Name: polygenic traits in human height
Uploaded: 2019-03-11T09:21:17.000Z
Duration: 1 min 18 s
Channel: JoVE

K12 Standards

Alabama Course of Study Science

9-12

Biology

heredity-inheritance-and-variation-of-traits

Heredity: Inheritance and Variation of Traits

9-12.B.3.11.b

Polygenic Traits

- Quanto molti geni cooperano

per influenzare un fenotipo,

il risultato è un tratto poligenico.

Uno di questi è l'altezza umana,

che si ritiene influenzata
da centinaia di loci.

Anche se ciascun gene
individualmente ha un ruolo minimo

nello stabilire l'altezza, i
loro effetti si moltiplicano

per stabilire quanto alto
sarà un individuo da adulto.

Parzialmente a causa del
numero dei generi coinvolti,

l'altezza umana varia considerevolmente.

Per esempio, l'altezza
minima di una donna adulta

in una popolazione è di circa 1.50 m,

mentre il massimo è 1.80 m.

Ma esistono donne di tutte
le altezze intermedie.

Metterle su un grafico rivela

una curva a campana.

Solo poche donne si avvicinano
al minimo o al massimo,

la maggior parte sta in mezzo, a 1.65 m.

A volte un singolo
fenotipo, come l'altezza,

che risulta da diversi fattori generici

può essere quantificata
e messa su un grafico

questo si addice anche

a altre caratteristiche poligeniche

come il peso, la pressione del sangue,

e il numero di fessure
nelle impronte digitali.

tratti poligenici

Quando più di un gene è responsabile di un dato fenotipo, il tratto è considerato poligenico. L'altezza umana è un tratto poligenico. Gli studi hanno scoperto centinaia di loci che influenzano l'altezza, e si ritiene che ci siano molti di più. A causa dell'elevato numero di geni coinvolti, nonché di fattori ambientali e nutrizionali, l'altezza varia in modo significativo all'interno di una determinata popolazione. La distribuzione dell'altezza forma una curva a campana, con relativamente pochi individui nella popolazione alle altezze minime o massime e la maggior parte della popolazione nella gamma di altezze medie. La maggior parte dei tratti poligenici, come il peso, la pressione sanguigna e gli aspetti dei modelli di impronte digitali, tracciano anche come curve a forma di campana.

<h4>L'Altezza Umana- un Tratto Poligenico</h4>

Anche se il lavoro fondamentale di Mendel sull'eredità genetica si è concentrato sui tratti che sono sorti da singoli geni, esperimenti come studi di associazione a livello di genoma hanno rivelato che molti tratti umani si sviluppano attraverso la cooperazione di più prodotti genici. La collaborazione di numerosi geni per influenzare un fenotipo costituisce un tratto poligenico (cioè determinato da "molti geni").

Un esempio di tratto poligenico è l'altezza umana. Centinaia di loci sono implicati nella variabilità dell'altezza umana, e si ritiene che ci siano più che non sono ancora stati identificati. Molti di questi geni influenzano direttamente o indirettamente la cartilagine nelle piastre di crescita, che si trovano nelle ossa lunghe delle braccia e delle gambe.

<h4>Distribuzione della popolazione dei tratti poligenici</h4>

L'altezza umana varia considerevolmente, in parte a causa di un gran numero di geni che la influenzano. L'altezza è influenzata anche da fattori ambientali e nutrizionali, come se la madre fumata o meno durante la gravidanza, la dieta della madre durante la gravidanza e la dieta della prole.

In una popolazione in cui l'altezza femminile minima è di circa cinque piedi, e l'altezza femminile massima è di circa sei piedi, sono presenti donne di tutte le altezze tra questi valori. Tracciando la distribuzione dell'altezza si ottiene una curva a forma di campana, con relativamente poche donne che si avvicinano alle altezze minime o massime e la maggior parte che mostra altezze vicino alla media di cinque piedi e mezzo. La maggior parte dei tratti poligenici, come il peso, la pressione sanguigna e gli aspetti dei modelli di impronte digitali, come il numero di creste, assumono anche distribuzioni a forma di campana a causa dell'elevato numero di possibili combinazioni di alleli.

