Topic 5: Genetics Review

Question 1

The Individual

Answer 1

• is the reservoir of genetic information
  ( each individual has unique genetic code)
  Is the unit of evolution

Question 2

DNA

Answer 2

An organisms cells contain identical strands
specific to the individual

Question 3

What is DNA composed of?

Answer 3

is composed of four different nucleotides arranged in an alpha helix
-A,C,T.G

Question 4

chromosomes

Answer 4

threadlike structures that contain DNA
* dont pass all of DNA to offspring

• come in matched pairs, one from each parent

Question 5

genes

Answer 5

(code for proteins)
- is organized into discrete subunits

Question 6

Tay-Sachs Disease

Answer 6

• The individual does not produce an enzyme (protein) called hexosaminidase A without which
  fatty tissue develops around nerve cells

Question 7

locus

Answer 7

particular location of a gene on a chromosome

Question 8

Alleles

Answer 8

• two or more alternative forms of a gene (code for particular trait)
  result from slight differences in the DNA sequence of the gene
  cause slight differences in form and function

Question 9

Heterozygote

Answer 9

– an individual that has different alleles at a particular locus on the pair of
chromosomes (Aa)

Question 10

Dominant and recessive

Answer 10

When one allele is expressed over another it is dominant, and the allele that is not expressed is
recessive
* blue eyed allele doesn’t produc epigment so if you have 1 gene that produces pigment your eye will be that colour
* everyone’s eye color is naturally blue

Question 11

Homozygote –

Answer 11

– an individual that has the same alleles at a particular locus on the pair of
chromosomes
-Dominant (AA)
-Recessive (aa)

Question 12

Explain tay sachs disease using dominant and recessive

Answer 12

A – codes for proper enzyme (protein)
• a – does not code for protein
• If AA, Aa → fine (at least one good copy of the gene)
• If aa → Tay-Sachs disease
* recessive condition is a result of not producing a functional protein

Question 13

Genotype

Answer 13

all the genetic characteristics of an individual (ie. Aa)
-encoded in the DNA
-FIXED during the life time of an individual
- “set of genetic instructions”
“all the genes, inherited gene from parents and don’t change

Question 14

Phenotype

Answer 14

= interaction of the genotype of an individual with its environment.
ex- blood types, diff gneotypes producing same phenotype

outward expression of genes in the physiology, appearance or behaviour of an individual

Responses of the individual to the environment may change
• In some cases Not Fixed during the lifetime of an individual
* put an organism in an enviroment with limited fppd= skinny lots of food= fat

Question 15

Mendelian Inheritance

Answer 15

breeding of two individuals results in multiple combinations of
alleles
• 1 allele present on each chromosome of a parent
• 1 chromosome (allele) is present in each gamete produced by a parent
• Gametes combine in offspring to form a new combination of alleles

Question 16

genetic recombination

Answer 16

all possible allele combinations from random mating of any combination of individuals in a population

Question 17

Mendelian Inheritance

Answer 17

• is how genetic variation is maintained

Question 18

phenotypic plasticity

Answer 18

: the ability of a genotype to alter its phenotypic expression under different
environmental conditions

Question 19

How can Phenotypic variation be expressed as

Answer 19

1. discrete
2. continous

Question 20

Discrete

Answer 20

alternative forms
e.g. Social insects – such as bees and ants
• two types of larvae hatch with essentially the same genetic material
Queens - adults that reproduce
Soldiers/workers – adults that defend the other larvae
* same genotype but diff phenotype
* colony of bees/ aunts all have the same genotype within same colony even though diff morphology

Characteristics controlled by a single gene (one copy inherited from each parent) tend to have phenotypes that fall into separate categories.

Question 21

Continuous

Answer 21

variations in form (continuously varying phenotypes)

Reaction norm = relationship between response of a continuously varying trait and
environmental conditions

1 genotype can result in many phenotypes

e.g. Daphnia – respond (pigmentation) to varying UV radiation
• level of pigmentation varies continuously in response to UV radiation and
predator abundance
* increased level of pigment protects them from uv radiation
* transparent daphnia- advantage is it helps protect from predators

Most characteristics are controlled by more than one gene and are described as being polygenic.

Polygenic characteristics have phenotypes that can show a wide range of values, with each value following on from the value before.

Question 22

level of pigmentation varies continuously in response to UV radiation and predation
predator abundance, is this an ex of evolution?

Answer 22

No b/c its an change on an indiv. basis

Question 23

The Population

Answer 23

: a group of individuals of the same species living together
Where the effects of evolution are observed

Question 24

Where can evolution occur?

Answer 24

• cant occur within an indivi.
• evolution only occurs within pop.

Question 25

Hardy-Weinberg Principle

Answer 25

the genetic composition (allele frequencies) within a population does not change (evolution does not occur) unless one of the following
assumptions are broken

Question 26

List the assumptions of the Hardy-Weinberg Principle

Answer 26

1. no mutations
2. no migration
3. large pop
4. random mating
5. no selection

Question 27

STATE ALL 5 ASSUMPTIONS and EXPLAIN how if each of the assumptions was broken evolution could occur according

Answer 27

No mutations
- Mutations result in a change in the DNA sequence of an organism
- For example genes could get deleted or substituted
- This would result in the creation of a new allele
- This mutation would then be passed on to future generations by reproduction
- If this assumption was broken a new allele would be introduced to a population resulting in a frequency of different alleles in a population
- This would result in evolution as the definition states “change in frequency of different alleles”

Random mating

If nonrandom mating were to occur this would mean that individuals would choose their mate based on certain genotypes/ phenotypes
This would not change allele frequencies but would change genotypic frequency which could lead to a change in allele frequencies over generations resulting in evolution

Large population size
- A small population means there is a higher chance that alleles are lost over generations whereas in a large population this is less likely to occur
- For example, in a small population with a small gene pool of just 4 alleles some alleles could get lost to the next generation due to chance events where in a large population this would not occur
- With a smaller population there is more likely a chance event to occur
- If alleles are lost, then evolution would occur as according to the definition there would be a change in allele frequencies over generations due to alleles being lost

No migration
- If migration to a population was to occur this would mean that individuals are leaving their population and new individuals are entering the population
- This would result in new alleles to be brought into populations or alleles to be taken away from that population
- If migration was to occur, in a population evolution could occur due to new alleles being introduced or taken away and resulting in different alleles in the population over generations due to mating

No selection
- If a certain allele is selected against this would mean that it would not be passed onto future generations
- This would alter the allelic frequency in future generation as certain alleles were being selected against and not being passed on resulting in change in allelic frequencies which is know as evolution