Key- vocabulary 

What is the term in the original belief of how genetics work?

PBIO 1210- Principles of Plant Biology

Test 3 study guide

genetics 

1. Blending inheritance- original belief of how genetics works

a. States that an offspring is a blend of its parents

2. Particulate inheritance- current belief, the “gene” idea

a. States that parents pass on heritable genetic units (genes)  

b. This was discovered by Gregor Mendel by breeding and observing pea plants i. He removed the anthers of the plants so they couldn’t self-pollinate and applied  pollen from another plant to its stigma

ii. When self-pollinated, offspring are identical (pure lines)

iii. He made controlled crosses of different varieties

Who is the first to propose an evolutionary mechanism?

iv. He looked at either/or characteristics (purple/white, round/wrinkles, etc.)

v. These characteristics disappeared in F1 ad reappeared in F2 with a 3:1 ratio 1. F1- first generation, F2- second generation

2. 75% dominant, 25% recessive

3. Phenotype- observable trait (Red)

4. Genotype- genetic trait (RR)

5. 2 alleles- diploid

6. Allele is found on locus of chromosome

vi. Punnett square- graph used to predict traits of offspring

1. Dominant- present allele, recessive- hidden allele

2. Dominant- uppercase, recessive- lowercase

3. Heterogeneous- Bb, Homogenous- BB or bb

Who is charles darwin?

4. Offspring segregate- parental characteristics reemerge  If you want to learn more check out morph chart engineering

5. Test cross- an unknown can be crossed with a purebred to determine  

whether it is homogenous or heterogeneous

reproduction

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Key- vocabulary 

evolution

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Key- vocabulary 

1. Jean Baptiste Lamarck 

a. First to propose evolutionary mechanism

b. Accepted chain of being  

c. Believed that lineages persist indefinitely

i. No new species form

ii. No extinction

d. He believed that there were two chains: Plants and animals

i. Some species don’t fit into a linear chain

e. Changes are directional

f. He hypothesized that:

i. Traits emerge through use/disuse

ii. Acquired traits are passed to offspring

iii. EX: Early giraffe stretches its neck to reach food and this is passed to its  

offspring

2. Charles Darwin 

a. Makes observations on the Galapagos Islands, such as snakes with hind legs and finches  with different beaks

i. EX: the finches’ beaks are adapted to different food sources

b. Phenotypes can be used to track environmental changes over time

i. Artificial selection can be used as evidence

ii. EX: People save plants that produce the most fruit and the allele for that trait  will be passed through the generations Don't forget about the age old question of chapter 6 accounting study guide

c. His book, The Origin of Species, explained that many species of organisms on earth are  descendants of their ancestors

i. Decent with modification (Evolution)

ii. Two main ideas:

1. Evolution explains life’s unity/diversity

2. Natural selection is the main cause of evolutions

3. Theory- principle/conclusion derived from a large body of observations/experiments a. Every species is capable of producing offspring that cab survive/reproduce b. The sizes of natural populations tend to remain constant over time

i. This is typically governed by available resources  

c. Thus, there will be competition for survival/reproduction  

d. Individuals in a population vary affect their chance of survival/reproduction e. Individuals with the most advantageous traits are:

i. More likely to survive and produce the most offspring

ii. Favorable traits will become more common in a population over time

4. Using molecules to track evolution

a. Protein/DNA sequences can be used to reconstruct species’ relationships

b. Closely related organisms are more similar on a DNA/protein level

c. Darwin believed that the history of life resembled a tree

i. Multiple branches from a common trunk

ii. The tips show the diversity of living organisms  Don't forget about the age old question of Who discovered that if you excite the brain with electricity it can cause motor function?

d. Gaps in the fossil record are being filled in slowly over time

Key- vocabulary 

Allele frequency 

1. Evolution- the change of allele frequencies in a population over time

a. Population- certain species in a particular area

b. Gene pool- all alleles present in a given population Don't forget about the age old question of an essential management tool that communicates

c. Genotype frequency- proportion of a population with a certain genotype  

i. Not necessarily equal to phenotype frequencies

d. Allele frequency- proportion of gene copies of a certain type  

e. Monomorphic- one allele

f. Polymorphic- multiple alleles  

2. Genotype vs allele frequencies example

a. plants total

i. RR= 2

ii. RR1=1

iii. R1r= 1

iv. R1R1= 2

v. Rr= 1

vi. Rr=1

b. 16 alleles total

i. R=6 (.375)

ii. R1= 6 (.375)

iii. R= 4 (.25)

3. These factors can alter allele frequencies:

a. Mutation- any change in genetic material

i. Ultimate cause of all genetic variation

ii. Occurs randomly in replication/crossing over

iii. Can affect individual genes and chromosomal regions

b. Non-random mating 

i. Inbreeding- affects genotype frequencies

ii. EX: Self-fertilization increases homozygous alleles, exposing recessive alleles,  leading to disorders

iii. EX: Aa x Aa (100% heterozygous) -> AA, Aa, aa (50% heterozygous)

c. Genetic drift- random changes in allele frequencies caused by a new allele i. What determines a mutations fate?

1. Extinction/loss- the allele helps/hinders an organisms chance of  

reproduction

2. Fixation-Even if selection plays a role (and especially if it doesn’t)

d. Population bottlenecks- Large populations may experience sudden, temporary declines  in size

e. Founder effect- Colonization of new area by a small part of the original population f. Fewer founders, larger effect

g. Natural selection- explained below

h. Gene flow- explained below

Key- vocabulary 

selection 

1. natural selection 

a. (Organisms with lower fitness are less likely to survive and produce offspring) b. Abiotic- temperature, elevation, moisture, chemicals

c. Biotic- mating, competition, cooperation  

d. Intraspecific (within species)- competition, herbivory, parasitism, mutualism e. Pressures on environment can change over time

2. directional selection 

a. (Individuals with one extreme phenotype are favored over ones with the other extreme) b. EX: for weedy plants on island, dispersal causes drowning

i. Decreased pappus and increased seed size is favored

c. Shift can happen quickly in less than a decade

d. Favors resistance, disfavors susceptibility  

e. Results in a fixation of the favored allele

3. stabilizing selection 

a. (Favors individuals with intermediate phenotypes)

b. Results on the narrowing of phenotype distribution

c. Allele value remains unchanged

d. EX: too few flowers causes less reproduction, too many is costly

4. Disruptive selection 

a. (Extreme traits are favored while intermediate traits are disfavored)

b. Results I phenotypic divergence

c. Promotes outbreeding in floral structures

d. EX: Beak size in African finches

5. Gene flow 

a. (transfer of alleles from one organism to another through mating)

b. Causes hybridization