TEST 1: Genetics Flashcards
Components of DNA
Phosphate
Sugar (deoxyribose)
Base
Structure/function of
Phosphate in DNA
-ONE part of the backbone, alternates with deoxyribose
-links individual nucleotides together
-Connects 3’ carbon of one dexoyribose sugar to the 5’ carbon of the next dexoyribose sugar in the strand
-Phosphate group is negatively charged giving DNA an over all negative charge
Structure/function of Deoxyribose in DNA
-ONE part of the backbone, alternates with phosphate
-Pentose sugar
-Provides structure and attachment site for nitrogenous bases.
DNA Bases and which is their attachment counter part
Adenine A-T
Thymine
Cytosine C-G
Guanine
Structure of DNA vs RNA
DNA: double helix, deoxyribose sugar and phosphate backbone, A-T-C-G bases with hydrogen bonds.
RNA: Single stranded, ribose sugar and phosphate backbone, A-U-C-G bases
Function of DNA vs RNA
DNA: storage of genetic information and template for RNA.
RNA: transfers genetic information from DNA to ribosomes for protein synthesis (mRNA), carries amino acids during protein synthesis (tRNA), and catalyzes peptide bond formation (rRNA)
Stability of DNA vs RNA
DNA: Stable double helix
RNA: Prone to degradation as its single stranded. Presence of ribonucleases that can break down RNA.
Location of DNA vs RNA
DNA: Cell nucleus and mitochondria. Remain in nucleus
RNA: Nucleus, cytoplasm, and ribosomes.
Role in protein synthesis DNA vs RNA
DNA: template for RNA synthesis (transcription). NOT directly involved in protein synthesis.
RNA: crucial role in protein synthesis. Carries genetic info from DNA to ribosomes and coordinates the translation of genetic code into proteins.
Replication DNA vs RNA (Broad)
DNA: duplication of entire double stranded molecule wit high fidelity and accuracy resulting in two identical DNA molecules.
RNA: replication called transcription. Synthesizes a single stranded RNA molecule that is complementary to a specific DNA template, allowing for expression of genetic info and protein synthesis.
DNA Polymerase
Main enzyme responsible for catalyzing the addition of nucleotides to the growing DNA strand.
Helicase
Enzyme that unwinds and separates the DNA from the helix to expose the template strands for replication
Primase
Synthesizes RNA primers that serve as starting points for DNA synthesis.
Ligase
Seals the nicks in sugar/phosphate backbone to create a continuous DNA strand
What cellular phase is DNA replicated
S phase
What are the 5 steps in DNA replication
- Helicase unwinds the helix creating a replication fork
- Primase synthesizes RNA primers on the template strands
- DNA polymerase adds complimentary nucleotides to the exposed template strands in the 5’ to 3’ direction
- Leading and lagging strands are synthesized simultaneously, but discontinuous synthesis occurs on the lagging strand, forming Okazaki fragments
- DNA ligase joins the Okazaki fragments to create a continuous strand
Meaning of semi-conservative replication
where DNA replication where each daughter DNA molecule have both a parental strand and a newly synthesized strand.
RNA plymerase
Enzyme that Catalyzes synthesis of RNA using one strand of DNA as a template.
Promoter
DNA sequence where RNA polymerase bins to initiate transcription
Terminator
Sequence signaling the end of the gene and the completion of transcription.
What are the 4 steps of RNA replication
- transcription in the nucleus where RNA is synthesized from DNA template
- RNA polymerase binds to the promoter sequence on DNA template
- Initiates RNA synthesis via complementary base pairing in the 5’ to 3’ direction using (A-U-G-C)
- Transcription stops at the terminator sequence and newly synthesized RNA molecule is released.
3 Replication differences in DNA vs RNA
- RNA is a single strand to a single strand
- RNA polymerase does not require a primer to initiate synthesis (DNA polymerase does)
- RNA synthesis is less accurate as it is less controlled.
What is a codon
sequence of 3 nucleotides that encode a specific amino acid or signal the start or stop of protein synthesis
What is the role of the codon
to correspond to a specific amino acid allowing the mRNA to be read and translated into a protein
aka specificity, like bookmark
What is the start codon
AUG methionine serves as start for protein synthesis
What are the 3 stop codons
UAA
UAG
UGA
What is an anticodon
complementary three nucleotide sequence on tRNA that bind to the corresponding codons on mRNA during translation
What is the role of the anticodon
pair with codons on mRNA to facilitate accurate insertion of amino acids into a growing peptide chain. Fidelity.
