BIO EVENTS
elinaa
Event10.pptxEvent 10
Monozygotic (identical) twins
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Event 10
Review of previous activities.
Last Event’s topic: Growth, development and sexual reproduction
How could you improve?
On-line (and upcoming) activities
Human body weight: Genetic and environmental effects.
Assignment, Event 10
Quiz
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Last Event: Growth, development and sexual reproduction
Assignment, Event 9:
Submitting drafts resulted in much better essays. (Another essay with drafts For Event 14.)
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On-line activities, Event 10
CHAPTER 6: Inheritance
Module 18: Chapter Introduction*
Module 19: Non-Mendelian Inheritance*
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* Module with quiz.
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UNIT 3 The Cell
UNIT 4 Metabolism
UNIT 5 Cell Division
UNIT 6 Classical Genetics
UNIT 7 Evolution
UNIT 2 Introduction
to Chemistry
UNIT 8 Ecology
UNIT 1 Introduction
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Obesity
= A medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health. When body mass index (BMI)* exceeds 30 kg/m2.
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* BMI = [body weight (kg)]/[height (m)]2
Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems.[1] [2] People are considered obese when their body mass index (BMI), a measurement obtained by dividing a person's weight in kilograms by the square of the person's height in metres, exceeds 30 kg/m2.[3]
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Body Mass Index
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Weight = 165 lbs = 74.84 kg
Height = 6 ft = 1.83 m
BMI has been used by the WHO as the standard for recording obesity statistics since the early 1980s. In the United States, BMI is also used as a measure of underweight, owing to advocacy on behalf of those suffering with eating disorders, such as anorexia nervosa and bulimia nervosa.[citation needed]
BMI can be calculated quickly and without expensive equipment. However, BMI categories do not take into account many factors such as frame size and muscularity.[19] The categories also fail to account for varying proportions of fat, bone, cartilage, water weight, and more.[citation needed]
Despite this, BMI categories are regularly regarded as a satisfactory tool for measuring whether sedentary individuals are underweight, overweight or obese with various exemptions, such as: athletes, children, the elderly, and the infirm.[citation needed]
One basic problem, especially in athletes, is that muscle weight contributes to BMI. Some professional athletes would be overweight or obese according to their BMI, despite carrying little fat, unless the number at which they are considered overweight or obese is adjusted upward in some modified version of the calculation.[citation needed] In children and the elderly, differences in bone density and, thus, in the proportion of bone to total weight can mean the number at which these people are considered underweight should be adjusted downward.
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Body Mass Index
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BMI SS = 74.84 kg/(1.83 m)(1.83 m)
BMI SS = 74.84 kg/3.35 m2
BMI SS = 22.34 kg/m2
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Body Mass Index
BMI Categories
≤ 18.5: Underweight
18.5-24.9: Normal weight
25.0-29.9: Overweight
≥ 30.0: Obese
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% of population
42% in 2020
Obesity
Possible health consequences
Hypertension
Type-2 diabetes
Coronary heart disease
Stroke
Gallbladder disease
Osteoarthritis
Sleep apnea and respiratory problems
Endometrial, breast and colon cancers
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Waist circumference or waist:hip ratio (“central obesity”)?
94 cm = 37 in; 80 cm = 31.5 in
Very complex interactions
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Genetics
Behavior
Metabolism
Biological
regulation
Environment
Disease
Week 11
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Week 11
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nature
nurture
Genetic material
(DNA)
Environment
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nature
nurture
nature
nurture
Blood type
Eye color
Height
Blood potassium
Neuroticism
Genetic material
(DNA)
Environment
Energy intake, use and storage
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Energy intake
Energy
use
Intake = Use
Weight is stable
Energy intake, use and storage
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Energy intake
Energy
use
Energy
storage
Intake > Use
Storage Weight gain
Energy intake, use and storage
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Energy intake
Energy
use
Stored
energy
Use > Intake
Utilize storage Weight loss
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“You cannot outrun a bad diet.”
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Why you shouldn’t exercise to loose weight, explained with 60+ studies. Vox
https://www.vox.com/2016/4/28/11518804/weight-loss-exercise-myth-burn-calories
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Body weight in humans
Environment effects “Nurture”
Food consumption
Energy use (exercise)
Disease
Genetic (family) effects “Nature”
Body size and composition
Metabolism
Disease
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Body weight in humans
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| Father (kg) | Mother (kg) | Parental mean (kg) | ♂ Child (kg) |
| 91.1 | 65.4 | 78.3 | 81.4 |
| 71.6 | 50.1 | 60.9 | 52.1 |
| 88.6 | 53.6 | 71.1 | 108.3 |
“midparent”
value
91 kg = 200 lbs
70 kg = 155 lbs
65 kg = 145 lbs
50 kg = 111 lbs
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Body weight in humans
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| Father (kg) | Mother (kg) | Parental mean (kg) | ♂ Child (kg) |
| 91.1 | 65.4 | 78.3 | 81.4 |
| 71.6 | 50.1 | 60.9 | 52.1 |
| 88.6 | 53.6 | 71.1 | 108.3 |
91 kg = 200 lbs
70 kg = 155 lbs
65 kg = 145 lbs
50 kg = 111 lbs
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| Father (kg) | Mother (kg) | Parental mean (kg) | Child (kg) | D (kg) | D/Parental mean |
| 104.2 | 77.8 | 91.0 | 77.9 | -13.1 | -0.144 |
Body weight in humans
D = (Child − Parental mean)
91.0 – 77.9 = 13.1
Child’s weight is 14.4% less than the parental
mean value.
