Milk and Mammalian Topic Flashcards
(127 cards)
1
Q
Why is milk used as a case study in this course?
A
Because it helps illustrate genetic and biochemical pathways from production in animals to human digestion and potential disorders.
2
Q
What makes genetic modification in mammals more ethically complex than in crops or microbes?
A
It involves stricter ethical and welfare considerations, especially in relation to food safety and animal well-being.
3
Q
What is a mutation and why is it significant in genetics?
A
A mutation is a change in the DNA sequence; even a small change can result in major differences in protein function or organism traits.
4
Q
What is SNP (Single Nucleotide Polymorphism) used for in genomics?
A
To identify genetic differences among individuals, especially for traits like disease resistance or allergenic response.
5
Q
How can SNPs be used in livestock genetics?
A
By analyzing DNA across a herd, researchers can find regions of genetic variation and relate them to observable traits (phenotypes).
6
Q
What are some practical and ethical considerations in mammalian genetic research?
A
ncludes animal welfare, food safety, regulatory approval, and public trust—particularly when modifying animals for food.
7
Q
What is the significance of studying allergenic components of milk genetically?
A
To potentially identify and modify genes responsible for producing allergenic proteins.
8
Q
Why is it important to focus on key ideas rather than technical detail at this level?
A
To build understanding of core concepts that relate to real-world applications in food systems and health.
9
Q
What disorders are associated with milk consumption that have a genetic basis?
A
Lactose intolerance and milk protein allergies.
10
Q
Why are SNPs important in genomics ?
A
SNPs are single base pair changes in DNA used to track genetic variations and link to traits
11
Q
How can SNP analysis help in animal genetics?
A
By identifying genetic differences tied to desirable traits like milk yield, disease resistance, or allergenicity.
12
Q
What is a mutation in a genetic context?
A
A change in the DNA sequence that can result in altered proteins and observable traits.
13
Q
How do genetic mutations affect proteins?
A
Even a small change in the amino acid sequence can significantly alter protein function or expression.
14
Q
What is the role of genes in protein production?
A
Genes carry the instructions for synthesizing proteins, which are responsible for traits and biological functions.
15
Q
How can genes be manipulated to alter food properties?
A
Through techniques like gene editing or selection, specific genes can be modified to produce different or safer proteins.
16
Q
What ethical concerns arise in mammalian genetic modification?
A
Concerns include animal welfare, long-term effects, and regulatory issues—more complex than with plants or microbes.
17
Q
Why is genetic engineering more tightly regulated in mammals than in crops?
A
Due to ethical, welfare, and biological complexity, especially when used for food production.
18
Q
What sugar is primarily found in milk?
A
Lactose
19
Q
What enzyme breaks down lactose in the small intestine?
A
lactase
20
Q
into which two sugars does lactase break lactose?
A
Glucose and galactose.
21
Q
Do all infant mammals produce lactase?
A
Yes, to digest their mother’s milk
22
Q
What happens to lactase production in most mammals after weaning?
A
It decreases or stops, causing lactose intolerance.
23
Q
What symptoms can lactose intolerance cause?
A
Bloating, gas, cramps, and diarrhoea due to undigested lactose fermented by gut bacteria.
24
Q
Which species is unique for some adults continuing to digest milk?
A
Humans.
25
What term describes adults who can digest lactose?
Lactase persistent.
26
What cultural development likely influenced lactase persistence?
Animal domestication and dairy consumption.
27
What is this an example of in evolutionary biology?
Gene-culture co-evolution.
28
Does lactase persistence result from changes in the lactase gene coding region?
No, it's due to changes in regulatory DNA ("switches").
29
What specific genetic change is linked to lactase persistence?
A T instead of a C in a non-coding region near the lactase gene on chromosome 2.
30
What is the inheritance pattern of lactase persistence?
It’s genetically regulated, not purely Mendelian, involving regulatory elements.
31
Name one natural milk product that contains less lactose.
Yogurt (due to fermentation into lactic acid).
32
Name three biotechnological solutions for lactose intolerance.
Exogenous lactase enzyme supplements.
Probiotics/prebiotics/symbiotics.
Lactose-free or plant-based milk alternatives (e.g., soy, almond).
