Genetics: Autosomal Recessive Disorders
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Questions and Answers

What must be true for a person to have an autosomal recessive disorder?

  • The disorder affects males only.
  • The disorder is inherited from the father only.
  • Both copies of the recessive allele must be present. (correct)
  • Only one copy of the recessive allele is needed.

Males can be carriers for sex-linked diseases.

False (B)

What genetic notation represents a healthy individual in autosomal recessive disorders?

C

Cystic fibrosis is an example of an autosomal ______ disorder.

<p>recessive</p> Signup and view all the answers

Which of the following statements about sex chromosomes is correct?

<p>Y chromosome genes are responsible for male characteristics. (D)</p> Signup and view all the answers

Match the following genetic disorders with their inheritance type:

<p>Cystic fibrosis = Autosomal recessive Huntington's disease = Autosomal dominant Color blindness = Sex-linked Sickle cell disease = Autosomal recessive</p> Signup and view all the answers

In males, sex-linked traits are expressed due to the lack of a second ______ chromosome.

<p>X</p> Signup and view all the answers

What characteristic is true of autosomal dominant disorders?

<p>Both males and females are equally likely to be affected. (B)</p> Signup and view all the answers

In autosomal recessive traits, affected parents will always have affected offspring.

<p>True (A)</p> Signup and view all the answers

What is the genotype for a person with a widow's peak?

<p>Ww or WW</p> Signup and view all the answers

If both parents are carriers of an autosomal recessive trait, the probability of having an affected child is _____%.

<p>25</p> Signup and view all the answers

Match the type of inheritance with its characteristic:

<p>Autosomal Dominant = Affected offspring in every generation Autosomal Recessive = Normal parents may have affected children Sex-Linked = Typically transmitted through X chromosome Autosomal = Both genders can inherit the trait equally</p> Signup and view all the answers

Which of the following traits is X-linked recessive?

<p>Color blindness (B)</p> Signup and view all the answers

Female mammals express both copies of sex-linked genes due to random X chromosome inactivation.

<p>False (B)</p> Signup and view all the answers

What is codominance?

<p>Both alleles of a gene are expressed completely.</p> Signup and view all the answers

The _____ gene can overshadow the expression of other genes for a specific trait.

<p>epistatic</p> Signup and view all the answers

Match the sex-linked traits to their type:

<p>Haemophilia = X-linked recessive Rett Syndrome = X-linked dominant Albinism = Epistasis Color blindness = X-linked recessive</p> Signup and view all the answers

What percentage of F1 offspring will have blood group O from a male with IA i and a female with IB i blood group?

<p>25% (C)</p> Signup and view all the answers

Human eye color is considered a polygenic trait.

<p>True (A)</p> Signup and view all the answers

Provide an example of a trait influenced by environmental factors.

<p>Sex of turtles based on incubation temperature.</p> Signup and view all the answers

Female turtles bury their eggs in the sand, and warmer temperatures lead to the development of _____ turtles.

<p>female</p> Signup and view all the answers

What is the expected percentage of females that are color blind in the F1 generation when a color blind male mates with a heterozygous normal female?

<p>50% (B)</p> Signup and view all the answers

Males can be carriers for X-linked disorders.

<p>False (B)</p> Signup and view all the answers

What are the genotypes of the predicted F1 offspring when a color blind male mates with a heterozygous normal female?

<p>XcX, XcY, XX, XY</p> Signup and view all the answers

Males have _____ chromosomes, which include one X and one Y.

<p>XY</p> Signup and view all the answers

Match the following genotypes with their corresponding phenotypes:

<p>XcX = Heterozygous normal female XcY = Color blind male XX = Normal female XY = Normal male</p> Signup and view all the answers

What is the probability of color blind males in the F1 generation?

<p>50% (C)</p> Signup and view all the answers

Color blindness is a dominant disorder.

<p>False (B)</p> Signup and view all the answers

What type of inheritance is demonstrated when a curly haired man and a straight haired woman produce 100% wavy haired offspring?

<p>Incomplete dominance (A)</p> Signup and view all the answers

Describe what a pedigree is used for.

<p>A pedigree is a chart used to trace phenotypes and genotypes in a family to determine if individuals carry recessive alleles.</p> Signup and view all the answers

All males will be affected by hypertrichosis if a male with the condition marries a normal female.

<p>True (A)</p> Signup and view all the answers

Females can be _____ of X-linked disorders due to their XX chromosome composition.

