Genetics Unit 2: Extensions to Mendelian Analysis

Multiple alleles play a crucial role in genetic stability and diversity within a population.

The different allelic forms of a gene exhibit variations in their nucleotide sequences, leading to distinct levels of activity in their respective gene products.

The four alleles are C (wild-type), cch (chinchilla), ch (Himalayan), and c (albino).

<p>The order of dominance is C &gt; cch &gt; ch &gt; c.</p> Signup and view all the answers

<p>The wild-type allele in rabbits refers to the C allele, which is dominant and results in the full color phenotype.</p> Signup and view all the answers

<p>The homozygous dominant genotype (CC) expresses the full color phenotype.</p> Signup and view all the answers

<p>Mutant alleles, such as cch, ch, and c, contribute to genetic diversity and variability among individuals in a population.</p> Signup and view all the answers

<p>Multiple alleles lead to varied phenotypic expressions, which affects the ratios of different genotypes in the offspring.</p> Signup and view all the answers

<p>Mendel's work laid the foundation for the principles of heredity, demonstrating how traits are inherited from parents to offspring.</p> Signup and view all the answers

<p>Codominance occurs when both alleles in a heterozygote are fully expressed, resulting in offspring with a phenotype that is neither dominant nor recessive. An example is the AB blood type in humans.</p> Signup and view all the answers

<p>Epistasis is when one gene's expression is affected by another gene, influencing the phenotypic outcome. It can mask or modify the effects of other genes.</p> Signup and view all the answers

<p>Incomplete dominance occurs when the phenotype of a heterozygote is an intermediate between the phenotypes of the two homozygotes. This contrasts with complete dominance, where one allele completely masks the other.</p> Signup and view all the answers

<p>Lethal alleles are alleles that can cause the death of an organism when present in a certain genotype, often leading to modified Mendelian ratios in offspring. For example, certain alleles in mice can lead to death if homozygous.</p> Signup and view all the answers

<p>Pleiotropy refers to a single gene influencing multiple phenotypic traits. An example is the gene responsible for sickle cell disease, which affects red blood cell shape and can lead to various health complications.</p> Signup and view all the answers

<p>Multiple alleles refer to the existence of more than two alleles for a genetic locus. An example in humans is the ABO blood type system, which includes A, B, and O alleles.</p> Signup and view all the answers

<p>Gene interactions can modify the expected Mendelian ratios by altering the expression and dominance relationships between genes, leading to phenotypic ratios that are different from those predicted by simple Mendelian inheritance.</p> Signup and view all the answers

<p>The phenotypic ratio is 9:7.</p> Signup and view all the answers

<p>Dominant alleles from both gene pairs are required to synthesize anthocyanin pigment, resulting in a purple flower phenotype.</p> Signup and view all the answers

<p>The epistatic gene is the one that masks the expression of another gene, while the hypostatic gene is the one whose expression is masked.</p> Signup and view all the answers

<p>The phenotypic ratio in dominant epistasis is 12:3:1.</p> Signup and view all the answers

<p>The 'W' gene for white fruit color is dominant and suppresses the expression of the 'Y' gene for yellow fruit color.</p> Signup and view all the answers

<p>When both the W and Y genes are absent, the phenotype expressed is green.</p> Signup and view all the answers

<p>Complementary gene interaction refers to a situation where two different genes must have dominant alleles to express a particular phenotype.</p> Signup and view all the answers

<p>A recessive pair of either gene C or P will prevent the formation of the anthocyanin pathway, resulting in white flowers.</p> Signup and view all the answers

<p>A dominant allele expresses its phenotype while a recessive allele's expression is suppressed in the heterozygous condition.</p> Signup and view all the answers

<p>Incomplete dominance results in an intermediate phenotype due to blending, while co-dominance expresses both phenotypes equally.</p> Signup and view all the answers

<p>The F2 phenotypic ratio in complementary gene interaction is 9:7.</p> Signup and view all the answers

<p>Epistasis occurs when one gene masks the expression of another non-allelic gene, affecting the observed phenotype.</p> Signup and view all the answers

<p>The phenotypic ratio associated with dominant epistasis is 12:3:1.</p> Signup and view all the answers

<p>Multiple alleles refer to the presence of more than two alleles controlling a trait, such as the ABO blood groups in humans.</p> Signup and view all the answers

<p>The phenotypic ratio for recessive epistasis is 9:3:4.</p> Signup and view all the answers

<p>Supplementary gene interaction involves one dominant gene requiring another for expression, with a phenotypic ratio of 12:3:1.</p> Signup and view all the answers

<p>Complete dominance occurs when one allele completely masks the expression of another allele.</p> Signup and view all the answers

<p>A heterozygous organism displays the dominant phenotype, while a homozygous recessive organism displays the recessive phenotype.</p> Signup and view all the answers

<p>The dominant allele masks the expression of the recessive allele, which is only expressed in the homozygous condition.</p> Signup and view all the answers

