Topic 7: Nucleic Acids

Quaternary structure

________: Exists in proteins with more than one polypeptide chain.

gene expression

The impact of the environment on ________: ● Human behaviour or phenotype should be attributed to environment or to heredity.

H1

________ (histone number 9) serves to bind DNA to the core particle of 8 histones.

E

O tRNA moves to ________ site and is released; subsequent tRNA binds to P site, with growing polypeptide chain and a new tRNA binds to A site.

Post transcriptional modification

________: Does not occur in prokaryotes.

Elongation

________: Synthesis of the polypeptide involves a repeated cycle of events o Ribosome translocates three bases along the mRNA.

Tertiary structure

________: 3D shape of a protein.

Amino acids

● ________ in a polypeptide have polar covalent bonds in their backbones; they fold in a way that allows for hydrogen bonds between carboxyl groups and ________.

O Dideoxyribonucleotides

________ have H instead of OH on the 3rd carbon, which prevents the binding of a phosphate group to it, hence stopping the DNA replication process.

Primary structure

________: ● Number and sequence of amino acids in a polypeptide is the ________.

Transcription

________ and translation: Occurs concurrently in prokaryotes due to absence of nuclear membranes.

ATP

O Once ________ and amino acid are attached, the amino acid is activated by the formation of a bond between the enzyme and AMP (adenosine monophosphate)

Energy

________ from ATP is needed to attach the amino acid onto the active site of the enzyme.

Acetylation

________ neutralises positive charges that stops binding of lysine (on DNA) to other negatively charged DNA therefore stopping tight packaging and allowing for higher transcription levels.

Bound ribosomes

________: Synthesise proteins primarily for secretion or use in lysosomes.

Telomeres

________: Occur at the ends of eukaryotic chromosomes.

● Adenine

________ has a surplus positive charge and Thymine has a surplus negative charge.

DNA profiling

________: Variable number tandem repeats (VNTR) distinguishes individuals based on the number of times this short sequence of DNA repeats.

● Prokaryotic cells

________: o Environmental factors influence regulation of gene expression.

Secondary structure

________: ● Secondary structure is the formation of alpha helices and beta- pleated sheets stabilised by hydrogen bonds.

Proteins

________ involved in replication: Proteins are involved as enzymes at each stage but also serve several other functions.

● Maternal lineage

________ can be deduced by analysing variations in mitochondrial DNA at specific hyper- variable region.

Chemical modification

________ increases the accessibility of genes to transcription factors.

Insulin

________ is made of two chains and haemoglobin of four.

tRNA

Activation of the ________ occurs when ________ activating enzyme adds an amino acid to the 3 terminal.

Bases

________ are upside down in relation to one another as strands are antiparallel.

Tropomyosin

________ is spliced differently in different tissues resulting in five forms of the protein.

Prokaryotic expression

________ occurs during transcription, not after.

O Promoter proximal elements

________: near to the promoter region.

Morphogens

________: impact gene expression in the embryo depending on where the embryo cells are placed (endo /meso /ectoderm)

The role of nucleosomes in DNA packing

● Nucleosomes help to supercoil DNA

The leading strand and the lagging strand

● Replication is continuous on the leading strand along the replication fork as it opens; and discontinuous on the lagging strand moving away from the replication fork

Proteins involved in replication

● Proteins are involved as enzymes at each stage but also serve several other functions

Direction of replication

● Replication begins at the origin of replication, where the RNA primer is placed by DNA primase

● Replication occurs in the 5 to 3 direction (nucleotides are added to the 3 end of the primer) ● Non-coding regions of DNA have important functions

● Non-coding DNA has some function

● Repetitive sequences

o 60% of human genome

● Telomeres

o Occur at the ends of eukaryotic chromosomes

DNA profiling

● Variable number tandem repeats (VNTR) distinguishes individuals based on the number of times this short sequence of DNA repeats

DNA sequencing

● Copies of DNA are placed into test tubes with deoxyribonucleotides and enzymes for replication

● Prokaryotic cells

o Environmental factors influence regulation of gene expression

● Eukaryotic gene expression is regulated in response to environmental conditions

o Regulation of gene expression is crucial during embryonic development and cellular differentiation

o Silencers

slow down transcription rates

o Promoter-proximal elements

near to the promoter region

The impact of the environment on gene expression

● Human behaviour or phenotype should be attributed to environment or to heredity

● Morphogens

impact gene expression in the embryo depending on where the embryo cells are placed (endo/meso/ectoderm)

Nucleosomes regulate transcription

● Tails of histones are chemically modified to impact transcription

● Epigenome

sum of all epigenetic tags

o 1% survives

this is called imprinting

The direction of transcription

● Transcription occurs in a 5 to 3 direction

Post-transcriptional modification

● Does not occur in prokaryotes

mRNA splicing

● Impacts number of proteins an organism can produce, ● Alternatively spliced mRNAs will differ in their AA sequence and biological functions because particular exons may not be included in the mature mRNA

● Three binding sites

o Aminoacyl

o Peptidyl o Exit ● tRNA

o loops of seven unpaired bases

tRNA-activating enzymes

● Activation of the tRNA occurs when tRNA activating enzyme adds an amino acid to the 3 terminal

Initiation of translation

● Initiation of translation involves assembly of the components that carry out the process

Elongation

● Synthesis of the polypeptide involves a repeated cycle of events o Ribosome translocates three bases along the mRNA

Termination

● Disassembly of the components follows termination of translation

Free ribosomes

● Proteins for use primarily within the cell

Bound ribosomes

● Synthesise proteins primarily for secretion or use in lysosomes

Transcription and translation

● Occurs concurrently in prokaryotes due to absence of nuclear membranes

Primary structure

● Number and sequence of amino acids in a polypeptide is the primary structure

Secondary structure

● Secondary structure is the formation of alpha helices and beta-pleated sheets stabilised by hydrogen bonds

Tertiary structure

● 3D shape of a protein

Quaternary structure

● Exists in proteins with more than one polypeptide chain