Gene
segment of DNA that codes for a protein/trait
Allele
Version of a gene
How many alleles per gene do haploid cells have?
1
Meiosis I
homologous chromosomes separate, replicated sister chromatids stay tg in 2 daughter cells
Meiosis II
2 daughter cells divide to separate sister chromatids –> 4 daughter haploid cells
metaphase in mitosis vs meiosis
meiosis: homologous chromosome pairs line up side by side
Mitosis: individual duplicated chromosomes line up single file
crossing over
paternal and maternal homologos physically exchange genetic segments at chiasmata during late prophase I
- genes are located far apart on the SAME chromosome
synaptonemal complex
ensures that only the exact right amount gets exchanged during crossing over
recombination nodules
mark where crossing over will occur at chiasmata, then cuts & rejoins DNA
Independent Assortment
the line up between maternal and paternal homologous chromosomes at the metaphase plate (meiosis I) are RANDOM
How does indep. assortment work?
spindle fibers randomly attach to chromosomes at the kinetochore on the centromere, making chromosome movement to the plate RANDOM
nondisjunction
when chromosomes fail to separate properly during anaphase I or II
- inflexible cohesion protein: homologs dont separate after crossing over
Outcrossing
genetics from diff individuals combine = more genetic variation
Self-fertilization
2 gametes from the same individual combine = less genetic variation although the offspring are diff from parent
Non mendellian patterns of inheritance
genes on sex chromosomes or linked genes (located close tg on the same chromosome)
Silent point mutation
no effect
nonsense point mutation
normal codon –> STOP codon
- severe effect bc translation stops too early so protein is too short
conservative missense (point) mutation
amino acid gets swapped w/ one that has similar properties so mild effect
non-conservative missense (point) mutation
amino acid gets swapped for one NOT in the same category of properties, severe effect
Deletion
if 3 nucleotides gets deleted an entire amino acid will be missing = severe effect
OR
if entire gene is deleted no amino acid will be made at all = severe effect
upstream
“before”, termination to promoter, opposite of RNA polymerase
downstream
“after”, promoter to termination signal, same as RNA polymerase
How transcription works in prokaryotes
sigma binds to RNA polymerase –> guides it to promoter and binds them tg by recognizing -35 and -10 regions –> transcription begins at the +1 so the promoter sequence is NOT transcribed ONLY the coding region and termination signal
How transcription works in eukaryotes
RNA polymerase II transcibes protein coding genes, some transcription factors bind to DNA to guide RNA polymerase to promoter while others bind to DNA and remove chemical groups making the DNA available to be bound –> pre-mRNA made
