Voice of the genome Flashcards by Sophie Blue

Structural differences between prokaryote and eukaryote cells

Circular DNA; linear DNA
Pili; no pili
70S ribosome; 80S ribosome
No nucleus; nucleus
Plasmid; no plasmid
Capsule; no capsule

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How proteins are made and transported out of the cell

Proteins produced by ribosomes
Folded in ER
Packaged in vesicles to Golgi apparatus
Vesicles fuse with Golgi apparatus
Proteins modified in Golgi apparatus and packaged in vesicle
Vesicle fuses with cell membrane
Exocytosis

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Sperm adaptation

Flagellum: movement by rotating
Acrosome: contains enzymes for digesting zona pellucida
Mitochondria: provide energy for flagellum

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Ovum adaptation

Follicle cells: release enzymes to attract sperms
Zona pellucida: thickens to prevent polyspermy
Lysosomes: release enzymes to thicken zona pellucida

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Genetic variation reasons

Independent assortment
Crossing over

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Stages in mitotic cell division

Interphase
Mitosis
Cytokinesis

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Interphase stages and function

G1: synthesis of new organelles and cell growth
S: DNA replication
G2: synthesis of new organelles and cell growth

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Prophase events

Chromosomes condense
Microtubules form spindle
Centrioles move to opposite poles
Spindle fibres form
Nuclear envelope breaks down
Nucleolus disappears

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Metaphase events

Chromosomes line up at equator of the cell
Centromeres attach to spindle fibres

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Anaphase events

Spindle fibres shorten, pulling sister chromatids apart to opposite poles
Spindle breaks down

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Telophase events

Chromosomes decondense
Nuclear envelope reforms around each group of chromosomes

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Cytokinesis events

Cell surface membrane constricts around centre of cell
Plant cell: cell plate synthesised between the two new cells

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Stem cell definition

Undifferentiated
Keep dividing (no Hayflick limit)
Give rise to specialised cells
Replace damaged cells

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Totipotent, pluripotent, multipotent meaning

Any cell type
Most cell type
Some cell type

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Embyronic stem cell issues

Ethical issue (kill embryo)
Rejection by immune system
Costly
Difficult

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Therapeutic cloning/somatic cell nuclear transfer meaning

Diploid cell nucleus removed
Ovum nucleus removed
Diploid cell nucleus fused with ovum
Cell undergoes mitosis to blastocyst
Stem cells isolated

Epigenome definition

DNA, histones and chemical markers

2 ways to prevent transcription

Methylation so RNA polymerase cannot bind
Modify histones to affect how tightly it is wound

Differential gene expression meaning

Genes can be switched on and off/expressed

Consequence of differential gene expression

Stimulus detected (hormone, environment)
Genes expressed/switched off
mRNA from expressed genes is produced and translated
Protein synthsised
Proteins permanently modify cell
Cell becomes specialised

Causes for switching on/off genes

Protein repressor molecules attach to DNA of promotor region
Protein regulator (starts transcription) cannot attach
Protein repressor molecules attach to protein regulators, preventing them from attaching

FOP cause

Gene mutation
Genes for making proteins for bone cell is not switched off in white blood cells
When tissue is damaged, white blood cells move to site of damage
Protein produced, diffusing into muscle cells
Muscle cells turn into bone cells

Level of organisation in organisms

Cell
Tissue
Organ
Organ system

Phenotype and genotype definition

Characteristics of organism resulting from interaction of the organism with environment and genotype
All the alleles of an organism

Polygenic definition

More than one gene involved in inheritance of a characteristic Continuous variation

Multifactorial definition

Several genetic factor and environmental factors are involved

How melanin is made in skin

Exposure to UV light MSH is produced MSH receptors form on surface of melanocytes Melanin is produced and placed into melanosomes Melanosomes collect around nucleus of skin cell to protect it from UV light damage

Why only ears, paws and tail of Himalayan rabbit is dark

Mutant alleles for tyrosinase, which changes amino acid tyrosine into melanin Tyrosinase made is unstable and inactivated at normal body temperature Ears, paws and tail are cooler than body temperature Tyrosinase active, melanin produced there

Diet affects epigenome in mice

Agouti gene is normally methylated, leading to brown healthy mice When agouti gene is expressed, agouti protein bind to MSH receptors and prevents production of melanin Caused by lack of methyl in diet Agouti protein binds to receptors in brain area involved in feeding bahaviour Mice become obese and yellow

Behaviour causes change in epigenome in rats

GR gene prevents stress Methylated GR gene leads to stressed rats Licking and grooming activates GR genes Good mother with anxious pups: high licking and grooming, leads to activation of GR gene, so the pups are calm Bad mother with good pups: low licking and grooming, leads to methylation of GR gene, so the pups are stressed

Cause of cancer

When rate of cell multiplication is faster than the rate cell death Tumour growth Usually caused by damage to DNA

Oncogene's role in cancer

Code for proteins that stimulate transition from one stage to the next in mitosis Less methylation causes cell cycle to be always active More mitosis

Tumour suppressor gene's role in cancer

Produce suppressor proteins that stop the cycle More methylation causes cell cycle to have no brake on mitosis

Environmental factors for cancer

Smoking UV light Diet Virus infection