Name: genotype, phenotype, and inheritance
Uploaded: 2019-03-11T09:21:16.000Z
Duration: 1 min 11 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Life Science

LS.10

LS.10.c

Genetic Lingo

- Alelos são formas diferentes do mesmo gem. 
Recebemos um de cada pai, resultando em um organismo diplóide, dois alelos no mesmo lócus para cada gem envolvido. 
Cada par é conhecido como genótipo de um gem em particular e a expressão física e observável, o fenótipo, como cor dos olhos, é determinado pela combinação herdada. 
Nesse caso, um dos gens contém dois alelos para as cores em potencial, castanho e azul. 
Se as duas formas forem idênticas, o genótipo é chamado homozigoto. 
Quando o par é diferente, o genótipo é heterozigoto. 
O interessante é que o mesmo fenótipo, como olhos castanhos, pode ser expressado por diferentes genótipos. 
Isso é porque o alelo dominante, marrom, representado por uma letra maiúscula, se sobrepõe ao alelo recessivo, azul, escrito em letra minúscula. 
Então, o único jeito de expressar um alelo recessivo é se ambas as cópias forem recessivas.

Fay, David e Andy Spencer. Mutações dominantes. Livro de minhocas, 2006. [<a href="https://www.ncbi.nlm.nih.gov/books/NBK19699/" target="__blank">Fonte</a>].

linguagem genética

<h4>Visão Geral</h4>
 
 Um organismo é diplóide se herdar duas variantes, ou alelos, de cada gene, uma de cada progenitor. Estes dois alelos constituem o genótipo para um determinado gene. O termo genótipo também é usado para se referir ao conjunto completo de genes de um organismo. Um organismo diplóide com dois alelos idênticos tem um genótipo homozigótico, enquanto que dois alelos diferentes indicam um genótipo heterozigótico. Características observáveis decorrentes de genótipos são chamadas fenótipos, que também podem ser influenciados por fatores ambientais. Um alelo é dominante se for necessária apenas uma cópia para manifestar um fenótipo associado e recessivo se forem necessárias duas cópias para a expressão fenotípica.
 
 <h4>Alelos Podem Influenciar Fenótipos</h4>
 
 Organismos diplóides, incluindo humanos, a maioria dos outros animais, e muitas plantas, têm um conjunto duplicado de cromossomas em células somáticas (não sexuais). Esses cromossomas duplicados são homólogos, com comprimentos, posições de centrómero e localizações genéticas semelhantes. Organismos diplóides herdam duas versões de cada gene, uma de cada progenitor. Estas duas variantes genéticas, ou alelos, estão localizadas no mesmo locus relativo, ou posição, em dois cromossomas homólogos. Cada cromossoma contém muitos loci genéticos, e muitas vezes há vários alelos possíveis de um determinado gene.
 
 Os dois alelos herdados por um organismo diplóide constituem o seu genótipo no locus. O termo genótipo também se refere ao conjunto total de genes de um organismo. Diferentes genótipos podem resultar em fenótipos distintos, ou características observáveis (por exemplo, cor dos olhos). Os fenótipos surgem como resultado de genótipos, embora múltiplos genótipos possam causar o mesmo fenótipo. Os fenótipos também são frequentemente influenciados por fatores ambientais.
 
 <h4>Um Genótipo Pode Consistir de Dois Alelos Idênticos ou Distintos</h4>
 
 Para um determinado gene, os dois alelos herdados podem ter sequências de nucleótidos idênticas ou distintas. Um organismo com dois alelos idênticos tem um genótipo homozigótico (ou é um homozigoto). Um organismo com dois alelos diferentes tem um genótipo heterozigótico (ou seja, é um heterozigoto). Se os dois alelos são diferentes (genótipo heterozigótico), mas apenas um afeta o fenótipo, o alelo que influencia o fenótipo é dominante. O outro alelo, que não afeta o fenótipo, é recessivo.
 
 Originalmente, pensava-se que a cor dos olhos era determinada por um único gene, e, portanto, é frequentemente usada para ilustrar a dominância (olhos castanhos) e recessividade (olhos azuis) genética. No entanto, os cientistas descobriram pelo menos oito genes que regulam a cor dos olhos. Embora o gene OCA2 seja responsável por quase três quartos da variação no espectro de cores azul-castanho dos olhos, outros genes ocasionalmente modificam ou se sobrepõem a esses efeitos. No entanto, a cor dos olhos pode ser um exemplo útil para ilustrar alelos dominantes e recessivos.
 
 Em seguida, utilizamos o exemplo simplificado da cor dos olhos para ilustrar a relação entre genótipo e fenótipo. O alelo para olhos castanhos é denotado como B, e o alelo para olhos azuis é b. Um heterozigoto teria genótipo Bb como resultado de receber um alelo dominante de um dos progenitores e um alelo recessivo do outro. Este indivíduo teria olhos castanhos, o fenótipo dominante. O alelo dominante (B) sobrepõe-se ou “esconde” as instruções do alelo recessivo para olhos azuis. Assim, um indivíduo com olhos azuis teria necessariamente o genótipo bb, enquanto que um indivíduo com olhos castanhos poderia ter genótipo BB ou Bb.
 
