ap bio (first half)

test cross

a genetic cross between a homozygous recessive individual and an individual with an unknown genotype to determine the unknown genotype's alleles.

liked genes

find recombination %

add up recombinants + divide by total # of offspring - This number also indicated the map units between the genes ! 

Incomplete dominance

when neither allele is dominant over the other - Ex: WW (white) x RR (red) = all WR (pink)

codominance

qual expression of both alleles 

- Ex: AB blood type (both A + B alleles are expressed) 

polygenic inheritance

ach gene has a small effect on a particular trait 

- Ex: height, skin color, and weight 

Non-nuclear inheritance

 mitochondrial inheritance is always through maternal line! (from eggs)

 DIHYBRID: heterozygous (BbAa) x heterozygous (BbAa)

9:3:3:1 

 DIHYBRID: heterozygous (BbAa) x homozygous recessive (bbaa)

1:1:1:1 

 Built (by DNA polymerase)

5 to 3, s phase

 Read (by RNA polymerase)

3 to 5, in translation

phase of transcrip and translate

DNA -- transcription → mRNA -- translation → protein

Transcription

takes place in the nucleus,  unedited, pre-mRNA molecule, Specific sequences of nucleotides along the DNA mark where gene transcription begins and ends

- RNA polymerase attaches and initiates transcription at the promoter, ‘upstream’ the information contained in the gene 

- Terminator signals the end 

- Template strand carries DNA

 C → G (& vice versa), T → A , A → U 

 Post-transcriptional modifications

mRNA splicing/processing: gives the mRNA its correct sequence

5’ cap: added to the 5’ end (or beginning of) a pre-mRNA molecule

- poly-A tail: added to the 3’ end (or end of) a pre-mRNA molecule  

spliceosome is the complex that includes snRNPs. This complex cuts introns and joins exons to make the final message molecule. When RNA performs an enzymatic function, we label it a ribozyme. 

translation

ribosomes in the cytoplasm

“decoding” a messenger RNA (mRNA) and using its information to build a polypeptide, or chain of amino acids 

aug - met - start

promoter

a specific DNA sequence located upstream of a gene, acting as the binding site for RNA polymerase to initiate transcription

enhancer

distant, cis-acting DNA sequences that increase transcription rates of specific genes by binding activator proteins

Methylation

adding methyl group inhibits transcription (tightens DNA, harder for RNA polymerase to access)

 Acetylation

adding acetyl group promotes transcription (relaxes DNA, easier access for RNA polymerase) 

RNA processing

 5’ cap or poly-A tail

 RNA editing

removal of introns (creates mature strand of RNA, stimulating protein synthesis by creating a strand that is ready to be translated)

Signal Molecules of Gene Expression

 Cytoplasmic determinants (gametes → zygote

Transcription factors — coded for by hox genes* (important for setting up body plan) (ex. myoD)

Cytoplasmic determinants

early activators”

determination precedes differentiation” 

Endosymbiotic theory

proposes that eukaryotic cells formed from a symbiotic relationship among prokaryotic cells (prokaryotic cell was engulfed by another cell, forming the emdosymbiotic relationship ex.mitochondria/chloroplast contains their own DNA 

- mitochondria/chloroplast contain a double membrane 

- mitochondria/chloroplast have a similar size to prokaryotic cells

 Osmosis in Plant Cells 

When placed in a hypertonic solution, water will leave the cell + plasmolysis will occur (water moves out, cell becomes dehydrated) 

- When placed in a hypotonic solution, water will enter the cell (cell wall will swell) = turgid which is the normal state for a (blank) cell, giving it a swollen appearance