Exam 3 Flashcards
3 categories of chromosome mutations
- chromosome rearrangements
- aneuploidy
- polyploidy
aneuploidy
- number if chromosomes is altered such that one or more are added or deleted
- changes number of INDIVIDUAL chromosomes in a set
- ex. 2n+1, 2n-1, 2n+2, 2n-2
polyploidy
- one or more complete sets of chromosomes are added
- 2n+n=3n, 3n, 4n
chromosome rearrangements
-structure of chromosome is altered in some way
-4 basic types:
~deletions
~duplications
~inversions
~translocations
deletions
- worst chromosome rearrangement, usually fatal (genetic material is lost)
- ABCDEF (deletion) ACDEF
duplications
- get extra copy of gene
- bad bc increase gene dosage + fusion genes
- tandem: ABCDEF (duplication) ABC(BC)DEF
- reversed: ABCDEF (duplication) ABC(CB)DEF
- displaced: ABCDEF (duplication) ABCD(BC)EF
inversions
-chrom is rearranged from end to end
-bad bc fusion genes
-paracentric: centromere not involved
ABC•DEFG (inversion) ABC•(GFED)
-pericentric inversion: around centromere
ABC•DEFG (inversion) AB(F•EDC)G
translocations
- part of chrom breaks and attaches to different chrom
- bad bc gene dosage + fusion genes
- simple: lil piece of 3 end up on chrom 8
- reciprocal: piece of 3 ends up on 8, piece of 8 ends up on chrom 3
euploidy
- normal number of chromosomes in somatic and gamete cells
- 23 homologous chromosome pairs
- 46 chromosomes
nullisomy
- loss of homologous pair of chrom
- 2n-2
monosomy
- loss of a single chromosome
- 2n-1
- lethal
trisomy
- addition of one chrom to diploid set
- 2n+1
- autosomal trisomy is common (down syndrome)
tetrasomy
- gain an additional homologous pair
- 2n+2
nondisjunction
- failure of chromosomes to separate at anaphase
- most common cause of aneuploidy
polyploidy
- increased number of chromosome sets
- ex. 2n + n becomes 3n (triploidy) or 4n (tetraploidy)
auto-polyploidy
- all chromosome sets are from a single species
- results from errors in meiosis in gamete formation, fertilization, or mitosis after fert
allo-polyploidy
- chromosome sets are from two or more species/ hybridization of 2 species
- common in plants
most common cause of spontaneous abortion is _________
- triploidy (2n+n)
- 15-18% of all abortions
good genetic material must…
- contain complex info in a stable fashion
- replicate faithfully and w/high fidelity
- must encode the phenotype
genes are made up of ______
nucleic acids (people debated this vs. proteins bc they are more complex)
Johanne Friedrich Miescher
- isolated nuclein from nuclei of white blood cells (with pus)
- nuclein contained C, H, O and N, P (later found in DNA)
Walter Flemming
-identifies “threadlike bodies” (chromosomes) during cell division
Walter Sutton
-linked chromosomes as carriers of Mendel’s units of heredity (genes)
Fred Griffith
- elegant experiment increased our knowledge of chemical nature of genes
- mice injected with live R cells (harmless) and heat-killed S cells: mice die, live S cells in blood
- hypothesized “transforming principle” (DNA) from S was responsible for conversion of R to S strain
- 1st clue to unit of heredity
Avery, MacLeod, McCarty
- extended Griffiths’s experiment (mice)
- mixed R strain with DNA from S
- proteases did not prevent transformation
- DNase abolished transformation of R to S colonies
Alfred Hershey and Martha Chase [first experiment]
- experimented with T2 bacteriophage (only contain DNA and protein)
- P^32 labeled DNA
- S^35 labeled protein
- P^32 DNA traveled into e.coli cell and made new virus babies, where S^35 protein stayed inside phage
Alfred Hershey and Martha Chase [second experiment]
- blended S^35 protein and P^32 separatly
- centrifuged
- S^35 dyed material (protein) rose to top of beaker
- P^32 dyed material (DNA) sunk to bottom bc more dense and heavier
- concludes DNA is genetic material in bacteriophages
- proved nucleic acid is genetic material and chemical component of heredity
Rosalind Franklin and Maurice Wilkins
- xray crystallography and diffraction data
- didn’t get credit for basically discovering the structure of DNA
Erwin Chargaff
- discovered the predetermined base pair ratio
- A-T, C-G
Watson and Crick
- used info discovered by Franklin and Chargaff to claim:
- DNA is made up of 2 anti-parallel polynucleotide chains coiled to form a double helix
covalent bond
- chemical bond involving sharing of electron pairs btwn atoms
- bond btwn 5’ phosphate group and 3’ OH group of another nucleotide
hydrogen bond
- force of attraction btwn hydrogen atom and more electronegative atom
- bonds connect A to T and C to G
biological organisms contain 2 types of _______ (DNA and RNA), which are made up of ________.
