Genetic Material Flashcards
Relationship b/w DNA, genes, chromosomes
genes –> DNA –> chromosomes
- chromosomes contain multiple genes, and so are able to code for multiple proteins; and since each chromosome is made of a single DNA strand then the same is said for DNA
each gene is made of a DNA sequence
What are chromosomes (include stuff about condensation)?
- threadlike single DNA strand/mlc wraps around histones to form nucleosomes that condense into chromatin
- chromatin is normally decondesned (so no visible chromosomes) when the cells is NOT undergoing division
- chromatin is going to tightly condense into distinct chromosomes to prep for cell division, so that chromosomes are equally split b/w the nuclei.
- a SINGLE DNA mlc.
What are genes?
- each gene contains a DNA sequence
- the mlcr unit of heredity (passed on from parent to offspring)
gene variant = alleles
What do genes code for?
proteins
genetic code is PERMANENTLY STORED in DNA
What is the diploid and haploid status of human cells
- diploid (2n) = 46 chromosomes - 1 copy from mom and 1 copy from dad of the 23 unique chromosomes
- haploid (1n) = 23 chromosomes - 23 homologous pairs/ 23 unique chromosomes
DNA
* what is the monomer
* what are 2 other major characteristics of DNA?
- monomer: nucleotides [ phosphate + pentose sugar + nitrogenous base]
- double helix + anti-parallel
DNA vs RNA (what are the 3 key differences?)
- pentose sugar in nucleotide (deoxyribose in DNA and ribose in RNA)
- nitrogenous base in nucleotide (Thymine in DNA and Uracil in RNA but still pairs with adenine)
- helix status (double in DNA and single in RNA)- but RNA is rarely found in single strand form bc complementary parts within the single strand fold back on itself
What is the base pairing rules? How many bonds (and what type of bonds) are b/w the base pairs?
- A pairs with T (apples on trees) (T is U in RNA) - 2 H bonds
- C pairs with G (cars need gas) - 3 H bonds
What are the purines? What are the pyrimidines? How many rings for each group?
- purines (2 rings)- AGgies (adenine and guanine) are PURe
- pyrimidine (1 ring) - C and T
What is the backbone of DNA? What bonds the backbone together?
- phosphate group + pentose sugar
- phosphodiester bond, which is covalent
Describe the sense strand
- aka coding strand
- runs from 5’ to 3’ direction
- strand used in translation and the result of/ exact sequence after DNA replication and transcription
Describe the anti-sense strand
- aka TEMPLATE strand, complementary strand
- runs in 3’ to 5’ direction
- used as template strand for DNA replication and DNA transcription so able to add on nucleotides in the 5’ to 3’ direction
In what direction are nucleotides ALWAYS being added?
5’ to 3’ direction
Explain DNA replication
- DNA helicase unzip and unwind the 2 DNA strands at the origin of replication (breaking the H- bonds) in both directions [ topoisomerase is preventing the supercoiling upstream of helicases]
- RNA polymerase (aka DNA primase) adds on RNA primer in 5’ to 3’ direction on both DNA strands
- DNA polymerase adding DNA nucleotides in 5’ to 3’ direction after the RNA primer (continuously for the leading strand)
- lagging strand: multiple RNA polymerases and DNA polymerases adding nucleotides in 5’ to 3’ direction but whole strand moving in the opposite direction (3’ to 5’)
- DNA polymerase changes the RNA primer into DNA nucleotides
- DNA ligase seals the fragments (of okazaki fragments and leading and lagging strands)
Explain transcription
DNA –> RNA (mRNA, tRNA, rRNA)
- RNA polymerase attaches to the template DNA strand {3’ to 5’ strand} promoter region to unzip DNA
- RNA polymerase adds RNA nucleotides (T sub for U) in the 5’ to 3’ direction to make PRE-MRNA
- pre-mRNA undergoes splicing of interfering introns and splice together exons as well as alternative splicing
- final mRNA exits through the nuclear pores of nuclear envelope to be translated in cytoplasm
Explain translation
mRNA –> protein
- ribosome scans 5’ to 3’ mRNA transcript for the start codon, AUG, and then brings in tRNA with correct anticodon and AA of methionine to start translation
- reads the next codon to bring in AA into the ‘A’ of ribosome
- peptide bond forms b/w P and A spot AA
- empty tRNA goes to E spot and growing peptide chain goes to P spot and ready to accept another tRNA with the right anticodon and AA
- continues until hit a stop codon on mRNA [UAA, UGA, UAG]
- ribosome releases tRNA, mRNA, and protein
When and Where does DNA replication occur? What is the result?
- when: interphase (S phase)
- where: nucleus of the cell
- result: 2 identical DNA strands (2 chromosomes) attached at centromere as 2 sister chromatids
Why is the lagging strand lagging (2 reasons)?
- direction of adding of nucleotides (5’ to 3’ direction) vs. direction whole strand is actually headed (3’ to 5’ direction)
- multiple RNA poly’s and DNA poly’s being used
What is the lagging strand made of?
okazaki fragments
What does the DNA ligase do (including what type of bonds to seal)?
seal all the fragments (okazaki fragments and leading and lagging strands) using phosphodiester bonds, which are covalent b/w the phosphate group and pentose sugar
DNA helicase breaks up what bonds?
H- bonds b/w nitrogenous bases
Where is transcription vs. translation happening inside a cell?
- transcription: inside of the nucleus
- translation: outside of the nucleus in the cytoplasm
Where is rRNA made?
made inside the nucleolus of the nucleus, along with the ribosomes
What is a codon
a sequence of 3 nucleotide sequence on mRNA that is used in translation to code for AA
Where is the codon found? Where is the anticodon found?
- codon is found on mRNA [5’ to 3’]
- anticodon is found on tRNA [3’ to 5’]
What happens to the mRNA before it goes to the cytoplasm for _____
- translation
- mRNA is processed through splicing (splice out introns) and alternative splicing
When does translation stop?
when ribosome hits a stop codon on mRNA
UAA, UGA, UAG
What are the stop codons?
UAA, UGA, UAG
the trna that matches with the mRNA codon has to have ideally matching what 2 things?
- complementary anticodon that is carrying the right amino acid
What type of bonds are found b/w AA’s? (specific and general)
- peptide; covalent
What does the amino acid sequence of protein determine?
- protein structure AND so protein function
What type of bond bonds the 2 strands of DNA together? Describe them (2).
H- bonds (b/w purine and pyrmidines), which are NON-covalent and weak (compared to ionic and covalent bonds)
What permanently stores the coded instructions that are required for the body to produce proteins?
DNA
mRNA is TEMPORARY!!!!
What are sister chromatids
the duplicated chromosome (2 identical DNA strands) that are attached at the centromere
eukaryotes vs prokaryotes number’s of chromosomes and shape of chromosomes
- eukaryotes: multiple linear chromosomes
- prokaryotes: 1 circular chromosome
What is the start codon?
AUG- codes for methionine
Why is RNA almost never found in single strand form even though it is a “single helix”?
the parts of RNA within the single strand that are complementary will pair up and fold back on itself
DNA or DNA is stable under alkaline conditions?
DNA
