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Biology HL > Genetics 1.6, 3.3, 3.4, 10.1, 10.2 > Flashcards

Genetics 1.6, 3.3, 3.4, 10.1, 10.2 Flashcards

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1
Q

When does mitosis occur?

A
  • tissue repair
  • growth
  • embryonic development
  • asexual reproduction
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2
Q

How is the cell cycle divided?

A

Interphase: G1, S, G2, *G0
Division: mitosis and meiosis

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3
Q

What happens in S phase?

A
  • DNA replication
    • indicator for division
    • 2n + c —> 2n + 2c
  • chromatin = relaxed chromosome
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4
Q

What happens in growth phases?

A
  • G1: organelles are duplicating
  • G2: cell growth + preparation for mitosis
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5
Q

How do chromosomes condense?

A
  • condensation needed to pack DNA
  • DNA coils to make chromosomes shorter = supercooling
    • around histones
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6
Q

What happens at the end of G2?

A
  • centrosomes (perpendicular centrioles) duplicate
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7
Q

What happens in the prophase?

A
  • centrosomes move to opposite sides of the cell
    • mitotic spindle starts to form
  • nucleus disappears
    • nuclear membrane breaks down
  • DNA coils (very tightly) and separates into individual chromosomes (= metaphase chromosomes)
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8
Q

What happens in metaphase?

A
  • microtubules attach to centromeres
  • kinetochore — protein connected to microtubules (in centromere)
    • sends signals when cell is ready to split
  • microtubules are put under tension to test attachment
    • shortening attachment
  • chromosomes line at metaphase pate (cell equator)
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9
Q

What happens in anaphase?

A
  • centromeres divide
  • microtubules shorten
  • chromatids are separated and pulled to the opposite sides of the cell
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10
Q

What happens in telophase?

A
  • separated chromatids form a new nucleus
  • nucleolus and nuclear envelope reappears
    • chromosomes uncoil

Cytokinesis — cytoplasm divides

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11
Q

What is mitotic index?

A
  • ratio between cells undergoing mitosis and whole population
    • too high indicates cancerogenesis
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12
Q

What is the difference between plant and animal cell cytokinesis?

A
  • cytokinesis occurs when there are 2 nuclei (telophase)
In animals
- plasma membrane pulled inwards 
	- cleavage furrow 
- accomplished by ring of contractile protein inside plasma membrane 
- pinches apart 
In plants
- vesicles move to the equator 
	- fuse and form tubular structures 
- 2 layers of membrane formed 
- by exocytosis cells receives pectins
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13
Q

What are cyclins?

A
  • proteins that control cell cycle
    • activating cyclin dependent kinase enzymes (CDK)
  • different types of cyclins activating different CDKs
  • right concentration of cyclins reached → cell to the next stage
  • decreases cancer risk
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14
Q

What are CDKs?

A
  • enzymes activating proteins into the new stage of cell cycle
  • phosphorylation
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15
Q

How is cycle regulated?

A
  • growth hormones, proteins stimulating quicker division
  • checkpoints
    • G1: nutrients, growth factor and DNA damage
    • G2: cell size
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16
Q

What are carcinogens?

A
  • chemicals and agents that cause cancer
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17
Q

What is a tumour?

A
  • abnormal group of cells developing at any stage of life
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18
Q

What are mutagens?

A
  • set of genes that causes cancer → mutagens
  • radiation (UV, X-ray)
    • ionising nucleotides in DNA → switch into different nucleotide
  • chemicals
    • cigarettes ingredients (nitrosamines), metals (As, Ni)
    • alcohol increases cell division
      • destroys cells which have to recover = higher possibility of mutation
  • viruses (HPV, HepC virus)
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19
Q

What are protooncogenes and oncogenes?

A
  • mutated gene may become oncogene (cancerous gene)
  • stimulates cell division and inhibit cell differentiation
  • oncogene = protooncogene gains potential to cause cancerogenesis
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20
Q

What are different types of tumours?

A
  • primary — place in which it occurred first (organs, tissue)
  • metastasis = movement of cells from primary tumour to set up secondary
  • metastatic tumour — moves onto different tissues (affects multiple organs)
    • increased risk of mutation = cancer change
  • secondary — place in which cancer develops after moving
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21
Q

What is the difference between mitosis and meiosis?

A
  • mitosis creates two diploid cells
  • meiosis creates four haploid cells
22
Q

What is sexual and asexual reproduction?

A
  • sexual = differences between offsprings and parents chromosomes
  • asexual = the same chromosomes in parents and children
23
Q

What is fertilisation?

A
  • union of sex cells (gametes) from 2 different parents
24
Q

What happens in prophase I?

A
  • homologous chromosomes form pairs = bivalents
    • before condensation
    • process called synapsis
    • protein structure - synaptonemal complex connects chromosomes
  • crossing over
    • 2 new chromosomes (mix of parent chromosomes) → genetic variety
  • microtubules attach to different chromosomes (instead of chromatids)
    • disjunction = separation of bivalent chromosomes
25
Q

How do chromosomes cross over?

A
  • in non sister chromatids junction is created
    • chromatid breaks and rejoins with the non sister
      - connection points called chiasmata
    • later slides down the bivalent to separate chromosomes
  • random, at least 1
  • new allele combination are produced
    • recombination
26
Q

How are chromosomes orientated before meiosis?