<p>An example is allele 'A' being dominant and allele 'a' being recessive.</p> Signup and view all the answers

<p>Mendel's studies indicate that traits can be traced through generations and are controlled by dominant and recessive alleles.</p> Signup and view all the answers

<p>Dominant traits can be recognized in an organism with just one dominant allele, while recessive traits require two recessive alleles for expression.</p> Signup and view all the answers

<p>The homozygous condition for recessive alleles is significant because it is the only way these alleles can be fully expressed.</p> Signup and view all the answers

<p>Heterozygosity refers to having two different alleles for a trait, such as 'Aa', where the dominant allele is expressed.</p> Signup and view all the answers

<p>Rh factor is crucial for blood compatibility and can cause Rh incompatibility in pregnancies.</p> Signup and view all the answers

<p>Rh factor was discovered by Karl Landsteiner and Alexander Wiener in 1937.</p> Signup and view all the answers

<p>It can be tested by reacting a blood sample with anti-Rh serum to observe if agglutination occurs.</p> Signup and view all the answers

<p>The D antigen is encoded by the RHD gene.</p> Signup and view all the answers

<p>Rh+ indicates the presence of the D antigen, while Rh- indicates its absence.</p> Signup and view all the answers

<p>Weiner's theory posits that there is one Rh gene with multiple alleles producing various Rh antigens.</p> Signup and view all the answers

<p>Fisher-Race nomenclature identifies five antigens: D, C, c, E, and e.</p> Signup and view all the answers

<p>The antigens C and c, as well as E and e, are considered antithetical.</p> Signup and view all the answers

The process by which traits are passed from parents to offspring.

The observable characteristics or traits of an organism.

A form of inheritance, one allele completely masks the expression of another.

A form of inheritance where the heterozygote exhibits a phenotype intermediate between the two homozygous phenotypes.

A form of inheritance, where both alleles are expressed equally in the heterozygote.

The existence of more than two alleles for a single gene.

A gene interaction where one gene's expression masks or modifies the expression of another gene.

The ways in which genes affect the traits or phenotypes of an organism, going beyond single genes to look at the influences of multiple genes and their interplay.

The allele that masks the expression of another allele in a heterozygote.

The allele whose expression is masked by a dominant allele in a heterozygote.

An organism with two different alleles for a particular trait.

An organism with two identical alleles for a particular trait.

Initial genetic experiments that focused on pea plants.

Different forms of a gene

Different alleles of a gene can have varying levels of activity due to slight differences in their nucleotide sequences.

The 'normal' or most common allele for a gene, often associated with the typical, functional phenotype.

Any allele that differs from the wild-type allele, potentially resulting in a different phenotype.

A classic example of multiple alleles, showcasing how different alleles of a single gene influence coat color in rabbits.

Multiple alleles often exhibit a dominance hierarchy, where one allele may completely mask the expression of others.

The visible traits or characteristics resulting from the interaction of different alleles within an organism.

The relative frequencies of different allele combinations within a population, influenced by multiple alleles and their dominance relationships.

A blood group system related to the presence or absence of certain antigens on red blood cells, discovered by Karl Landsteiner and Alexander Wiener.

Blood that contains the Rh D antigen, resulting in a positive reaction with anti-Rh serum.

Blood lacking the Rh D antigen, resulting in a negative reaction with anti-Rh serum.

A condition where a pregnant woman with Rh- blood is carrying a fetus with Rh+ blood, potentially causing complications.

The inheritance of Rh factors follows a simple dominant pattern, with the Rh+ allele dominant over the Rh- allele.

A nomenclature for Rh antigens, recognizing five major antigens: D, C, c, E, and e.

Antigens that are opposite or complementary to each other, e.g., C and c.

The most immunogenic Rh antigen, encoded by the RHD gene, responsible for the Rh+ phenotype.

A type of gene interaction where two genes work together to produce a specific phenotype. Both genes need to have at least one dominant allele for the phenotype to be expressed.

A pigment responsible for purple coloration in many flowers, including Lathyrus odoratus. Its synthesis requires the presence of dominant alleles from both genes.

The flower will be white because the pathway for anthocyanin synthesis is incomplete, and therefore, purple pigmentation doesn't occur.

The gene that masks the expression of another gene in epistasis.

The gene whose expression is masked by the epistatic gene in epistasis.

A type of epistasis where a dominant allele of one gene masks the expression of another gene.

The F2 phenotypic ratio in dominant epistasis is 12:3:1. This ratio reflects the masking of the hypostatic gene by the dominant allele of the epistatic gene.

An allele that masks the expression of another allele in a heterozygote.

When two genes work together, and at least one dominant allele from each gene pair is needed to produce the specific phenotype.

Similar to recessive epistasis, one gene may be able to express its trait, while the other dominant gene needs the presence of the first gene to be fully expressed.