Tratti poligenici

When more than one gene is responsible for a given phenotype, the trait is considered polygenic. Human height is a polygenic trait. Studies have uncovered ...

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polygenic traits in human height

Polygenic traits are traits controlled by more than one gene. Human height is a clear example of this kind of inheritance. Because many genes work together, the final trait can vary a lot from person to person.

Researchers have found hundreds of loci, or gene locations, that influence height. There are likely many more that have not yet been identified. Many of these genes affect cartilage in the growth plates of the long bones in the arms and legs, either directly or indirectly.

Height is also shaped by environmental and nutritional factors. These include whether the mother smoked during pregnancy, the mother’s diet during pregnancy, and the offspring’s diet. This is one reason height can differ so much within a population.

When height is plotted for a population, it usually forms a bell-shaped curve. Few people are close to the minimum or maximum heights, and most fall near the middle range. Other polygenic traits, such as weight, blood pressure, and some fingerprint features like ridge number, often show the same pattern because so many allele combinations are possible.

Polygenic Traits in Human Height

genetic lingo

Genotype, Phenotype, and Inheritance

Genotype, phenotype, and inheritance help explain how traits and disease risk are passed from parents to offspring. In diploid organisms, including humans, most other animals, and many plants, somatic cells carry a duplicate set of chromosomes. These chromosome pairs are homologous, with similar length, centromere position, and gene locations. Diploid organisms inherit two versions of each gene, one from each parent. These versions are called alleles, and they sit at the same relative locus,...

punnett squares

Punnett Squares for Predicting Traits

Punnett squares help predict which traits offspring may inherit from two parents. They show possible genotypes, which are pairs of alleles, and can also show the chance of a phenotype, or visible trait, when the inheritance pattern is known. These grids work best for traits controlled by a single gene locus and passed on independently during meiosis. Punnett squares were developed in the early 1900s by Reginald Punnett. His work came after Gregor Mendel’s pea plant experiments revealed the...

monohybrid crosses

Mendel’s Pea Plant Inheritance Ratios

Gregor Mendel used pea plants to study how traits are passed from parents to offspring. His breeding experiments in the 1850s and 1860s showed that inheritance follows clear patterns. He crossed true-breeding plants that differed in one trait and found that dominant traits can hide recessive traits. Mendel focused on seven pea plant traits, and each trait had two forms controlled by a single gene locus. He noticed that true-breeding plants always produced offspring with the same phenotype, or...

dihybrid crosses

Mendel's Law of Independent Assortment

Mendel’s law of independent assortment explains how two traits can be inherited separately. Gregor Mendel tested this idea with pea plants that differed in two characteristics, such as pea color and pea shape. He used true-breeding parents that were homozygous for both traits but showed different phenotypes. In one example, Mendel crossed round, yellow peas with wrinkled, green peas. The parental generation had RRYY and rryy genotypes. Their first-generation offspring were all dihybrids,...

law of segregation

Mendel’s Pea Cross Ratios

Mendel’s pea plant crosses show how traits can disappear in one generation and return in the next. When he crossed plants, one parental trait sometimes seemed to vanish in the F1 generation and reappear in the F2 generation. Mendel used this pattern to explain why some traits are dominant and others are recessive. He proposed that traits are controlled by alleles, which are different versions of a gene. An organism inherits two copies of each gene, one from each parent. In his model, a...

law of independent assortment

Mendel’s Dihybrid Cross and Trait Ratios

Mendel’s dihybrid cross shows how two traits are inherited at the same time. A dihybrid cross is a cross in which both parents are homozygous for two distinct traits, and the F1 generation is heterozygous for both traits. Mendel used pea plants with round yellow peas and wrinkled green peas as an example. One parent had genotype YYRR, and the other had genotype yyrr. In the F1 generation, every plant showed the dominant traits, so the plants were YyRr and had yellow, round peas. The F2...

probability laws

Inheritance Risk with Sum and Product Rules

Inheritance risk can be calculated with the sum rule and the product rule. The sum rule applies to mutually exclusive events, or events that cannot happen at the same time. The product rule applies to independent events, or events that do not affect one another. These rules describe theoretical probability, which is the chance of an event before it happens. Empirical probability is different because it is based on events that have already occurred. These probability rules are useful in...

