RNA (mRNA). amino acids are linked together to form proteins

Elongation (transcription/translation)

Middle stage. transcription - nucleotide bases are added to mRNA strand, it gets longer. translation - amino acids are added to amino acid chain, it gets longer.

Termination (transcription/translation)

End stage. transcription - RNA polymerase transcribes terminator sequence and releases DNA template. translation - ribosome reaches the stop codon (UAA, UAG, UGA) and protein is released.

Transcription Bubble

A molecular structure formed during DNA transcription when a limited portion of the DNA double helix is unwound. The size of this ranges from 12 to 14 base pairs.

Template/Nontemplate Strand

The template one is the one that RNA polymerase uses as the basis to build the RNA. . The non-template one has the identical sequence of the RNA (except for the substitution of U for T).

Promoter

a region of DNA upstream of a gene where relevant proteins (such as RNA polymerase and transcription factors) bind to initiate transcription of that gene, also defines the direction of transcription and indicate which DNA strand will be transcribed

RNA polymerase

an enzyme that is responsible for copying a DNA sequence into an RNA sequence, duyring the process of transcription. acts as all the other enzymes (primase, ligase, etc) in DNA replication.

Nucleotide cap

Attaches to the 5’ end, protects mRNA from degradation and helps in ribosome binding during translation.

Poly-A tail

Attaches to the 3’ end, 200 adenines, protects mRNA from degradation and helps in ribosome binding during translation.

Intron

The sequence of DNA in between exons that is initially copied into RNA but is cut out of the final RNA transcript and therefore does not change the amino acid code.

Exon

The sequence of DNA present in mature messenger RNA, some of which encodes the amino acids of a protein.

Polypeptide

A substance that contains many amino acids (the molecules that join together to form proteins).

Large Subunit

contains the active site of the ribosome: the site that creates the new peptide bonds when proteins are synthesized.

Small Subunit

In charge of information flow during protein synthesis. It initially finds a messenger RNA strand and, after combining with a large subunit, ensures that each codon in the message is paired with the anticodon in the proper transfer RNA.

Amino Acids

molecules that combine to form proteins

Codons

A sequence of three consecutive nucleotides in a DNA or RNA molecule that codes for a specific amino acid.

Start Codon

the first codon of a messenger RNA (mRNA) transcript translated by a ribosome (AUG)

Stop Codon

a sequence of three nucleotides (a trinucleotide) in DNA or messenger RNA (mRNA) that signals a halt to protein synthesis in the cell (UAA, UAG and UGA)

A site

a binding site for charged t-RNA molecules during protein synthesis. One of three such binding sites, the first location the t-RNA binds during the protein synthesis process

P site

the second binding site for tRNA in the ribosome. holds the tRNA which is linked to the growing polypeptide chain.

E site

third and final binding site, tRNA goes here after it is empty, meaning that it has transferred its polypeptide to another tRNA (which now occupies the P site).

Initiation step (transcription/translation)

Beginning stage. transcription - RNA polymerase binds to the region called the promoter. translation - initiator tRNA interacts with AUG start codon

Point Mutation

a change in a single base pair of DNA by substitution, deletion, or insertion of a single nitrogenous base.

Silent Mutation

when the change of a single DNA nucleotide within a protein-coding portion of a gene does not affect the sequence of amino acids that make up the gene's protein.

Missense Mutation

a point mutation in which a single nucleotide change results in a codon that codes for a different amino acid.

Nonsense Mutation

occurs in DNA when a sequence change gives rise to a stop codon rather than a codon specifying an amino acid.

Frameshift Mutation

An insertion or deletion involving a number of base pairs that is not a multiple of three, which consequently disrupts the triplet reading frame of a DNA sequence.

Insertion

A type of genetic change that involves the addition of a segment of DNA

Deletion

A type of genetic change that involves the absence of a segment of DNA.

CRISPR

is a highly precise gene editing tool that is changing cancer research and treatment.

Gene Expression

the process by which the instructions in our DNA are converted into a functional product, such as a protein.