13.1/91.0 = 0.144 = 14.4%
Body weight in humans
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| Father (kg) | Mother (kg) | Parental mean (kg) | ♂ Child (kg) | D as % of par. mean |
| 91.1 | 65.4 | 78.3 | 81.4 | + 3.96 |
| 71.6 | 50.1 | 60.9 | 52.1 | − 14.4 |
| 88.6 | 53.6 | 71.1 | 108.3 | + 52.3 |
With little environmental effect, offspring will closely resemble
average of parents
D = (Child − Parental mean)
91 kg = 200 lbs
70 kg = 155 lbs
65 kg = 145 lbs
50 kg = 111 lbs
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Parental weight appears unrelated to child’s weight
“midparent” value
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Parental weight more closely related to child’s weight
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http://www.smithsonianmag.com/science-nature/brief-history-twin-studies-180958281/?no-ist
Body weight in humans
Twin studies*
Two organisms, very similar genetically
May be raised in similar or different environments
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4 twin scenarios…
* Twins: monozygotic/”identical.”
Identical (monozygotic) twins one fertilized egg divides and forms two embryos
3/1000 births worldwide.
A blastocyst (70-100 cells) essentially divides into two two embryos with same placenta
Monozygotic twins are genetically nearly identical and they are always the same sex unless there has been a mutation during development. The children of monozygotic twins test genetically as half-siblings (or full siblings, if a pair of monozygotic twins reproduces with another pair or with the same person), rather than first cousins. Identical twins do not have the same fingerprints, due to the fact that even in a small space inside the womb, people have contact with different parts of this environment, which gives small variations in the same digital, making them unique.[20] Monozygotic twins always have different phenotypes. Normally due to an environmental factor or the deactivation of different X chromosomes in female monozygotic twins, and in some extremely rare cases, due to aneuploidy, twins may express different sexual phenotypes, normally from an XXY Klinefelter syndrome zygote splitting unevenly.[21] [22] [23]
Although monozygotic twins are genetically very similar, a study of 92 pairs of monozygotic twins, carried out in November of 2012, has found that monozygotic twins acquire hundreds of genetic differences early in fetal development, due to mutations (or copy errors) taking place in the DNA of each twin after the splitting of the embryo. It is estimated that, on average, a set of monozygotic twins will have about 360 genetic differences that occurred early in fetal development.
Another cause of difference between monozygotic twins is epigenetic modification, caused by differing environmental influences throughout their lives, which affects which genes are switched on or off. A study of 80 pairs of monozygotic twins ranging in age from three to 74 showed that the youngest twins have relatively few epigenetic differences. The number of epigenetic differences increases with age. Fifty-year-old twins had over three times the epigenetic difference of three-year-old twins. Twins who had spent their lives apart (such as those adopted by two different sets of parents at birth) had the greatest difference.[24] However, certain characteristics become more alike as twins age, such as IQ and personality. This phenomenon illustrates the influence of genetics in many aspects of human characteristics and behavior.[25] [26] [27]
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19 yrs
109 lbs
Different
“environments”
112 lbs
1
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19 yrs
109 lbs
112 lbs
Phenotypes similar
Genetically ≈ equal
Environments different
Genetics ＞ Environment
1
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19 yrs
109 lbs
128 lbs
Different
“environments”
2
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19 yrs
109 lbs
128 lbs
2
Phenotypes different
Genetically ≈ equal
Environments different
Environment ＞ Genetics
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19 yrs
109 lbs
Similar
“environment”
128 lbs
3
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19 yrs
109 lbs
Phenotypes different
Genetically ≈ equal
Environment similar
Environment ＞ Genetics?
128 lbs
3
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19 yrs
109 lbs
Similar
“environment”
4
112 lbs
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19 yrs
109 lbs
Phenotypes similar
Genetically ≈ equal
Environment similar
No conclusions possible
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112 lbs
Heritability
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= proportion of variation for a trait within a population that is due to genetic differences.
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19 yrs
109 lbs
112 lbs
Phenotypes similar
Genetically ≈ equal
Environments different
Genetics ＞ Environment
1
Heritability is high, i.e., close to 100%
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19 yrs
109 lbs
128 lbs
2
Phenotypes different
Genetically ≈ equal
Environments different
Environment ＞ Genetics
Heritability is low, i.e., much less than 100%
Heritability of body weight
Studies using twins and other relatives shows heritability of body weight in humans is about 70-80%.
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Heritability of body weight
Studies using twins and other relatives shows heritability of body weight in humans is about 70-80%.
Caveats
What “population?”
What “environments?”
Effects of shared family environment.
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Assignment, Event 10:*
Examine the TWIN BODY WT.xlxs dataset (in Content).
Based on the Event 10 lecture and your interpretation of the dataset, write a one-sentence statement of a reasonable hypothesis that the experimenters who generated these data might have formulated.
Analyze these data to either support or refute this hypothesis and present your conclusions along with a description of the data analysis procedure(s) that you used. (Submit only a MS Word file.)
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TWIN BODY WT.xlxs
Assignment, Event 10:
Review activities from Events 3 and 5. You may want to incorporate learning from these Events in your assignment.
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Assignment, Event 10:*
Examine the TWIN BODY WT.xlxs dataset.
Based on the Event 10 lecture and your interpretation of the dataset, write a one-sentence statement of a reasonable hypothesis that the experimenters who generated these data might have formulated.
Analyze these data to either support or refute this hypothesis and present your conclusions along with a description of the data analysis procedure(s) that you used. (Submit only a MS Word file.)
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Quiz
Describe a trait in humans other than body weight that you believe also has relatively high heritability. (2 points)
Thinking like a scientist, briefly explain why you believe this is true. (3 points)
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