<p>carriers</p> Signup and view all the answers

What is the genotype of a normal male in the context of hemophilia?

<p>XHY</p> Signup and view all the answers

Which of the following statements is true regarding X-linked disorders?

<p>Males are more likely to be affected than females. (B)</p> Signup and view all the answers

In Rett syndrome, the genotype for a heterozygous female is XHXh, where H represents __________.

<p>affected</p> Signup and view all the answers

Match the genetic disorders with their inheritance types:

<p>Rett syndrome = X-linked dominant Hemophilia = X-linked recessive Hypertrichosis = Y-linked Hair texture inheritance = Incomplete dominance</p> Signup and view all the answers

What will be the likely phenotype percentage of offspring from a heterozygous female and a normal male regarding hemophilia?

<p>50% affected males, 0% affected females (B)</p> Signup and view all the answers

In the scenario involving a normal male and a heterozygous female with Rett syndrome, all offspring will be normal.

<p>False (B)</p> Signup and view all the answers

What percentage of the F1 generation will be affected when a male with hypertrichosis marries a normal female?

<p>0%</p> Signup and view all the answers

In the Punnett square for hemophilia, the percentage of females that might be hemophilic is __________.

<p>0%</p> Signup and view all the answers

How does temperature affect the sex of turtle offspring?

<p>Cooler temperatures result in male turtles. (C)</p> Signup and view all the answers

Flashcards

Autosomes

Chromosomes other than sex chromosomes. They do not determine sex.

Autosomal traits

Traits determined by genes located on autosomes. These traits are equally likely to appear in males and females.

Carrier

A person who carries a recessive allele for a genetic disorder but does not exhibit the disorder.

Recessive disorder

A genetic disorder caused by a recessive allele. Two copies of the recessive allele are needed for the disorder to appear.

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Dominant disorder

A genetic disorder caused by a dominant allele. A single copy of the dominant allele is enough for the person to exhibit the disorder.

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Sex-linked genes

Genes located on sex chromosomes. These genes can influence traits related to sex, but they can also affect other traits.

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Sex-linked recessive disorder

A genetic disorder caused by a recessive allele on the X chromosome. Males are more likely to be affected because they have only one X chromosome.

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Incomplete dominance

A type of inheritance where the heterozygous genotype expresses a phenotype that is a blend or intermediate between the two homozygous phenotypes.

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X-linked disorder

A genetic disorder where the gene responsible for the disorder is located on the X chromosome.

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Dominant inheritance

A type of inheritance where one allele completely masks the expression of another allele.

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Codominance

A type of inheritance where both alleles are expressed equally in the phenotype.

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Y-linked disorder

A type of inheritance where the gene responsible for the disorder is located on the Y chromosome.

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Genotype

The possible genetic makeup of an individual, represented by the combination of alleles they possess.

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Phenotype

The observable characteristics or traits of an individual, determined by their genotype and environmental factors.

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Punnett square

The diagram used to predict the possible genotypes and phenotypes of offspring from a cross between two parents.

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Sex-linked trait

A trait determined by genes located on the sex chromosomes (X or Y). These traits can affect characteristics related to sex and other traits.

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ABO blood group

A blood group system where three alleles (IA, IB, and i) determine a person's blood type. IA and IB are codominant, while i is recessive.

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Polygenic traits

Traits that are influenced by multiple genes. This means several genes contribute to the expression of a single trait. This leads to a wide range of phenotypes, rather than just two distinct possibilities.

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Epistasis

A type of gene interaction where one gene (epistatic gene) can mask the expression of other genes, even if those other genes have different alleles. The effects of the epistatic gene overshadow the other genes.

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Albinism

A genetic condition where the body cannot produce melanin, the pigment that gives color to skin, hair, and eyes. This is caused by an epistatic gene that blocks pigment production.

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Genotype-environment interaction

The interaction between genes and environmental factors that ultimately determines a person's traits. Genes provide the blueprint, but the environment can influence how those genes are expressed.

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Rett syndrome

A sex-linked syndrome that primarily affects females, causing problems with brain development, coordination, and social interaction. It is caused by a dominant mutation on the X chromosome.

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Hemophilia

A genetic disorder that impairs the blood's ability to clot properly. This can lead to excessive bleeding after injury. It is caused by a recessive mutation on the X chromosome.

