Level 2 Bio: Gene Expression Flashcards
Anticodon
Three consecutive bases on the tRNA
Codon
Three consecutive bases on the mRNA
Deletion mutation
A mutation on the DNA where a base(s) is removed, resulting in a frame shift
DNA
Deoxyribose nucleic acid, A joins with T, C joins with G. Double stranded, helix shaped large molecule, a whole chromosome. Deoxyribose sugar
Enzyme
A folded protein which acts as a biological catalyst to speed up the rate of a chemical reaction in an organism
Frameshift
Change in bases that the ribosome reads
Gene
A piece of DNA which codes for the making of a protein/feature
Gene expression
The process where the instructions on our DNA are converted into a functional protein, includes transcription, translation and protein folding
Genotype
The genetic makeup of an organism for a feature
Insertion mutation
A mutation on the DNA where a base(s) is added resulting in a frame shift
Metabolic pathway
A series of enzyme controlled reactions, where the product of one reaction becomes the substrate of the next
Missense mutation
A change of the base on the DNA which codes for a different amino acid. This may or may not alter the shape of the protein and therefore its function.
mRNA
Messenger RNA. Made during transcription in the nucleus. Carries the instructions of the ribosome to make a polypeptide chain. Contains codons.
Mutagen
Environmental factor which causes the mutation e.g x-rays etc
Mutation
A sudden permanent change in the DNA base sequence
Non-sense mutation
A change of the base on the DNA which changes the instructions so a STOP codon occurs in the wrong place. Protein is greatly affected.
Peptide bond
Bond formed between 2 amino acids during translation
Phenotype
The physical appearance of a feature.
Point mutation
A change of only one or a few bases on the DNA
Protein
A substance made up of many amino acids joined together to form a polypeptide chain, which gets folded into a functional protein (enzymes area type of protein)
Redundancy
The fact that multiple codons code for the same amino acid, eg CCU, CCC, CCA and CCG all code for the amino acid Pro
Same-sense mutation
A change of the base on the DNA where the bases still code for the same amino acid. This is due to the redundancy of the genetic code.
Silent mutation
A mutation that is neither favourable nor harmful, that remains in a population.
Start codon
The start signals on the mRNA which initiates translation. Always AUG.
Stop codon
These 3 codons on the mRNA (UAA, UAG, UGA) do not code for an amino acid therefore telling the ribosome where to stop translation.
Substitution mutation
A mutation where the base(s) on the DNA are swapped
Transcription
The process by which DNA going to mRNA, occurs in the nucleus. Controlled by RNA polymerase
Translation
The process by which mRNA going to polypeptide chain, occurs in the cytoplasm on the ribosome
Triplet
Three consecutive bases on the DNA
tRNA
Transfer RNA. Carries an amino acid to the ribosome. 3 bases on the mRNA= an anticodon
What is gene expression
Gene expression is the process by which information from a gene is used to make a protein.
What does the base sequence of a DNA molecule code for
The base sequence of a DNA molecule codes for the amino acids that make up proteins.
What codes for 1 amino acid
A sequence of 3 bases in DNA (a triplet) codes for 1 amino acid
A sequence of many amino acids joined together with peptide bonds forms a __________
A sequence of many amino acids joined together with peptide bonds forms a POLYPEPTIDE.
One gene codes for one _________ (basic protein, most proteins made of many Polypeptides).
One gene codes for one POLYPEPTIDE (basic protein, most proteins made of many Polypeptide).
What is the primary structure
The primary structure is the simplest type of protein structure. It is the linear chain of amino acids that make up a protein.
The primary shape is bent or twisted into a helix or pleated sheet. The shape is held in place by _________ bonds. The secondary structure is the folded structures that forms within a polypeptide when atoms interact on the “backbone”.
The primary shape is bent or twisted into a helix or pleated sheet. The shape is held in place by HYDROGEN bonds. The secondary structure is the folded structures that forms within a polypeptide when atoms interact on the “backbone”.
In the alpha helix the carbonyl of one amino acid is hydrogen bonded to the amino H of an amino acid 4 down the chain. This bonding pattern pulls the polypeptide chain into a ________ structure resembling a curled ribbon.
In the alpha helix the carbonyl of one amino acid is hydrogen bonded to the amino H of an amino acid 4 down the chain. This bonding pattern pulls the polypeptide chain into a HELICAL structure resembling a curled ribbon.
