Mendel, Heredity And Modern Synthesis

Question 0

Germ plasm theory

Answer 0

Only gonads contribute genetic material to sex cells (continuity of germ plasm) germ line —> germ line but germ line —> soma when passed on
*Correct

Question 1

Pangenesis theory

Answer 1

All body parts contribute genetic material to sex cells (what you do to your body and what happens is passed on), soma—> germ line
*Incorrect

Question 2

Blending inheritance

Answer 2

Genetic info passed on but you lose a gene through passing it on, red + white = pink but pink + white = light pink and thus no backtracking

Question 3

Early criticisms of Darwinian natural selection

Answer 3

1. Favorable types will be swamped by blending inheritance
2. How can populations move beyond existing variation (mutation)
3. Natural variation too small to have an effect on fitness

Question 4

Gene

Answer 4

A sequence of DNA (nucleotides) that codes for a particular protein or RNA molecule

Question 5

Locus

Answer 5

The position a gene occupies on a chromosome

Question 6

Allele

Answer 6

One of the alternative forms of a single gene (eye color)

Question 7

Homozygous

Answer 7

In diploid organisms, an individual with the same allele on both chromosomes (ss or SS)

Question 8

Heterozygous

Answer 8

In diploid organisms, an individual with different alleles on each chromosome (Ss)

Question 9

Genotype

Answer 9

Genetic constitution of an individual at one or more genes

Question 10

Phenotype

Answer 10

The physical, chemical or behavioral expression of the genotype in a particular environment

Question 11

Principle of dominance

Answer 11

Gregor Mendel discovered with pea plants, there is a dominant allele and a recessive allele, discovered that the dominant allele is expressed as homozygous and sometimes heterozygous while a recessive allele is expressed only through homozygous genotypes

Question 12

Dominance

Answer 12

An allele that is more prominent or that that specific allele drives the phenotype

Question 13

Dominant allele

Answer 13

Expressed whenever it is part of the genotype even if it is only one of the two alleles of a heterozygous genotype

Question 14

Recessive allele

Answer 14

Expressed only in homozygous genotypes, no obvious phenotypic effect when in a heterozygous genotype with a dominant allele

Question 15

Segregation

Answer 15

The separation of alleles that leads to creation of separate genotypes

Question 16

Principle of segregation

Answer 16

Gregor Mendel discovered, during meiosis alternate alleles of a single gene separate out to different gametes and this remain distinct and don’t blend, see no loss of genes and found no blending

Question 17

Independent assortment

Answer 17

Alleles of two different unlinked genes inherited randomly in all possible combinations

Question 18

Principle of independent assortment

Answer 18

Gregor Mendel discovered, a gamete will contain a random assortment of the possible combinations of alleles across different genes on different chromosomes, see no set pattern to suggest assortment is not random

Question 19

No blending inheritance

Answer 19

The principle of independent assortment supports no blending, alleles separate out so don’t blend

Question 20

Inheritance of combinations of traits across multiple genes

Answer 20

Principle of independent assortment, inheritance of one unlinked gene is independent of the inheritance of another

Question 21

Discrete variation

Answer 21

Variation in a qualitative trait that falls into distinct categories (blood type, eye color, hitch hikers thumb)

Question 22

Continuous variation

Answer 22

Variation in a quantitative trait that falls along a numerical continuum (height, beak length), can calculate a mean

Question 23

Predicted ratio of offspring genotypes and phenotypes given parents

Answer 23

Use a punnet square

Question 24

Pea experiments

Answer 24

Mendel used discrete traits when testing his peas

Question 25

Mendelians

Answer 25

Followers of Mendel and de Vries

Question 26

Mendelian arguments

Answer 26

1. Only discrete variation important for evolution
2. Continuous variation has no genetic basis
3. Evolution happens by rapid changes in discrete traits
4. Mutation is the primary mechanism of evolution by creating new species suddenly not through gradual selection
   Problem: couldn’t explain family resemblance

Question 27

Biometricians

Answer 27

Followers of Darwin

Question 28

Biometrician arguments

Answer 28

1. Continuous variation important for evolution
2. Discrete traits are rare
3. Natural selection is the primary mechanism of evolution causing gradual changes in continuous traits
4. Continuous traits are found in family resemblance (height)
   Problem: not understand inheritance of continuous traits

Question 29

Factors contributing to continuous variation

Answer 29

1. Environmental effects (water, food, shelter)
2. Co-dominant alleles (intermediate stage: tall, short and medium)
3. Multiple genes affect a trait (more genes make it look more continuous)
4. Epistasis (one gene can mask it’s counterpart)
5. Recombination and sex (create variation in genotype)

Question 30

Co-dominance

Answer 30

Crossing to homozygous for each trait results in an intermediate stage, one gene with an intermediate

Question 31

Epistasis

Answer 31

The interaction of two or more genes to control a single phenotype, typically where one gene interferes with or masks the phenotypic expression of another gene

Question 32

Modern synthesis

Answer 32

Neo-Darwinian synthesis or evolutionary synthesis, same heredity for continuous and discrete traits, gradualism supported (gradual microevolution lead to macroevolution), mutation doesn’t act alone but creates the raw variation for natural selection

Question 33

Discrete vs continuous traits

Answer 33

Both follow same principles of Mendelian inheritance, alleles are dominant and recessive, there is segregation and independent assortment, continuous may just have more alleles playing into one trait at once