Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
108 Cards in this Set
- Front
- Back
|
What is the structure of DNA? |
Double helix |
|
|
What is a gene? |
Small section of DNA that codes for a particular combination of amino acids which make a specific protein |
|
|
What is an allele? |
Alternate forms of a gene |
|
|
What types of cells do eukaryotic cells include? |
Animal, Plant & Fungal cells |
|
|
Where is DNA found? |
Within a distinct nucleus, surrounded by the nuclear envelope |
|
|
How is a nucleosome formed? |
DNA double helix wrapped around histone proteins |
|
|
What happens to nucleosomes once formed? |
Coiled up to form chromatin which is organised into chromosomes |
|
|
What is the benefit of DNA being compact? |
Large amounts can be stored in a small space and organised |
|
|
What is an intron? |
Non-coding base sequences - repeated and found in DNA |
|
|
What determines the function/characteristics of a cell? |
Sequence of bases in DNA determines sequence of amino acids in a polypeptide chain which determines shape and function of a protein |
|
|
How are chromosomes in eukaryotic cells found? |
In homologous pairs |
|
|
What is a locus? |
A fixed position/location of the genes on the chromosomes |
|
|
What do genes code for? |
Amino acid sequence of a polypeptide or functional RNA - tRNA or rRNA |
|
|
How many base pairs in a kilobase pair? |
1000 |
|
|
What do prokaryotic cells include? |
Bacteria and archaea |
|
|
What are the features of prokaryotic DNA? |
No true nucleus Shorter Circular Not wrapped around histone proteins 1 chromosome |
|
|
How is prokaryotic DNA condensed to fit in the cell? |
Supercoiling |
|
|
Where is prokaryotic DNA found? |
In a main chromosome and several smaller plasmids |
|
|
Where are mitochondria and chloroplasts found? |
In eukaryotic cells |
|
|
What is the role of chloroplasts? |
Site of photosynthesis |
|
|
What is the role of mitochondria? |
Where aerobic respiration takes place |
|
|
What would the DNA in each organelle code for? |
Enzymes that catalyse reactions of photosynthesis + aerobic respiration Membrane proteins transport substance in/out organelles Functional RNA |
|
|
What are the features of eukaryotic DNA? |
Longer Linear 46 molecules |
|
|
What are the arguments for the treatment of mitochondrial disease? |
Saves money on treatment Reduces suffering Allows parents to have kids Highly regulated |
|
|
What are the arguments against the treatment of mitochondrial disease? |
Permanent Long term effects unknown Designer babies Expensive Unethical Destruction of embryos Uncertainty and stress |
|
|
How is genetic information stored as? |
A sequence of the 4 organic bases in DNA |
|
|
What is a gene? |
A base sequence that codes for a single polypeptide |
|
|
How many bases code for a single amino acid? |
3 |
|
|
What name is given to the number and order of amino acids in a polypeptide chain? |
Primary sequence |
|
|
How many different types of amino acids are used to build polypeptides? |
20 |
|
|
What does it mean for the genetic code to be degenerate? |
Some amino acids are coded for by more than 1 triplet code |
|
|
How are the triplets read? |
Once in sequence |
|
|
What does it mean for the genetic code to be non-overlapping? |
Base triplets don't share bases |
|
|
What does it mean for the genetic code to be universal? |
The same specific base triplet codes for the same amino acid in all living organisms |
|
|
What do some regulatory DNA triplets code for? |
The start and the end of a gene |
|
|
What is non-coding DNA? |
Intron - doesn't code for polypeptides |
|
|
What is coding DNA? |
Exon |
|
|
What are multiple base repeats? |
Non-coding DNA repeated many times between genes in eukaryotic DNA |
|
|
What is messenger RNA? |
A single, short helical polynucleotide strand |
|
|
Where is mRNA made? |
In the nucleus during transcription |
|
|
What does mRNA do? |
Carries genetic code into cytoplasm to make protein in translation as can pass through nuclear pores |
|
|
What is a codon? |
Three adjacent bases in mRNA (also called a triplet) |
|
|
