Bio Class 6 Flashcards
When is it diploid vs haploid?
When homologous chromosome is present it is diploid, when it is not it is haploid
Prophase I
- DNA condenses, mitotic spindle forming, nuclear membrane breaks down
- synapsis (pair homologous chromosomes)
- crossing over - exchange of DNA
Tetrad
Pair of homologous chromosomes (4 chromosomes together
Metaphase I
Tetrads align at cell center
Anaphase I
Separate homologous chromosomes
Cytokinesis begins
Ring of actin forms (cleavage burrow)
Telophase I
- Reverse of prophase I
- Finish cytokinesis
At the end of meiosis I you have 2 haploid cells
Moves to meiosis II
Prophase II
similar to prophase I
Metaphase II
similar to metaphase I
Anaphase II
Separation of sister chromatids
Telophase II
similar to telophase I
End result of meiosis I & II
You have 4 cells, each with 23 chromosomes
All chromosomes are different from each other & parent ell
Meiosis is also called…
Reductive division
Nondysjunction
Failure to divide DNA during meiosis
Anaphase I failure: all 4 gametes are abnormal
Anaphase II failure: 2 will be normal, 2 will be abnormal
Gene
Piece of DNA that codes for product
- includes regulatory regions (eg. promoter, untranslated region)
Trait
- known as phenotype
- physical characteristics resulting from genes
a. Polymorphic
b. polygenic
Allele
Version of gene
Superscript differs in capital/lowercase
Polymorphic
many forms due to the expression of many alleles
Polygenic
many forms due to expression of many genes
Non-classical dominance
- Incomplete dominance - heterozygote is blended phenotype; genotype will have 2 different uppercase letters
- Codominance - alleles are expressed independently of each other at same time
- Epistasis - dominance between genes (expression of one gene regulates expression of another gene)
Classical dominance
1 allele is dominant, 1 is recessive
Human ABO Blood group gene
On surface of RBC, you have an area that codes for protein on the surface
3 versions of alleles: Ia (codes for A protein), Ib (codes for B protein) & i (codes for no protein
Universal donor? Universal receipent?
Donor is: O- because no proteins to trigger reaction in recipient
Acceptor is: AB+ because has A/B/Rh factor
Blood typing Process
- Rh factor: determined through classical dominance (R codes for Rh protein) r (doesn’t)
RR or Rr = Rh+ / rr = Rh- - Complete blood type is combo of ABO and Rh genotype
- Transfusion Reactions
- Immune system designed to recognize foreign proteins
Mendel’s Laws
- Law of Segregation
2. Law of Independent Assortment
Law of segregation
Alleles are separated during gamete formation (anaphase I + II)
Law of independent assortment
How one pair of alleles separates is independent of another pairs separation (depends on how chromosomes meet in metaphase)
Exception: If linked, it will not be independent
Mendel’s Law
- Law of segregation - Alleles are separated during gamete formation
- Law of Independent Assortment - One pair of alleles separation is independent of another pairs separation
4 basic single gene crosses
- Heterozygote x Heterozygote
Phenotype: 25% dominant, 50% hetero, 25% recessive
Genotype: 75% dominant, 25% recessive - Homozygote x same Homozygote
Phenotype: 100% parental
Genotype: 100% parental - Heterozygote x Homozygote (recessive/dominant)
Phenotype: 50% dominant, 50% homozygote x
Genotype: 50% heterozygote, 50% homozygote x - Homozygous dominant x homozygous recessive
Phenotype: 100% dominant
Genotype: 100% heterozygote
Rules of probability
Rule of multiplication (A & B happening at same time)
Probability (A and B) = prob (A) x prob (B)
Rules of addition (probability of A OR B happening at same time
Mutually exclusive (nothing in common) prob (A) + prob (B)
Nonmutually exclusive
prob (A) + prob (B) - (prob A x prob B)
Linked genes
found close together on the same chromosome so when cross over happens it does not separate
To know if genes are linked, you have to look at F2 generation
Unlinked ratio
d/d 9/ 1
d/r 3/ 1
r/d 3/ 1
r/r 1/ 1
Recombinant frequency
Recombinant frequency (RF) = # of recombinants/ total # of offspring x 100%= - unit: map units (mu)
Hardy-weinberg principle
Allele frequencies do not change from generation to generation
H-W equations
Phenotype frequency:
p + q = 1
Genotype frequency:
pp + 2pq + qq = 1
p= dominant allele q = recessive allele pq = heterozygote
What are the 5 conditions that hold true for the H-W equations?
- Mating has to be random
- No migration (no inward or outward flow of alleles)
- No natural selection (bc this would increase the probability of good alleles)
- Large population (small population means it’ll be affected by small events)
- No mutation