33
What is the difference between digestion and metabolism?
Digestion breaks down food; metabolism uses the absorbed nutrients for energy and function.
34
What is galactosemia?
A metabolic disorder where galactose cannot be adequately broken down.
35
What causes galactosemia?
A deficiency in enzymes needed to metabolize galactose, usually due to autosomal recessive inheritance.
36
What is the risk of having an affected child if two carriers have children?
25% chance of an affected child, 50% carrier, 25% unaffected.
37
What is an autosomal recessive trait?
A trait expressed only when two copies of a defective gene (one from each parent) are inherited.
38
Is galactosemia a dominant or recessive disorder?
Autosomal recessive.
39
How are autosomal recessive disorders inherited?
Both parents must be carriers; each child has a 25% chance of being affected per conception.
40
Why is each child's genetic outcome independent in autosomal recessive inheritance?
Each conception involves independent assortment and recombination of genes.
41
What causes classic galactosaemia?
Mutation in the GALT gene leading to deficient galactose-1-phosphate uridyltransferase.
42
What is the main consequence of galactosaemia?
Accumulation of galactose-1-phosphate causing toxicity and metabolic complications.
43
How is galactosaemia managed?
Lifelong galactose-restricted diet (e.g., plant-based or lactose-free milk).
44
What is cow's milk protein allergy (CMPA)?
An immune reaction to milk proteins, mainly beta-lactoglobulin and casein.
45
What are strategies to reduce milk allergenicity?
Heat treatment, enzymatic hydrolysis, and genetic modification (e.g., gene knockout).
46
How has gene editing advanced dairy production?
Enables production of hypoallergenic milk and high-yield animal breeds.
47
What is artificial selection?
Human-directed breeding to enhance desirable traits (e.g., sweetness in corn).
48
Name 3 ethical concerns in gene editing of animals or humans.
Compromised animal welfare
Disruption of ecosystems/food chain
Creation of genetically constrained individuals (loss of consent/autonomy)
49
What is Terminator Technology in crop genetics?
Genetic modification that makes harvested seeds sterile, forcing farmers to repurchase seeds each season.
50
Why is Terminator Technology controversial?
It threatens seed independence and biodiversity while protecting corporate genetics.
51
What are major ethical issues in genome editing?
Consent, irreversible genetic changes, harm to biodiversity, and socioeconomic inequality.
52
Why was the first gene-edited human embryo case controversial?
it bypassed ethical approvals, lacked transparency, and led to the scientist's imprisonment.
53
How can pest-resistant GM crops affect ecosystems?
They may unintentionally harm non-target species like bees and butterflies, disrupting biodiversity.
54
What is Neuralink, and what ethical concern surrounds it?
A brain-computer interface by Elon Musk; concerns include animal welfare and informed consent.
55
How can rapid genetic growth in animals raise welfare issues?
It may lead to pain, deformities, or poor mobility (e.g., broilers with leg problems).
56
What’s the risk of breeding disease-resistant animals?
Neglected hygiene or management due to false sense of immunity.
57
What global risks are associated with unregulated gene editing?
Bio-weapon development, lab leaks (e.g., COVID-19 theories), and loss of public trust.
58
Why is non-coding DNA significant in genetics?
It influences epigenetics and inheritance without altering coding DNA sequences.
59
What drives most innovations in genome technology?
Global needs: food security, allergy reduction, disease resistance, biodiversity conservation.
60
What is the equation representing phenotype ?
P=G+E ( phenotype = genetics + environment )
61
What is a gene environment interaction?
When environmental factors influence gene expression, often through mechanisms like epigenetics
62
What are mendelian traits ?
Traits controlled by a single gene
63
What are polygenic traits ?
Traits controlled by many genes, often affected by the environment
64
How does selective breeding improve traits ?
By choosing animals with desirable phenotypes to breed, improving the trait over generations
65
What are the main components of milk ?
Lactose, fat, protein, water, vitamins, minerals
66
What is the only organ that produces lactose ?
The lactating mammary gland
67
What are the two sugars that make up lactose ?
Glucose and galactose
68
Which milk components are influenced by genetics?
Casein proteins, enzymes, fat synthesis (via gene-regulated pathways in mammary epithelial cells).
