Week 1 Flashcards
What are changes in DNA sequences linked to?
Phenotypic variation
DNA Strands orientation
Phosphodiester bonds link the 5’ phosphate group of one nucleotide to the 3’ hydroxyl group of another nucleotide
- Strands have polarity
- Run antiparallel
- Have complementary base pairs
Def: Covalent Bond
Type of chemical bond where two atoms are connected to each other by the sharing of two or more electrons
Nucleotides
DEOXYRIBOSE SUGAR
- 5 carbon sugar
NITROGENOUS BASE ( A,C,T,G)
- attached to deoxyribose sugar at 1’ carbon by covalent bond
PHOSPHODIESTER BOND
- 5’ carbon with phosphate group and the 3’ carbon of the next nucleotide
Types of nitrogenous bases
PYRIMIDINES
- Cytosine and Thymidine
- One ring
PURINES
- Adenosine and Guanine
- 2 ring structure, larger
Form hydrogen bonds with different DNA strands
Def: Hydrogen bonds
Noncovalent bonds that form between partial charges that are associated with hydrogen, oxygen and nitrogen atoms of nucleotide bases
Why are DNA stands antiparallel?
5’ to 3’ polarity of the phosphodiester bonds is in the opposite orientation
Chargaff’s Rule
Percentages of adenine and thymine are approximately equal and the same for cytosine and guanine
- Bond with each other
How is DNA semiconservative?
Two complementary strands separate and each acts as a template for the synthesis of a new complementary strand
- Daughter cell contains one new and 1 original strand
Central Dogma of Molecular Biology
INFORMATION FLOW IN BIOLOGICAL SYSTEMS
DNA to RNA: RNA transcription
RNA to DNA: Reverse transcription
DNA to DNA: DNA replication
RNA to RNA: RNA replication (viruses)
RNA to Protein: Protein translation
Pro to Pro: Prions, inteins, and posttranslational modification
Protein to DNA: DNA methylation
Transcription
- The use of one strand of DNA to direct synthesis of a single-stranded RNA
Fate of transcribed RNA
- Some translated into protien
- Other is not translated and has enzymatic or regulatory function as RNA - without encoding protein
Regulation of transcription
PROMOTOR REGION
- Promoters do not get transcribed
- Control the transcription of downstream regions
- In bacteria and archaea, one promotor can regulate transcription of multiple genes - typically not the case in eukaryotes, with some exceptions (ribosomal RNA)
EXONS AND INTRONS
- In eukaryotes, genes may have exons and introns
- Introns are removed before translation (splicing)
- In bacteria and archaea, there is only one exon (no splicing)
- Some exons contain UTRs (untranslated regions) - upstream and downstream buffer regions
- Exons may be completely or partially translated
Translation
- mRNA to Polypeptide
- Nucleotides have a non-overlapping, triplet codon that encodes the sequence of amino acids to proteins
Def: Monohybrid Cross
A cross between two individuals that are heterozygous at a gene that controls a phenotype of interest
Def: Test Cross
When an individual with a dominant phenotype is crossed with a homozygous recessive individual in order to determine whether the dominant phenotype is due to a homozygous or heterozygous genotype
- If the dominant phenotype is due to a heterozygous genotype, the phenotypic ratio of the test cross is 1:1
Mendel’s Law of Segregation
The alleles of an individual separate during the formation of gametes
- Diploid individuals have two versions of each gene (Alleles) and each gamete contains only one of these alleles
Def: Dihybrid Cross
A cross between parents that are heterozygous at two different genes that control two different phenotypes
Def: Double Heterozygous
Generated by crossing two lines that are pure breeding for two traits
Mendel’s Law of independent Assortment
The alleles of two (or more) different genes get sorted into gametes independently of one another
What are the three major types of information carrying biopolymers
DNA, RNA, Protein
What are the three major types of information exchange between information carrying biopolymers?
Replication - DNA to DNA
Transcription - DNA to RNA
Translation - RNA to protein
Do all exons of protein coding genes encode protein?
No, some exons are entirely 5’ UTRs or 3’UTRs
Are all enzymes made up of amino acids
No, there are also RNA enzymes
Are promotors transcribed or translated?
Neither
Are Exons Transcribed or translated?
Transcribed and sometimes translated
Are Intros transcribed or translated?
Transcribed but not translated
Are Poly-A transcribed or translated?
Neither
Are UTRs transcribed or translated?
Transcribed but not translated
What is meant by DNA being polar
DNA polarity refers to the way the ribose sugars within each strand of DNA are linked together from the 5’ C to the 3’ C
What is meant by DNA being anti-parallel?
DNA being antiparallel refers to double stranded DNA having the polarity of one strand oriented in the opposite direction from the other strand
What DNA component determines polarity
Deoxyribose sugar
Which amino acid does the start codon encode?
Methionine
Which amino acid does the stop codon encode?
None
What is a phosphodiester bond?
A type of covalent bond that links 5’ phosphate group of one nucleotide to the 3’ hydroxyl group of another nucleotide
Are Watson-Crick base pairs between two purines or two pyrimidines or between purine and pyrimidine
Between Purine and Pyrimidine
- C (a pyrimidine) pairs with G (a purine)
- T (pyrimidine) pairs with A (purine)
What type of chemical bond is involved with base-pairs between different strands of DNA?
Hydrogen bonds - non covalent
What is Chargaff’s Rule and what is the biological basis for this rule?
The percentage of A and T are about the same and the percentage of G and C are about the same because they are Watson-Crick base pairs in DNA
