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AP Biology: Unit 5 Cheat Sheet (DRAFT) by

Meiosis and Heredity

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Comparing Reprod­uction

ASEXUAL vs. SEXUAL
asexual
simila­rities
sexual
- 1 parent
- creates offspring
- 2 parents
- identical genetics
- offspring gorw/d­evelop
- genetic variation
- quicker & less energy
- use DNA
- slower & more energy
advantages
  
advantages
- well-a­dapted (stable enviro­nment)
  
- increased diversity
- large # offspring quickly
  
- adapt to changed (unstable enviro­nment)
- reliable (fewer steps)
  
- genetic variation
- no need for a mate
    
- less time & energy
    
MEIOSIS vs. MITOSIS
meiosis
simila­rities
mitosis
- 2 divisions = 4 daughter cells
- interphase
- 1 division = 2 daughter cells
- genetic variation
- forms of reprod­uction
- geneti­cally identical
- half # chromo­somes (23)
- stage names
- same # chromo­somes (46)
- sex cells/­gametes
  
- somatic cells

Meiosis Defini­tions

- heredity:
transm­ission of traits from 1 generation to the next
- gametes:
haploid reprod­uctive cells (egg/s­perm)
- gene locus:
gene's specific location on the length of a chromosome
- karyotype:
display of chromo­somes matched up with their pairs (based on length)
- homologous chromo­somes:
pair of chromo­somes that have the same length, stain pattern, and genes contro­lling the same charac­ter­istics
- sex chromo­some:
chromosome respon­sible for determ­ining the sex of an individual
- autosome:
chromosome NOT directly involved in determ­ining sex
- diploid cell~
2 chromosome sets (2n) = 46; somatic cells
- haploid cell~
1 chromosome set (n) = 23; gametes

Meiosis Background

Meiosis I is called?
↳ reduct­ional division
Meiosis II is called?
↳ equational division
Original source of all genetic diversity?
↳ mutations
Term for different version of a gene?
↳ alleles

Variation

- crosing over: genetic rearra­ngment between sister chromatids by exchanging corres­ponding segments of DNA
↳ combining DNA from 2 parents into a single chromosome = variation
- indepe­ndent assort­ment: each pair of homologous chromo­somes are positioned indepe­ndently of other pairs
↳ each daughter cell represents 1 outcome --- formula: 2n
- random fertil­iza­tion~
↳ fusion of gametes (223 x 223) = variation

Genetics Defini­tions

- blending hypoth­esis~
genetic material contri­buted by both parents mixes (like paint)
- partic­ulate hypoth­esis~
parents pass on genes that retain their separate identities in offspring (like deck of cards)
- true-b­reeding strain~
plants, that after many generation of self-p­oll­ina­tion, have produced only the same variety as the parent (homoz­ygous)
- hybrid­iza­tion:
crossing of 2 true-b­reeding varieties
- P genera­tion:
the true-b­reeding parent indivi­duals
- F1 genera­tion:
hybrid offspring arising from a parental cross ('first filial)
- F2 genera­tion:
offspring from the interb­reeding of the F1 generation (second filial)
- homozy­gous:
2 identical alleles
- hetero­zygous:
2 different alleles
- phenotype:
physic­al/­phy­sio­logical traits
- genotype:
genetic makeup/set of alleles
- testcross:
breeding an organism of unknown genotype w/ homozygous recessive to determine the unknown genotype
- monohybrid cross:
cross between 2 organisms that hetero­zygous for the trait
- dihybrid cross:
cross between 2 organisms that are hetero­zygous for both traits
 

Mendel's 3 Laws

Probab­ility

- multip­lic­ation rule of probab­ility: probab­ility of indepe­ndent events occurring at the same time is the product of their individual proaba­bilties
- addition rule of probab­ility: probab­ility of mutually exclusive events occurring is the sum of their individual probab­ilities

Incomplete Dominance

- incomplete dominance: phenotype between both parents
↳ genotype isn't completely dominant
↳ use capital letter with a supers­cript
↳ C ➜ protein ➜ trait

Codomi­nance

- codomi­nance: 2 alleles that each affect the phenotype in separate ways
↳ use capital letter and supers­cript
↳ R' ➜ protein ➜ item A ➜ red
↳ R ➜ protein ➜ item B ➜ pink

Blood Types

A
IAIA/IAi
B
IBIB/IBi
O
ii
AB
IAIB
alleles present=
3
recessive allele=
O
codominant alleles=
A & B

Sex-linked Genes

- male = XY
- female = XX
- X inacti­vation: most of 1 X chromosome in each cell becomes inacti­vated
- Barr bodies: inactive X chromosome condenses
-gene SRY (sex-d­ete­rmining region of Y): Y gene results in a male
↳ makes transc­ription factor that binds to other genes causing them to transcribe
- sex-linked genes: genes on sex chromo­somes
- father passes Y to sons & X to daughters
- mother passes X to sons/d­aug­hters

- sex determ­ination in birds:
↳ sex chromosome in egg
↳ male = ZZ
↳ female = ZW

Pedigree Chart

Chromo­somal Mutations

- large scale chromo­somal mutation = change in phenotype
- three possible causes of mutations:
1. physic­al/­che­mical distur­bances
2. errors during meiosis
3. random mutation

Chromo­somal Disorders

- nondis­jun­ction:
pair of homologous chromo­som­es/­sister chromatids fail to separate
- aneupl­oidy:
1 or more chromo­somes have extra copies­/de­ficient number
- monosomic (monosomy):
diploid cell that has 1 copy of a chromosome (not 2)
- trisomic (trisomy):
diploid cell that has 3 copies of a chromosome (not 2)
- polypl­oidy:
organism has more than 2 complete chromosome sets
- Down syndrome:
extra chromosome 21 (trisomy)
- Klinef­elter syndrome:
extra X chromosome in males (XXY)
- Turner syndrome:
loss of X chromosome in females (X0)
- XXY:
extra Y chromosome in males
- XXX:
extra X chromosome in females

Genomic Imprints

genomic imprints:
expression of an allele in offspring depends on whether the allele is inherited from mother­/father
When does it occur?
during gamete formation
What chemical change does it involve?
methyl group added to cytosine nucleo­tides (inact­ivates alleles)
Which organelles contain their own DNA?
mitoch­ondria & chloro­plasts
When do these organelles get passes to offspring?
during fertil­iza­tion, mitoch­ondrial DNA from mother
Why are genetic defects of mitoch­ondrial genes likely to affect the functi­oning of the nervou­s/m­uscular system?
they are the most suscep­tible to energy depriv­ation (which ATP comes from mitoch­ondria)

Linkage Group

- linkage group: all the loci that "move togeth­er" in inheri­tance
- frequency of recomb­ina­tion: the frequency that crossing over will occur between two genes
- gene map: chromosome map that shows the relative locations of genes
- linked genes: located close enough together on a chromosome that they tend to be inherited together
- 'wild type': phenotype most commonly observed