- 2 types of nucleic acids
- made up of nucleotides
components of a nucleotide (adenine/A , guanine/G, thymine/T, cytosine/C)
- phosphate group (backbone)
- sugar (deoxyribose)
- nitrogen-containing base
- 5’
- 3’ hydoxyl
DNA is a “directional molecule”
- has 2 ends that are not identical
- base pairing makes two strands complimentary in base composition/ antiparallel
how DNA is compacted so many times into chromosomes
- DNA is supercoiled in the nucleus using topoisomerase enzymes
- DNA wound around positively charged histone proteins to form chromatin
- chromatin compacts into nucleosomes (then supercoiled)
DNA polymerase
- enzymes that synthesize DNA
- have smooth track (mutation free DNA) to go fast and accurately
- translesion polymerases used if obstruction/ mutation
lower case greek letters vs. roman numerals
- greek: (eukaryotic) used to describe DNA polymerase in eukaryotic cells
- roman: (prokaryotic) DNA polymerase in E.coli
semiconservative replication
- each daughter strand is composed on one new strand and one old strand
- each site on double helix acts as a template for complementary base-pairing
Meselson and Stahl
- proved replication is semiconservative (not conservative or dispersive)
- semiconservative: spun then two regular N15 tubes, 2 tubes with new N14 DNA
- conservative: spun, then three tubes new N14 jDNA, one tube norm N15
- dispersive: mixed hybrids, band goes up for N15
linear replication
-happening in straight line
theta replication
- replication type for circular chromosomes like in E.coli
- produces 2 circular DNA molecules
- DNA unwinds at origin, producing replication bubble
- 2 replication forks
- bidirectional replication (replicates in opposite directions)
DNA replication requires….
- single-stranded template DNA (ssDNA)
- raw materials (nucleotides, Mg)
- numerous enzymes (to unwind DNA, read template, assemble new strand of DNA, supercoil DNA)
- DNA synthesized only in a 5’ to 3’ manner
okazaki fragments
- short segments that synthesize the lagging strand in 5’ to 3’ direction, away from replication fork
- joined by enzyme DNA ligase
4 stages of DNA replication
- initiation
- unwinding
- elongation
- termination
initiation
-initiator protein recognizes and binds to oriC site
unwinding
- helicase unwinds DNA
- single-stranded binding proteins (SSBPs) come in
- gyrase relaxes supercoiling
- primase synthesizes short RNA primers so 3’-OH present
elongation
- DNApols synthesize new DNA
- nicks are sealed by DNA ligase
termination
- last step in DNA replication
- occurs when replication forks meet
- or if Tus blocks further replication in eukaryotic
evidence that RNA predates DNA
- can’t make DNA without RNA (DNA replication needs RNA)
2. RNA has so many functions (it could survive w/out DNA)
telomeres
-ends of chromosomes
telomerases
- enzymes that extend DNA
- fill the gap left when RNA primer is removed
genetic code
- direct relationship of nucleotides to amino acids:
- info for animno acid is carried in sequence of 3 nucleotides
transfer of genetic info
- transcription (DNA transcribed into RNA)
- translation (RNA translated into protein)
translation stop and start codons
- one start codon: AUG
- 3 stop codons
translation stop and start codons
- one start codon: AUG
- 3 stop codons
transcription start and stop
- start at promoter sequence
- stop at terminator sequence
mRNA
- messenger RNA
- carries genetic codes for proteins
- in cytoplasm and nucleus
rRNA
- ribosomal RNA
- structural and formational components of ribosome
- cytoplasm
hnRNA
- heterogeneous nuclear RNA
- synthesized pre-mRNA from DNA template in transcription
mRNA
- messenger RNA
- single stranded RNA molecule complementary to the DNA
- follows hn-RNA when transcribed by RNA polymerase, then translated by ribosome to make polypeptide chain
- carries genetic codes for proteins
- in cytoplasm and nucleus
tRNA
- transfer RNA
- helps incorporate/carries amino acids into polypeptide chains