 <h4>Padrões Hereditários de Doenças Dominantes e Recessivas estão Relacionados com o Risco de Doenças</h4>
 
 Embora a maioria das características sejam controladas por múltiplos genes em vez de um único gene causal, esses princípios podem ser úteis para prever a probabilidade de resultados importantes. Por exemplo, a doença de Huntington (DH) é uma condição progressiva e neurodegenerativa que causa movimentos descontrolados e distúrbios cognitivos e emocionais. A DH é considerada um único distúrbio genético porque é causada por uma mutação em um único gene (HTT), embora outros genes modifiquem o seu início e progressão. A DH é causada por uma mutação dominante, o que significa que um único alelo mutado leva à expressão da doença. Se um progenitor tem uma variante genética normal e uma mutada, a progenia tem 50% de probabilidade de receber o alelo mutante e desenvolver a doença. A DH também não se manifesta normalmente até o meio da vida adulta. Assim, embora a realidade seja desagradável, uma pessoa com um progenitor afetado pode submeter-se a testes genéticos para determinar se tem o alelo causal e, por sua vez, informar o seu planeamento familiar.

Linguagem Genética

Visão geral

Um organismo é diplóide se herda duas variantes, ou alelos, de cada gene, um de cada pai. Esses dois alelos constituem o genótipo ...

Education

JoVE Core

Biology

Biologia

Genetics

Genética

Classical and Modern Genetics

Genética Clássica e Moderna

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

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, or position, on homologous chromosomes. The two alleles at a locus make up an organism’s genotype for that gene. Genotype can also mean the organism’s complete set of genes.

Different genotypes can produce different phenotypes, which are the observable traits of an organism. Eye color is one example. Phenotypes can also be shaped by environmental factors, and more than one genotype can sometimes lead to the same phenotype.

For a given gene, the two alleles may be identical or different. A homozygous genotype has two identical alleles. A heterozygous genotype has two different alleles. If a heterozygote shows the effect of only one allele, that allele is dominant, and the other is recessive.

Brown and blue eye color are often used to show dominance and recessiveness. In this simplified example, B stands for the brown-eye allele and b stands for the blue-eye allele. A person with Bb has brown eyes because the dominant B allele hides the blue-eye instructions from b. A person with blue eyes must have bb, while a person with brown eyes can have BB or Bb.

These same ideas also help explain disease inheritance. Huntington disease is a progressive neurodegenerative condition that can cause uncontrolled movements and changes in thinking and mood. It is a single-gene disorder caused by a mutation in the HTT gene, although other genes can affect when it starts and how it progresses. The mutation is dominant, so one mutated allele can cause the disease. If a parent has one normal allele and one mutated allele, each child has a 50% chance of inheriting the mutation. Because Huntington disease often appears in middle to late life, genetic testing can help affected families with planning.

Genotype, Phenotype, and Inheritance

genetic lingo

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...

polygenic traits

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...

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...

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

Learn how genotypes, alleles, dominant and recessive traits, and Huntington disease inheritance connect genes to visible traits and disease risk.

Genotype, Phenotype, and Inheritance | JoVE K12

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A coleção JoVE Core dá vida à biologia através de mais de 300 vídeos de animação concisos e fáceis de entender que explicam conceitos-chave de biologia, além de mais de 150 vídeos de Cientistas em ação que mostram experimentos reais em pesquisa realizados nos laboratórios atualmente.

Next Generation Science Standards

High School

heredity-inheritance-and-variation-of-traits

Heredity: Inheritance and Variation of Traits

HS-LS3-1

Florida Department of Education

SC.912.L.16

SC.912.L.16.1

new-york-state-science-learning-standards

New York State Science Learning Standards

Inheritance and Variation of Traits

HS-LS3-1.

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LS.10.a

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LS.10.b

Overview

An organism is diploid if it inherits two variants, or alleles, of each gene, one from each parent. These two alleles constitute the genotype ...

Punnett Squares

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A Punnett square displays the possible genotypes offspring can inherit from two parental genotypes. If a trait&#x2019;s inheritance pattern ...

Monohybrid Crosses

Overview

In the 1850s and 1860s, Gregor Mendel investigated inheritance by performing monohybrid crosses in pea plants. He crossed two plants that were ...

Dihybrid Crosses

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Law of Segregation

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Law of Independent Assortment

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Test Cross

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An allele is ...

Pedigree Analysis

Overview

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X-linked Traits

In most mammalian species, females have two X sex chromosomes and males have an X and Y. As a result, mutations on the X chromosome in females may be ...

Sex-linked Disorders

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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 ...

The student will investigate and understand that organisms reproduce and transmit genetic information to new generations. Key ideas include Punnett squares are mathematical models used to predict the probability of traits in offspring.

Genotype, Phenotype, and Inheritance

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