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IB Biology 22-24 > Topic 10: Genetics and Evolution (Notes) > Flashcards

Topic 10: Genetics and Evolution (Notes) Flashcards

1
Q

Purpose of mitosis

A
  • To separate the genome and produce two daughter cells identical to the parent cell
  • Required for growth, repair, asexual reproduction
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2
Q

Purpose of meiosis

A
  • To create gametes/sex cells
  • Allows production of four genetically distinct haploid daughter cells from a diploid parent cell
  • Used to fulfill specialization (e.g. sperm cells -> sperm production)
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3
Q

Define synapsis

A

When two homologous chromosomes align alongside each other

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4
Q

Define homologous chromosomes

A

A set of one maternal and one paternal chromosome

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5
Q

Define bivalent

A

Composed of two chromosomes

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6
Q

Define tetrad

A

Composed of four chromatids

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7
Q

Define crossing over

A

The exchange of DNA material/DNA material between non-sister homologous chromatids

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8
Q

Explain the process of crossing over

A
  • Prophase I: Homologous chromosomes pair up, in close proximity
  • Non-sister chromatids get entangled and cross over
  • Entanglement places stress on DNA molecules
  • A section of chromatids from one chromosome may break and re-join with chromatid from other chromosome
  • Catalyzed by endonuclease and DNA ligase
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9
Q

Define recombination and recombinant

A

Recombination

  • Process involving breaking and re-joining of DNA to create new combinations of genetic information

Recombinant

  • Chromosomes that exchanged DNA through breaking and re-joining of DNA
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10
Q

Define chiasma

A

Crossing point of DNA strands, developing an X-shaped join

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11
Q

Why are there an infinite range of DNA combinations during crossing over?

A
  • Random nature of how chromatids align and where they break
  • No two individuals will have exactly the same genotype (except identical twins)
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12
Q

What happens in meiosis I?

A

Homologous chromosomes separate

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13
Q

Explain prophase I

A
  • DNA replicated and condensed, visible as chromosomes
  • Each chromosome has two sister chromatids joined by a centromere
  • Chromosomes arranged side-by-side in homologous pairs
  • Centrioles migrate to opposite poles, form spindle
  • Nuclear envelope breaks down, nucleolus disintegrates
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14
Q

Explain metaphase I

A
  • Bivalents line up along spindle equator
  • Spindler fibers attach to centromeres
  • Bivalents line up by independent assortment (random orientation)
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15
Q

Explain anaphase I

A
  • Homologous pairs separated
  • Microtubules pull whole chromosomes to opposite ends of spindle
  • Centromeres do not split
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16
Q

Explain telophase I

A
  • Chromosomes arrive at opposite poles
  • Spindle fibers start to break down
  • Nuclear envelopes form around two groups of chromosomes, nucleoli reforms
  • Some plants go straight to meiosis II without nucleus reformation
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17
Q

Why is meiosis I reduction division?

A
  • Homologous chromosomes separate and move to opposite poles of the cell
  • No. of chromosomes per cell reduced by factor 2
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18
Q

Define independent assortment/random orientation

A
  • Production of different allele combinations in gamete cells
  • Due to metaphase I: random alignment of homologous pairs along the equator of spindle
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19
Q

Explain prophase II

A
  • Nuclear envelope breaks down
  • Chromosomes condense
  • Spindle forms at right angle to old ones
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20
Q

Explain metaphase II

A
  • Chromosomes line up in single file along equator of spindle
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21
Q

Explain anaphase II

A
  • Centromeres divide
  • Individual chromatids pulled to opposite poles
  • Sister chromatids separate
  • Creates four groups of chromosomes with half the number of parent cell chromosomes
22
Q

Explain telophase II

A
  • Nuclear membranes form around each chromosome group
23
Q

Explain telophase II

A
  • Nuclear membranes form around each group of chromosomes
  • Followed by cytokinesis: cytoplasm divides as new cell surface membranes form to create four haploid cells
24
Q