test cross

Using Test Crosses to Identify Genotypes

Test crosses are used to identify the genotype of an organism with a dominant trait. A genotype is the pair of alleles inherited for a gene, and alleles are different forms of the same gene. In diploid organisms, including humans, each gene usually has two alleles, one from each parent. An allele is recessive when its effect is hidden by another allele at the same gene location. Pea plants provide a clear example with flower color. White flowers are recessive, because one copy of the purple...

pedigree analysis

Reading Family Traits in Pedigrees

Pedigrees are family trees used to track how a trait passes through generations. They help scientists and students see whether a trait is dominant or recessive, whether it is autosomal or sex-linked, what genotypes family members may have, and what phenotypes may appear in future generations. For families with a history of inherited disease, this information can be important for family planning. In plants and animals, inheritance is often studied with crosses. Monohybrid crosses can show...

polygenic traits

Polygenic traits are traits controlled by more than one gene. Human height is a clear example of this kind of inheritance. Because many genes work together, the final trait can vary a lot from person to person. Researchers have found hundreds of loci, or gene locations, that influence height. There are likely many more that have not yet been identified. Many of these genes affect cartilage in the growth plates of the long bones in the arms and legs, either directly or indirectly. Height is...

multiple allele traits

Blood Type and Allele Interactions

Multiple alleles can shape traits through blood type, sickle cell anemia, incomplete dominance, and codominance. Multiple allelism means a gene has three or more allelic forms. Diploid organisms, including humans, usually carry only two alleles for each gene, but many human genes exist in multiple forms in the population. Human blood type is a clear example of multiple allelism. The blood type gene has three alleles: I A , I B , and i. These alleles help determine which blood type a person has...

epistasis

Gene Masking in Rabbit Fur Color

Epistasis describes how one gene can mask or change the effect of another gene. In high school genetics, this helps explain why many traits do not follow a simple single-gene pattern. Instead, alleles at different locations can work together to shape the final phenotype. Mendel studied seven unrelated pea traits, but most traits involve multiple gene interactions. Epistasis often happens when one gene interferes with the expression of another gene. It can also occur when genes are part of the...

nature and nurture

Genes and Environment Shape Height

Genes and environment both shape human height and other traits. Genes are the inherited instructions we get from our parents. Environment includes factors such as diet, stress, and social conditions. Many phenotypes, or observable traits, reflect both influences. Some also show up later in life, including cancer and other diseases. Height is a clear example of this interaction. Scientists estimate that 70-90% of height variation comes from genetic differences among people. The remaining 10-30%...

pleiotropy

SOX10 and Multiple Traits in Pleiotropy

Pleiotropy is when one gene affects more than one trait. The SOX10 gene is a clear example because it can influence pigmentation, hearing, and intestinal movement. These traits may seem unrelated, but they can all be linked to the same gene change. In humans, a deleted region in SOX10 can cause Waardenburg Syndrome Type 4, or WS4. WS4 is an autosomal recessive disorder, which means a person usually inherits two altered copies of the gene. Common signs include a white forelock,...

sex-linked disorders

X- and Y-Linked Disorder Patterns

X- and Y-linked disorders come from mutations in genes on the sex chromosomes. These genes, like those on autosomes, are needed for normal body function. When a mutation causes a biological problem, the condition is called sex-linked. Y-linked disorders come from changes in the Y chromosome. They affect only males, because only males carry a Y chromosome. Mutations in this small chromosome can affect male sexual function and secondary sex characteristics. One example is Y-chromosome...

x-linked traits

X-Linked Inheritance in Families

X-linked inheritance explains how traits on the X chromosome are passed through families. In most mammalian species, females have two X sex chromosomes, while males have one X and one Y. A mutation on one X chromosome may be masked in females by a normal allele on the other X. In males, that same mutation is more likely to show because there is no second normal X to balance it. Traits caused by changes on the X chromosome are called X-linked traits. Color blindness is a well-studied example.

