L8 Nucleic acids

elements in nucleic acids

C,H,O,N,P

2 functions of nucleic acid

information storage information transfer

nucleotide polymer

▪ Polymers of nucleic acids are chains of nucleotides joined by condensation reactions ▪Each nucleotide is bonded to the next one in a strand by a bond between the sugar group on one nucleotide and the phosphate group of the next one. This is referred to as the sugar-phosphate backbone. ▪Bonds between nucleotides are strong covalent bonds and are called phosphodiester bonds.

what are the two types of nucleic acids in living things

Deoxyribonucleic acid (DNA) -2 chains of nucleotides held together by H bonds Ribonucleic acid (RNA)- single chain

how many strands is DNA made up of

Made of two strands of nucleotides forms a double helix

what does DNA store?

it stores hereditary information -recipes for the proteins

where is DNA found in the cell

nucleus

what are the 4 bases of DNA

adenine thymine guanine cytosine

what does each nucleotide consist of

a five carbon sugar (deoxyribose) a phosphate group a base

what groups are the bases divided into?

purines-2 rings of carbon and nitrogen atoms pyrimidines-single ring of carbon and nitrogen atoms

what group are adenine and guanine

purines

what group are thymine and cytosine

pyrimidines

what does a DNA molecules consists of

two polynucleotide strands wound around each other

what does adenine bond with

thymine

what does cytosine bond with?

guanine

what is a double helical structure held together by

▪The 2 strands intertwine in a double helical (spiral) structure which is held together by hydrogen bonds between the bases on one strand and the bases on the other strand.

RNA

RiboNucleic Acid

describe RNA

Single strand of nucleotides Can form a single helix Transfers information from the DNA to the ribosomes - carries a protein recipe to the ribosome - ribosomes are structures in a cell that make protein

RNA structure

▪The sugar group is a ribose instead of deoxyribose ▪The four bases are Adenine, Guanine, Cytosine and Uracil, ( so A bonds with U, G still bonds with C ) ▪Most cellular RNA molecules are single stranded. ▪E.g. messenger RNA(mRNA) always single stranded ▪But another type of RNA called transfer RNA(tRNA) is partially double stranded

Packing of genetic material with the eukaryotic cell

DNA packing is the process of tightly packing DNA molecule to fit into the nucleus of the cell. And is very important as DNA is the blue print for the cell and requires all instructions required to function.

chromosomes

distinct structures composed of DNA and proteins, only visible in the nucleus during cell division Chromatin condenses into chromosomes

centromere

the part of a chromosome at which the two sister chromatids are joined

histone proteins

roteins found in nucleus which help condense DNA and form the DNA molecule.

DNA replication overview

• Replication begins at a particular point on the chromosome called the origin of replication • The DNA double helix unwinds, breaking the hydrogen bonds that join the base pairs, and forming two separate strands. • New strands of DNA are built using the old strands as templates. With the four different nucleotides attach themselves to the bases on the old strands by complementary base pairing. • This synthesis of a new strand is done by an enzyme called DNA polymerase • You now have 2 double stranded molecules identical to the old molecule.

what is DNA replication referred to as?

semi conservative

why is DNA replicaton referred to as semi conservative

This is because when the double helix replicates, each of the two daughter molecules will have one old strand, derived from the parent molecule and one newly made strand.

why is cell division required for DNA replication

DNA replication is required for cell division as it allows for a 'copy' of the genome to be made and for two daughter cells to be made.

name a similar process to DNA replication

transcription

what is transcription

Transcription is the process of synthesizing RNA from a DNA Template.

what does transcription require

the enzyme RNA polymerase

what process are single stranded RNA used in?

Single stranded RNA can the be used in a process called Translation to produce polypeptide chains which can be modified to form proteins.

where does translation occur

ribosomes

what happens in translation

In this process the specific mRNA sequence will bind to amino acids bound to tRNA which have a particular codon sequence.

Importance of DNA & appropriate gene expression and protein synthesis.

• DNA stores all the information required for the cell/organism to continue to grow and survive • Appropriate gene expression and protein synthesis allows cells to react to environmental stimuli and helps keep the system "healthly". • Examples where DNA/gene expression deviates from the norm. • Down syndrome (trisomy 21) occurs when individuals are born will an entire extra copy of chromosome 21 or part of an extra chromosome. • Cystic Fibrosis. Inherited disorder where individuals are born with a mutation in the alleles of the gene for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. This mutation leads to abnormal secretion e.g. in the lungs.