The tertiary structure is the folding of what?
The tertiary structure is the folding of secondary structures bent into a globular shape & is the 3D structure of the protein.
Quaternary structures are made of 2 or more ____________ chains held loosely together.
Quaternary structures are made of 2 or more POLYPEPTIDE chains held loosely together.
Globular proteins have what kind of a function
Globular proteins have a chemical function
Fibrous protein molecules form long chains or fibres (they have primary, __________, tertiary and __________ structure). Their fibrous nature makes them __________ in water
Fibrous protein molecules form long chains or fibres (they have primary, SECONDARY, tertiary and QUATERNARY structure). Their fibrous nature makes them INSOLUBLE in water
mRNA=??
Messenger RNA
rRNA=??
Ribosomal RNA
tRNA=??
Transfer RNA
DNA codes for_________
Proteins
Where are proteins synthesised
In ribosomes
RNA stands for
Ribonucleic acid
DNA stands for
Deoxyribonucleic acid
Nucleic acids (make up DNA) are ________ composed of monomers (smaller units) called a ________
Nucleic acids (make up DNA) are POLYMERS composed of monomers (smaller units) called a NUCLEOTIDE
What is the monomer of DNA
Nucleotide: sugar, base & phosphate
The bases in DNA are=??
Cytosine with Guanine & Thymine with Adenine
The bases in RNA are=??
Cytosine with Guanine & Uracil with Adenine
The length of RNA is much _________ than DNA
The length of RNA is much SHORTER than DNA
What are the 3 different types of RNA
1) messenger RNA: mRNA
2) Transfer RNA: tRNA
3) Ribosomal RNA: rRNA
What does mRNA do
copies a gene on DNA & transfers this genetic information to a ribosome & acts as a template
What does tRNA do
picks up specific amino acids & takes them to the ribosome to assemble into proteins.
What does rRNA do
clicks the amino acids together into proteins & folds them into three dimensional shapes
What are the similarities between DNA & RNA
Both have nucleotides, Both found in all cells, They both have 4 bases
How is DNA different to RNA in terms of structure
It is double stranded & longer, more stable
How is RNA different to DNA in terms of structure
It is single stranded & shorter, less stable
How is DNA different to RNA in terms of location
Only in nucleus
How is RNA different to DNA in terms of location
In and out of nucleus
How is DNA different to RNA in terms of bases/base pairing
Has Adenine, Guanine, Cytosine & Thymine. A to T, C to G
How is RNA different to DNA in terms of bases/base pairing
Has Adenine, Guanine, Cytosine & Uracil. A to U, C to G
How is DNA different to RNA in terms of sugars
Deoxyribose sugar
How is RNA different to DNA in terms of sugars
Ribose sugar
What are the main reasons for the significant differences between DNA and RNA
DNA has to be really big because it contains all of the genetic material for the organism. It is a double helix to allow it to be more stable. Because it is such a big molecule it can’t leave the nucleus. RNA has to be small so that it can leave the nucleus.
Summary of what mRNA does
carries a copy of the gene
Summary of what rRNA does
forms the structure of a ribosome (the site where proteins are made)
Summary of what tRNA does
transfers amino acids to the ribosome.
Describe the role of mRNA
Copies the gene from the DNA, carries the copy out of the nucleus to the ribosome.
Describe the role of rRNA
forms the structure of the ribosome, enables amino acids to form peptide bonds, making a polypeptide chain.
Describe the role of tRNA
picks up a specific amino acid and TRANSFERS it to the ribosome.
What are the monomers of proteins
amino acids
What is a purine
A purine is a double ringed molecule
What is a pyrimidine
A single ringed molecule
Name the 2 functional groups found in all amino acids
1) Amino group
2) Carboxylic group
Primary structure
Peptide bonds link amino acid within proteins. The sequence of amino acids is known as the primary structure of a protein. The peptide bonds, along with the a-carbon atoms wo which r-groups are attached, form the protein backbone.
Secondary structure
Segments of polypeptides often fold locally into stable structures that include helices and sheets. In a helix (alpha helix), the polypeptide backbone follows a helical path. The helical shape is held in place by hydrogen bonds. In a sheet (beta sheets), strands of protein lie adjacent to one another and are held in place by hydrogen bonds between the peptide backbones.
