Molecula 1, Structure of DNA Flashcards
What polymer makes up DNA?
Nucleotide
What are the three molecules that DNA?
- 2 deoxyribose sugar
- Base A?T?C?G
- Phosphate group
How many individual phosphates does a nucleotide have? Can you name them using alpha beta and gamma
3
The closest to sugar alpha and furthest gamma
Which bases are Pyrimidines?
Cytosine and Thymine
Which bases are purines?
Adenine and guanine
How many bonds does AT and CG have each?
- AT = 2 hydrogen bonds
- CG = 3 hydrogen bonds
Which carbon numbers make the bonds in-between DNA nucleotides?
Carbon 3 of first nucleotide
Carbon 5 of Second nucleotide
What is the advantage of hydrogen bonds within DNA?
· Complementary bases (A/G and C/T) held together by weak hydrogen bonds which is useful as it allows DNA strands to easily separate and join (DNA helicase and DNA polymerase)
What does Chargaff’s rule state?
Chargaff’s rule states that the total number of purines and pyrimidines will be equal.
What are the 3 types of DNA helix forms?
A-DNA
B-DNA
Z-DNA
How does each form of DNA differ from each other? Also include when each is formed?
— A-DNA = (nw) narrow major groove, wide minor groove
Function= rare only forms when there is not enough water around- dehydrating conditions
— B-DNA = (wn) wide major groove narrow minor groove.
Most common type of DNA
— Z-DNA = (fn) Flat major groove, narrow minor groove
What is INTERGENIC DNA?
DNA regions within coding GENES
How is DNA lenght measured?
Measure in BASE PAIRS
Two different gene, Gene A and Gene B are 10000 and 100 bp long, does this indicate that gene A has 100 times more genetic material than gene B? No, why not? Yes, why yes?
No because genes are discontinuous: containing EXONS and INTRONS
· Exons – contain the information required to make a protein
· Introns – information that is not needed to make protein
What is the average length of an exons?
145 bp
What is the average length of an intron?
Average mean length of an intron (useless) is 3365 bp
Of the total RNA produced in the nucleus what percentage is coding? What is the rest of the RNA for?
Of the total RNA made in the nucleus 4% is coding-RNA, the rest 96% is non-coding RNA which is used in many other functions for example tRNA. Non-coding doesn’t indicate that is useless.
What type of gene families are there within the DNA?
- Simple- gene families = these are genes that are identical within the DNA
- Complex gene families=
Genes are not the same, but they have a similar DNA sequence
code for similar protein
Provides proteins with slightly different function which allows organismal complexity
How do genes in multigene families arise?
Genes in a multigene family arise by gene duplication
Onw gene duplicates, which eventually leads to gene families
How are complex genes families formed?
The duplicated genes start gradually changing by mutations; therefore, the members of the gene family have slightly different sequences.
Why and HOW does time affect genes families?
· The greater the time has passed since duplication, the greater the differences in code between the pair of genes.
How can you tell a recent duplication from an ANCIENT duplication?
Difference in DNA base sequence can be used to estimate how recently the duplication has occurred.
Recent duplication (slight difference) whereas Ancient duplication (significant difference)
Define molecular clock
The molecular clock is a measure of the rate at which the sequence of a gene changes
What can be molecular clock used for?
· We can use the molecular clock to work out an estimate of when a pair of genes were formed by duplication.
Remember the more recent the duplication the more similar the gene as mutation changes the sequences of duplicates over time.
What are PSEUDOGENES?
Pseudogenes are genes that have mutated in such a way that they no longer make sense, so they do not code for protein anymore