69
Which milk components are influenced by diet/environment?
fatty acid profile, lactose content (through glucose availability), some minerals/vitamins.
70
What are the major energy sources for milk production in cows?
Glucose (for milk), acetate (for the cow’s body).
71
What are VFAs (Volatile Fatty Acids) and their roles?
Acetate (milk fat synthesis), propionate (glucose/lactose synthesis), butyrate (energy).
72
What happens to lactose and proteins during digestion?
Lactose is broken down by lactase into glucose and galactose; proteins are digested by pepsin and trypsin into amino acids.
73
How is milk fat digested and used in the body?
Lipase breaks fat into fatty acids and glycerol, which are used for energy or stored as fat.
74
What happens to excess energy from milk?
It's stored as glycogen or fat through processes like gluconeogenesis and lipogenesis.
75
Does dairy fat increase heart disease risk?
Recent studies suggest dairy fat has a neutral or slightly beneficial effect on cardiovascular health.
76
How can genetics influence milk allergen content?
Variants in milk protein genes can reduce allergens like β-lactoglobulin.
77
Why is milk yield considered a polygenic trait?
It's controlled by multiple genes, each contributing to overall production.
78
How are genes linked to milk yield identified?
Through genome-wide association studies (GWAS) comparing DNA sequences and milk records.
79
Why use mice in milk gene studies?
Their cells can mimic milk production, helping link nutrients, genes, and output.
80
What influences gene expression beyond DNA sequence?
Epigenetic factors and environmental conditions like diet.
81
How can we alter milk quality through diet or genetics?
Genetics mainly influences proteins; feeding strategies impact fat composition.
82
What is the food science definition of milk?
Milk is an aqueous solution of proteins, lactose, minerals, and vitamins, carrying emulsified fat globules and a colloidal dispersion of casein micelles.
83
Which milk components are dispersed rather than dissolved?
Fat globules and casein micelles are dispersed in the aqueous phase.
84
Which components are dissolved in the aqueous (serum) phase?
Whey proteins, lactose, and about half of the mineral content.
85
What is "milk plasma"?
Milk plasma is milk with the fat removed.
86
What is the "serum phase"?
The aqueous portion of milk where water-soluble constituents are dissolved.
87
What are the major solids in milk and their approximate mass percentages?
Water: ~87%
Fat: 3.5–3.9%
Protein: ~3.4%
Lactose (Carbohydrate): ~4.4%
Minerals (Ash): ~0.7%
88
What is the typical diameter of fat globules in milk?
2 to 10 microns.
89
What is the diameter of casein micelles?
20 to 200 nanometres.
90
What are the three major macronutrients in milk?
Fats, proteins, and carbohydrates.
91
What vitamins are present in milk?
Milk contains all essential vitamins, but not all in significant dietary amounts.
92
What can affect the vitamin content in milk?
Breed of cow, feed composition, and milk type (e.g., whole vs. semi-skimmed).
93
Why must nutrient tables be critically evaluated?
Because errors may occur during data conversion, and nutrient values vary by source, processing, and milk type.
94
What is a more realistic value for folate in breast milk per 100ml?
Approximately 14.1 micrograms per 100ml.
95
According to the European Milk Forum, what role does dairy play in nutrition?
It significantly contributes to both macronutrient and micronutrient intakes in European adults.
96
What’s the difference in nutrient contribution between whole and semi-skimmed milk?
Whole milk provides more fat-soluble vitamins; semi-skimmed has less fat but retains most other nutrients.
97
What is lactose and where is it found?
Lactose is a disaccharide made of glucose and galactose linked by a β(1→4) glycosidic bond. It's almost unique to milk.
98
What is mutarotation and why is it important?
Mutarotation is the interconversion between α and β forms of sugars in solution. In lactose, the glucose part mutarotates, affecting solubility and crystallisation.
99
What are the solubilities of α- and β-lactose?
α-lactose: ~7 g/100 g water
β-lactose: ~50 g/100 g water
Both equilibrate to ~17 g/100 g due to mutarotation.
100
Why does lactose cause caking in milk powder?
Amorphous lactose in powders can absorb moisture and crystallise into α-lactose monohydrate, forming hard clumps (caking).
