Lecture 5

Question 1

what are Mendel’s Three “Laws”

Answer 1

The Law of Segregation states that for every trait, there are two alleles (one from mom, one from dad); each of the four post-‐meiosis haploid cells contains one of these alleles.
The Law of Independent Assortment states that genes for different traits assort independently of one another in the formation of germ cells
The Law of Dominance states that dominant alleles will mask recessive alleles

Question 2

what is the Law of independent Assortment

Answer 2

Each gene at a single location (locus) on a pair of chromosomes (one from dad, other from mom) is equally likely to be transmitted when sex cells are formed
true only for genes on different chromosomes, or those far enough apart on the same chromosome to be separated by recombination…

Question 3

What is a species?

Answer 3

The most common (and practical) definition is a population of individuals capable of mating and producing fertile offspring

Question 4

what are the 2 types of mating

Answer 4

random and non-random

Question 5

what is Random mating

Answer 5

(theoretically) occurs when there are no restrictions (either genetic or behavioral) to sexual reproduction within a species population in a given area

Question 6

what is the The Hardy-‐Weinberg equilibrium

Answer 6

imagines that allele/gene frequencies will remain constant if random mating alone is at work. It’s used to test the impacts of the factors it doesn’t take into account (e.g., natural selection, mutation, genetic drift and gene flow).

Question 7

The vast majority of sexual reproduction in the animal kingdom is the result of what

Answer 7

non-‐random mating

Question 8

what is non-‐random mating

Answer 8

whereby we choose—or are limited by—available partners within our population

Question 9

what is assortative mating

Answer 9

When choice and desirability are factors in mate selection, we call this assortative mating, which can be either ‘positive’ or ‘negative.’

Question 10

what is Positive assortative mating

Answer 10

is when individuals mate with partners having similar phenotypes (and, by extension, genotypes).

Question 11

what does Positive assortative mating result in

Answer 11

This tends to result in more homozygous alleles (AA, aa) in descendent generations

Question 12

what is Consanguinious mating

Answer 12

(inbreeding) could be considered a form of positive assortative mating.
It results in more homozygous alleles in future generations because close family members share a large number of genes.
It can result in a greater incidence of negative mutations being passed along, as well as increased transmission of beneficial mutations
Example: Haemophilia (recessive trait among European Royal Families)

Question 13

what is Negative assortative mating

Answer 13

is the result of a preference for mates with differing phenotypes/genotypes.

Question 14

what does Negative assortative mating result in

Answer 14

This results in more heterozygous alleles (Aa) in descendent generations

Question 15

what is Sexual selection

Answer 15

is one part of the natural selection process. It favors any adaptation that increases an individual’s chance of

1) Attracting mates
2) Having as many couplings as possible

Question 16

what are the typical key movers of sexual selection

Answer 16

1) male competition

2) female choice

Question 17

what is Sexual dimorphism

Answer 17

the differences in appearance between males and females of the same species, such as in colour, shape, size, and structure, that are caused by the inheritance of one or the other sexual pattern in the genetic material

Question 18

Does monogamy make evolutionary sense?

Answer 18

Many bird species are monogamous (lasts for one nesting)
Social monogamy seems to be more common than sexual monogamy
Males invest their time to ensure their offspring (and, by extension, their genes) survive

Question 19

what is Genetic Drift

Answer 19

is the action of random changes in the allele frequencies in a population over time. The changes are the result of the inherent chance in sexual reproduction and mutation, and cannot be predicted with any degree of certainty

Question 20

How significant is the impact of genetic drift on evolution?

Answer 20

Within a very small population, likely very significant. Two separate processes are related to genetic drift.

Question 21

what are the 2 types of genetic drift

Answer 21

a population bottleneck

The founder effect

Question 22

what is population bottleneck

Answer 22

is a reduction in genetic stock due to a natural or artificial disaster

Question 23

what is the founder effect

Answer 23

occurs when a breakaway subset of a population of a species becomes isolated from the original group

Question 24

what is Gene flow

Answer 24

is the transfer of alleles/genes into or out of a population within a species. This is the result of individuals moving into a population (immigration) or out of one (emigration).
Typically, barriers to gene flow are physical (oceans, mountain ranges, etc.)

Question 25

Today, humans comprise only one species, what is it

Answer 25

Homo sapiens

Question 26

was humans as one species always the case

Answer 26

This wasn’t always the case! At various points in the recent past we were divided into several species

Question 27

Why isn’t our genus currently divided into multiple species?

Answer 27

There are two possibilities:

1) all of us are descended from one sub-‐population that evolved into our modern form recently; or
2) gene flow has always been occurring among the earth’s dispersed human populations

Question 28

what is a Phylogeny

Answer 28

an evolutionary tree indicating relatedness and divergence of taxonomic groups

Question 29

A strand of DNA is composed of what

Answer 29

A strand of DNA is composed of base pairs of interlocking nucleobases: adenine, thymine, guanine and cytosine

Question 30

what was the Human genome project— (1990-2003)

Answer 30

was a multi year endeavour to create a reference genome

a mosaic, not representing any one individual

Question 31

If our genomes are so similar, why do humans and great apes appear so distinct and behave so differently?

Answer 31

Relatively small genetic changes can produce major phenotypic changes. 
Long stretches (~98%) of seemingly “junk” DNA may actually initiate (or ‘trigger’) different responses in otherwise identical genes.

Question 32

There exist two basic sources of variation in human beings, what are they

Answer 32

1) Genetic

2) Environmental

Question 33

Natural selection occasionally favours specific environmental adaptations strong enough to overcome the homogenizing effects of gene flow, what is an example of this

Answer 33

The ability to tolerate lactose is a good example of such an adaptation

Question 34

is race a biological category

Answer 34

Today, most biologists and social scientists understand that race is a social construct, not a valid biological category.
There is no ‘natural’ classification system for human races; they’re all somewhat arbitrary

Question 35

what is a folk taxonomy

Answer 35

A folk taxonomy is a customary, unscientific means of categorizing things. Many cultures have well-‐developed and culture-‐specific folk taxonomies for living things.
Since Linnean classification for human races is impossible, folk taxonomies for race are the only means of classification

Question 36

Some have suggested practical medical benefits to establishing race as a biological category, what are these

Answer 36

Sickle-‐cell anemia is a homozygous recessive blood disorder affecting mainly West African-‐descended people.
Inheritance of disease stems from genes and ancestry, not race