DNA Flashcards
What is a monomer of DNA called?
A nucleotide
What is DNA made up of?
- deoxyribose sugar
- nitrogenous base
- phosphate group
How do dinucleotides and polynucleotides of DNA form?
- condensation reaction
- between hydroxyl group of deoxyribose and hydroxyl group of phosphate group
- forms phoshophideser bonds
Describe the structure of DNA
- deoxyribose sugar
- double helix (bigger, long)
- unable to leave the nucleus
- contains thymine
Describe the DNA double helix
- strands are antiparallel
- hydrogen bonds between bases
- sugar-phosphate backbone between bases (makes mutations relatively uncommon)
What is the benefit of the sugar-phosphate backbone?
makes mutations relatively uncommon
What is 5’?
The carbon 5 of the deoxyribose is closest to the end
What is 3’?
The carbon 3 of the deoxyribose is closest to the end
Describe the hydrogen bonding between base pairs
- C-G = 3 bonds
- A-T = 2 bonds
Hence, if there are more C-G base pairs, the molecule of DNA is more stable
Describe the structure of DNA in relation to its function
- very stable -> passes from generation to generation without changing
- two strands -> weak hydrogen bonds allow the strand to be separated so the core can be read and copied for DNA replication and protein synthesis. Complementary base pairing ensures accuracy
- large -> carries a lot of information
- sugar-phosphate backbone -> code (more chemically reactive nitrogenous base pairs) protected from chemical and physical dangers and damage
- sequence of base pairs -> contain genetic info to code for proteins, achieved through infinite variability of polynucleotide chains
- forms genetic code -> base sequence along polynucleotide chains determines the characteristics of an organism that are inherited from its parents
- strong -> many hydrogen bonds
- double-helix -> compact
- two complementary strands -> two copies of information, useful for repair, copying and error checking
How many possible codons are there?
64
Describe the severity of different types of mutation
- substitution -> can have no effect
- insertion -> can have no effect/a big effect
- délétion -> has a big effect
What is a purine?
- a heterocyclic aromatic organic compound
- consists of a pyrimidine ring fused to an imidazole ring (double it ring structure)
- guanine and adenine
What is a pyrimidine?
- a heterocyclic aromatic organic compound
- contains 2 nitrogen atoms at positions 1 and 3 of a six member ring (single ring structure)
- cytosine and thymine
- similar time benzène and pyridine
What is a gene
A short section of DNA that codes for a polypeptide chain
What is a cistron?
A posh, scientific word for gene! It
What is a locus?
The location of a gene in the DNA strand
What relevance does DNA have to proteins?
- the sequences of DNA causes the sequence of amino acids
- if there is a mutation, the shape of the protein changes because the bonds form in different places, causing it to hold differently, so the protein may not be able to complete its function
What are introns?
Non-coding DNA
What are exons?
Coding DNA
What is degenerate code? Hence, how is DNA a degenerate code?
- more than one DNA triplet codes for the same amino acid
- some amino acids are only coded for by a single DNA triplet
- some amino acids can be coded for by up to 6 DNA triplets
What is the start DNA triplet?
The triplet which codes for MET (an amino acid)
How many stop triplets are there?
3
What are chromosomes?
- only visible when a cell is dividing
- how we can tell if a cell is undergoing mitosis and calculate mitotic index
- appear as two chromatids attaches at the centromere (when DNA replication has occurred)
Describe the centromere
- non-coding DNA
* contains kinetochore
What are histones?
Proteins that are associated with DNA strands that make us have chromosomes
What is chromatin?
DNA associated with histones
How is DNA wound?
Around histones, coiled and looped
What are homologous chromosomes?
A cell with a full set of chromosomes, 23 maternal and 23 parental, whic carry the same genes
What are alleles?
Alternative versions of a gene
How do alleles differ from one another?
Different base sequence and therefore….:
• différent primary structure
• différent tertiary structure
Define universal
Triplets code for the same amino acid across all organisms
Define non-overlapping
DNA triplets are only read once
Which level of protein structure is encoded in DNA?
Primary
What is DNA?
Deoxyribonucleic acid (CHONP)
What is a nucleotide?
- nitrogen-containing organic substances which play a vital role in every aspect of an organism’s life
- can occur singly (mononucleotide) or combined (polynucleotide)
- composed of 1 nitrogen-containing organic base, à pentose sugar and 1 or more phosphate group
What is a nucleic acid?
- chain of nucleotides formed by condensation reactions
- joined by phosphodiester bonds between the hydroxyl groups of the phosphate group and the pentose sugar
- AKA: polynucleotides
Describe the shape of DNA
- two helical polynucleotide chains forming a double helix
- sugar-phosphate backbone protects the pairs of bases which hold the polynucleotide chains together through complementary base pairing
Describe nitrogenous bases
- held together by complementary base pairing: hydrogen bonds between the hydrogen atom of a base in one chain and the oxygen and nitrogen atoms of the complementary base in the other chain
- bases can only form in their pairs because of their sizes and shapes; they are specific
- guanine and adenine are both purines
- cytosine and thymine are both pyrimidines