Tertiary structure
Tertiary protein structure refers to the compete 3D folding of a protein and gives the protein a specific shape. It is held in place by salt ridges, hydrogen bonds and disulphide bonds.
Quaternary structure
Quaternary structures contain two or more tertiary units. For example, haemoglobin consists of two alpha chains and two beta chains. Collagen consists of three helices.
Name the type of bonding that occurs between amino acids within the primary structure of proteins
peptide bonds
name the type of bonding that maintains the secondary structure of proteins
Hydrogen bonds
Name the 2 types of secondary protein structure
alpha helix and beta sheets
Describe the main differences between the Primary and secondary structure of proteins
the primary structures is the sequence of amino acids within the protein. Secondary structure is how the protein folds with the hydrogen bonds found between peptide backbones.
Describe the main differences between the tertiary and quaternary structure of proteins
tertiary structure is the 3D folding of a protein and gives it a specific shape. Quaternary structure is 2 or more tertiary units.
What is a fibrous protein
Fibrous proteins form long protein filaments, that are shaped like rods. They are usually inert, insoluble in water and very tough. Fibrous proteins are typically used for structural support and movement (e.g skin, collagen)
What is a globular protein
Globular proteins are polypeptide chains folded into large, round molecules. They are soluble in water and therefore easily transported through the body. However, they are relatively unstable and susceptible to slight changes in temperature and pH . These globular proteins typically have a chemical function such catalysing reactions, transporting chemicals, regulation and protection
What are the 2 key things to do with reading protein synthesis
“read up” 3’ to 5’
“Write down” 5’ to 3’
What does RNA polymerase form
RNA polymerase forms mRNA, RNA nucleotides COMPLEMENTARY base pair with the template strand of DNA.
What are the 2 parts of protein synthesis
1) Transcription
2) Translation
What happens in transcription
First a copy of a gene on the template strand of the DNA is made by mRNA. This moves out from the nucleus through the nuclear pore into the cytoplasm to a ribosome.
The ribosome then connects the large and small sub unit around the mRNA.
The copy of each triplet in the DNA which is on the mRNA is now called a codon.
What happens in translation
The ribosome moves along the MRNA reading the series of codons (3 bases on the mRNA). Each of these codons code for a specific amino acid.
What is a summary of protein synthesis in 8 steps
1) DNA unwinds
2) RNA polymerase brings nucleotides to complementary base pair
3) DNA coils up again using base pairing rules
4) The copied mRNA leaves the nucleus through the nuclear pores.
5) tRNA with the anticodon comes in to bind to the codon on the mRNA.
6) Anticodon binds to the triplet making part of a polypeptide chain.
7) The tRNA leaves to make space for the next one
8) Amino acid bonds to tRNA with the correct anticodon
What are the 10 structures involved in protein synthesis
1) DNA
2) Nucleotides
3) Enzyme Polymerase
4) DNA template strand
5) Nuclear membrane
6) Nuclear pore
7) tRNA molecule
8) Amino acids
9) Ribosome
10) Polypeptide chain
How many different amino acids & nucleotides are there
There are 20 different amino acids and only 4 different nucleotides
With 20 different amino acids and 4 different nucleotides how many possible combinations are there
64
What are some amino acids coded for by…..
Some amino acids are coded for by more than one codon e.g Serine is made form one of six codons. This is called REDUNDANCY. This is a back up in case a mutation occurs.
Why are the first 2 bases critical
The first 2 bases are critical in determining which amino acid is coded for. The third base can be anything. This is called DEGENERACY. If a mutation happens to affect the 3rd base, the correct amino acid will still be made and used.
What is the purpose of Transcription
This is when the code (for making a specific protein) on DNA is written across “transcribed” onto the mRNA molecule so that the “code” to build the protein can get to the ribosome.
What is the purpose of Translation
This is when the copied (transcribed) code sequence carried on the mRNA out to the ribosome is ‘translated’ and used to create a polypeptide chain and functional protein.
What is the 1st step of Transcription
RNA Polymerase unwinds/separates the DNA double helix - along the GENE TO BE COPIED, forming a ‘transcription bubble” - the nucleotide bases get exposed
What is the 2nd step of Transcription
One strand of the DNA is used as a TEMPLATE strand (pattern) to make mRNA by using the complimentary base pair sequence A-U and G-C. The other strand remains as the PARENT/CODING/sense strand.
