Genetics Final
nucleosomes
"pearls on a string" histones with DNA wrapped around them folds up and forms chromatin which is important for dna storage
polycistronic mRNA
1 mRNA for multiple proteins
mendels postulates
1. unit factors exist in pairs 2. dominant vs recessive 3. segregation occurs independently during gamete formation
human chromosome number
23 pairs
dna polarity
5' to 3' because of carbon bonding on the base
transcription
DNA ---> RNA rna polymerase process: opens up dna (histone acetylation) and unwinds dna (gyrase) activation of promoter to bind polymerase via transcription factors processing (splicing, 5' cap, poly A tail to 3' end) leaves nucleus
dihybrid cross
F2 genotype: ----- F2 phenotype: 9:3:3:1 traits from two different genes
monohybrid cross
F2 genotype: 1:2:1 F2 phenotype: 3:1 traits from one gene
bases of RNA
G-C A-U
bases of DNA
G-C: strongest bond (3H) A-T: 2H
translation
RNA-----> proteins ribosomes in the cytoplasm (rRNA)
PCR
amplification of a specific gene region uses TAQ polymerase (copies 5' to 3' forward direction) temp changes and primers instead of cellular machinery
dna strands
antiparallel, complementary
phosphodiester bonds
backbones of DNA
hydrogen bonds
bonds between opposing DNA strands
codominance
both alleles are expressed eg: AB blood type
incomplete dominance
both alleles are partially expressed and form an intermediary phenotype eg: red and white flowers=pink flowers
lethal alleles
cause death dihybrid: 2:1 eg: huntingtons (progressive lethality) or agouti (early development/fetal lethality)
frame shift mutation
caused by a mutation that changes A of AUG
multiple alleles
different forms of a gene are expressed in a population
euchromatin vs heterochromatin
euchromatin: gene expression, can become heterochromatin through methylation heterochromatin: regulatory, no transcription
recombination
exchange of genetic material between homologous chromosomes exchanged at points called chiasmata genes that are close together are less likely to go through recombination
genotype
genetic profile of an organism
dna methylation
increases compactness
histone acetylation
increases relaxedness by making histones less positively charged
nondisjunction
is when chromosomes fail to separate properly eg down syndrome
sex linkage
linkage due to being on the X chromosome eg: eye color in flies
chromatin
more condensed during cell division and is more relaxed during G phase most relaxed during gene expression
chromosomes
not uniform because of centromeres, telomeres, genes, and regulatory sequences ( lines, sines, transposons) gene areas are less dense compared to highly repetitive areas majority non coding dna
phenotype
observed traits of an organism
dna replication
occurs in the S phase makes 1 copy semiconservative enzymes: helicase: opens helix gyrase: relaxes tension polymerase III: copies dna and proofreads polymerase I: fills gaps after primer removal rna primers: binds polymerase made by primase attaches to leading and lagging strands 5' to 3' direction to proofread (cant go 3' to 5' because there is no phosphate energy source) exonuclease: removes primers dna ligase: attaches ends together via phosphodiester bonds origin: place where dna replication starts humans have many plasmids have one (circular dna)
epistasis
one gene masks a different gene can be dominant or recessive, agonistic or antagonistic eg: H factor blood type
histones
parts of nucleosomes that are the disc-shaped octamer protein complex
parts of dna
phosphate group, nitrogenous base, deoxyribose sugar
gene linkage
probability of genes on the same chromosome being inherited together far apart: not likely (increased independent assortment) close together: likely to be inherited together
primers
small pieces of dna that work by complementing the template strand and allowing polymerase to bind for dna synthesis
start and stop codons
start: AUG stop: UGA UAG UAA
meisosis
steps: P: crossing over, breakdown of nuclear envelope M: chromosome alignment A: chromosome/allele separation T: chromosome recondensation 2 haploid cells P: new spindle formation M: chromosome alignment A: sister chromatid separation T: chromosome recondensation 4 non identical haploid cells 2n ----> 4n 4 copies of chromatids reduces genetic material by half
genes
the basic units of heredity
gene expression
turning on transcription or translation regulation: transcription factors: activators, repressors regulatory sequences: enhancers, silencers activators bind enhancers repressors behind silencers operons: one promoter controlling multiple genes eukaryotes do NOT have operons operators are regulatory sequences
heterozygous
two different alleles
homozygous
two of the same alleles