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Carrier (X-linked)

A female who carries a recessive allele for an X-linked disorder but does not exhibit the disorder herself.

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Pedigree

A diagram used to track the inheritance of traits within a family. Helps identify carriers and predict the likelihood of inheriting a specific disorder.

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Affected Male (X-linked)

A male who carries a recessive allele for an X-linked disorder and therefore exhibits the disorder.

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Heterozygous

A female who carries one copy of the dominant allele and one copy of the recessive allele for a specific trait. She will express the dominant trait.

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Hemizygous

A male who has only one copy of the X chromosome. This makes him more susceptible to X-linked recessive disorders.

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F1 Generation

The offspring produced from a specific mating.

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Probability of affected offspring

The probability that an offspring will inherit a specific trait or disorder from their parents.

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Predicting offspring

The process of determining the potential genotypes and phenotypes of offspring based on the known genotypes of the parents.

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Autosomal Dominant Inheritance

A pattern of inheritance where a trait is equally likely to be passed on to male and female offspring. The trait is expressed regardless of whether the individual has one or two copies of the dominant allele.

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Autosomal Recessive Inheritance

A pattern of inheritance where a trait is expressed only if the individual has two copies of the recessive allele. Carriers of the recessive allele do not exhibit the trait but can pass it on to their offspring.

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Gene

A single gene controlling a specific trait that does not influence other traits. It is a fundamental unit of inheritance.

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Allele

An alternate form of a gene, located at the same locus on homologous chromosomes. It's a variation within a gene.

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Study Notes

Chromosomes and Phenotype

  • The chromosomes' location of genes affects trait expression.
  • Sex chromosomes determine sex (XX = female, XY = male).
  • Autosomes are the other chromosomes.
  • Two copies of each autosomal gene impact phenotype.
  • Mendel studied autosomal traits (e.g., hair texture).
  • Autosomal traits are carried on autosomes (22 pairs in humans).
  • Genotype is expressed by letters (e.g., eye color).

Disorders Caused by Autosomes

  • Recessive alleles must be present for a disorder.
  • Someone with heterozygous alleles is a carrier.
  • Cystic fibrosis is an autosomal recessive disorder.

Disorders Caused by Dominant Alleles on Autosomes

  • Huntington's disease (affects nervous system) is a dominant trait.
  • When the affected allele is present, the phenotype will be affected

Expression of Sex-Linked Genes

  • Males express recessive sex-linked genes.
  • Males cannot be carriers of X-linked diseases.

Sex-Linked Disease Example

  • Color blindness and hemophilia are examples of X-linked recessive traits.
  • Rett syndrome is an X-linked dominant trait.

Incomplete Dominance

  • Defined: Neither allele is completely dominant.
  • Heterozygous traits show a blended phenotype.
  • Multiple phenotypes are possible.
  • An example is flower color.

Codominance

  • Codominant alleles are fully expressed.
  • They are neither dominant nor recessive.
  • Blood types are an example of codominance.

Polygenic Traits

  • Multiple genes interact to create a trait.
  • Human skin color and eye color are examples.

Epistasis

  • One gene can overshadow others.
  • Epistatic gene interferes with other genes' expression (e.g., controlling pigment production).
  • Mouse fur and albinism are examples of epistasis.

The Environment and Phenotype

  • Phenotype is influenced by both genotype and environment.
  • Environmental factors can alter a trait (like sunlight lightening hair).
  • Sea turtle sex is influenced by incubation temperature.

Practice Problems:

  • Specific questions and answers are given for practical examples of trait inheritance patters, including problems regarding genetic disorders, predicting offspring genotypes in cross breeding cases, and using Punnett squares are provided
  • Various alleles and inheritance patterns are illustrated in practice questions and answers, such as those related to hemophilia, color blindness, practice pedigrees and more intricate inheritance patterns such as polygenic traits and epistatic interactions.

Gene Linkage and Mapping

  • Linked genes are on the same chromosome.
  • Often inherited together, but not always.
  • Crossing over breaks up linkages during meiosis.
  • Linkage maps display gene locations relative to each other. This is influenced by the frequency on crossing over events.

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Related Documents

Chromosomes and Phenotype Presentation PDF

Description

Test your knowledge on autosomal recessive disorders and inheritance patterns. This quiz covers essential concepts such as genetic notation, examples of disorders, and the characteristics of genetic traits. Challenge yourself to match disorders with their inheritance types and calculate probabilities related to these genetic traits.

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