What is the 3rd step of Transcription
RNA Polymerase binds to the DNA Template strand at (a special sequence of nucleotides) called the PROMOTER (this also identifies the Template Strand)
What is the 4th step of Transcription
RNA Polymerase builds the mRNA - attaches free nucleotide bases complimentary (to the template strand) A-U and G-C . (so that the mRNA molecule is complimentary to the DNA template)
What is the 5th step of Transcription
The enzyme RNA Polymerase is the enzyme that copies the “specific code” for each specific protein onto newly built mRNA
What is the 6th step of Transcription
Once RNA Polymerase reads the TERMINATOR CODON - Transcription is complete for that specific protein code - the mRNA detaches - non coding regions of DNA called introns are removed to create a “mature” RNA molecule ready to leave the nucleus (via the nuclear pores) to go to the Ribosome
What is the 7th step of Transcription
After completion of the mature RNA the two DNA strands rejoin (anneal) by reformation of the H bonds. Ready for the next protein to be made and for the process to repeat.
What is the 1st step of Translation
A start codon initiates the start of translation - this is always codes for the amino acid Methionine and is AUG
What is the 2nd step of Translation
mRNA arrives at the ribosome and forms a ‘complex” with it - by binding to it. (ribosomes are usually close to the nucleus)
What is the 3rd step of Translation
The ribosome is an organelle which “reads” mRNA bases in a code of 3 bases at at time. (normally several ribosomes move along the mRNA at any one time ensuring rapid synthesis of the needed protein)
What is the 4th step of Translation
Peptide bonds form between each amino acid on the polypeptide chain. As each new amino acid arrives the ribosome moves along the mRNA along 3 bases and the next tRNA arrives with it complementary anticodon and aa and so on
What is the 5th step of Translation
The tRNA with its complementary anticodon collects the appropriate amino acid when the anticodon on the rRNA “matches” up codon on mRNA it clicks in the correct amino acid to the next part of the sequence on the growing polypeptide chain. Codon-anticodon match=correct Amino acid delivered
What is the 16th step of Translation
The polypeptide chain is released from the ribosome and “folds” into a 3D structure becoming a functional protein
What is the 7th step of Translation
A STOP codon ends translation. (there are 3 stop codons)
What are the 2 types of mutations
1) Chromosome mutations
2) Gene or point mutations
What is a chromosome mutation
whole genes or complete chromosome changes
What is a gene or point mutation
a change in the DNA base sequence
What are the 2 main types of Gene/Point mutations
1) Base substitution
2) Base insertion or deletion
What are the 3 types of base substitution
1) Silent/same sense
2) nonsense
3) missense
What is a silent/same sense mutation
different base but no change in the amino acid because of code redundancy eg ATA and ATG both code for try (tyrosine)
What is a nonsense mutation
the substitute base results in a stop codon which results in an early termination of a protein, major consequences
What is a missense mutation
when a base is substituted that does affect the amino acid. It alters the protein shape. This means the protein cant function properly and it can disrupt metabolic pathways
What is a base insertion or deletion mutation
This causes a frameshift i.e it alters all the codons that follow the insertion or deletion of a base. (MISSENSE MUTATION)
Describe the difference between a ‘somatic mutation’ and a ‘gametic mutaiton’
A somatic mutation is an alteration of the DNA sequence and does not get passed down to offspring as it occurs in somatic (body) cells. Whereas a gametic mutations occur in the germ-line cell/egg & sperm producing cells.
List 3 examples of mutagens
1) X-rays
2) UV radiation
3) Peroxides
Distinguish between a mutagen and carcinogen
A mutagen is an environmental factor that changes the genetic material and increases the likelihood of a mutation. Whereas a carcinogen is a type of mutagen that causes cancer.
Distinguish between haploid and diploid
Haploid means half only 1 set of chromosomes (n) whereas diploid means full, contains 2 sets of chromosomes (2n)
Explain the term ‘autosomal recessive condition’
Autosomal recessive condition means the mutation has occurred in the gene on an autosome and not on a sec chromosome’s and it is recessive as the alleles are recessive.
What is a frameshift
a change in bases that the ribosome reads