101
Is lactose a reducing sugar?
Yes. Its free aldehyde group can reduce copper ions (Cu²⁺ → Cu⁺), forming a red precipitate.
102
Role in food processing?
Lactose promotes Maillard browning in baked goods. It's not metabolised by yeast, so it stays available during baking.
103
What causes lactose intolerance?
loss of the enzyme lactase, which breaks lactose into glucose and galactose. Undigested lactose is fermented in the gut, causing discomfort.
104
What is the main lipid in milk?
Triacylglycerol (TAG) – makes up the majority of milk fat.
105
What surrounds the fat droplets in milk?
The Milk Fat Globule Membrane (MFGM) – a triple-layered membrane made of phospholipids and proteins.
106
What type of emulsion is milk?
Milk is an oil-in-water emulsion – fat globules are dispersed in the continuous aqueous phase.
107
What are typical diameters of milk fat globules?
Raw milk: ~0.2 to 15 µm (average 2–10 µm)
Homogenised milk: ~0.2 to 2 µm (smaller and more uniform)
108
What is the role of the MFGM?
Reduces interfacial tension
Allows stable dispersion of fat in water
Contains bioactive lipids and proteins with possible health benefits
109
Where do milk fat globules originate?
They form in mammary secretory cells, first coated by the ER membrane, then enveloped by the plasma membrane as they are secreted.
110
What lipids are found in milk besides TAGs?
Phospholipids (in the MFGM)
Cholesterol
Free fatty acids
Glycolipids
111
What is the major lipid in milk?
Triacylglycerol (TAG) – composed of a glycerol backbone and 3 fatty acids.
112
How many fatty acids are in cow's milk?
Over 200, but only 20 are major ones.
113
Name the major fatty acids in cow’s milk.
Palmitic acid (C16:0)
Stearic acid (C18:0)
Oleic acid (C18:1)
Myristic acid (C14:0)
Capric acid (C10:0) (notable in goat’s milk)
114
What is the melting range of cow's milk fat?
-40°C (solid) to +40°C (liquid) – due to its wide range of fatty acid chain lengths.
115
What positions do fatty acids occupy on the TAG glycerol backbone?
Short-chain: Mainly at SN-3
Medium-chain: Often at SN-1
Long-chain: Prefer SN-2
(Not a random distribution)
116
What enzymes digest milk TAGs and where do they act?
Gastric lipase: SN-3 position (stomach)
Pancreatic lipase: SN-1 and SN-3 positions (small intestine)
117
Why are short and medium chain fatty acids absorbed faster?
They’re directly absorbed into the portal vein and sent to the liver, unlike long-chain fatty acids.
118
What are the three main sources of fatty acids in ruminant milk fat?
Diet (e.g., grass)
Microbial action in the rumen
De novo synthesis in the mammary gland
119
What are conjugated linoleic acids (CLAs), and where do they come from?
They are biohydrogenated products of unsaturated C18 fatty acids (e.g., rumenic acid) with potential health benefits.
120
What is biohydrogenation?
A process by which rumen microbes convert unsaturated fatty acids into saturated ones (e.g., linoleic acid → stearic acid).
121
Why is grass a key source of C18 fatty acids in milk?
Because grass is rich in chloroplasts, which contain galactolipids like α-linolenic acid.
122
What are the two main protein types in milk and their proportions?
Cow’s milk: 80% casein, 20% whey
Human milk: 40% casein, 60% whey
123
What is a casein micelle made of?
~20,000 casein proteins
Calcium phosphate nanoclusters
Diameter: 50–300 nm
Suspended in the aqueous phase of milk
124
Why do casein micelles form?
Due to phosphoserine residues binding calcium phosphate
Hydrophobic interactions between casein molecules
κ-casein at the surface provides stabilisation
125
What keeps casein micelles dispersed in milk?
Electrostatic repulsion (negative surface charge at pH 6.7)
Steric repulsion (from κ-casein’s glycosylated tails)
126
What happens at the isoelectric point of casein (~pH 4.6)?
Micelles lose charge and aggregate, forming curds (important in cheese/yogurt making)
127
How do casein and whey proteins differ in heat stability?
Casein is heat-stable
Whey proteins denature with heat
