Hort 1001 Lecture 26

Front 1

True or False: Genetics is an old science.

Back 1

FALSE: It is only about 140 years old.

Front 2

Jean-Baptiste Lamarck

Back 2

First accepted genetics "belief." Lamarck stated that individuals lost characteristics that they did not use, and acquired characteristics that they did use. Acquired characters were then passed on to offspring.

Front 3

Charles Darwin

Back 3

Father of Natural Selection and evolution. He published "On the Origin of Species" and stated that individuals with favorable phenotypes that provided higher fitness were more likely to survive and reproduce than those individuals with less fit phenotypes.

Front 4

Darwin believed that over long spans of time, natural selection could result in adaptations that allow plants to ____ for niches and result in the development of new species that have incorporated so many adaptations that they are reproductively isolated from the original plants.

Back 4

Darwin believed that over long spans of time, natural selection could result in adaptations that allow plants to SPECIALIZE for niches and result in the development of new species that have incorporated so many adaptations that they are reproductively isolated from the original plants.

Front 5

True or False: When Darwin published "On the Origins of Species," it immediately became "accepted."

Back 5

FALSE: Lamarck's ideas were still accepted more at the time of publication.

Front 6

Gregor Mendel

Back 6

Geneticist who published a report to introduce his 2 laws which were not accepted at first (took 2 years). Mendelian inheritance was based solely on genes and these genes are not altered by experiences during the individual's lifetime.

Front 7

Mendelian genetics was contrary to _____'s proposal of acquired traits and the idea that characteristics that an individual used were passed on to the next generation and those characteristics that were not used were not passed on.

Back 7

Contrary to Lamarck's proposal

Front 8

True or False: Mendel and Darwin were scientifically active during the same time period.

Back 8

True

Front 9

Why was Mendel's work criticized?

Back 9

Mendel's proposal was criticized because, while it described a mechanism for genetic control of qualitative (one gene, big effect) traits, most characteristics of individuals appeared to be quantitatively inherited.

Front 10

R.A. Fisher

Back 10

In 1918, he showed statistically how the accumulation of effects of many discrete loci could result in the observed continuous variation associated with quantitative traits.

Front 11

Whobridged the gap between Mendelian genetics and observed quantitative / continuous variation?

Back 11

R.A. Fisher

Front 12

Neo-Darwinism

Back 12

The name for the current synthesis of concepts first proposed by Darwin and Mendel with the statistical support of R. A. Fischer in bridging the gap between qualitative and quantitative inheritance.

Front 13

True or False: Neo-darwinism is the current biological model that addresses the question of how the organismic diversity that we witness on Earth arose.

Back 13

True

Front 14

True or False: If all individuals are genetically identical, then natural selection has nothing on which to operate. If all genotypes are identical, then only the environment can cause phenotypes to vary.

Back 14

True

Front 15

Mutation

Back 15

Primary source of new alleles.

Front 16

Natural selection favors those mutations that provide plants with a ____ advantage, and weed out those that are deleterious.

Back 16

Natural selection favors those mutations that provide plants with a SELECTIVE advantage, and weed out those that are deleterious.

Front 17

Point Mutations

Back 17

Point mutations are changes in that code that affect the base sequence by changing one of the bases into another.

Front 18

Three Types of Point Mutations

Back 18

Substitution of single base

Insertion of base

Deletion of base

Front 19

Sequence Mutations

Back 19

Occur when bigger segments of DNA flip around, duplicate or moving to a new place on the same chromosome.

Front 20

Three Types of Sequence Mutations

Back 20

Inversions: a segment of DNA flips end to end

Duplications: a segment of DNA is copied and pasted right after the original segment

Rearrangements: a segment of DNA moves from one place to another place on the same chromosome

Front 21

Chromosomal Mutations

Back 21

Mutations where segments of chromosomes move to different chromosomes or where whole chromosomes are duplicated:

Front 22

Three Types of Chromosomal Mutations

Back 22

Translocation: a segment moves to a different chromosome

Chromosome duplication: the cell has an extra chromosome

Genome duplication: the cell has an additional set of chromosomes (3 homologs instead of 2)

Front 23

What are two causes of mutation?

Back 23

Errors in replication or cell division

Chemicals, radiation and age

Front 24

How frequent are mutations?

Back 24

Very rare and they don't have much of an impact.

Front 25

Most of the mutations to DNA that actually do affect protein synthesis are detrimental and quickly eliminated by what process?

Back 25

Natural selection

Front 26

True or False: The likelihood of a mutation that affects protein synthesis and that has a positive impact on fitness is very, very high. However, only a very small amount of positive mutation is all that is necessary to fuel natural selection.

Back 26

FALSE: The likelihood of a mutation that affects protein synthesis and that has a positive impact on fitness is very, very LOW. However, only a very small amount of positive mutation is all that is necessary to fuel natural selection.

Front 27

Population Genetics

Back 27

Affected by many genes, each with relatively small effect, and affected by environment.

Front 28

Complete

Back 28

Front 29

I have 25 AA plants, 50 Aa plants and 25 aa plants. Assume aa plants perish before reproduction. How many plants are left for reproduction?

Back 29

25 AA + 50 Aa = 75 plants

Front 30

Calculate frequency of A and a if there are 25 AA plants, 50 Aa plants and 25 aa plants if aa plants perish before reproduction.

Back 30

If each of these 75 plants contributes two gametes to the reproductive gene pool:

A alleles from AA individuals = 2 x 25 = 50

A alleles from Aa individuals is 1 x 50 = 50

So the total number of A alleles in the reproductive pool of gametes from this group of 100 plants is 50 + 50 = 100.

Now again, in this same group of 100 plants:

The number of a alleles from Aa individuals is 1 x 50 = 50

Amnt. of a alleles contributed from aa individuals = 0 x 25 = 0 (they perish)

So the total number of a alleles in the reproductive pool of gametes from this group of 100 plants is 50 + 0 = 50.

Since the total number of alleles in the reproductive pool is 100 A + 50 a = 150, the frequency of the A alleles in the reproductive pool as 100/150 = 2/3 and the allele in this reproductive pool as 50/150 = 1/3

Final Answer:

A = 2/3

a = 1/3