How are messenger RNA chemically unstable? |
Broken down within days |
|
|
What is transfer RNA? |
Smallest single polynucleotide strand |
|
|
What is the shape of transfer RNA? |
Clover shape held by hydrogen bonds |
|
|
Where is tRNA made? |
In the nucleus, found throughout the cell |
|
|
How many bases in tRNA? |
Anti-codon of 3 bases |
|
|
What does tRNA contain? |
Amino acid binding site - binds specific amino acid and carries to a ribosome |
|
|
What can anti-codon bases form? |
Complimentary base pairs with specific mRNA codons so lining up the amino acid it carries |
|
|
How stable is tRNA? |
More stable than mRNA and less stable than DNA |
|
|
What is transcription? |
Producing mRNA copy of gene from DNA which takes place in nucleus in eukaryotic cells but in cytoplasm of prokaryotic cells |
|
|
What is the first stage of transcription? |
RNA polymerase attaches to DNA double helix at beginning of gene and hydrogen bonds between 2 DNA strands in gene break, separating the strands. |
|
|
What is the second stage of transcription? |
DNA molecule uncoils, exposing bases. 1 strand used as a template to make an mRNA copy |
|
|
What is the third stage of transcription? |
RNA polymerase lines up free RNA nucleotides along exposed bases on template strand. Free bases attracted to exposed bases + base pairing means mRNA strand is complementary copy of DNA template strand. |
|
|
What is the fourth stage of transcription? |
Once RNA nucleotides have paired up with their specific bases on the DNA strand, they're joined together by RNA polymerase forming an mRNA strand |
|
|
What is the fifth stage of transcription? |
RNA polymerase moves along DNA assembling mRNA strand. Hydrogen bonds between coiled strands of DNA reform once RNA polymerase has passed + strands coil back into double helix |
|
|
What is the sixth stage of transcription? |
When RNA polymerase reaches a particular sequence of DNA called a stop signal, it stops making mRNA and detaches from the DNA |
|
|
What is the seventh stage of transcription? |
In eukaryotes, mRNA moves out of nucleus through nuclear pore + attaches to ribosome in cytoplasm, where next stage of protein synthesis takes place |
|
|
How are transcribed introns removed? |
From RNA by splicing |
|
|
What is substitution? |
A base is substituted into the DNA code |
|
|
Why do some amino acids have more than one DNA triplet coding for them? |
Genetic code has a degenerate nature so not all substitutions result in a change in the primary structure of a polypeptide chain |
|
|
What is deletion? |
A base is removed from the DNA code |
|
|
When do mutations occur? |
Spontaneously |
|
|
What increases the rate of mutations? |
Certain mutagenic agents such as UV, ionising radiation or viruses e.g. HPV |
|
|
What increases probability of a mutation occuring? |
Age Job |
|
|
What is mitosis? |
Cell division that produces 2 genetically identical clones from 1 parent cell for growth and repair of tissues |
|
|
What is meiosis? |
Division producing 4 gametes from 1 parent cell that occurs in ovaries and testes |
|
|
What is the diploid number of chromosomes? |
Normal body cells - 2n - each cell contains 2 copies of each chromosome - 1 maternal and 1 paternal |
|
|
What is the haploid number of chromosomes? |
Gametes produced in meiosis - n - only 1 copy of each chromosome aka a half set |
|
|
What occurs in fertilisation? |
Diploid number of chromosomes is restored in zygote which divides by mitosis |
|
|
What are homologous chromosomes? |
Same size and genes are in the same position on the chromosomes |
|
|
What are chromatids? |
DNA unravels and replicates so that each chromosome consists of 2 copies of DNA in interphase |
|
|
What forms the primary structure of a protein? |
The sequence of amino acids in a polypeptide |
|
|
What determines the order of amino acids in a particular polypeptide? |
The order of bases in a gene - 3 genes make a triplet/codon |
|
|
What is the first stage of protein synthesis? |
DNA is copied into messenger RNA (mRNA) |
|
|
What do genes that don't code for a polypeptide code for? |