x-inactivation

Barr Bodies and X-Chromosome Balance

Barr bodies and X-chromosome balance help explain how female mammalian cells control gene activity from the X chromosome. The human X chromosome carries far more genes than the Y chromosome. Because males usually have one X chromosome and females have two, females would make twice as many of some proteins without a control system. To prevent that imbalance, female mammalian cells inactivate nearly all the genes on one X chromosome during early embryonic development. The inactive X condenses...

non-nuclear inheritance

Maternal DNA in Mitochondria and Chloroplasts

Maternal DNA in mitochondria and chloroplasts explains how some genes are inherited outside the nucleus. Most DNA is in the nucleus, but mitochondria and chloroplasts in the cell cytoplasm also carry their own DNA and can copy it independently of nuclear DNA. Mitochondria are found in both plant and animal cells. They are called the powerhouses of eukaryotic cells because they break down glucose to make energy for cellular activity. Mitochondrial DNA has about 37 genes, and many help with...

chromosomal theory of inheritance

How Genes Map to Chromosomes

Genes map to chromosomes, and this idea explains how Mendel’s inheritance patterns work. Gregor Mendel published his pea plant breeding results in 1866. He showed that physical traits follow predictable patterns. At the time, scientists did not yet know that genes existed. Mendel used the word "factors" for the hereditary units he studied. The details behind Mendel’s laws of segregation and independent assortment were still unknown for many years. In the late 1800s, better microscopes and...

key terms and concepts

Explore how multiple genes and environmental factors shape human height, and why polygenic traits often form a bell-shaped curve in populations.

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Inheritance and Variation of Traits

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Chi-square Analysis

The chi-square test is a statistical hypothesis test. It is used to check whether there is a significant difference between an expected value and an ...

Pedigree Analysis

Probability Laws

Overview

The probability of inheriting a trait can be calculated using the sum and product rules. The sum rule is used to calculate the probability of ...

11. Use probability and statistical models to explain the variation of expressed traits within a population. Examples: pedigree charts, family and population studies

9-12.B.3.11

Punnett Squares

Monohybrid Crosses

Dihybrid Crosses

Trihybrid Crosses

Trihybrid Crosses
Some of Mendel&#8217;s crosses examined three pairs of contrasting characteristics. Such a cross is called a trihybrid cross. A ...

Law of Independent Assortment

Multiple Allele Traits

Incomplete Dominance

Gregor Mendel&#39;s work (1822 - 1884) was primarily focused on pea plants. Through his initial experiments, he determined that every gene in a diploid ...

Lethal Alleles

Agouti: A Lethal Allele
Lucien Cu&#233;not discovered lethal alleles in 1905 while studying the inheritance of coat color in mice. The agouti gene is ...

background-and-environment-affect-phenotype

Background and Environment Affect Phenotype

Although the genetic makeup of an organism plays a major role in determining the phenotype, there are also several environmental factors, such as ...

X and Y Chromosomes

Among mammals, the gender of an organism is determined by the sex chromosomes. Humans have two sex chromosomes, X and Y. Every human diploid cell has 22 ...

The Y Chromosome Determines Maleness

The Y chromosome is a sex chromosome&#160;found in several vertebrates and mammals, including humans. In addition to 22 pairs of autosomes, the human ...

The Ratio of X Chromosome to Autosomes

In most organisms, sex is determined by the ratio of X and Y chromosomes. However, in some organisms, such as Drosophila and C.elegans, sex is determined ...

X-linked Traits

Sex Linked Disorders

Dosage Compensation

In animals, gender is determined by the number and type of sex chromosome. For example, human females have two X chromosomes, and males have one X and one ...

X-inactivation

Blood Types

Human blood is classified into different types based on the presence of antigens on the red blood cell&#39;s surface and antibodies in the plasma. Proper ...

Blood Transfusion and Agglutination

Blood transfusion is a therapeutic measure to restore the blood volume after extensive blood loss due to an accident or a medical procedure. Blood ...

a. Use mathematics and computational thinking to predict patterns of inheritance, including dominance, recessiveness, codominance, and incomplete dominance. Examples: Use a Punnett square to illustrate codominance in genes for blood types. Use probability rules to predict the phenotypes of offspring from different parental combinations.

