nucleic acids

two types of nucleic acids found in living systems

DNA (deoxyribonucleic acid) and RNA (ribonucleic acid)

what is the main function of DNA

store genetic information and act as a template to reproduce itself and direct protein synthesis

what is the main function of RNA

produced as a complementary copy from DNA and helps in protein synthesis

three main forms of RNA

messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA)

what are the components of a nucleotide

a sugar, phosphate group, and nitrogenous base

what is the difference between a nucleoside and a nucleotide

a nucleoside contains a sugar and base only, a nucleotide is a nucleoside with one or more phosphate groups attached

what sugar is found in DNA

a deoxyribose sugar

what sugar is found in RNA

ribose sugar

what are the four nitrogenous bases in DNA

adenine (A), thymine (T), cytosine (C), guanine (G)

which base is found in DNA but not RNA

thymine (T)

which base is found in RNA instead of thymine

uracil (U)

which bases are purines

adenine and guanine

which bases are pyrimidines

cytosine and thymine

what type of bond joins nucleotides together in DNA

phosphodiester bonds

what is the backbone of DNA made of

alternating sugar and phosphate groups

what does it mean that DNA strands are antiparallel

the two strands run in opposite directions (5’ > 3’ and 3’ > 5’)

what does the 5’ end of a DNA strand end in

phosphate group

what does the 3’ end of a DNA strand end in

deoxyribose sugar

base pairing rule

A-T, C-G

how many hydrogen bonds are between A and T

two hydrogen bonds

how many hydrogen bonds are between C and G

three hydrogen bonds

how is DNA stabilised

hydrogen bonding between bases and van der waals interactions along the helix

why is DNA being double stranded important for function

it protects genetic information and allows accurate replication

why is RNA being single-stranded important for function

allows it to move easily and participate in protein synthesis

what is DNA replication

process by which DNA makes an exact copy of itself

why is DNA replication essential

ensures genetic information is passed to daughter cells during division

DNA helicase

unwinds the double-stranded helix and breaks the hydrogen bonds between the bases, separating the strands

leading strand

DNA polymerase adds nucleotides in a 5’ to 3’ direction continuosly

lagging strand

synthesised in fragments by DNA polymerase in a 5’ to 3’ direction, fragments are then sealed together by ligase

what is the outcome of DNA replication

two identical DNA molecules

what is semi-conservative replication

each new DNA molecule contains one original strand and one newly made strand

what is transcription

the synthesis of RNA from a DNA template

where does transcription occur

in the nucleus

what type of RNA carries genetic information from DNA to ribosomes

mRNA

what is produced during transcription

a complementary RNA molecule

what is a promoter

a region at the start of the gene where RNA polymerase binds to begin transcription, acts as a ‘start here’ signal for RNA polymerase

role of RNA polymerase

separates the DNA strand so the template strand can be read, adds complementary RNA bases in a 5’ to 3’ directions, DNA strands re-zip together behind

why is only a small section of DNA opened at a time during transcription

to protect and maintain stability

what are the two additional RNA types

small nuclear RNA (snRNA) and micro RNA (miRNA)

what is the role of snRNA and miRNA

they are involved in mRNA splicing and regulation of gene expression

what is translation

the synthesis of a protein using information carried by mRNA

where does translation occur

in the ribosomes

what is a codon

a sequence of three bases on mRNA that codes for one amino acid

what is the role of tRNA in translation

it carries amino acids to the ribosome and matches anticodons to mRNA codons

what is an anticodon

a sequence on tRNA complementary to an mRNA codon

what is the role of rRNA

forms part of the ribosome structure and helps protein synthesis

what is PCR used for

to amplify specific DNA sequences and produce millions of copies

why is PCR important in molecular biology

it is fast, reliable, inexpensive, and highly sensitive

name three applications of PCR

biomedical research, criminal forensics, and molecular archeology

what are Short Tandem Repeats (STRs)

short DNA sequences (2-4 base pairs) repeated multiple times

why are STRs useful in DNA profiling

their patterns vary greatly between individuals

how are STRs analysed in DNA profiling

PCR amplifies the STR regions, then electrophoresis separates fragments by size

what is electrophoresis

a technique that separates DNA molecules according to size

how are STR markers inherited

one allele is inherited from each parent

name two uses of STR DNA profiling

criminal investigations and paternity testing

why is PCR important in STR profiling

it amplifies STR regions so they can be detected and analysed