DNA and gene expression Flashcards
What does DNA stand for?
deoxyribonucleic acid
How is a sugar phosphate backbone formed?
Nucleotides from chemical bonds between deoxyribose sugar and phosphate group
What are the four organic bases and what pairs with what?
- Adenine (A)
- Thymine (T)
- Cytosine (C)
- Guanine (G)
A-T C-G
What shape is DNA?
DNA takes the shape of a double helix
How many strands is in DNA?
DNA is a double stranded molecule
How is the double helix formed?
H bonds form between the bases
Where is the 3’ strand?
Always end on deoxyribose sugar
Where is the 5’ strand?
Always ends on phosphate group
What does DNA polymerase do and what’s this called?
it can only add nucleotides in one direction (results in one strand being replicated) (leading)
Whats meant by lagging?
the other strand to leading is replicated in fragments which are joined together by another enzyme (ligase)
What are the 5 requirements for DNA replication?
- Parental DNA
- Enzymes (Ligase + polymerase)
- free DNA nucleotides
- ATP
- Primers
What does PCR mean and what does it do?
PCR- Polymerase Chain Reaction
A technique used to amplify DNA using complementary primers (can make millions to billions of DNA copies)
What does amplification mean?
To make many copies
Whats a primer?
Small sections of nucleotides at two ends of region to be amplified
what is DNA polymerase (Taq)?
Heat tolerant enzyme used to replicate DNA at high temperature
Who might use PCR for a practical application?
Forensic and medical
What are the three types of RNA?
mRNA
tRNA
rRNA
What is each RNA nucleotide made up of?
Phosphate group
Organic base
Ribose sugar
What are the 4 RNA bases?
Adenine
Guanine
Cytosine
Uracil (replaces thymine)
What will gene expression involve?
transcription and translation of DNA sequences
Think about RNA structure diagram
You better have thought about that one
What are 2 ways molecule structure of mRNA differs from DNA?
- DNA has 2 strands, RNA has 1
2. DNA base pair for adenine is thymine but RNA base pair is Uracil
What is the sugar present in DNA then RNA?
DNA is deoxyribose sugar
RNA is ribose sugar
What are the requirements for translation?
- mRNA
- Ribosome (rRNA and protein)
- tRNA
- Amino acid
What is a ribosome made of?
rRNA and protein
What is the name of mRNA and its function?
Name- Messanger
Function- Carries copy of DNA code from nucleus to ribosome
Whats the repeating unit which makes up a molecule of DNA?
Nucleotides
What are the 4 steps of transcription?
(probably don’t need to know
Step one:
RNA polymerase unwinds DNA double helix. Moves along DNA strand causing it to unwind/ unzip by breaking H-bonds between bases
Step two:
RNA polymerase synthesises primary transcript of mRNA from free RNA nucleotides by completing base pairing with DNA
Step three:
RNA polymerase forms strong bonds between sugars and phosphates of RNA nucleotides, forming a sugar (Phosphate backbone, making chain/ strand of RNA)
Step four:
Primary transcript: RNA molecule separates from DNA strand (breaks H-bonds). contains introns and Exons. Once splicing has taken place, mature transcript exits nucleus via pore and heads to ribosome. DNA strand then reforms (ATP is also essential for process
What do stop codons release?
Polypeptide from ribosome
What is the result of alternative splicing?
Different proteins can be expressed from one gene
What are proteins? (list 3)
- Organic molecules
- chemical elements
- Amino acids joined by peptide bonds
What is primary structure?
Order of amino acids in the chain
What is secondary structure?
Interaction between polypeptide chains
How do you form polypeptides?
Amino acids are held together by chain peptide bonds
What is phenotype?
Proteins produced as result fo gene expression
Where does polymerase add nucleotides to deoxyribose sugar?
DNA polymerase adds nucleotides to the deoxyribose (3’)
What is the name of tRNA and what’s its function?
Name- Transfer
Function- Each tRNA molecule carries a specific amino acid
What’s the difference between introns and exons?
Introns are non-coding sections of DNA. Exons are coding sections of DNA
What’s the enzyme responsible for the primary transcript?
RNA polymerase
Name the process that involves the modification of the primary transcript to form the functional mRNA?
RNA splicing
does mRNA have an anti codon?
is has a codon
does tRNA have an anti codon or codon?
it has an anticodon
Whats rRNA name and its function?
Name- Ribosomal
Function- rRNA and proteins form a ribosome
Whats the difference between introns and exons?
Introns- Non coding sections of DNA
Exons- Coding sections of DNA
Whats the enzyme responsible for primary transcript?
RNA polymerase
What is DNA replicated by?
DNA polymerase
Why must DNA replicate before a cell divides?
Because it needs primers
Each type of human cell has a different structure and function because?
Each cell type expresses a different set of genes
A mature mRNA transcript is produced from a primary mRNA transcript by?
Removing an intron as exons may be retained
Name two parts of the cell where mRNA is found?
Nucleus and cytoplasm
What’s the four steps to PCR?
Heat up, Separation of DNA, Add primer then replicate
What’s difference between genotype and phenotype?
Genotype is determined by sequence of bases in genes and phenotype is determined by protein when genes are expressed