9-12.B.3.11.a

Epistasis

In addition to multiple alleles at the same locus influencing traits, numerous genes or alleles at different locations may interact and influence ...

Pleiotropy

Pleiotropy is the phenomenon in which a single gene impacts multiple, seemingly unrelated phenotypic traits. For example, defects in the SOX10 gene cause ...

Nature and Nurture

Many human characteristics, like height, are shaped by both nature&mdash;in other words, by our genes&mdash;and by nurture, or our environment. For ...

b. Obtain, evaluate, and communicate information about how the interplay of heritable risk factors, somatic mutations, and environment influences human disease. Examples: Because heart disease has heritable and environmental risk factors, a person's total risk needs to include both factors. Cancers have both heritable (breast, lung, colorectal, skin, cervical cancer) and environmental risk factors (smoking, diet, sun exposure, HPV exposure). Clarification: Epigenetics could be an extension of this standard.

Spermatogenesis

Spermatogenesis is the process by which haploid sperm cells are produced in the male testes. It starts with stem cells located close to the outer rim of ...

Oogenesis

In human women, oogenesis produces one mature egg cell or ovum for every precursor cell that enters meiosis. This process differs in two unique ways from ...

What is Meiosis?

Meiosis is the process by which diploid cells divide to produce haploid daughter cells. In humans, each diploid cell contains 46 chromosomes, half from ...

Meiosis I

Meiosis II

Meiosis vs. Mitosis

Crossing Over

Crossing over is the exchange of genetic information between homologous chromosomes during prophase I of meiosis I. Genetic recombination gives rise to ...

Nondisjunction

Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate correctly and move to the opposite poles of the cells. This ...

Karyotyping

12. Develop and use an evidence-based model to illustrate the formation of reproductive cells through the process of meiosis. Example: Use karyotype cutouts to illustrate independent assortment into reproductive cells.

9-12.B.3.12

Homologous Recombination

The basic reaction of homologous recombination (HR) involves two chromatids that contain DNA sequences sharing a significant stretch of identity. One of ...

Gene Conversion

Other than maintaining genome stability via DNA repair, homologous recombination plays an important role in diversifying the genome. In fact, the ...

overview-of-transposition-and-recombination

Overview of Transposition and Recombination

Transposons make up a significant part of genomes of various organisms. Therefore, it is believed that transposition played a major evolutionary role in ...

conservative-site-specific-recombination-and-phase-variation

Conservative Site-specific Recombination and Phase Variation

Because the DNA segments are cut and reorganized in a direction-specific manner, site-specific recombination has emerged as an efficient genetic ...

a. Construct an explanation of how new genetic combinations and variations occur during crossover.

9-12.B.3.12.a

Organization of Genes

Chromosome Structure

A functional eukaryotic chromosome must contain three elements: a centromere, telomeres, and numerous origins of replication.
The centromere is a DNA ...

Chromosome Replication

Before a cell can divide, it must accurately replicate all of its chromosomes, including the DNA and its associated histone and non-histone ...

Teratogenicity

The ability of a drug to produce structural deformations and functional abnormalities in the developing embryo or the fetus is called teratogenicity, and ...

Mutagenicity and Carcinogenicity

Mutagenicity and carcinogenicity refer to the ability of drugs to cause genetic defects and induce cancer, respectively. The International Agency for ...

An Overview of Genetic Analysis

An organism&#8217;s physical traits, or phenotype, are a product of its genotype, which is the combination of alleles (gene variants) inherited from its ...

Genetic Crosses

To dissect genetic processes or create organisms with novel suites of traits, scientists can perform genetic crosses, or the purposeful mating of two ...

Genetic Screens

Genetic screens are critical tools for defining gene function and understanding gene interactions. Screens typically involve mutating genes and then ...

b. Obtain, evaluate, and communicate information about how errors during meiosis and environmental factors affect the expression of traits. Examples: Translocation between chromosomes 8 and 11 can cause myeloproliferative disorder and lymphoma. Smoking and exposure to teratogenic chemicals can alter genes in reproductive cells that can be passed on to offspring.

9-12.B.3.12.b

Polygenic Traits in Human Height

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