Genetics Flashcards
Nucleotides consist of three things
Nitrogenous Base, Sugar, Phosphate
Bases of DNA
Adenine, Thymine, Cytosine, Guanine
Bases of RNA
Adenine, Uracil, Cytosine, Guanine
Function of DNA
Contains genes
How is DNA different from RNA?
DNA is double stranded with deoxyribose sugar and the base Thymine instead of Uracil
Function of mRNA
Encode amino acid sequence
Start and Stop Codons
AUG (Methionine)
UAA, UGA, UAG
Function of tRNA
Delivers amino acids to ribosome. Contains anticodon
Sites of the ribosome
E P and A sites, in that order from left to right
Function of Helicase
Unwinds DNA double helix
Function of Single-Stranded Binding Proteins
Keep DNA Helix separated during replication
Function of topoisomerases
Prevent knots from forming due to DNA unwinding by breaking and rejoining the double helix
Function of DNA Polymerase
Synthesize new dna in 5 to 3 direction. Needs a primer. Exhibits proofreading ability
Function of primase
Creates RNA primers
Function of ligase
Joins okazaki fragments
Function of telomerase
Attaches to end of template strand and adds DNA nucleotides so telomeres do not shorten
Differences between eukaryotic and bacterial chromosomes
Eukaryotic chromosomes are linear. Some DNA is lost from the ends during replication
Transcription is performed by what enzymes?
RNA polymerases
Transcription: Initiation
TATA box of DNA is promoter. RNA polymerase binds to DNA helix and unwinds it
Transcription: Elongation
RNA polymerase assembles RNA nucleotides in 5 to 3 direction.
Transcription: Termination
RNA poly comes to terminating sequence (AAAAAA tail)
The template strand of DNA has the _____ sequence of bases as the mRNA
Opposite
Does RNA polymerase need a primer?
No. DNA polymerase does however
mRNA processing
5’ methylated guanine cap, Poly-A tail, splicing (introns are excised and exons are joined together)
Translation: Initiation
Ribosome attaches to mRNA. tRNA brings methionine
Translation: Elongation
tRNA’s bring more amino acids. Amino Acids enter at A site, then go through P site and exit at E site
Translocation
Movement of amino acid from A to P site
Translation: Termination
Stop codon reached. Ribosome lets mRNA go.
What are point mutations?
Single nucleotide errors
Types of point mutations
Insertions, Deletions, Substitution
What is a frameshift
When a point mutation changes the reading frame of the DNA
Nonsense mutation
Premature STOP codon
Silent Mutation
Base is changed, but same amino acid is still encoded
Missense mutation
Single nucleotide change that results in a changed amino acid
What is binary fission?
Asexual reproduction used by bacteria. No genetic variation.
What is a plasmid?
Circular piece of DNA
What are episomes?
Plasmids that can be found in bacterial chromosomes
What is conjugation
Transfer of bacterial DNA through sex pillus
What is transduction?
Transfer of bacterial DNA through viruses
What is transformation?
DNA from surroundings is integrated by bacteria
What kind of operon is the Lac Operon?
Negative Inducible
What happens when lactose is ingested?
Lactose becomes allolactose and separates the repressor from the operator, allowing for translation
What happens when there are high levels of glucose in the Lac Operon?
No cAMP is made and no transcription takes place
What happens when there are high levels of trp?
Tryptophan binds to repressor, allowing it to bind to operator and stop transcription.
What happens when there are low levels of tryptophan?
Repressor can’t bind to operator, and trp operon makes more tryptophan
How does methylation affect transcription?
Decreases it
How does acetylation affect transcription?
Increases it
Histones
Proteins that DNA coils around
Nucleosome
DNA-histone complex
Chromatin
DNA mixed with proteins
Euchromatin
Loosely packed chromatin
Heterochromatin
Tightly packed chromatin
What is a testcross?
Test individual with homozygous recessive individual to determine genotype
Law of Segregation
Alleles separate during gamete formation
Law of Independent Assortment
The inheritance of one set of alleles does not affect the inheritance of another set
What is complete dominance?
One phenotype is completely dominant over another
What is codominance?
Both phenotypes are equally expressed (roan cow)
What is incomplete dominance?
Phenotype is a blend of both genotypes
What is pleiotropy?
When one gene has multiple phenotypes
What is epistasis?
When one gene masks the effect of another
Polygenic inheritance
When multiple genes contribute to a single phenotype
Nondisjunction
Chromosomes fail to separate during meiosis or mitosis
Linked genes
Genes on the same chromosome
Sex-linked inheritance
Genes located on the X chromosome. (Can be Y chromosomes as well)
X-inactivation
X chromosomes inactivated by Barr bodies to regulate protein production
What is aneuploidy?
Altered number of chromosomes due to nondisjunction
What is down’s syndrome?
Three chromosome 21’s
What is turner’s syndrome?
Single X
Chromosomal mutations
Duplications, Inversions, Translocations (segment of chromosome moves to another chromosome)
Telomere Replication
Telomerase ensures that telomeres do not shorten during consecutive replication events
Euchromatin
Chromatin that is loosely coiled and easily accessed by transcriptional factors
Heterochromatin
Chromatin that is tightly coiled and not able to be accessed by transcriptional factors
Transposons
Sequences of DNA that can be moved along the double helix
Acetylation
Loosening of DNA wrapping around histones. Leads to increased transcription
Methylation
Tightening of DNA wrapping around histones. Leads to decreased transcription
Northern Blot
Used to detect specific RNA sequences in an RNA mixture
