Genetics HL

Question 1

What is S phase of Interphase

Answer 1

DNA replication that will result in two chromosomes that contain two identical DNA strands

Question 2

What is S phase of Interphase

Answer 2

DNA replication that will result in two chromosomes that contain two identical DNA strands called sister chromatids. Held together by a centromere

Question 3

What happens to sister chromatids in meiosis II

Answer 3

Become independent chromosomes each made of a single DNA strand

Question 4

Meiosis Phases

Answer 4

Two divisions following the same pattern
Prophase, Metaphase, Anaphase, Telophase

Question 5

Meiosis I

Answer 5

reduction division (diploid → haploid) where chromosomes are separated
P-1: Chromosomes condense and the nuclear membrane breaks down. Homologous chromosomes form bivalent where they cross over

Question 6

Prophase I

Answer 6

Chromosomes condense and the nuclear membrane breaks down. Homologous chromosomes form bivalent where they cross over

Question 7

Metaphase I

Answer 7

Spindle fibres from opposing centrosomes connect to bivalent at the centromeres and align them along the middle of the cell

Question 8

Anaphase I

Answer 8

Spindle fibres contract and split at the bivalent and the homologous chromosomes move to opposite ends of cell

Question 9

Telophase I

Answer 9

Chromosomes condense and the nuclear membrane reforms. cell divides (cytokinesis) to form two haploid daughter cells

Question 10

Meiosis II

Answer 10

Separated the sister chromatids and are not identical during crossing over in prophase I

Question 11

Prophase II

Answer 11

Chromosomes condense and the nuclear membrane breaks down. Centrosomes move to opposite poles (perpendicular to before)

Question 12

Metaphase II

Answer 12

Spindle fibres from opposing centrosomes attach to chromosomes and align along equator

Question 13

Anaphase II

Answer 13

spindle contract and separate the sister chromatids. Now chromatids called chromosomes move to opposite poles

Question 14

Telophase II

Answer 14

Chromosomes decondense, nuclear membrane reforms, cells divide (cytokinesis) to form four haploid daughter cells

Question 15

What is the final product of meiosis

Answer 15

four genetically destinct haploid daughter cells

Question 16

independent assortment

Answer 16

how pairs of alleles separate independently from one another during gamete formation

Question 17

the inheritance of one trait is dependent to the inheritance of any other trait. True or false

Answer 17

False

it is independent

Question 18

How does Independent assortment come about

Answer 18

Random orientation of pairs of homologous chromosomes in meiosis I

Question 19

When will independent assortment not occur

Answer 19

if two genes are located on the same chromosome

Question 20

Synapsis

Answer 20

How homologous chromosomes become connected in prophase I. Connected by a protein-RNA

Question 21

bivalent

Answer 21

bi = two chromosomes

Question 22

autosomes always undergo synapsis during meiosis, sex chromosomes often remain unpaired. True or False

Answer 22

true

Question 23

Chiasmata

Answer 23

hold the homologous chromosomes together as a bivalent until anaphase I

Question 24

How do chiasmata form

Answer 24

1. non-sister chromatids break and recombine with their homologous partner (crossing over)
2. non-sister chromatids remain physically connected at these points of exchange

Chiasmata formation between non-sister chromatids can result in the exchange of alleles (recombination)

Question 25

Crossing over cannot increase genetic diversity. True or false

Answer 25

False

It can

Question 26

what does a large gene pool suggest

Answer 26

High amounts of genetic diversity increase the chances of biological fitness

Question 27

5 Mechanisms of Change

Answer 27

• Mutation
• Gene Flow
• Sexual reproduction
• Genetic Drift
• Natural Selection

Question 28

Population Bottlenecks

Answer 28

When a population side reduces by more than 50%. The surviving population has less genetic variability than before and will be subject to a higher level of genetic drift. As the newly developing gene pool will be divergent to the original

Question 29

Founder Effect

Answer 29

when a small group breaks away from a larger population to colonise a new territory. It does not have the same level of diversity and can result in more genetic drift. And as they increase in size the gene pool will not represent the original gene pool

Question 30

What are the three types of selection

Answer 30

Stabilising Selection
Directional Selection
Disruptive Selection

Question 31

Stabilising Selection

Answer 31

intermediate phenotype is favoured at the expense of both phenotypic extremes
- Remove extreme phenotypes and happens when environmental conditions are stable and competition is low

Question 32

Directional Selection

Answer 32

phenotypic extreme is selected at the cost of the other phenotypic extreme
- Clear shift in one direction the beneficial extreme
- Happens in response to gradual changes in environmental condition

Question 33

Disruptive Selection

Answer 33

both phenotypic extremes are favoured at the expense of the intermediate phenotypic ranges
- phenotypic distribution to deviate from the centre and results in a bimodal spread
- occurs when fluctuating environmental conditions
- Continued separation of phenotypic variants may eventually split the population into two distinct sub-populations

Question 34

Types of reproductive isolation

Answer 34

• Prezygotic isolation – occurs before fertilisation can occur (no offspring are produced)
• Postzygotic isolation – occurs after fertilisation (offspring are either not viable or infertile)

Question 35

Temporal Isolation

Answer 35

two populations differ in their periods of activity or reproductive cycles

Question 36

Behavioural Isolation

Answer 36

two populations exhibit different specific courtship patterns

Question 37

Geographic Isolation

Answer 37

two populations occupy different habitats

Question 38

Speciation

Answer 38

the evolutionary process that results in the formation of a new species from a pre-existing species. And occur when isolating mechanisms prevent two breeding organisms from producing fertile, viable offspring

Question 39

Two mechanisms can occur during speciation

Answer 39

• Allopatric speciation (geographical isolation)
• Sympatric speciation (reproductive isolation)

Question 40

Allopatric Speciation

Answer 40

when a geographical barrier physically isolates populations of an ancestral species

• two populations begin to evolve separately as a result of cumulative mutation, genetic drift and natural selection

Question 41

Sympatric Speciation

Answer 41

divergence of species within the same geographical location (no physical barrier)

• Results of reproductive isolation of two populations as a result of genetic abnormalities

Question 42

Polyploidy Offspring

Answer 42

viable and fertile but cannot interbreed with the original parent population

Question 43

what do fertile polyploid offspring require

Answer 43

two polyploid parents as reproduction with the original parent results I’m offspring with uneven amount of chromosome sets

Question 44

Phyletic Gradualism

Answer 44

continuous change

Question 45

Punctuated Equilibrium

Answer 45

Rapid change then stable