A
  • randomly
  • spindle microtubules attach to each centromere
    • a whole chromosome is pulled to one pole
  • orientation = the way the pair of chromosomes is facing
    • orientation of 1 bivalent, doesn’t affect the others
27
Q

What are methods used to obtain cells for karyotype analysis?

A
  • amniocentesis = passing needle through abdomen wall of a woman
    • using ultrasound
    • amniotic fluid taken (has fetal cells)
  • chorionic villus sampling = obtaining cells through chorion (membrane from which placenta develops)
  • risks of miscarriage
    • 2% chorionic villus
    • 1% amniocentesis
28
Q

What creates genetic diversity?

A
  • random orientation
    • 2^23
  • crossing over
    • increases number of allele combinations
29
Q

Why is fusion important?

A
  • new life
  • alleles from different individuals into one new individual
  • fusion of gametes = genetic variation of species
  • genetic variation essential for evolution
30
Q

What is the law of segregation?

A
  • one allele to every gamete (equal chances)
31
Q

What is the law of independent assortment?

A
  • pairs of alleles are sorted out independently
    • orientation of chromosomes is random and independent
    • determines which allele will move where
32
Q

What is the principle of dominance?

A

There are dominant and recessive alleles

33
Q

What is a non-disjunction?

A
  • disjunction — the act of being disjoined or disjoining
  • when non-disjunction occurs, the homologous pairs are not split
    • unequal number of chromosomes
  • diseases connected:
    - Trisomy (3 chromosomes) 21 → Down’s syndrome
    - Trisomy 18 → Edward’s syndrome
    - XXY → Klinefertel’s syndrome
    - X → Turner’s syndrome
  • the older the parents are, the more likely is a disjunction happening
34
Q

What was the procedure in Mendel’s experiment?

A 
- reproducing plants with the same phenotype (self-pollination)
- crossing different plants 
	- transferring male pollen to female
	- P x P —> F1
- reproducing offsprings
	- F1 x F1 = F2  
	- observing characteristics
35
Q

What are gametes and zygotes?

A
  • fuse together to create zygote
  • male gametes < female gametes
    • equal contribution of mother and father
36
Q

What are co-dominant alleles?

A
  • both alleles have affect on phenotype
  • example: M. jalapa
    • red and white flower = pink
37
Q

How are blood types distinguished?

A
  • blood groups = co-dominance
  • antigens present on red blood cells
    • A = antibodies B
  • alleles A and B are dominant ABO recessive
    • production of glycoprotein
      • A adds acetylgalactosamine
      • red blood cells have antigen A
  • in AB group neither antibodies are produced
  • group O produces basic glycoprotein
38
Q

Which alleles cause genetic diseases?

A
  • mostly recessive
  • one can be carrier but not ill
  • some can be caused by dominant or co-dominant or sex-linked
39
Q

What is cystic fibrosis?

A
  • recessive genetic disease
    • allele of CFTR gene
  • gene product are chloride channels
    • sweat, mucus
  • mutation = too much NaCl in sweat and too little in mucus and digestive juices
  • osmosis is not proper → viscous
    • sticky mucus in lungs
40
Q

What is Huntington’s disease?

A
  • dominant allele disease
  • mutation of HTT gene
    • gene produces huntingtin
    • degenerative changes in brain
      • thinking, emotions problems
41
Q

How are diseases inherited on sex-linked genes?

A
  • Morgan in D. melanogaster (fruit fly)
    • some male had white eyes (w)
    • female only red-eyed (w+)
    • sex-linkage because the allele is on chromosome X
42
Q

What are examples of sex-linked diseases?

A 
Red-green colour-blindness
- recessive allele of gene for a photoreceptor proteins on X chromosome 
	- detect wavelengths of light
- male with recessive gene → affected 
- female could be a carrier 
Haemophilia
- X chromosome
- inability to make Factor VIII 
	- proteins needed to clot blood 
- life expectancy = 10 yo (if untreated)
43
Q

Why are genetic diseases rare?

A

There’s a small likelihood that both parents will have the recessive gene and that the child will receive both e alleles.

44
Q

What are the consequences of radiation after nuclear bombing?

A
  • cancer
  • mutations causing stillbirths, malformation and death
  • stigmatisation
Chernobyl
- death of nature around
- thyroid gland collects iodine 
	- radioactive iodine causes cancer
45
Q

What is gene linkage?

A
  • genes on the same chromosome
  • more likely to occur together (than if they were unlinked)
  • disproves Mendelian theory
46
Q

On what does crossing over depend?

A
  • the closer to each other on the chromosome the 2 genes are (2 different traits), the less likely the chiasmata formed between them
  • random places
    • the smaller the distance the lower chance
47
Q

What are types of genetic variations?

A
  • discrete
    • blood type
    • no in between types
  • discontinuous
48
Q

What is continuous variation?

A
  • a lot of genes affect the same trait
  • number of genes increases
    • distribution comes close to normal distribution
    • height, intelligence
  • polygenic inheritance
49
Q

How can polygenic inheritance be influenced by environment?

A
  • skin colour
    • sunlight stimulates production of pigment melanin
  • nutrition received
  • in cats: temperature (colour of fur)
50
Q

What is chi square?

A
  • statistical test
  • compares observed to expected values

Biology HL (14 decks)

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