1. Topic 10 Genetics and Evolution

2. 10.1 Meiosis Chromosomes replicate during s-phase of interphase.
During Prophase I, crossing over can occur between chromatids of homologous chromosomes.
New Vocab. The pair of homologous chromosomes, once they are together they are called a bivalent
The actual spot where they touch is called the chiasma, there can be more than one

3. Homologous chromosomes separate during meiosis anaphase I, sister chromatids separate during meiosis anaphase II
Independent assortment during metaphase says that each allele can separate independent of the other based on how they line up.
During metaphase there are 223 ways the chromosomes can line up, not counting crossing over.

4. 10.2 Inheritance Dihybrid crosses Two traits FOIL method
RrYy = RY, Ry, rY, ry

5. Autosomes & Sex chromosomes
22 pairs of autosomes
2 sex chromosomes
Autosomal traits have genes on autosome
Sex linked trait has genes on sex chromosomes.

6. Linkage groups
Genes that are on the some chromosome are usually inherited together. Said to be linked.
In fruit flies, genes for body color and wing length are on the same chromosome.
G=grey
g=black
L=long wing
l=short wing

7. If the g’s and the l’s are on the same chromosome, you don’t give a genotype like this GgLl, you have to show that they are linked by doing this….G L
g l
So where the G goes, the L goes with it.
You cant foil this like normal

8. Polygenic Inheritance
More than one gene influencing the trait, not multiple alleles, multiple genes.
It is believed that most traits are polygenic.
Causes a spectrum of traits called Continuous variation. Skin color and height are examples.
Discontinuous variation is from one gene, blue-brown, disease or no disease, etc
Continuous traits create a bell curve

9. 10.3 Gene pools and speciation
Gene pool is all the genetic information in a certain population at a given time.
Large gene pools create large variation
Small gene pools create small variation
Allele frequency measures the proportion of a specific allele in a population.
Does not mean what % of the population have the allele.

10. Evolution and allele frequency
Frequency of alleles changes over time as good one increase and bad ones decrease.
Also, populations mixing can change allele frequency.
If allele frequency is changing, evolution is occurring, if it is not changing, evolution is not happening.

11. Hardy-Weinberg equation
Used to calculate the frequency of alleles.
Can be used to determine how fast a population is changing.
p=frequency of dominant allele
q=frequency of recessive allele
p + q =1
P2 + 2pq + q2 = 1

12. p2 = frequency of homozygous dominant
q2 = frequency of homozygous recessive
2pq = frequency of heterozygous

13. Reproductive Isolation
Something separates a population (gene pool)
Geographical isolation-land, water etc
Temporal isolation – time. Example is flowers reaching maturity at different times.
Behavioral isolation – lifestyle, habits, courtship dance.

14. Directional, stabilizing and disruptive selection
Directional selection – when a certain phenotype is favored over another. Causes the phenotype to increase in frequency. Occurs when the environment changes.
Stabilizing selection is when a phenotype that is different than both options is favored. Flower nectar. Move towards the mean
Disruptive selection – two different extremes are both favored. Move away from the mean

15. Polyploidy Sex cells have one set of chromosomes (n) Haploid
Somatic cells have two sets of chromosomes (2n). Diploid
Polyploidy is three or more sets of chromosomes. (3n), (4n) etc
More common in plants than animals.
More vigorous plant, larger fruit, resistant to disease

16. Polyploidy
Can create more replication errors, causes differences in how they evolve.
The process of a population changing enough to be unable to reproduce is called speciation.

17. Speciation due to divergence
Two main views as to rate of evolution.
Small, continuous, slow (gradualism)
Quick then long periods of time with little or no change. (punctuated equilibrium)
Gradualism – Darwin
Punctuated equilibrium – more recent, due to sudden environmental change.
Some species go for millions of years with little or no change. Sharks, cockroaches, horseshoe crabs
Incompleteness of fossil record makes it difficult