Key Area 3 Flashcards
What are genes made of?
DNA
Where are genes found?
On chromosomes inside the nucleus
What does a gene carry the code for?
A protein
What happens if a gene is expressed?
The protein that is coded for by that gene will be produced by the cell at a ribosome
What 2 processes are involved in gene expression?
Transcription and Translation
What 3 types of RNA are involved in transcription and translation?
mRNA (messenger)
rRNA (ribosomal)
tRNA (transfer)
What does RNA stand for?
Ribonucleic Acid
What is RNA?
A single stranded molecule composed of nucleotides
What is an RNA nucleotide composed of?
Ribose Sugar
Phosphate
Base
What are the 4 possible bases in RNA?
Adenine
Guanine
Cytosine
Uracil
How are RNA nucleotides joined?
In the same way as DNA nucleotides - sugar phosphate backbone etc.
What does mRNA do?
Carries a copy of the DNA code from the nucleus to the ribosome
How does mRNA carry the code from the nucleus to ribosome?
It is transcribed from DNA in the nucleus and translated into proteins by ribosomes in the cytoplasm
What is a codon?
A triplet of bases
What does each codon do?
Codes for a specific amino acid
What does rRNA do?
Forms the ribosome along with proteins
What is tRNA involved in?
The translation of mRNA into a polypeptide at a ribosome
What do tRNA molecules do?
Carry specific amino acids to the ribosome where they are joined together to produce a polypeptide
What is different about tRNA structurally?
It folds due to complementary base pairing
What is an anti codon?
An exposed triplet of bases
Describe the structure of tRNA
4 bits that stick out - amino attachment site at one end and anti codon at the other
Describe Transcription
RNA polymerase moves to the area of the chromosome that contains the gene which is to be expressed
RNA polymerase unwinds the double helix and breaks hydrogen bonds between bases
RNA polymerase synthesizes a primary transcript of mRNA nucleotides by complementary base pairs
The process continues along the gene and the nucleotides are joined together
The mRNA primary transcript detaches from the DNA and is ready to undergo splicing
What 2 regions do genes contain?
Coding and non coding
What are coding regions called?
Exons
What are non coding regions called?
Introns
What process do exons and introns undergo to give the primary transcript?
Transcription
What happens to introns during transcription?
They are removed
What happens to exons during transcription?
They remain and will be expressed
How are exons joined together?
Splicing
What happens to the order of the exons during splicing?
It remains unchanged
What happens to the mature transcript?
It leaves the nucleus and moves towards a ribosome for the process of translation
What will be at the beginning of the mature transcript?
A specific sequence known as the start codon
What will be at the end of the mature transcript?
A stop codon
Where does translation begin?
The start codon
Where does translation end?
The stop codon
How is the genetic code translated into a sequence of amino acids?
Anti codons bond to codons by complementary base pairing
How are amino acids joined together?
peptide bonds forming a polypeptide
What happens to tRNA as the polypeptide is formed?
It leaves the ribosome
What happens structurally to the polypeptide?
It will fold to create the 3D shape of a protein
How is the polypeptide structure maintained?
Hydrogen bonding and other interactions between individual amino acids
What does a protein’s shape determine?
It’s function
What do proteins produced by a cell as a result of gene expression determine?
Our phenotype
What is a phenotype?
Physical characteristics
What other factors can influence phenotype?
Environmental factors such as diet, chemicals, and radiation
How many genes are in the human genome?
25000
how many types of protein can a human cell produce?
Over 1 million
How is it possible for 1 gene to produce more than 1 protein?
Alternative Splicing
What happens in Alternative splicing?
different combinations of exons can be included in the mature transcript, meaning different proteins are produced after translation