Functional RNA |
|
|
What is functional RNA? |
RNA molecules other than mRNA which perform special tasks during protein synthesis |
|
|
What is a genome? |
The complete set of genes in a cell |
|
|
What is a proteome? |
The full range of proteins that the cell is able to produce |
|
|
When are introns in eukaryotes removed? |
During protein synthesis (so they don't affect the amino acid) |
|
|
Do prokaryotic DNA have introns? |
No |
|
|
What is a non-coding multiple repeats? |
Regions of multiple repeats outside of genes in eukaryotic DNA that repeat over and over |
|
|
What is non-coding DNA? |
nuclear DNA that doesn't code for polypeptides |
|
|
Why do alleles code for different versions of the same polypeptide? |
The order of bases in each allele is slightly different |
|
|
How many chromosomes do humans have? |
23 pairs, 46 in total |
|
|
What is the purpose of tRNA? |
Carries amino acids used to make proteins to ribosomes |
|
|
What is tRNA? |
Single polynucleotide strand folded into clover shape held by hydrogen bonds between specific base pairs |
|
|
What is an anti-codon? |
Specific sequence of 3 bases at one end of tRNA molecule |
|
|
What does tRNA contain? |
Anti-codon at one end and amino acid binding site at other end |
|
|
What does transcription produce? |
Different products in eukaryotes and prokaryotes |
|
|
What is copied in eukaryotes into mRNA during transcription? |
Introns and exons |
|
|
What is pre-mRNA? |
mRNA strands containing introns and exons |
|
|
What is splicing? |
Introns are removed and exons joined together in pre-mRNA forming mRNA strands in the nucleus |
|
|
What occurs after splicing? |
mRNA leaves the nucleus for the next stage of protein synthesis |
|
|
How is mRNA produced in prokaryotes? |
Directly from DNA without splicing as there are no introns in prokaryotic DNA |
|
|
What is translation? |
2nd stage of protein synthesis at ribosomes in cytoplasm in eukaryotes and prokaryotes |
|
|
What occurs during translation? |
Amino acids joined together to make polypeptide chain (protein), following sequence of codons carried by mRNA |
|
|
What is the first stage of translation? |
mRNA attaches to ribosomes + tRNA molecules carry amino acids to it. ATP provides energy for bond between amino acid and tRNA molecule to form |
|
|
What is the second stage of translation? |
tRNA molecule w/ anti-codon complementary to 1st codon on mRNA, attaches to mRNA by complementary base pairing. 2nd tRNA molecule attached to next codon on mRNA same way. |
|
|
What is the third stage of translation? |
2 amino acids attached to tRNA molecules joined by peptide bond and 1st tRNA molecule moves away, leaving amino acid behind |
|
|
What is the fourth stage of translation? |
3rd tRNA molecule binds to next codon on mRNA + it's amino acid binds to first 2 + 2nd tRNA molecule moves away. Continues to produce linked amino acid chain till stop signal on mRNA molecule |
|
|
What is the final stage of translation? |
Polypeptide chain (protein) then moves away from the ribosomes and translation is complete |
|
|
What is the genetic code? |
Sequence of base triplets (codons) in mRNA which code for specific amino acids which are read in sequence, separate from triplet before and after |
|
|
What is a stop signal? |
Base triplets that tell the cell when to stop production of a protein, found at the end of the mRNA. |
|
|
How does a change in a sequence of DNA bases result in a non-functional enzyme? |
Changes how bases are read by changing primary sequence so change in hydrogen/Ionic/disulphide bonds so change in tertiary structure so active site changes shape so not complementary to substrate |
|
|
What organelle is involved in translation? |
Ribosome |
|
|
What is the role of RNA polymerase in transcription? |
Join/attach nucleotides to form a strand along phosphate backbone / phosphodiester bonds |
|
|
How does substitution affect the polypeptide for which this section of DNA is part of the code? |
No change to sequence of amino acids, same amino acids coded for Change in sequence, bonds position may change |