Define unlinked genes

A

Genes of an organism carried on separate chromosomes, not on homologous copies

25
Q

Define monohybrid cross

A

How alleles of one gene transfers across generations

26
Q

Define dihybrid cross

A
  • How alleles of two genes transfer across generations
  • For double-heterozygous dihybrid crosses, expect 9:3:3:1 phenotypic ratio
27
Q

Define loci

A
  • The specific linear position on the chromosomes that genes occupy
  • Sex-linked if gene is on sex chromosome
28
Q

Define sex-linked

A
  • Only affects one gender of a species
  • Usually on X chromosome because Y chromosome contains fewer genes
  • E.g. color-blindness and hemophilia affects mostly males
29
Q

Define autosomal linkage

A
  • Linked genes on chromosomes 1-22, not on sex chromosome
  • Not all genes assort independently
30
Q

Define interspecific and intraspecific variation

A
  • Variation: the way organisms differ from one another
  • Interspecific: Occurs between species
  • Intraspecific: Occurs within the same species
31
Q

Define discrete variation

A
  • Individuals fall into clear-cut categories, no in-between
  • Occurs due to genetic factors
  • E.g. human blood groups
32
Q

Define continuous variation

A
  • Two or more genes affect the final characteristics
  • Occurs due to interaction between genetics and environment
  • E.g. height, determined by bone length, hormones, diet, etc.
33
Q

Define gene pools

A
  • Consists of all genes and different alleles in an interbreeding population
  • Multiple gene pools can exist (geographically isolated)
34
Q

Define allele frequencies

A
  • Relative abundance of alleles for a particular gene
  • Formula: No. of times allele of interest observed divided by Total no. of all alleles
35
Q

Outline conditions of a stable gene pool

A
  • Large population
  • Equal chance of mating
  • Random matings
  • No selective pressure based on phenotype
36
Q

Define evolution

A

Cumulative change in the heritable characteristics of a population

37
Q

Outline factors for evolution

A
  • Mutation: causes new alleles to form
  • Selection pressures: favor certain alleles and oppose others
38
Q

Define directional selection

A
  • Population changes towards one extreme (better adapted)
  • Happens with environmental changes
39
Q

Define stabilizing selection

A
  • Selects in favor of the average individual
  • Happens in stable environmental conditions
  • Favor individuals with advantageous alleles
  • Discards extreme phenotypes
  • Works mostly on polygenic traits, when characteristics influenced by >=2 genes
40
Q

Define disruptive

A
  • Selects against the average individual
  • Can cause speciation and forms new species
41
Q

Define reproductive isolation

A

Isolated from peers due to barriers, preventing inter-breeding

42
Q

Define temporal reproductive isolation

A
  • reproductive cycles at different times (seasonal)
  • e.g. changes in flowering patterns
43
Q

Define behavioral reproductive isolation

A
  • Different rituals or behavioral patterns
  • e.g. courtship and mating rituals
44
Q

Define geographical reproductive isolation

A
  • Natural or man-made barriers between populations
  • e.g. rivers, mountains
45
Q

Define sympatric

A
  • temporal and behavioral speciation
  • separately-developed species coexist in the same geographical location
46
Q

Define allopatric

A

Two separate species diverge with complete spatial separation

47
Q

Define speciation

A

The emergence of new and distinct species, reproductively isolated

48
Q

Explain the theory of gradualism speciation

A
  • Culmination of small changes over time
  • Darwin observed vestigial structures in fossil records
  • observable characteristics with no apparent function
  • residual parts from ancestors, e.g. human appendix
49
Q

Explain the theory of punctuated speciation

A
  • abrupt speciation
  • long periods without appreciable change, short rapid evolution
  • Bateson observed sudden mass extinctions from cataclysmic events
  • survivors restart reproduction with reduced gene pool (founder effect)
50
Q

Define polyploidy

A
  • when an organism has more than two sets of homologous chromosomes
  • results from chromosomal mis-events e.g. mitosis or meiosis abnormalities
  • e.g. egg fertilized by more than one sperm, failure of chromosomes separation in meiosis I
  • can form diploid gamete and fertilize with haploid gamete to produce fertile offspring

IB Biology 22-24 (13 decks)

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