What is wobble base pairing
due to degeneracy in the genetic code, some tRNAs can recognize multiple codons due to nonstandard base pairing at the third position of the codon, the wobble base pair.
3 phases of TRANSCRIPTION
- Initiation: RNA binds to promoter of DNA
- Elongation: RNA polymerase synthesizes complementary RNA from DNA template
- Termination: transcription ends when RNA polymerase reaches stop sequence and releases the mRNA strand.
What is an Exon
coding sequence on mRNA
What is an Intron
non coding sequence on mRNA
What 3 processes take place after
mRNA transcription to convert it from pre-mRNA to mRNA in preparation for translation
- 5’ capping- addition of 7-methylguanosine at 5’ end and
- 3’ polyphenylation - addition of poly A tail to 3’ end
- mRNA splicing- removal of introns and joining of exons
What is phase 1 of the 3 phases of TRANSLATION of RNA
Initiation:
-ribosomal subunit binds to mRNA at AUG (start)
- tRNA methionine (tRNAiMet) binds to AUG in p-site of ribosome
-large ribosomal subunit joins and ribosome is ready for translation
What is phase 2 of the 3 phases of TRANSLATION
Elongation:
-codon recognition: tRNA with anticodon binds to mRNA at A-site of ribosome
-peptide bond formation: amino acid carried by the tRNA, in the A-site forms a peptide bond with the growing polypeptide chain on the tRNA in the P-site
-Translocation: ribosome translocates along the mRNA moving tRNA and mRNA by one codon. empty tRNA exits ribosome and new tRNA enter the A-site
What is phase 3 of the 3 phases of TRANSLATION
Termination:
-release factors recognize stop codon and polypeptide chain detaches from the ribosome
-the ribosome disassembles releasing mRNA and the newly synthesized protein
What is a histone protein
structural protein that help package and condense DNA into compact structure within the chromosome
What is a non-histone protein
interact with DNA and histones to regulate gene expression, DNA replication, repair and chromosome organization
What is the centromere
central region of a chromosome where sister chromatids are joined and spindle fibers attach during cell division
What are telomeres
protective caps at the ends of chromosomes that help maintain chromosomal stability and prevent DNA degradation during replication
What are chromatids
Identical copies of chromosomes produced during DNA replication. They separate during cell division to ensure accurate distribution of genetic material
What is a genetic mutation
alterations in the DNA sequence that can lead to changes in gene function or the structure of gene products (proteins)
What is deletion
Loss of genetic material
Associated with cystic fibrosis
what is duplication
extra copies of genetic material
what is Insertion
addition of extra genetic material
what is substitutions
exchange of one nucleotide for another in DNA sequence
Ex: sickle cell disease due to a point mutation
Allele
variant form of a gene
-offspring inherit one allele from each parent
Heterozygous
passing two different alleles for a particular gene
Homozygous
having two identical alleles (from both parents) for a particular gene
Penetrance
the percentage of individuals carrying a specific genetic mutation who develop the associated phenotype
Phenotype
observable traits or characteristics by genotype
ex. down syndrom
Expressivity
the degree to which a genetic trait is expressed (varying degrees of phenotype manifestation)
risk of recurrence
probability that offspring will inherit a genetic disorder with each pregnancy and the same set of parents
Dominant inheritance
only one copy of the mutant allele is required for the trait to be expressed.
ex. polycystic kidney disease and HUNTINGTON’s disease
Recessive inheritance
both copies of the allele must be mutated for the trait to be expressed
ex. sickle cell anemia and cystic fibrosis
x-linked recessive inheritance
traits linked to x chromosome show a recessive pattern. the alleles in females may be carriers but clinically manifest in male offspring
ex: DUCHENE’S MUSCULAR DYSTROPHY, COLOR BLINDINESS, HEMOPHILIA A
Monohybrid cross
crossing two heterozygous parents for a single trait (Aa x Aa)
Dihybrid cross
crossing two parents heterozygous for two traits (AaBb x AaBb)
